No Mesoscale Discussions are in effect as of Tue Sep 3 22:46:02 UTC 2024.

No watches are valid as of Tue Sep 3 22:46:02 UTC 2024.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0500 PM CDT Tue Sep 03 2024 Valid 051200Z - 111200Z High pressure will build in across the western US D3/Thursday through D5/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 the driest in the west, though hot, dry, unstable conditions will lead to some increase in fire behavior. A return of isolated dry thunderstorm activity is expected beginning late D4/Friday and D5/Saturday across northern California into the Pacific Northwest as a trough approaches from the Pacific and precipitable water values steadily increase. For now, confidence is highest in including 10% probabilities on D4/Friday across the Sierra into western Nevada and south-central Oregon, where signal for thunderstorms is highest in multiple deterministic runs. Monsoonal moisture will slowly begin to return northward across the Southwest by D6/Sunday-D8/Tuesday. The Pacific trough will deepen and move inland by D7/Monday-D8 /Tuesday, bringing enhanced westerly flow across northern California, the Pacific Northwest, and into the Great Basin. This will lead to potential Elevated to Critical conditions, particularly on D8/Tuesday. For now, confidence remains too low to include areas based on model agreement, fuels, and potential rainfall. ..Thornton.. 09/03/2024 ...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 0259 PM CDT Tue Sep 03 2024 Valid 041200Z - 051200Z ...NO CRITICAL AREAS... No changes are needed to the D2 Fire Weather Outlook. See previous discussion below for more information. ..Thornton.. 09/03/2024 .PREV DISCUSSION... /ISSUED 0127 AM CDT Tue Sep 03 2024/ ...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. ...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 0259 PM CDT Tue Sep 03 2024 Valid 041200Z - 051200Z ...NO CRITICAL AREAS... No changes are needed to the D2 Fire Weather Outlook. See previous discussion below for more information. ..Thornton.. 09/03/2024 .PREV DISCUSSION... /ISSUED 0127 AM CDT Tue Sep 03 2024/ ...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. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 2045 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR SOUTHWESTERN WY INTO NORTH-CENTRAL UT AND EXTREME SOUTHEASTERN ID
Mesoscale Discussion 2045 NWS Storm Prediction Center Norman OK 0131 PM CDT Tue Sep 03 2024 Areas affected...southwestern WY into north-central UT and extreme southeastern ID Concerning...Severe potential...Watch unlikely Valid 031831Z - 032030Z Probability of Watch Issuance...20 percent SUMMARY...Scattered thunderstorm development is underway across southwestern WY into extreme southeastern ID and north-central UT. This is expected to continue through the afternoon with some severe gusts possible with the strongest storms. The overall threat is expected to remain low, and a watch is unlikely at this time. DISCUSSION...Numerous towering updrafts have developed in the last hour along the higher terrain across central UT and eastern NV per visible satellite imagery. These maturing storms are driven by diurnal heating and a weakening mid-level trough propagating eastward through the region. Deep, well-mixed boundary layers abound in this environment, as characterized by short-term RAP and NAM forecast profiles. Steadily increasing westerly flow is anticipated as the mid-level trough approaches, yielding relatively unidirectional 0-6-km shear around 25+ kts. This should support some updraft organization and rotation, possibly including transient, high-based supercell structures. Localized severe wind gusts are possible with microbursts forming from stronger cores that encourage descent through the deep, well-mixed boundary layer. This severe risk should continue through peak heating, but the overall threat is expected to remain rather marginal, and a watch appears unlikely at this time. ..Flournoy/Squitieri/Smith.. 09/03/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...RIW...GJT...SLC...PIH... LAT...LON 41221266 42161163 42981038 42980935 41890877 40480916 39461034 38791144 38741273 39551381 40691337 41221266 Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0244 PM CDT Tue Sep 03 2024 Valid 032000Z - 041200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN ROCKIES/GREAT BASIN AND ADJACENT HIGH PLAINS... ...SUMMARY... Scattered thunderstorms developing across the northern Rockies and adjacent portions of the Great Basin this afternoon will pose an isolated severe risk, before spreading eastward toward the northern High Plains this evening. ...20Z Update... The previous forecast remains on track, and no changes were made with this update. Widely scattered thunderstorms are evolving across the northern Rockies and adjacent Great Basin this afternoon. These storms are generally focused in a band of midlevel ascent preceding a compact midlevel low tracking eastward across central ID. This activity will continue spreading east-northeastward through the afternoon, with initial semi-discrete clusters/transient supercells posing a risk of sporadic, marginally severe hail and locally severe gusts. See MCDs 2044/2045 for details on the near-term severe risk. Later this afternoon, a more-focused corridor of severe-wind potential is possible from portions of northwest WY into southwest/south-central MT, especially with any upscale-grown clusters amid steep deep-layer lapse rates. A 15-percent wind-driven Slight Risk was considered here, though confidence in the development of an organized/consolidated cold pool remains too low for an upgrade. ..Weinman.. 09/03/2024 .PREV DISCUSSION... /ISSUED 1130 AM CDT Tue Sep 03 2024/ ...Northern Great Basin/Rockies into the Adjacent High Plains... Visible-satellite imagery this morning shows a smoke-encased mid to upper-level low/vorticity maximum over central ID. This upper feature will move to near southwest MT/eastern ID late tonight. The satellite data late this morning shows agitated cumulus developing immediately ahead of the vorticity max near the ID/MT border, and as large-scale ascent spreads east, additional thunderstorms (widely scattered to scattered coverage) should develop over the higher terrain through early afternoon in tandem with daytime heating. Forecast soundings across southwest MT into northwest WY show 500-1000 J/kg MLCAPE with some elongation of the hodograph. A few of the stronger storms will probably acquire transient supercell characteristics and have an associated hail/wind threat. Some clustering may eventually evolve by early evening as storms move into south-central MT and adjacent parts of northern WY. Somewhat more limited low-level moisture should be present this afternoon farther south into WY and northern UT. Even so, diurnal heating will aid in a deeply mixed boundary layer by this afternoon, and steep mid-level lapse rates are also expected to remain over this region. The net result will be high-based thunderstorms capable of producing isolated severe gusts initially developing across northern UT into far eastern ID, and subsequently moving east-northeastward over WY through the evening. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0244 PM CDT Tue Sep 03 2024 Valid 032000Z - 041200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN ROCKIES/GREAT BASIN AND ADJACENT HIGH PLAINS... ...SUMMARY... Scattered thunderstorms developing across the northern Rockies and adjacent portions of the Great Basin this afternoon will pose an isolated severe risk, before spreading eastward toward the northern High Plains this evening. ...20Z Update... The previous forecast remains on track, and no changes were made with this update. Widely scattered thunderstorms are evolving across the northern Rockies and adjacent Great Basin this afternoon. These storms are generally focused in a band of midlevel ascent preceding a compact midlevel low tracking eastward across central ID. This activity will continue spreading east-northeastward through the afternoon, with initial semi-discrete clusters/transient supercells posing a risk of sporadic, marginally severe hail and locally severe gusts. See MCDs 2044/2045 for details on the near-term severe risk. Later this afternoon, a more-focused corridor of severe-wind potential is possible from portions of northwest WY into southwest/south-central MT, especially with any upscale-grown clusters amid steep deep-layer lapse rates. A 15-percent wind-driven Slight Risk was considered here, though confidence in the development of an organized/consolidated cold pool remains too low for an upgrade. ..Weinman.. 09/03/2024 .PREV DISCUSSION... /ISSUED 1130 AM CDT Tue Sep 03 2024/ ...Northern Great Basin/Rockies into the Adjacent High Plains... Visible-satellite imagery this morning shows a smoke-encased mid to upper-level low/vorticity maximum over central ID. This upper feature will move to near southwest MT/eastern ID late tonight. The satellite data late this morning shows agitated cumulus developing immediately ahead of the vorticity max near the ID/MT border, and as large-scale ascent spreads east, additional thunderstorms (widely scattered to scattered coverage) should develop over the higher terrain through early afternoon in tandem with daytime heating. Forecast soundings across southwest MT into northwest WY show 500-1000 J/kg MLCAPE with some elongation of the hodograph. A few of the stronger storms will probably acquire transient supercell characteristics and have an associated hail/wind threat. Some clustering may eventually evolve by early evening as storms move into south-central MT and adjacent parts of northern WY. Somewhat more limited low-level moisture should be present this afternoon farther south into WY and northern UT. Even so, diurnal heating will aid in a deeply mixed boundary layer by this afternoon, and steep mid-level lapse rates are also expected to remain over this region. The net result will be high-based thunderstorms capable of producing isolated severe gusts initially developing across northern UT into far eastern ID, and subsequently moving east-northeastward over WY through the evening. Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0222 PM CDT Tue Sep 03 2024 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The threat for organized severe thunderstorms currently appears low on Thursday. ...Synopsis... A mid-level trough will amplify across the Upper Midwest and Canadian Prairies on Thursday. Ahead of this trough, an elongated frontal zone will extend from northern Ontario, across the Great Lakes, across the central Plains, and into the southern High Plains. Moisture will remain somewhat meager along this frontal zone with storm coverage likely focused near the higher terrain in New Mexico and the better forcing in the western Great Lakes. ...Western Great Lakes... Strong height falls/cooling temperatures aloft should be sufficient to allow for some scattered storm development along the cold front in the western Great Lakes vicinity on Thursday afternoon/evening. However, despite the strong forcing, instability will be somewhat limited and thus, severe storms are unlikely. ...Northeast New Mexico... A southeastward moving mid-level shortwave trough will move toward northeast New Mexico and provide ample forcing for storms Thursday afternoon/evening. Instability will remain weak, but may be sufficient for a few stronger storms. If greater instability can develop, enough deep-layer shear will be present for some storm organization (~25 knots), but at this time, instability remains too weak for a Marginal risk. ..Bentley.. 09/03/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0222 PM CDT Tue Sep 03 2024 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The threat for organized severe thunderstorms currently appears low on Thursday. ...Synopsis... A mid-level trough will amplify across the Upper Midwest and Canadian Prairies on Thursday. Ahead of this trough, an elongated frontal zone will extend from northern Ontario, across the Great Lakes, across the central Plains, and into the southern High Plains. Moisture will remain somewhat meager along this frontal zone with storm coverage likely focused near the higher terrain in New Mexico and the better forcing in the western Great Lakes. ...Western Great Lakes... Strong height falls/cooling temperatures aloft should be sufficient to allow for some scattered storm development along the cold front in the western Great Lakes vicinity on Thursday afternoon/evening. However, despite the strong forcing, instability will be somewhat limited and thus, severe storms are unlikely. ...Northeast New Mexico... A southeastward moving mid-level shortwave trough will move toward northeast New Mexico and provide ample forcing for storms Thursday afternoon/evening. Instability will remain weak, but may be sufficient for a few stronger storms. If greater instability can develop, enough deep-layer shear will be present for some storm organization (~25 knots), but at this time, instability remains too weak for a Marginal risk. ..Bentley.. 09/03/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1219 PM CDT Tue Sep 03 2024 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL ROCKIES...CENTRAL HIGH PLAINS...NORTHERN PLAINS...AND THE MIDWEST.... ...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 broad, positively tilted trough with several embedded shortwave troughs will become more consolidated and start to amplify across the northern Plains on Wednesday and Wednesday night. At the surface, a cold front will move southeast across the northern Plains with scattered thunderstorms possible. The greater thunderstorm coverage is expected during the afternoon/evening across the central Rockies, beneath the coldest air aloft, and across northwest Wisconsin/eastern Minnesota early Thursday morning as the low-level jet intensifies along the frontal zone. ...Central Rockies into the central High Plains... Scattered to widespread thunderstorms are expected across the central Rockies on Wednesday afternoon as cold air aloft (-12C at 500mb) combines with significant heating over the higher terrain. The greatest instability will be near the center of the vorticity maximum/cold air pocket where wind shear will be quite weak. Some wind gusts or isolated large hail will be possible, but a more organized threat seems unlikely. A more favorable wind profile will exist along the southern periphery of this trough from eastern Utah to southern Wyoming and northern Colorado. However, the warmer temperatures aloft within this corridor may limit storm coverage/intensity somewhat. Therefore, a few strong to locally severe storms are possible from southern Montana to northern Colorado, western Nebraska, and southwest South Dakota, however, a displacement between the best instability and wind shear should keep the threat somewhat limited. ...Upper Midwest... A mid-level shortwave trough will eject across the Dakotas, in the vicinity of the cold front, during the day Wednesday. Therefore, a few thunderstorms are possible along the cold front, but a lack of better moisture should mostly limit the daytime thunderstorm threat. However, as the low-level jet strengthens overnight, it will result in some moistening between 850mb and 700mb which will likely result in more widespread thunderstorm development after 06Z. During this period, mid-level flow will also strengthen from around 25 knots to near 35 knots by 12Z. This will improve the shear across the region and therefore, result in some threat for large hail and damaging wind gusts near sunrise as storms develop within a region of moderate instability and 30 to 35 knots of shear. ..Bentley.. 09/03/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1143 AM CDT Tue Sep 03 2024 Valid 031700Z - 041200Z No changes are needed to the current D1 Fire Weather outlook. See previous discussion below for more information. ..Thornton.. 09/03/2024 .PREV DISCUSSION... /ISSUED 0102 AM CDT Tue Sep 03 2024/ ...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). ...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 1143 AM CDT Tue Sep 03 2024 Valid 031700Z - 041200Z No changes are needed to the current D1 Fire Weather outlook. See previous discussion below for more information. ..Thornton.. 09/03/2024 .PREV DISCUSSION... /ISSUED 0102 AM CDT Tue Sep 03 2024/ ...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). ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Tue Sep 03 2024 Valid 031630Z - 041200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN ROCKIES/GREAT BASIN AND ADJACENT HIGH PLAINS... ...SUMMARY... Scattered thunderstorms developing across the northern Rockies and adjacent portions of the Great Basin this afternoon may yield an isolated severe risk, before spreading eastward toward the northern High Plains this evening. ...Northern Great Basin/Rockies into the Adjacent High Plains... Visible-satellite imagery this morning shows a smoke-encased mid to upper-level low/vorticity maximum over central ID. This upper feature will move to near southwest MT/eastern ID late tonight. The satellite data late this morning shows agitated cumulus developing immediately ahead of the vorticity max near the ID/MT border, and as large-scale ascent spreads east, additional thunderstorms (widely scattered to scattered coverage) should develop over the higher terrain through early afternoon in tandem with daytime heating. Forecast soundings across southwest MT into northwest WY show 500-1000 J/kg MLCAPE with some elongation of the hodograph. A few of the stronger storms will probably acquire transient supercell characteristics and have an associated hail/wind threat. Some clustering may eventually evolve by early evening as storms move into south-central MT and adjacent parts of northern WY. Somewhat more limited low-level moisture should be present this afternoon farther south into WY and northern UT. Even so, diurnal heating will aid in a deeply mixed boundary layer by this afternoon, and steep mid-level lapse rates are also expected to remain over this region. The net result will be high-based thunderstorms capable of producing isolated severe gusts initially developing across northern UT into far eastern ID, and subsequently moving east-northeastward over WY through the evening. ..Smith/Flournoy/Squitieri.. 09/03/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Tue Sep 03 2024 Valid 031630Z - 041200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN ROCKIES/GREAT BASIN AND ADJACENT HIGH PLAINS... ...SUMMARY... Scattered thunderstorms developing across the northern Rockies and adjacent portions of the Great Basin this afternoon may yield an isolated severe risk, before spreading eastward toward the northern High Plains this evening. ...Northern Great Basin/Rockies into the Adjacent High Plains... Visible-satellite imagery this morning shows a smoke-encased mid to upper-level low/vorticity maximum over central ID. This upper feature will move to near southwest MT/eastern ID late tonight. The satellite data late this morning shows agitated cumulus developing immediately ahead of the vorticity max near the ID/MT border, and as large-scale ascent spreads east, additional thunderstorms (widely scattered to scattered coverage) should develop over the higher terrain through early afternoon in tandem with daytime heating. Forecast soundings across southwest MT into northwest WY show 500-1000 J/kg MLCAPE with some elongation of the hodograph. A few of the stronger storms will probably acquire transient supercell characteristics and have an associated hail/wind threat. Some clustering may eventually evolve by early evening as storms move into south-central MT and adjacent parts of northern WY. Somewhat more limited low-level moisture should be present this afternoon farther south into WY and northern UT. Even so, diurnal heating will aid in a deeply mixed boundary layer by this afternoon, and steep mid-level lapse rates are also expected to remain over this region. The net result will be high-based thunderstorms capable of producing isolated severe gusts initially developing across northern UT into far eastern ID, and subsequently moving east-northeastward over WY through the evening. ..Smith/Flournoy/Squitieri.. 09/03/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0734 AM CDT Tue Sep 03 2024 Valid 031300Z - 041200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN ROCKIES/GREAT BASIN AND ADJACENT HIGH PLAINS... ...SUMMARY... Thunderstorms developing across the northern Rockies and adjacent portions of the Great Basin this afternoon may produce occasional strong to severe wind gusts, before spreading eastward toward the northern High Plains this evening. ...Northern Great Basin/Rockies into the Adjacent High Plains... An upper trough/low over the Pacific Northwest this morning will continue moving eastward today across the northern Rockies. This feature is forecast to gradually weaken through the period, but enhanced mid-level west-southwesterly flow will persist across parts of the northern Great Basin into the northern Rockies and adjacent High Plains. As large-scale ascent associated with the upper trough overspreads the northern Rockies, thunderstorms should develop over the higher terrain through early afternoon in tandem with daytime heating. Latest surface observations show somewhat greater low-level moisture across this region, with surface dewpoints generally in the mid 40s to low 50s across central ID into southwest MT. Although instability is forecast to remain fairly modest this afternoon, deep-layer shear around 25-35 kt should be sufficient to support organized convection, including the potential for a couple of marginal supercells initially with associated hail/wind threat. With steepened low/mid-level lapse rates present, this activity should continue to pose some threat for isolated strong to severe wind gusts as it congeals and spreads east-northeastward across parts of the northern High Plains through this evening. Somewhat more limited low-level moisture should be present this afternoon farther south into WY and northern UT. Even so, diurnal heating will aid in a deeply mixed boundary layer by this afternoon, and steep mid-level lapse rates are also expected to remain over this region. The net result will be high-based thunderstorms capable of producing isolated strong to severe winds initially developing across northern UT into far eastern ID, and subsequently moving east-northeastward over WY through the evening. Confidence in a more concentrated corridor of severe winds remains generally low at this time given the weak instability and modest deep-layer shear forecast, especially with southward extent into the northern Great Basin and WY. ..Gleason/Leitman.. 09/03/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0734 AM CDT Tue Sep 03 2024 Valid 031300Z - 041200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN ROCKIES/GREAT BASIN AND ADJACENT HIGH PLAINS... ...SUMMARY... Thunderstorms developing across the northern Rockies and adjacent portions of the Great Basin this afternoon may produce occasional strong to severe wind gusts, before spreading eastward toward the northern High Plains this evening. ...Northern Great Basin/Rockies into the Adjacent High Plains... An upper trough/low over the Pacific Northwest this morning will continue moving eastward today across the northern Rockies. This feature is forecast to gradually weaken through the period, but enhanced mid-level west-southwesterly flow will persist across parts of the northern Great Basin into the northern Rockies and adjacent High Plains. As large-scale ascent associated with the upper trough overspreads the northern Rockies, thunderstorms should develop over the higher terrain through early afternoon in tandem with daytime heating. Latest surface observations show somewhat greater low-level moisture across this region, with surface dewpoints generally in the mid 40s to low 50s across central ID into southwest MT. Although instability is forecast to remain fairly modest this afternoon, deep-layer shear around 25-35 kt should be sufficient to support organized convection, including the potential for a couple of marginal supercells initially with associated hail/wind threat. With steepened low/mid-level lapse rates present, this activity should continue to pose some threat for isolated strong to severe wind gusts as it congeals and spreads east-northeastward across parts of the northern High Plains through this evening. Somewhat more limited low-level moisture should be present this afternoon farther south into WY and northern UT. Even so, diurnal heating will aid in a deeply mixed boundary layer by this afternoon, and steep mid-level lapse rates are also expected to remain over this region. The net result will be high-based thunderstorms capable of producing isolated strong to severe winds initially developing across northern UT into far eastern ID, and subsequently moving east-northeastward over WY through the evening. Confidence in a more concentrated corridor of severe winds remains generally low at this time given the weak instability and modest deep-layer shear forecast, especially with southward extent into the northern Great Basin and WY. ..Gleason/Leitman.. 09/03/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0323 AM CDT Tue Sep 03 2024 Valid 061200Z - 111200Z ...DISCUSSION... On D4/Friday, on upper-level trough is forecast to amplify as it digs southeastward across the Great Lakes region. In response, a surface low is forecast to deepen in the vicinity of the lower Great Lakes, though the timing and intensity of cyclogenesis continues to vary among extended-range guidance. Depending on the timing of the upper-level trough and attendant cold front, strong storms could develop across parts of the Ohio Valley during the afternoon and evening as low/midlevel flow strengthens, though generally weak instability could tend to limit severe potential. Uncertainty regarding the synoptic evolution on D4/Friday continues into D5/Saturday. However, there will be some potential for low-level moisture to be drawn northward into parts of the Mid Atlantic and Northeast, in advance of the cold front. Instability may remain quite weak, but rather strong flow could support convection with gusty-wind potential, if adequate prefrontal buoyancy can develop. For D6/Sunday and beyond, most guidance keeps richer low-level moisture confined near the Gulf Coast, which could generally limit severe potential across much of the CONUS. One possible exception is the High Plains vicinity, where modest low-level moisture return could support some increase in convective potential, especially if a northwesterly flow regime can be maintained between the deep eastern trough and an upper ridge that may become reestablished near the Four Corners region. However, predictability regarding synoptic details begins to substantially wane into early next week. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0223 AM CDT Tue Sep 03 2024 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The threat for organized severe thunderstorms currently appears low on Thursday. ...Synopsis... An upper-level trough is forecast to amplify over the central/northern Great Plains into parts of the upper Midwest/Great Lakes on Thursday. The trailing portion of the trough, associated with a weakening embedded shortwave, is forecast to move into the south-central High Plains during the day. A cold front is expected to continue moving southeastward across parts of the upper Midwest into the central/southern Plains. ...South-central Plains into the upper Midwest/Great Lakes... Guidance continues to vary regarding both timing of the front and the magnitude of destabilization in its vicinity. Richer low-level moisture will remain confined near the Gulf Coast, but dewpoints generally in the upper 50s to low/mid 60s F will support at least modest destabilization during the afternoon. Thunderstorm development will be possible near the front, and also potentially within a relatively moist post-frontal regime, with stronger drying expected to lag the initial wind shift. Deep-layer flow and midlevel lapse rates are forecast to be relatively weak across the region where storm development is currently expected. If pockets of greater diurnal heating/destabilization can develop, and/or if somewhat stronger midlevel flow (associated with the amplifying upper trough) can impinge on areas of storm development, then some severe threat could evolve during the afternoon and evening. Confidence is currently too low to include probabilities. ..Dean.. 09/03/2024 Read more

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