SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 AM CDT Tue Sep 10 2024 Valid 121200Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE DEEP SOUTH AND THE NORTHERN HIGH PLAINS... ...SUMMARY... A low-probability tornado threat may persist into Thursday across parts of the Deep South. Isolated large hail and severe gusts will be possible over the northern High Plains vicinity on Thursday afternoon and evening. ...Deep South/TN Valley... TC Francine is forecast by NHC to be in a weakening phase on Thursday as it tracks northward across parts of the Lower MS Valley to Mid-South. Model consensus suggests the bulk of strong low-level wind fields will become increasingly confined within the northeast quadrant of the cyclone. This will yield decreasing low-level hodograph curvature through the period, initially along the central/northeast Gulf Coast and gradually expanding northward. This will result in decreasing overlap of favorable SRH with rich tropical moisture, characterized by 70s surface dew points. Tornado potential may be less than on D2, but should still have a diurnal morning to afternoon peak before diminishing during the latter half of D3. Confidence is low with the northern extent of the low-probability tornado threat, which will likely contain scant surface-based instability coincident with moderate to large SRH. The TN Valley vicinity appears to be the northern demarcation. ...Eastern MT to western Dakotas... The northern Rockies to Great Basin shortwave trough should shift east into the northern High Plains to central Rockies by Thursday evening. Guidance has above-average consistency with the depiction of an embedded impulse and attendant meridional mid-level jet impinging on the eastern MT/WY region during the late afternoon to early evening. This will increase large-scale ascent and deep-layer shear, becoming favorably timed with peak boundary-layer heating. Two convective regimes are apparent, one within the post-frontal upslope flow regime in central to eastern MT and the other near the lee surface trough/cyclone close to the MT/Dakotas border area. Isolated large hail will be favored in the western regime, while isolated severe gusts should be favored east. The primary limiting factor to greater severe probs is progged weak buoyancy, with pre-convective surface dew points around the upper 40s to low 50s. ..Grams.. 09/10/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 AM CDT Tue Sep 10 2024 Valid 121200Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE DEEP SOUTH AND THE NORTHERN HIGH PLAINS... ...SUMMARY... A low-probability tornado threat may persist into Thursday across parts of the Deep South. Isolated large hail and severe gusts will be possible over the northern High Plains vicinity on Thursday afternoon and evening. ...Deep South/TN Valley... TC Francine is forecast by NHC to be in a weakening phase on Thursday as it tracks northward across parts of the Lower MS Valley to Mid-South. Model consensus suggests the bulk of strong low-level wind fields will become increasingly confined within the northeast quadrant of the cyclone. This will yield decreasing low-level hodograph curvature through the period, initially along the central/northeast Gulf Coast and gradually expanding northward. This will result in decreasing overlap of favorable SRH with rich tropical moisture, characterized by 70s surface dew points. Tornado potential may be less than on D2, but should still have a diurnal morning to afternoon peak before diminishing during the latter half of D3. Confidence is low with the northern extent of the low-probability tornado threat, which will likely contain scant surface-based instability coincident with moderate to large SRH. The TN Valley vicinity appears to be the northern demarcation. ...Eastern MT to western Dakotas... The northern Rockies to Great Basin shortwave trough should shift east into the northern High Plains to central Rockies by Thursday evening. Guidance has above-average consistency with the depiction of an embedded impulse and attendant meridional mid-level jet impinging on the eastern MT/WY region during the late afternoon to early evening. This will increase large-scale ascent and deep-layer shear, becoming favorably timed with peak boundary-layer heating. Two convective regimes are apparent, one within the post-frontal upslope flow regime in central to eastern MT and the other near the lee surface trough/cyclone close to the MT/Dakotas border area. Isolated large hail will be favored in the western regime, while isolated severe gusts should be favored east. The primary limiting factor to greater severe probs is progged weak buoyancy, with pre-convective surface dew points around the upper 40s to low 50s. ..Grams.. 09/10/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0202 AM CDT Tue Sep 10 2024 Valid 111200Z - 121200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE GREAT BASIN... ...Synopsis... The upper trough over the western US will quickly intensify Wednesday, as a shortwave perturbation and mid-level jet streak move onshore over the West Coast. As the trough strengthens, mid-level flow over much of the West will increase. A surface low will deepen over the northern Great Basin, while a cold front moves onshore and also strengthens. To the east, TS Francine will approach the Gulf Coast with offshore winds likely over parts of the mid South. Strong surface winds, low humidity, and thunderstorms over parts of the West and central US will support critical fire-weather concerns Wednesday. ...Great Basin... Ahead of the deepening trough, a potent mid-level jet streak will move over parts of the western Great Basin beginning early Wednesday. A deepening surface low in parts of the eastern Basin will drive 20-25 mph winds over much of NV into western UT. Augmented by downslope flow off the Sierra and the approaching cold front, a brief period of winds of 25-30 mph will be possible along with RH below 15%. Widespread critical fire-weather conditions are likely over parts of the Great Basin. Fire-weather concerns should diminish behind the front as cooler and more quiescent conditions are expected behind the front into early Thursday. ...Lee of the Rockies and High Plains... As the trough approaches, height falls and stronger flow aloft will overspread the Rockies and High Plains. A surface low will deepen first in eastern MT, with a lee trough extending south into the central High Plains. Near the lee trough, strong southerly winds will overlap with areas of low RH and drying fine fuels. Elevated fire weather concerns are expected over parts of the High Plains Wednesday afternoon and evening. ...Mid South... As Francine approaches the Gulf Coast Wednesday and Wednesday night, offshore pressure gradients will increase over parts of the lower MS Valley and Mid South. While humidity values are not expected to be overly low with the tropical air mass approaching, strong gusts are expected to overlap with areas of relatively dry fuels and little recent rainfall. Brief elevated fire-weather conditions are possible before rain chances increase into early Thursday. ...Northwest Thunder... Ahead of the cold front, increasing mid-level moisture and strong lift from the trough will promote scattered thunderstorms Wednesday afternoon. Lightning may interact with areas of somewhat drier fuels over parts of the Northwest and northern Rockies before broader wetting rainfall develops. However, these storms will likely have higher precipitation efficiency with a cooler air mass and more plentiful Pacific moisture in place. This lends significant uncertainty on the threat for any lightning ignitions. ..Lyons.. 09/10/2024 ...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 0202 AM CDT Tue Sep 10 2024 Valid 111200Z - 121200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE GREAT BASIN... ...Synopsis... The upper trough over the western US will quickly intensify Wednesday, as a shortwave perturbation and mid-level jet streak move onshore over the West Coast. As the trough strengthens, mid-level flow over much of the West will increase. A surface low will deepen over the northern Great Basin, while a cold front moves onshore and also strengthens. To the east, TS Francine will approach the Gulf Coast with offshore winds likely over parts of the mid South. Strong surface winds, low humidity, and thunderstorms over parts of the West and central US will support critical fire-weather concerns Wednesday. ...Great Basin... Ahead of the deepening trough, a potent mid-level jet streak will move over parts of the western Great Basin beginning early Wednesday. A deepening surface low in parts of the eastern Basin will drive 20-25 mph winds over much of NV into western UT. Augmented by downslope flow off the Sierra and the approaching cold front, a brief period of winds of 25-30 mph will be possible along with RH below 15%. Widespread critical fire-weather conditions are likely over parts of the Great Basin. Fire-weather concerns should diminish behind the front as cooler and more quiescent conditions are expected behind the front into early Thursday. ...Lee of the Rockies and High Plains... As the trough approaches, height falls and stronger flow aloft will overspread the Rockies and High Plains. A surface low will deepen first in eastern MT, with a lee trough extending south into the central High Plains. Near the lee trough, strong southerly winds will overlap with areas of low RH and drying fine fuels. Elevated fire weather concerns are expected over parts of the High Plains Wednesday afternoon and evening. ...Mid South... As Francine approaches the Gulf Coast Wednesday and Wednesday night, offshore pressure gradients will increase over parts of the lower MS Valley and Mid South. While humidity values are not expected to be overly low with the tropical air mass approaching, strong gusts are expected to overlap with areas of relatively dry fuels and little recent rainfall. Brief elevated fire-weather conditions are possible before rain chances increase into early Thursday. ...Northwest Thunder... Ahead of the cold front, increasing mid-level moisture and strong lift from the trough will promote scattered thunderstorms Wednesday afternoon. Lightning may interact with areas of somewhat drier fuels over parts of the Northwest and northern Rockies before broader wetting rainfall develops. However, these storms will likely have higher precipitation efficiency with a cooler air mass and more plentiful Pacific moisture in place. This lends significant uncertainty on the threat for any lightning ignitions. ..Lyons.. 09/10/2024 ...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 0159 AM CDT Tue Sep 10 2024 Valid 101200Z - 111200Z ...Synopsis... Broad troughing over the Northwest will gradually intensify later today and tonight, as a stronger shortwave and mid-level jet approach from the eastern Pacific. Increasing flow aloft will move inland, supporting the potential for strong surface winds and low humidity over parts of the Northwest and Great Basin. Elevated to near-critical fire-weather conditions are likely. ...Great Basin... As the upper trough shifts east, mid-level flow should strengthen over parts of the western Great Basin. Gusty downslope winds are likely in the lee of the Sierra and across parts of southern NV and western UT. Surface winds of 15-25 mph should overlap with RH below 15%, and within areas of dry fuels this afternoon. Elevated to near-critical fire-weather conditions are likely across much of NV and into portions of northern CA, southern ID and far western UT. Confidence in the development of nearly to briefly critical meteorological conditions is highest over parts of southern NV where winds are expected to be slightly stronger. However, fuels here are also slightly less receptive, and the overlap of favorable wind/RH may also be briefer. Thus, confidence remains too low for critical highlights currently. ...Cascades and Columbia Gorge... Increasing mid-level winds will combine with a strong onshore pressure gradient behind the departing cold front to drive 15-20 mph winds through Cascade Gaps and into the western Columbia Basin. While cooler and more moderate, pockets of RH below 25% should overlap with the stronger winds. The duration of these breezy and somewhat dry conditions may be somewhat limited, but elevated to briefly critical fire weather conditions are possible within dry fuels. ..Lyons.. 09/10/2024 ...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 0159 AM CDT Tue Sep 10 2024 Valid 101200Z - 111200Z ...Synopsis... Broad troughing over the Northwest will gradually intensify later today and tonight, as a stronger shortwave and mid-level jet approach from the eastern Pacific. Increasing flow aloft will move inland, supporting the potential for strong surface winds and low humidity over parts of the Northwest and Great Basin. Elevated to near-critical fire-weather conditions are likely. ...Great Basin... As the upper trough shifts east, mid-level flow should strengthen over parts of the western Great Basin. Gusty downslope winds are likely in the lee of the Sierra and across parts of southern NV and western UT. Surface winds of 15-25 mph should overlap with RH below 15%, and within areas of dry fuels this afternoon. Elevated to near-critical fire-weather conditions are likely across much of NV and into portions of northern CA, southern ID and far western UT. Confidence in the development of nearly to briefly critical meteorological conditions is highest over parts of southern NV where winds are expected to be slightly stronger. However, fuels here are also slightly less receptive, and the overlap of favorable wind/RH may also be briefer. Thus, confidence remains too low for critical highlights currently. ...Cascades and Columbia Gorge... Increasing mid-level winds will combine with a strong onshore pressure gradient behind the departing cold front to drive 15-20 mph winds through Cascade Gaps and into the western Columbia Basin. While cooler and more moderate, pockets of RH below 25% should overlap with the stronger winds. The duration of these breezy and somewhat dry conditions may be somewhat limited, but elevated to briefly critical fire weather conditions are possible within dry fuels. ..Lyons.. 09/10/2024 ...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 1241 AM CDT Tue Sep 10 2024 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN SOUTH LA TO THE COASTAL WESTERN FL PANHANDLE... ...SUMMARY... A few tornadoes are possible across the central Gulf Coast vicinity on Wednesday into Wednesday night, in association with Tropical Cyclone Francine. ...Central Gulf Coast... Per latest NHC forecasts and ensemble guidance, Tropical Storm Francine is expected to become a hurricane over the northwest Gulf and make landfall along the LA coast around Wednesday evening. A low-probability tornado threat with outer-band convection should reach coastal LA by Wednesday morning. The more favorable overlap of strengthening low-level shear/SRH and intrusion of deeper tropical moisture (surface dew points in the mid/upper 70s F) is expected during the afternoon and evening across parts of south-central to southeast LA and far southeast MS/southwest AL. As the TC progresses inland and weakens Wednesday night, some broadening of the favorable SRH/surface-based buoyancy environment should spread east into the coastal FL Panhandle. The northern extent of a low-probability tornado threat remains uncertain, with surface-based buoyancy potentially remaining quite limited into parts of central MS and interior south AL Wednesday night. ...Interior Northwest to the northern High Plains... A shortwave trough will progress inland from the coastal Pacific Northwest, likely reaching the northern Rockies to central Great Basin by 12Z Thursday. Large-scale ascent and cooling mid-level temperatures attendant to the approaching trough will support scattered thunderstorms across the interior Northwest on Wednesday afternoon. While the bulk of strong mid-level flow will remain displaced west of the shortwave trough, moderate enhancement of southwesterlies will occur ahead of it. This should be adequate for marginal updraft rotation amid weak surface-based buoyancy. Isolated strong to localized severe gusts along with small to marginally severe hail will be possible into the early evening. Separately, isolated to widely scattered high-based, low-topped thunderstorms should form in the late afternoon along a lee trough towards a quasi-stationary front over the northern High Plains. Meager buoyancy and modest deep-layer shear within a meridional wind profile suggest sporadic severe gusts in microbursts will be the main threat. Along the immediate north of the front, a confined corridor of greater moisture/instability should be in place during the afternoon/evening, but capping will likely limit surface-based development. A few stronger elevated storms will be possible into Wednesday night, but potential for severe hail appears negligible. ..Grams.. 09/10/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1233 AM CDT Tue Sep 10 2024 Valid 101200Z - 111200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE LA COAST... ...SUMMARY... Some tornado threat associated with Tropical Cyclone Francine may approach the Louisiana Coast by early Wednesday morning. ...Synopsis... A shortwave trough is expected to be off the Northeast Coast early Tuesday morning, with continued eastward progression into the northern Atlantic expected thereafter. A relatively zonal pattern is anticipated west of this shortwave trough across the majority of the CONUS throughout much of the period. A low-amplitude shortwave trough is forecast to move within this zonal flow across the northern Plains and the Upper Midwest, but with minimal pattern amplification. Some amplification is expected late Tuesday/early Wednesday across the Pacific Northwest, ahead of a strong shortwave trough approaching the coast. Surface pattern early Tuesday will feature high pressure centered over the central Appalachians and covering much of the OH Valley. This ridging is expected to gradually shift eastward/northeastward throughout the period. Surface troughing associated with the northern Plains shortwave trough will extend across the central Dakotas early Tuesday, before then shifting eastward throughout the day. Farther south across the northwest Gulf of Mexico, TC Francine is expected to reach hurricane strength while gradually progressing northeastward. ...TC Francine - LA Coast... Rainbands from Francine will likely spread across the northwest Gulf Coast throughout the day, but the stronger flow will remain displaced south throughout much of the period. Beginning around 06Z, the stronger flow may be far enough north to influence any deeper updrafts that develop along the LA Coast, with an attendant risk for brief tornadoes. ...Upper Midwest... Moderate low-level moisture, characterized by surface dewpoints in the upper 50s/low 60s, is expected across the region Tuesday afternoon ahead of the approaching shortwave trough and associated surface trough. Steep mid-level lapse rates will aid in the development of strong buoyancy across the region, supporting a conditional severe-thunderstorm risk. However, despite moderate low-level moisture and strong daytime heating, warm mid-level temperatures are forecast to keep capping in place, precluding afternoon thunderstorm development. ...Elsewhere... Afternoon thunderstorms are expected again across the eastern Great Basin and northern/central Rockies, where orographic effects and modest large-scale ascent will combine with modest moisture and buoyancy to support thunderstorm development. Increasing thunderstorm potential is anticipated late Tuesday into early Wednesday across the Pacific Northwest ahead of the approaching shortwave trough. ..Mosier/Lyons.. 09/10/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0733 PM CDT Mon Sep 09 2024 Valid 100100Z - 101200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected this evening and overnight. ...01Z Update... The overall severe threat across NY continues to decrease as the airmass stabilizes. Isolated thunderstorms will continue, but the reduced severe threat merits removal of the severe probabilities. Isolated thunderstorms will also remain possible from the Great Basin into the central Rockies/central High Plains this evening, before expanding eastward/northeastward into the central Plains and Mid MO Valley overnight into Wednesday morning. Lastly, thunderstorms will remain possible along the Gulf Coast and FL Peninsula. Highest coverage is anticipated across the TX Coast as rainbands associated TC Francine move across the region. Severe potential within these bands is expected to be very low. ..Mosier.. 09/10/2024 Read more

No Mesoscale Discussions are in effect as of Mon Sep 9 22:34:02 UTC 2024.

No watches are valid as of Mon Sep 9 22:34:02 UTC 2024.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0332 PM CDT Mon Sep 09 2024 Valid 111200Z - 171200Z A potent upper-level trough will move through the Northwest and into the Great Basin by midweek. This trough will then lift northeastward with time before moving into the Canadian Prairie this coming weekend. Strong surface winds are expected along with and ahead of the trough as the surface pressure gradient increases in response. TC Francine will increase surface winds across parts of the Southeast/Mid-South where dry fuels exist. Another amplified upper trough is forecast to move into the West Coast by late this weekend into next week. Details of where dry/windy conditions will be or what mid-level moisture will be present remain uncertain at this time. ...Great Basin... A broad area of the Basin will likely experience critical fire weather on Wednesday. A deepening surface low/trough in parts of the eastern Basin will drive 15-25 mph winds over much of Nevada into western Utah. The mid-level jet will approach the northern Sierra and be roughly perpendicular to the terrain. At least a brief period of winds 25+ mph will be possible along with potentially intense wind gusts. RH in northwest Nevada will tend to see some improvement through the afternoon into the evening, but this is not expected to be significant enough to mitigate large fire potential. ...Northern/Central Plains... Fire weather concerns in parts of the Plains/High Plains will increase beginning Wednesday as the trough approaches and a surface low deepens first in eastern Montana and moving northward into the Canadian Prairie on Thursday. A lee trough will extend into the central High Plains. With preceding dry and windy days, fine fuels will continue to dry ahead of the increase in winds. Furthermore, it seems more likely than not that moisture return northward will be more limited than some guidance suggests (namely the ECMWF) especially with the stronger offshore winds developing around TC Francine. Winds will be stronger on Thursday given a stronger 850 mb jet that will last through the day. One point of uncertainty will be potential for storms to develop in the lee trough on Wednesday. That activity still appears to be quite isolated and should not have significant impact. Critical probabilities may need to be increased on Thursday depending on trends in guidance and updated fuel information. ...Mid-South... As TC Francine moves north and east, the surface pressure gradient inland should increase ahead of the cyclone. There is potential for at least locally elevated conditions in parts of the Mid-South on Wednesday as fuels in the region remain quite dry per latest ERC data. High cloud cover limits overall confidence in duration and magnitude of these conditions, however. ...Northern California... As the upper-level trough moves through the Great Basin, strong mid-level flow on the western flank of the trough will overspread northern California on Thursday. Additionally, surface high pressure will briefly build into the Northwest. Some north/northeasterly downslope winds are possible leading to some potentially locally elevated fire weather. The mid-level winds will be in the process of weakening through the day. Given the marginal conditions and likely limited duration, no highlights will be added. ..Wendt.. 09/09/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0234 PM CDT Mon Sep 09 2024 Valid 092000Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF NEW YORK... ...SUMMARY... Isolated damaging winds remain possible this afternoon across parts of New York. ...20Z Update... No changes have been made to the Day 1 Convective Outlook. With storms continuing to increase in coverage and intensity over western NY, atop marginal boundary-layer-based instability, an instance or two of damaging gusts remain possible with one of the stronger storms. Similarly, a severe gust cannot be ruled out with one of the stronger storms over the Interior West given the presence of steep tropospheric lapse rates. Please see the previous outlook (below) for more details. ..Squitieri.. 09/09/2024 .PREV DISCUSSION... /ISSUED 1126 AM CDT Mon Sep 09 2024/ ...New York... Within large-scale upper troughing over the Northeast and eastern Canada, an embedded shortwave trough over southern Ontario and the upper Great Lakes will continue to move across the Northeast this afternoon and evening. Ascent associated with this shortwave trough and related mid-level jet is supporting isolated thunderstorms across southern Ontario and vicinity. This activity will spread east-southeastward this afternoon across parts of NY. The airmass over this region should become only weakly unstable as filtered daytime heating occurs, with poor mid-level lapse rates, persistent cloud cover, and modest low-level moisture limiting destabilization. Still, gradually increasing west-northwesterly winds at low/mid levels will foster around 25-35 kt of deep-layer shear. This should support modest thunderstorm organization, with multicells/small clusters potentially evolving along and downstream of Lake Ontario. Isolated strong to damaging winds should be the main threat with this convection as it moves across much of NY this afternoon and early evening, before eventually weakening with eastward extent with the loss of daytime heating. ...Northern/Central Rockies and High Plains... Isolated to widely scattered thunderstorms should develop this afternoon over portions of the northern/central Rockies as a weak shortwave trough continues eastward. Low-level moisture and related instability are both expected to remain rather meager into the High Plains, which should limit updraft intensities. Still, isolated strong/gusty winds may occur with this high-based activity across parts of MT/WY where low-level lapse rates can become steepened. Greater low-level moisture is present farther east into the Dakotas, along/east of a weak surface low/trough. But, increasing low/mid-level temperatures and a strong cap should generally inhibit thunderstorm development through much of the day with eastward extent across the northern/central Plains. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0234 PM CDT Mon Sep 09 2024 Valid 092000Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF NEW YORK... ...SUMMARY... Isolated damaging winds remain possible this afternoon across parts of New York. ...20Z Update... No changes have been made to the Day 1 Convective Outlook. With storms continuing to increase in coverage and intensity over western NY, atop marginal boundary-layer-based instability, an instance or two of damaging gusts remain possible with one of the stronger storms. Similarly, a severe gust cannot be ruled out with one of the stronger storms over the Interior West given the presence of steep tropospheric lapse rates. Please see the previous outlook (below) for more details. ..Squitieri.. 09/09/2024 .PREV DISCUSSION... /ISSUED 1126 AM CDT Mon Sep 09 2024/ ...New York... Within large-scale upper troughing over the Northeast and eastern Canada, an embedded shortwave trough over southern Ontario and the upper Great Lakes will continue to move across the Northeast this afternoon and evening. Ascent associated with this shortwave trough and related mid-level jet is supporting isolated thunderstorms across southern Ontario and vicinity. This activity will spread east-southeastward this afternoon across parts of NY. The airmass over this region should become only weakly unstable as filtered daytime heating occurs, with poor mid-level lapse rates, persistent cloud cover, and modest low-level moisture limiting destabilization. Still, gradually increasing west-northwesterly winds at low/mid levels will foster around 25-35 kt of deep-layer shear. This should support modest thunderstorm organization, with multicells/small clusters potentially evolving along and downstream of Lake Ontario. Isolated strong to damaging winds should be the main threat with this convection as it moves across much of NY this afternoon and early evening, before eventually weakening with eastward extent with the loss of daytime heating. ...Northern/Central Rockies and High Plains... Isolated to widely scattered thunderstorms should develop this afternoon over portions of the northern/central Rockies as a weak shortwave trough continues eastward. Low-level moisture and related instability are both expected to remain rather meager into the High Plains, which should limit updraft intensities. Still, isolated strong/gusty winds may occur with this high-based activity across parts of MT/WY where low-level lapse rates can become steepened. Greater low-level moisture is present farther east into the Dakotas, along/east of a weak surface low/trough. But, increasing low/mid-level temperatures and a strong cap should generally inhibit thunderstorm development through much of the day with eastward extent across the northern/central Plains. Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 PM CDT Mon Sep 09 2024 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF SOUTHEAST LA AND SOUTHERN MS... ...SUMMARY... A few tornadoes are possible across the central Gulf Coast vicinity on Wednesday, in association with Tropical Cyclone Francine. ...Synopsis... Tropical Cyclone Francine is currently forecast to make landfall sometime later Wednesday afternoon or evening near the LA Gulf Coast, potentially as a hurricane. Meanwhile, a relatively deep mid/upper-level trough will move eastward across the Northwest into the Great Basin and central/northern Rockies. In response to the this trough, some deepening of surface low pressure is expected from the eastern Great Basin into Montana. ...Central Gulf Coast vicinity... See NHC forecasts and advisories for additional information regarding Francine. Some tornado threat will spread inland as Francine approaches the coast during the day before making landfall by evening. Based on current forecasts/guidance, the most favorable overlap of strengthening low-level shear/SRH and inland intrusion of tropical moisture (with dewpoints in the mid/upper 70s F) is expected across parts of southern LA/MS, where a small Slight Risk has been included. The northern extent of an appreciable tornado threat remains uncertain, with surface-based buoyancy potentially remaining quite limited into parts of central MS Wednesday night, but the Marginal Risk has been expanded based on the expected track of Francine into early Thursday morning. ...Interior Northwest... Large-scale ascent and cooling temperatures aloft attendant to the approaching trough will support isolated to scattered thunderstorm development across the interior Northwest on Wednesday. Wind profiles will become favorable for organized convection, but moisture will likely remain rather limited, and uncertainty remains regarding whether buoyancy will become sufficient for a severe threat. Locally gusty winds and small hail could accompany the strongest storms. ...Central/northern High Plains... Isolated high-based convection may develop across parts of the central/northern High Plains during the afternoon, to the south of a stationary front that will extend eastward across parts of eastern MT into the Dakotas. While this convection may remain rather disorganized, inverted-v profiles could support localized strong gusts. Near and immediately north of the front, somewhat more favorable moisture and instability may be in place during the afternoon/evening, but capping will tend to limit surface-based development. A few stronger elevated storms will be possible, but potential for any organized severe threat remains uncertain at this time. ..Dean.. 09/09/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 PM CDT Mon Sep 09 2024 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF SOUTHEAST LA AND SOUTHERN MS... ...SUMMARY... A few tornadoes are possible across the central Gulf Coast vicinity on Wednesday, in association with Tropical Cyclone Francine. ...Synopsis... Tropical Cyclone Francine is currently forecast to make landfall sometime later Wednesday afternoon or evening near the LA Gulf Coast, potentially as a hurricane. Meanwhile, a relatively deep mid/upper-level trough will move eastward across the Northwest into the Great Basin and central/northern Rockies. In response to the this trough, some deepening of surface low pressure is expected from the eastern Great Basin into Montana. ...Central Gulf Coast vicinity... See NHC forecasts and advisories for additional information regarding Francine. Some tornado threat will spread inland as Francine approaches the coast during the day before making landfall by evening. Based on current forecasts/guidance, the most favorable overlap of strengthening low-level shear/SRH and inland intrusion of tropical moisture (with dewpoints in the mid/upper 70s F) is expected across parts of southern LA/MS, where a small Slight Risk has been included. The northern extent of an appreciable tornado threat remains uncertain, with surface-based buoyancy potentially remaining quite limited into parts of central MS Wednesday night, but the Marginal Risk has been expanded based on the expected track of Francine into early Thursday morning. ...Interior Northwest... Large-scale ascent and cooling temperatures aloft attendant to the approaching trough will support isolated to scattered thunderstorm development across the interior Northwest on Wednesday. Wind profiles will become favorable for organized convection, but moisture will likely remain rather limited, and uncertainty remains regarding whether buoyancy will become sufficient for a severe threat. Locally gusty winds and small hail could accompany the strongest storms. ...Central/northern High Plains... Isolated high-based convection may develop across parts of the central/northern High Plains during the afternoon, to the south of a stationary front that will extend eastward across parts of eastern MT into the Dakotas. While this convection may remain rather disorganized, inverted-v profiles could support localized strong gusts. Near and immediately north of the front, somewhat more favorable moisture and instability may be in place during the afternoon/evening, but capping will tend to limit surface-based development. A few stronger elevated storms will be possible, but potential for any organized severe threat remains uncertain at this time. ..Dean.. 09/09/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0157 PM CDT Mon Sep 09 2024 Valid 101200Z - 111200Z No changes to the ongoing forecast. There is some potential for very isolated thunderstorms in the vicinity of the Blue Mountains in Oregon, but confidence in initiation is quite low. Additional thunderstorms are possible in parts of southwest Montana, but that activity would quickly move into a higher PWAT airmass. ..Wendt.. 09/09/2024 .PREV DISCUSSION... /ISSUED 0151 AM CDT Mon Sep 09 2024/ ...Synopsis... Broad troughing over the Northwest is forecast to gradually intensify Tuesday as a stronger shortwave and mid-level jet approach from the eastern Pacific. Falling heights and increasing flow aloft will move inland, supporting the potential for strong surface winds and low humidity over parts of the Northwest and Great Basin. ..Great Basin... Fire weather concerns will increase on Tuesday with the approach of the strong trough/mid-level jet. Initially weak surface winds will intensify over northwest and southern Nevada to 15-25 mph as flow aloft increases. Several hours of elevated to locally critical fire-weather conditions are likely as the stronger surface winds develop with a dry air mass with RH values below 20%. Fuels are driest across parts of the northern Great Basin and ID where rainfall has been sparse. However, fuels farther south in NV and CA remain sufficiently dry, and with stronger winds, elevated to near critical conditions are likely. ...Cascades and Columbia Gorge... Increasing mid-level winds will combine with a strong onshore pressure gradient to drive 15-20 mph winds through the Gorge and the western Columbia Basin along with RH potentially near 15%. The duration of breezy and somewhat dry conditions may be somewhat limited, but elevated to briefly critical fire weather may occur on Tuesday. ...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 0157 PM CDT Mon Sep 09 2024 Valid 101200Z - 111200Z No changes to the ongoing forecast. There is some potential for very isolated thunderstorms in the vicinity of the Blue Mountains in Oregon, but confidence in initiation is quite low. Additional thunderstorms are possible in parts of southwest Montana, but that activity would quickly move into a higher PWAT airmass. ..Wendt.. 09/09/2024 .PREV DISCUSSION... /ISSUED 0151 AM CDT Mon Sep 09 2024/ ...Synopsis... Broad troughing over the Northwest is forecast to gradually intensify Tuesday as a stronger shortwave and mid-level jet approach from the eastern Pacific. Falling heights and increasing flow aloft will move inland, supporting the potential for strong surface winds and low humidity over parts of the Northwest and Great Basin. ..Great Basin... Fire weather concerns will increase on Tuesday with the approach of the strong trough/mid-level jet. Initially weak surface winds will intensify over northwest and southern Nevada to 15-25 mph as flow aloft increases. Several hours of elevated to locally critical fire-weather conditions are likely as the stronger surface winds develop with a dry air mass with RH values below 20%. Fuels are driest across parts of the northern Great Basin and ID where rainfall has been sparse. However, fuels farther south in NV and CA remain sufficiently dry, and with stronger winds, elevated to near critical conditions are likely. ...Cascades and Columbia Gorge... Increasing mid-level winds will combine with a strong onshore pressure gradient to drive 15-20 mph winds through the Gorge and the western Columbia Basin along with RH potentially near 15%. The duration of breezy and somewhat dry conditions may be somewhat limited, but elevated to briefly critical fire weather may occur on Tuesday. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1229 PM CDT Mon Sep 09 2024 Valid 101200Z - 111200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE LA GULF COAST... ...SUMMARY... Some tornado threat associated with Tropical Cyclone Francine may approach the Louisiana Gulf Coast by early Wednesday morning. ...Synopsis... Tropical Storm Francine will potentially intensify into a hurricane as it moves north-northeastward across the western Gulf of Mexico. Meanwhile, a strong mid/upper-level shortwave trough is forecast to dig southeastward into the Pacific Northwest and northern CA. Diurnal thunderstorms capable of locally gusty winds will be possible from the eastern Great Basin into parts of the Rockies, and also across the FL Peninsula. More isolated storms will also be possible from the central Plains into the parts of the upper Midwest, which may also be capable of locally gusty winds. Organized severe-thunderstorm potential is expected to remain low, with the possible exception of the LA Gulf Coast region late in the period in association with Francine. ...LA Gulf Coast vicinity... Refer to NHC forecasts and advisories for more information regarding Tropical Storm Francine. Based on the current forecast track, the most favorable environment for low-topped supercells associated with Francine should remain offshore for most of the forecast period. However, some outer bands may begin to approach the LA Gulf Coast prior to 12Z Wednesday morning, accompanied by an increase in low-level shear/SRH. A small Marginal Risk has been included near the immediate LA Gulf Coast for the potential of an increasing tornado threat prior to the end of the forecast period. ..Dean.. 09/09/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1133 AM CDT Mon Sep 09 2024 Valid 091700Z - 101200Z Minor modifications have been made to the ongoing forecast based on recent observations and model guidance. See the previous discussion for greater details. ..Wendt.. 09/09/2024 .PREV DISCUSSION... /ISSUED 0150 AM CDT Mon Sep 09 2024/ ...Synopsis... Broad trouhging over the Northwest should continue today as an embedded perturbation moves eastward over the northern Rockies. Southwesterly flow aloft is forecast to increase over much of the West as the broad trough slowly shifts east. At the surface, a cold front will move into the Rockies, bringing a cooler air mass to parts of the Northwest, but gusty winds to parts of the Cascades. A lee trough developing east of the Rockies will help support isolated dry thunderstorms over parts of WY and MT. Periods of stronger surface winds and low RH will support elevated to near-critical fire-weather conditions. ...Northwest and Great Basin.... Stronger flow aloft is expected to persist today over much of the Northwest and northern Great Basin. Surface winds should increase to 15-25 mph as momentum from aloft mixes down. Downsloping and mid-level drying should keep the air mass quite dry with diurnal RH minimums below 15% likely. Several hours of widespread elevated to near-critical fire-weather conditions are likely across the northern Sierra and Great Basin. Farther north, more moderate RH of 25-30% is expected beneath the upper trough and behind the cold front. Despite the arrival of a cooler Pacific air mass, downslope winds of 15-25 mph should overlap with dry fuels and pockets of lower RH during the day. Overlapping with recent lightning and fire activity, a few hours of elevated to near-critical conditions are possible in the lee of the Cascades as winds increase. ...Northern Rockies... Stronger westerly flow head of the embedded shortwave will aid in deepening a lee trough east of the Rockies. Westerly surface winds should strengthen in turn, supporting pockets of downslope winds of 15-25 mph across parts of MT and WY. With hot temperatures and little recent rainfall, afternoon RH values should remain quite low, generally below 20%. Increasing winds, receptive fuels, and persistent dry conditions should support several hours of elevated to near critical fire-weather conditions over parts of the northern Rockies. ...Dry Thunder... Isolated, high-based thunderstorms appear likely over parts of the Rockies (mainly WY and MT) today ahead of the shortwave trough. Weak buoyancy, and PWATs of 0.5 to 0.7 inches, atop dry and well-mixed low levels will support poor precipitation efficiency and the potential for strong outflow winds. At least isolated storms are expected over areas of receptive fuels. Thus, dry lightning ignitions are possible, especially across parts of north-central WY, where storm coverage appears greatest. ...Please see www.spc.noaa.gov/fire for graphic product... Read more