SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0127 AM CDT Tue Sep 03 2024 Valid 041200Z - 051200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns are expected to be limited for Wednesday across the country. The upper-level low currently over parts of the Pacific Northwest is forecast to de-amplify and drift east into the Plains. As this occurs, weak ascent will support widespread cloud cover as well as isolated to scattered showers and thunderstorms across the central Rockies to central Plains. The surface pressure trough currently in place along the High Plains will shift east/southeast through the day, and while breezy conditions are likely just ahead of the boundary, increasing moisture return into the Plains will modulate diurnal RH reductions. Across the West, building surface high pressure should limit wind speeds. Consequently, the potential for elevated fire weather concerns appears limited with no highlights required. ..Moore.. 09/03/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0102 AM CDT Tue Sep 03 2024 Valid 031200Z - 041200Z ...Synopsis... Fire weather concerns will continue into today across parts of the northern Great Basin/northern Rockies as well as the Plains. The upper trough currently over OR is forecast to slowly shift east over the next 24 hours, reaching the northern Rockies by early Wednesday. As this occurs, breezy surface winds within the dry slot of the maturing low will support dry/windy conditions across parts of NV and ID. Over the Plains, a tightening surface pressure gradient will maintain windy conditions through the afternoon, resulting in areas of elevated to critical fire weather conditions. ...Nevada into Idaho... A pronounced dry slot is developing in low-level water-vapor imagery across the northwestern Great Basin/southern OR as the upper low continues to mature. This dry slot is forecast to spread east through this afternoon, which will limit cloud and precipitation chances for northern NV and central to eastern ID and help support RH reductions into the teens. Numerous lightning strikes have been observed over the past 24 hours across this region with GOES IR imagery showing active large fires as of 05 UTC. This fire activity demonstrates the very receptive nature of the current fuel landscape (with the exception of the few locations that received wetting rainfall), and any holdover fires that resulted from the recent lightning activity may become more active today as west/southwest winds increase by late afternoon. Latest deterministic and ensemble solutions continue to suggest 15-20 mph winds will be common, especially through the Snake River Plain of southern/eastern ID and in the lee of the Independence and Ruby Mountains in northeast NV. A few locations may see periods of critical wind/RH conditions, but recent guidance suggests elevated conditions are more likely. Away from the dry slot, isolated to scattered thunderstorms are expected again today across the broader central/northern Rockies region. Forecast storm motions near 30 knots and PWAT values between 0.6 to 0.8 inches suggest dry lightning strikes are possible. However, higher MLCAPE values and lower LCL heights compared to yesterday (Monday) are mitigating factors for predominantly dry thunderstorms. Additionally, latest guidance shows a better QPF signal compared to previous days, which further limits confidence in the dry lightning threat. While this concern precludes risk highlights, any lightning strike may support fire starts given the very dry fuel conditions (ERCs above the 90th percentile). ...Wyoming into Nebraska and South Dakota... Surface pressure has been steadily falling across western NE/SD over the past 12-24 hours, and is expected to fall further through the afternoon as a lee trough continues to deepen. This will maintain breezy southerly winds across the central Plains as well as strengthen westerly downslope flow across eastern WY this afternoon. Downslope warming/drying will result in another day of 15-20% RH minimums across eastern WY and far western NE/SD. Elevated fire weather conditions appear likely within the downslope regime prior to the arrival of clouds (and potentially showers/thunderstorms) around early evening. To the east, modest moisture return into the Plains is ongoing, which will result in a zonal moisture gradient across the Plains by mid afternoon. Recent solutions suggest that the strongest winds may lie within this moisture gradient, resulting in a somewhat confined corridor of elevated fire weather conditions where 15-25 mph winds (gusting to 30-35 mph at times) will overlap with 15-25% RH values. Although guidance occasionally struggles to accurately capture the degree of boundary-layer mixing within these return flow regimes, latest deterministic solutions appear to be capturing moisture trends well and don't show substantial signs of a moist bias. This lends confidence to the ongoing forecast of predominantly elevated fire weather conditions across the region (although some locations may see periods of critical conditions). ..Moore.. 09/03/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0102 AM CDT Tue Sep 03 2024 Valid 031200Z - 041200Z ...Synopsis... Fire weather concerns will continue into today across parts of the northern Great Basin/northern Rockies as well as the Plains. The upper trough currently over OR is forecast to slowly shift east over the next 24 hours, reaching the northern Rockies by early Wednesday. As this occurs, breezy surface winds within the dry slot of the maturing low will support dry/windy conditions across parts of NV and ID. Over the Plains, a tightening surface pressure gradient will maintain windy conditions through the afternoon, resulting in areas of elevated to critical fire weather conditions. ...Nevada into Idaho... A pronounced dry slot is developing in low-level water-vapor imagery across the northwestern Great Basin/southern OR as the upper low continues to mature. This dry slot is forecast to spread east through this afternoon, which will limit cloud and precipitation chances for northern NV and central to eastern ID and help support RH reductions into the teens. Numerous lightning strikes have been observed over the past 24 hours across this region with GOES IR imagery showing active large fires as of 05 UTC. This fire activity demonstrates the very receptive nature of the current fuel landscape (with the exception of the few locations that received wetting rainfall), and any holdover fires that resulted from the recent lightning activity may become more active today as west/southwest winds increase by late afternoon. Latest deterministic and ensemble solutions continue to suggest 15-20 mph winds will be common, especially through the Snake River Plain of southern/eastern ID and in the lee of the Independence and Ruby Mountains in northeast NV. A few locations may see periods of critical wind/RH conditions, but recent guidance suggests elevated conditions are more likely. Away from the dry slot, isolated to scattered thunderstorms are expected again today across the broader central/northern Rockies region. Forecast storm motions near 30 knots and PWAT values between 0.6 to 0.8 inches suggest dry lightning strikes are possible. However, higher MLCAPE values and lower LCL heights compared to yesterday (Monday) are mitigating factors for predominantly dry thunderstorms. Additionally, latest guidance shows a better QPF signal compared to previous days, which further limits confidence in the dry lightning threat. While this concern precludes risk highlights, any lightning strike may support fire starts given the very dry fuel conditions (ERCs above the 90th percentile). ...Wyoming into Nebraska and South Dakota... Surface pressure has been steadily falling across western NE/SD over the past 12-24 hours, and is expected to fall further through the afternoon as a lee trough continues to deepen. This will maintain breezy southerly winds across the central Plains as well as strengthen westerly downslope flow across eastern WY this afternoon. Downslope warming/drying will result in another day of 15-20% RH minimums across eastern WY and far western NE/SD. Elevated fire weather conditions appear likely within the downslope regime prior to the arrival of clouds (and potentially showers/thunderstorms) around early evening. To the east, modest moisture return into the Plains is ongoing, which will result in a zonal moisture gradient across the Plains by mid afternoon. Recent solutions suggest that the strongest winds may lie within this moisture gradient, resulting in a somewhat confined corridor of elevated fire weather conditions where 15-25 mph winds (gusting to 30-35 mph at times) will overlap with 15-25% RH values. Although guidance occasionally struggles to accurately capture the degree of boundary-layer mixing within these return flow regimes, latest deterministic solutions appear to be capturing moisture trends well and don't show substantial signs of a moist bias. This lends confidence to the ongoing forecast of predominantly elevated fire weather conditions across the region (although some locations may see periods of critical conditions). ..Moore.. 09/03/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Tue Sep 03 2024 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL/NORTHERN ROCKIES AND PLAINS INTO MUCH OF MINNESOTA... ...SUMMARY... Isolated strong to severe storms are possible on Wednesday across parts of the central and northern Rockies and Plains into parts of Minnesota. ...Synopsis... A shortwave trough initially over the Great Basin/Intermountain West is forecast to move east-southeastward and gradually deamplify on Wednesday, as it begins to merge with a more prominent upper-level trough that will cover parts of the Canadian Prairies into the northern/central Plains. Multiple embedded shortwaves within the larger trough will likely move across parts of the Dakotas and Minnesota. A weak surface wave may develop during the afternoon along a cold front that will extend from parts of MN and the Dakotas into the central Plains. ...Parts of the northern/central Rockies/Plains into Minnesota... A large area of at least low-end severe potential may evolve from parts of the central/northern Rockies/Plains into Minnesota. The Marginal Risk has been maintained with some minor adjustments; further refinement to the risk area is likely if areas of relatively lower or higher threat become evident with time. Scattered thunderstorms may develop relatively early in the day across the higher terrain of CO/WY/MT, in association with the shortwave trough emerging from the Intermountain West. While low-level moisture will likely remain rather limited, steep midlevel lapse rates and modestly favorable deep-layer shear could support a few organized multicells and perhaps a marginal supercell or two, as convection spreads towards the central/northern High Plains. Isolated strong to severe gusts and hail will be possible. Some outflow consolidation could support one or more loosely organized clusters evolving with time, with a threat of strong to locally severe gusts as storms move eastward into the evening. Farther northeast, details regarding destabilization and storm development/evolution from the eastern Dakotas into MN remain uncertain. Some guidance suggests potential for an embedded shortwave or MCV to move across the region during the afternoon/evening, which could aid in isolated storm development near the front, if sufficient moistening and destabilization can occur. There will also be some potential for storms to develop and/or spread into the region from the west during the evening, as the larger-scale upper trough begins to amplify. Relatively steep midlevel lapse rates and adequate deep-layer shear could support isolated hail and damaging gusts with the strongest storms. ..Dean.. 09/03/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Tue Sep 03 2024 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL/NORTHERN ROCKIES AND PLAINS INTO MUCH OF MINNESOTA... ...SUMMARY... Isolated strong to severe storms are possible on Wednesday across parts of the central and northern Rockies and Plains into parts of Minnesota. ...Synopsis... A shortwave trough initially over the Great Basin/Intermountain West is forecast to move east-southeastward and gradually deamplify on Wednesday, as it begins to merge with a more prominent upper-level trough that will cover parts of the Canadian Prairies into the northern/central Plains. Multiple embedded shortwaves within the larger trough will likely move across parts of the Dakotas and Minnesota. A weak surface wave may develop during the afternoon along a cold front that will extend from parts of MN and the Dakotas into the central Plains. ...Parts of the northern/central Rockies/Plains into Minnesota... A large area of at least low-end severe potential may evolve from parts of the central/northern Rockies/Plains into Minnesota. The Marginal Risk has been maintained with some minor adjustments; further refinement to the risk area is likely if areas of relatively lower or higher threat become evident with time. Scattered thunderstorms may develop relatively early in the day across the higher terrain of CO/WY/MT, in association with the shortwave trough emerging from the Intermountain West. While low-level moisture will likely remain rather limited, steep midlevel lapse rates and modestly favorable deep-layer shear could support a few organized multicells and perhaps a marginal supercell or two, as convection spreads towards the central/northern High Plains. Isolated strong to severe gusts and hail will be possible. Some outflow consolidation could support one or more loosely organized clusters evolving with time, with a threat of strong to locally severe gusts as storms move eastward into the evening. Farther northeast, details regarding destabilization and storm development/evolution from the eastern Dakotas into MN remain uncertain. Some guidance suggests potential for an embedded shortwave or MCV to move across the region during the afternoon/evening, which could aid in isolated storm development near the front, if sufficient moistening and destabilization can occur. There will also be some potential for storms to develop and/or spread into the region from the west during the evening, as the larger-scale upper trough begins to amplify. Relatively steep midlevel lapse rates and adequate deep-layer shear could support isolated hail and damaging gusts with the strongest storms. ..Dean.. 09/03/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1233 AM CDT Tue Sep 03 2024 Valid 031200Z - 041200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO THIS EVENING ACROSS PARTS OF CENTRAL IDAHO...MUCH OF SOUTHERN MONTANA...WYOMING...MUCH OF NORTHERN UTAH AND ADJACENT NORTHWESTERN COLORADO...INTO PARTS OF THE WESTERN DAKOTAS... ...SUMMARY... Thunderstorms developing across the northern Rockies and adjacent portions of the Great Basin by this afternoon may produce scattered strong to locally severe wind gusts, before spreading eastward toward the northern Great Plains into this evening. ...Synopsis... Downstream of split mid/upper flow across the eastern Pacific, Alaska and Canadian Yukon vicinity, the stronger westerlies remain confined to the higher latitudes, with weaker zonal flow prevailing across the northern tier of the U.S., on the northern periphery of weak/suppressed subtropical ridging. Seasonably moist boundary-layer air has generally become confined to the southern tier of the U.S., to the south of notable surface ridging. Little change appears likely through this period, though the center of the ridge may shift from the lower Great Lakes/upper Ohio Valley into the northern Mid Atlantic. It does appear that the westerlies may undergo some amplification across the northeastern Pacific into Canada later today through tonight, including building mid-level ridging offshore of the Pacific Northwest and British Columbia coast and digging mid-level troughing to the lee of the Canadian Rockies. As this occurs, a remnant mid-level trough over the interior northwestern U.S. is forecast to slowly shift into and across the northern Rockies. ...Northern Intermountain Region and Rockies... Models indicate that the mid-level trough will weaken while shifting eastward today, but it still appears that mid-level forcing for ascent and cooling will remain sufficient to support continuing convective development, including considerable thunderstorm activity this afternoon and evening across the higher terrain. Near the mid-level cold core, destabilization, including mixed-layer CAPE on the order of 500-1000 J/kg, might support a few thunderstorms capable of producing marginally severe hail across the mountains of southwestern Montana. Otherwise, more modest CAPE, based above a warm and deeply mixed boundary layer, may still become supportive of locally strong to severe downburst winds across the higher terrain of western Wyoming and northern Utah, into the Great Salt Lake Desert. Eastward into the northern high plains, severe weather potential, and the extent to which destabilization is able to maintain thunderstorm development, remains more uncertain. However, some model output, perhaps most notably the past few runs of the NAM, has been suggestive that convective development near/north of the Absaroka Range and Big Horn Basin vicinity may generate sufficient consolidating outflow to support a substantive east-southeastward propagating surface cold pool to the lee of the higher terrain. Although 03/00Z NAM forecast soundings, for example, are not particularly indicative that vigorous thunderstorm development will be maintained, they suggest that 35-50 kt winds may accompany a surging gust front, in this run across southeastern Montana and adjacent northeastern Wyoming by late evening and into western South Dakota overnight. ..Kerr/Moore.. 09/03/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1233 AM CDT Tue Sep 03 2024 Valid 031200Z - 041200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO THIS EVENING ACROSS PARTS OF CENTRAL IDAHO...MUCH OF SOUTHERN MONTANA...WYOMING...MUCH OF NORTHERN UTAH AND ADJACENT NORTHWESTERN COLORADO...INTO PARTS OF THE WESTERN DAKOTAS... ...SUMMARY... Thunderstorms developing across the northern Rockies and adjacent portions of the Great Basin by this afternoon may produce scattered strong to locally severe wind gusts, before spreading eastward toward the northern Great Plains into this evening. ...Synopsis... Downstream of split mid/upper flow across the eastern Pacific, Alaska and Canadian Yukon vicinity, the stronger westerlies remain confined to the higher latitudes, with weaker zonal flow prevailing across the northern tier of the U.S., on the northern periphery of weak/suppressed subtropical ridging. Seasonably moist boundary-layer air has generally become confined to the southern tier of the U.S., to the south of notable surface ridging. Little change appears likely through this period, though the center of the ridge may shift from the lower Great Lakes/upper Ohio Valley into the northern Mid Atlantic. It does appear that the westerlies may undergo some amplification across the northeastern Pacific into Canada later today through tonight, including building mid-level ridging offshore of the Pacific Northwest and British Columbia coast and digging mid-level troughing to the lee of the Canadian Rockies. As this occurs, a remnant mid-level trough over the interior northwestern U.S. is forecast to slowly shift into and across the northern Rockies. ...Northern Intermountain Region and Rockies... Models indicate that the mid-level trough will weaken while shifting eastward today, but it still appears that mid-level forcing for ascent and cooling will remain sufficient to support continuing convective development, including considerable thunderstorm activity this afternoon and evening across the higher terrain. Near the mid-level cold core, destabilization, including mixed-layer CAPE on the order of 500-1000 J/kg, might support a few thunderstorms capable of producing marginally severe hail across the mountains of southwestern Montana. Otherwise, more modest CAPE, based above a warm and deeply mixed boundary layer, may still become supportive of locally strong to severe downburst winds across the higher terrain of western Wyoming and northern Utah, into the Great Salt Lake Desert. Eastward into the northern high plains, severe weather potential, and the extent to which destabilization is able to maintain thunderstorm development, remains more uncertain. However, some model output, perhaps most notably the past few runs of the NAM, has been suggestive that convective development near/north of the Absaroka Range and Big Horn Basin vicinity may generate sufficient consolidating outflow to support a substantive east-southeastward propagating surface cold pool to the lee of the higher terrain. Although 03/00Z NAM forecast soundings, for example, are not particularly indicative that vigorous thunderstorm development will be maintained, they suggest that 35-50 kt winds may accompany a surging gust front, in this run across southeastern Montana and adjacent northeastern Wyoming by late evening and into western South Dakota overnight. ..Kerr/Moore.. 09/03/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0742 PM CDT Mon Sep 02 2024 Valid 030100Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS EVENING ACROSS PARTS OF NORTHEASTERN OREGON...SOUTHEASTERN WASHINGTON...CENTRAL IDAHO AND ADJACENT SOUTHWESTERN MONTANA... ...SUMMARY... Widely scattered strong to severe wind gusts remain possible near lingering thunderstorm activity across parts of the northern Intermountain Region through this evening. ...01Z Update... Lower/mid-tropospheric subsidence and drying are probably tending to suppress ongoing scattered thunderstorm development across the Great Basin into adjacent northern Intermountain Region. However, widely scattered stronger thunderstorm development remains possible into this evening, within favorable large-scale forcing for ascent in the exit region of a vigorous upper jet streak (including 70+ kt around 300 mb) nosing north-northeastward through eastern Oregon, and in the downstream lower/mid-level warm advection regime overspreading central Idaho. Even within this regime, higher precipitable water on the order of .7-.8 inches appears to be supporting only weak CAPE (e.g. little more than 100 J/kg of mixed-layer CAPE in the 03/00Z sounding from Boise, ID), and this is limiting the strength of the updrafts and associated precipitation, which in turn is limiting the strength of downdraft potential despite being rooted above a warm and deeply mixed boundary layer. The potential for stronger gusts, aided by downward mixing of higher momentum from aloft, seems likely to remain generally focused across the higher elevations of north central and northeastern Oregon into the mountains of central Idaho, before convection weakens later this evening. ..Kerr.. 09/03/2024 Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0454 PM CDT Mon Sep 02 2024 Valid 041200Z - 101200Z Fire concerns will remain low in the extended. High pressure will build in across the western US D3/Wednesday through D6/Saturday, with a warming and drying trend. As this occurs, monsoonal moisture will gradually shift southward with drying conditions extending into the desert Southwest through D5/Friday. Winds will remain mostly light where fuels are dry, keeping fire weather concerns low. Moisture will slowly begin to return northward by D7/Sun-D8/Mon. Across the High Plains, southerly flow will slowly bring moisture northward, with several disturbances will bringing occasional chances for rain and thunderstorm activity. This should bring some relief to very dry conditions and help improve status of fuels. Occasional post-frontal northwesterly breezes will be possible, but relative humidity looks to remain above critical thresholds. ..Thornton.. 09/02/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Mon Sep 2 21:23:02 UTC 2024.

MD 2043 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF EASTERN OREGON INTO NORTHEAST NEVADA AND WESTERN INTO CENTRAL IDAHO
Mesoscale Discussion 2043 NWS Storm Prediction Center Norman OK 0356 PM CDT Mon Sep 02 2024 Areas affected...portions of eastern Oregon into northeast Nevada and western into central Idaho Concerning...Severe potential...Watch unlikely Valid 022056Z - 022230Z Probability of Watch Issuance...5 percent SUMMARY...A couple of strong to severe gusts may accompany the deeper storm cores that manage to develop. Any severe threat that materializes should be sparse, and a WW issuance is not expected. DISCUSSION...A pronounced 500 mb vort max is currently traversing the CA/OR border, aiding in the ascent of marginally buoyant boundary-layer based parcels. MRMS mosaic radar imagery shows convective initiation underway from the lee of the Cascades toward eastern ID. These storms are developing atop a very dry boundary layer (evident via 50-60 F surface temperature/dewpoint spreads), with RAP forecast soundings showing inverted-v soundings extending up to 500 mb. As such, these storms will be high-based in nature. Strong mid-level flow is overspreading portions of the Interior West ahead of the approaching trough, contributing to 30+ kts of effective bulk shear. As such, a few storms may become marginally organized, capable producing strong to potentially severe gusts. However, severe potential is highly dependent on how vertically deep storm cores can become. The severe gust threat is expected to be sparse, and a WW issuance is not anticipated. ..Squitieri/Smith.. 09/02/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...TFX...SLC...PIH...MSO...BOI...LKN...OTX...PDT... MFR... LAT...LON 44142133 44812118 45552062 46051987 46361816 45771419 44861296 43951263 41821330 40791411 40221486 40001533 40001577 40221636 40551693 41031717 41781741 42351781 42831848 43191920 43472024 43572053 44142133 Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0250 PM CDT Mon Sep 02 2024 Valid 022000Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE NORTHERN GREAT BASIN AND THE NORTHWEST... ...SUMMARY... Isolated to scattered thunderstorms across the northern Great Basin and parts of the interior Pacific Northwest may be capable of occasional strong to severe wind gusts this afternoon and evening. ...20Z Update... Minor adjustments were made to the general thunderstorm area to account for current observed trends. The remainder of the forecast is unchanged. See the previous discussion for additional details. ..Wendt.. 09/02/2024 .PREV DISCUSSION... /ISSUED 1118 AM CDT Mon Sep 02 2024/ ...Interior Pacific Northwest into the Northern Great Basin/Rockies... Water-vapor imagery this morning shows a closed low near the northern CA/southern OR coast. This upper feature will move east through OR and be situated along the OR/ID border by daybreak Tuesday. A belt of stronger flow (30-50 kt 500-mb winds) will move through the base of the larger-scale mid-level trough and overspread northern NV into southwestern ID and eastern OR this afternoon into the early evening. Large-scale ascent associated with the upper disturbance and the development of weak buoyancy (mainly via heating), will facilitate the development of isolated to scattered high-based thunderstorms beginning later this afternoon and persisting into the evening. Forecast soundings show large surface temperature-dewpoint spreads (50 degrees F) with 9+ degrees C lapse rates into the mid levels and a dry sub-cloud layer. Evaporative cooling of the more intense downdrafts will probably yield a risk for isolated 60-70 mph gusts before weakening later this evening. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0250 PM CDT Mon Sep 02 2024 Valid 022000Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE NORTHERN GREAT BASIN AND THE NORTHWEST... ...SUMMARY... Isolated to scattered thunderstorms across the northern Great Basin and parts of the interior Pacific Northwest may be capable of occasional strong to severe wind gusts this afternoon and evening. ...20Z Update... Minor adjustments were made to the general thunderstorm area to account for current observed trends. The remainder of the forecast is unchanged. See the previous discussion for additional details. ..Wendt.. 09/02/2024 .PREV DISCUSSION... /ISSUED 1118 AM CDT Mon Sep 02 2024/ ...Interior Pacific Northwest into the Northern Great Basin/Rockies... Water-vapor imagery this morning shows a closed low near the northern CA/southern OR coast. This upper feature will move east through OR and be situated along the OR/ID border by daybreak Tuesday. A belt of stronger flow (30-50 kt 500-mb winds) will move through the base of the larger-scale mid-level trough and overspread northern NV into southwestern ID and eastern OR this afternoon into the early evening. Large-scale ascent associated with the upper disturbance and the development of weak buoyancy (mainly via heating), will facilitate the development of isolated to scattered high-based thunderstorms beginning later this afternoon and persisting into the evening. Forecast soundings show large surface temperature-dewpoint spreads (50 degrees F) with 9+ degrees C lapse rates into the mid levels and a dry sub-cloud layer. Evaporative cooling of the more intense downdrafts will probably yield a risk for isolated 60-70 mph gusts before weakening later this evening. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0243 PM CDT Mon Sep 02 2024 Valid 031200Z - 041200Z No changes are needed to the D2 Fire Weather Outlook. See previous discussion below for more information. ..Thornton.. 09/02/2024 .PREV DISCUSSION... /ISSUED 0218 AM CDT Mon Sep 02 2024/ ...Synopsis... Fire weather concerns will continue into Tuesday as an upper wave (currently moving onshore along the northern CA coast) translates east across the northern Rockies. However, fire weather conditions are not expected to be as intense or widespread as compared to Monday across on either side of the continental divide. ...Nevada into Idaho... Portions of northeast NV and central ID are forecast to remain within the dry slot of the maturing upper-level low. This will maintain clear skies/warm conditions across the region, but will also support broad scale subsidence/drying and windy conditions across the region. Regional orographic influences - namely the Snake River Plain in eastern ID as well as the Independence and Ruby mountains of northeast NV, will augment the dry/windy conditions and should support several hours of elevated fire weather conditions. Isolated to scattered thunderstorms are also anticipated across northern ID, MT, and WY by late afternoon as the low shifts east. While a few dry thunderstorms are possible based on forecast thermal profiles, recent ensemble guidance shows a stronger signal for wetting rainfall compared to Monday, limiting confidence in the dry-lightning threat. ...Central/Northern Plains... A lee trough is expected to become established over the next 24 hours, but will see more substantial deepening through Tuesday afternoon amid increasing synoptic-scale ascent ahead of the approaching upper wave. This will result in not only strengthening westerly downslope flow across eastern WY, but will also bolster pressure gradient winds across central NE into SD. Recent ensemble guidance shows reasonably high confidence in maintaining at least a few hours of elevated fire weather conditions for both regions with 15-20 mph winds and RH reductions into the teens and low 20s. Persistent southerly flow overnight Monday into Tuesday will support some degree of moisture return into the Plains, which is expected to limit the spatial coverage of elevated fire weather conditions. That said, guidance typically struggles to accurately capture boundary-layer mixing/RH reductions in such return flow regimes, and fire weather conditions may be more widespread across NE/SD than currently depicted. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0243 PM CDT Mon Sep 02 2024 Valid 031200Z - 041200Z No changes are needed to the D2 Fire Weather Outlook. See previous discussion below for more information. ..Thornton.. 09/02/2024 .PREV DISCUSSION... /ISSUED 0218 AM CDT Mon Sep 02 2024/ ...Synopsis... Fire weather concerns will continue into Tuesday as an upper wave (currently moving onshore along the northern CA coast) translates east across the northern Rockies. However, fire weather conditions are not expected to be as intense or widespread as compared to Monday across on either side of the continental divide. ...Nevada into Idaho... Portions of northeast NV and central ID are forecast to remain within the dry slot of the maturing upper-level low. This will maintain clear skies/warm conditions across the region, but will also support broad scale subsidence/drying and windy conditions across the region. Regional orographic influences - namely the Snake River Plain in eastern ID as well as the Independence and Ruby mountains of northeast NV, will augment the dry/windy conditions and should support several hours of elevated fire weather conditions. Isolated to scattered thunderstorms are also anticipated across northern ID, MT, and WY by late afternoon as the low shifts east. While a few dry thunderstorms are possible based on forecast thermal profiles, recent ensemble guidance shows a stronger signal for wetting rainfall compared to Monday, limiting confidence in the dry-lightning threat. ...Central/Northern Plains... A lee trough is expected to become established over the next 24 hours, but will see more substantial deepening through Tuesday afternoon amid increasing synoptic-scale ascent ahead of the approaching upper wave. This will result in not only strengthening westerly downslope flow across eastern WY, but will also bolster pressure gradient winds across central NE into SD. Recent ensemble guidance shows reasonably high confidence in maintaining at least a few hours of elevated fire weather conditions for both regions with 15-20 mph winds and RH reductions into the teens and low 20s. Persistent southerly flow overnight Monday into Tuesday will support some degree of moisture return into the Plains, which is expected to limit the spatial coverage of elevated fire weather conditions. That said, guidance typically struggles to accurately capture boundary-layer mixing/RH reductions in such return flow regimes, and fire weather conditions may be more widespread across NE/SD than currently depicted. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0220 PM CDT Mon Sep 02 2024 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER MUCH OF THE CENTRAL TO NORTHERN ROCKIES... ...SUMMARY... A risk of isolated strong to severe storms capable of producing gusty/locally damaging winds will exist from parts of Montana/Wyoming/Colorado into the northern Plains Wednesday/Wednesday night. Marginal hail with stronger storms may also occur across the northern Plains region. ...Synopsis and Discussion... A weak upper trough providing cooling aloft and modest flow will move across the northern Plains on Wednesday, while a cold front moves across the Dakotas, trailing southwestward into the central High Plains by 00Z. High pressure will remain over much of the East, providing stable conditions there, and enhancing southerly winds over the Plains ahead of the front. In general, a plume of 50s to lower 60s F dewpoints will spread north toward the front late in the day. Scattered storms will first form over the higher terrain across eastern MT, WY, and into central CO, with steep lapse rates and modest deep-layer shear favoring marginal hail. Storms will also form along the cold front, from eastern CO into the Dakotas. Backed low-level winds and veering winds with height may support a few supercells, though multicellular clusters will also be likely as winds aloft are on the marginal side for better organized storm structures. Still, favorable time of day and steep low-level lapse rates will likely favor gusty to locally severe gusts as activity spreads across the northern and central Plains through the evening. ..Jewell.. 09/02/2024 Read more

No Mesoscale Discussions are in effect as of Mon Sep 2 17:43:02 UTC 2024.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1227 PM CDT Mon Sep 02 2024 Valid 031200Z - 041200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER MUCH OF THE NORTHERN ROCKIES AND INTO THE EASTERN GREAT BASIN... ...SUMMARY... Scattered strong storms with isolated severe may produce damaging wind gusts and marginal hail from the northern Intermountain region eastward into the northern High Plains, and southward into Utah. ...Synopsis... On Tuesday, an upper trough will weaken as it moves from the Northwest into the northern Rockies, providing cooling aloft and increased mid and high level flow. To the east, a large upper trough will exit the northeastern states, with height rises over the north-central CONUS. At the surface, a weak cold front will move across the eastern Great Basin, ID, western WY and southwest MT by early afternoon, increasing lift/convergence. Elsewhere, a moist air mass will remain from TX eastward across the Gulf Coast, with scattered non-severe storms likely. ...Eastern Great Basin into the Northern Rockies... As heating accelerates and cooler temperatures overspread the region, steep lapse rates will yield a large area of thunderstorms, developing relatively early in the afternoon, from much of UT into southwest MT. The strongest instability with 500 to 1000 J/kg MUCAPE will be roughly from far northern UT into MT, where temperatures aloft will be coolest. Deep-layer effective shear will increase to around 40 kt, especially across ID, MT, and northwest WY, which will aid cellular storm mode and hail potential to around 1.00" in diameter. Otherwise, scattered storms across the entire area will produce outflows, with progressive clusters of storms producing strong to locally severe gusts. A few storms may make it as far east as western SD by late evening, with generally decreasing intensity after sunset. ..Jewell.. 09/02/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1227 PM CDT Mon Sep 02 2024 Valid 031200Z - 041200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER MUCH OF THE NORTHERN ROCKIES AND INTO THE EASTERN GREAT BASIN... ...SUMMARY... Scattered strong storms with isolated severe may produce damaging wind gusts and marginal hail from the northern Intermountain region eastward into the northern High Plains, and southward into Utah. ...Synopsis... On Tuesday, an upper trough will weaken as it moves from the Northwest into the northern Rockies, providing cooling aloft and increased mid and high level flow. To the east, a large upper trough will exit the northeastern states, with height rises over the north-central CONUS. At the surface, a weak cold front will move across the eastern Great Basin, ID, western WY and southwest MT by early afternoon, increasing lift/convergence. Elsewhere, a moist air mass will remain from TX eastward across the Gulf Coast, with scattered non-severe storms likely. ...Eastern Great Basin into the Northern Rockies... As heating accelerates and cooler temperatures overspread the region, steep lapse rates will yield a large area of thunderstorms, developing relatively early in the afternoon, from much of UT into southwest MT. The strongest instability with 500 to 1000 J/kg MUCAPE will be roughly from far northern UT into MT, where temperatures aloft will be coolest. Deep-layer effective shear will increase to around 40 kt, especially across ID, MT, and northwest WY, which will aid cellular storm mode and hail potential to around 1.00" in diameter. Otherwise, scattered storms across the entire area will produce outflows, with progressive clusters of storms producing strong to locally severe gusts. A few storms may make it as far east as western SD by late evening, with generally decreasing intensity after sunset. ..Jewell.. 09/02/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1201 PM CDT Mon Sep 02 2024 Valid 021700Z - 031200Z ...CRITICAL FIRE WEATHER AREA FOR SOUTHERN OREGON INTO FAR NORTHEAST CALIFORNIA AND FAR NORTHWEST NEVADA... ...CRITICAL FIRE WEATHER AREA FOR SOUTHEAST OREGON AND SOUTHWEST IDAHO...NORTHEAST NEVADA...AND FAR NORTHWEST UTAH... ...CRITICAL FIRE WEATHER AREA FOR NORTHWEST NEBRASKA INTO WESTERN SOUTH DAKOTA... An active day of fire weather is anticipated across the Pacific Northwest, Great Basin, and portions of the High Plains. Morning 12z observed soundings from SLC (Salt Lake City, UT) and LKN (Elko, NV) indicate precipitable water values around 0.60". Midlevel moisture should increase through the day ahead of forcing for ascent with a midlevel wave currently just offshore in the Pacific Northwest. A mix of isolated to scattered wet/dry thunderstorms is expected by the afternoon with potential for new ignitions from lightning. In addition, Critical conditions are likely in the lee of the Sierra across Nevada and in the High Plains. No changes have been made to this forecast. See previous discussion for more information below. ..Thornton.. 09/02/2024 .PREV DISCUSSION... /ISSUED 0150 AM CDT Mon Sep 02 2024/ ...Synopsis... An active fire weather day is anticipated across the High Plains and Pacific Northwest/northern Great Basin. Fire weather concerns across the West will be associated with a progressive upper wave currently moving onshore along the northern CA coast, which is forecast to migrate into the interior Pacific Northwest over the next 24 hours. As this occurs, strengthening low-level winds will support dry/windy conditions, and lift ahead of the wave will promote isolated to scattered thunderstorms. To the east, flow across the northern to central Rockies is forecast to strengthen slightly within the apex of an upper ridge. This will result in modest surface pressure falls along the High Plains, which when juxtaposed with a building surface high over the Midwest will yield strong southerly winds and dry conditions. Fuels across both regions remain very dry (ERCs at or above the 90th percentile) after multiple days of dry conditions, which will support the fire weather concerns. ...Pacific Northwest/Great Basin... Regional VWPs along the West Coast are beginning to observe the influence of the approaching wave with winds in the lowest few kilometers slowly strengthening since 00 UTC. Further intensification of the low-level wind field is anticipated, which will strengthen downslope flow off the central to northern Sierra Nevada. Dry conditions are already in place and will be maintained within the augmented downslope regime. Latest ensemble guidance continues to show a strong signal for afternoon RH values to fall into the teens with 15-25 mph winds. The strongest winds (and highest probability for sustained critical conditions) are expected from northeast CA into southern OR and far northwest NV as the mid-level jet max passes overhead around peak heating. Over the past several days, a plume of monsoonal moisture has been tracked from southern AZ into northern NV and central to eastern OR. The 00 UTC MFR sounding sampled this air mass well, which is characterized by sufficient mid-level moisture to support weak convection, but a very dry boundary layer favorable for dry thunderstorms. Over the past two days, thunderstorms within this air mass across the Great Basin have been predominantly dry, and are expected to mainly be dry once again today for much of the region (one exception is from the Blue Mountains in northeast OR to the Salmon River Mountains in central ID where orographic ascent should support more prolonged convection with a higher probability for wetting rainfall). Stronger synoptic-scale forcing for ascent should result in greater thunderstorm coverage compared to previous days, warranting a scattered dry thunderstorm risk area from eastern OR into ID, northeast NV, and far northwest UT where latest CAM guidance shows the best convective signal. ...High Plains... A recent frontal intrusion into the Plains/Midwest has shunted seasonally rich moisture southward into the southern Plains. A strong surface high in the wake of the front will shift east through the day concurrent with the deepening of a weak lee trough. A dry return flow regime will become established through the day as winds become more southerly. Latest deterministic and ensemble solutions show a fairly strong signal for 20-25 mph winds (gusting to 35 mph) across western NE into western SD with RH values falling into the low 20s to teens. Consequently, confidence in sustained critical conditions over an appreciable area has increased enough to warrant introducing a Critical risk area. ...Please see www.spc.noaa.gov/fire for graphic product... Read more