SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Wed Sep 11 2024 Valid 112000Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE GULF COAST... ...SUMMARY... Hurricane Francine will pose a tornado threat through tonight across the middle Gulf Coast region. ...20z Update... The forecast remains on track with no changes needed to the current D1 Outlook. Hurricane Francine continues to move northeastward, with an increasing threat for tornadoes expected across southern Louisiana shifting into southeastern Mississippi, southern Alabama, and the Florida panhandle this evening. See previous discussion below for more information. ..Thornton/Guyer.. 09/11/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Wed Sep 11 2024/ ...Gulf Coast - Hurricane Francine... Hurricane Francine will continue to generally move northeastward toward the southern Louisiana coast. Reference NHC for the latest forecast track and intensity details. As Francine approaches the coast later this afternoon into evening, a considerable strengthening of east-southeasterly winds on its east-northeast periphery will lead to an increasing near-shore/inland supercell risk. This will be in tandem with a northward shift of a maritime warm front and associated moisture-rich air, which will tend to stay with about 50-75 miles within the Gulf Coast spanning southeast Louisiana to the Florida Panhandle. The supercell/tornado risk is expected to steadily increase this afternoon across southeast Louisiana, transitioning northeastward toward southeast Mississippi, southern Alabama and the Florida Panhandle into this evening and overnight, with a few tornadoes possible regionally. ...Northern Rockies and northern High Plains... High-based thunderstorms are expected to pose an isolated severe risk late this afternoon into evening, with severe-caliber wind gusts a possibility, along with some hail possible as well across the northern Rockies including parts of Idaho and western Montana. This is influenced by the lead portion of a Pacific Northwest upper-level trough, with preceding height falls and the exit region of the upper jet overspreading the northern Rockies and northern High Plains through tonight. Thunderstorms should increase in coverage/intensity by late afternoon, especially from far southeast Oregon into southern Idaho, southern Montana and northwest Wyoming. Around 250-750 J/kg MLCAPE coincident with 25-35 kt of effective shear will support clusters and bands of storms capable of hail and stronger wind gusts. Additional widely scattered storms are expected across the northern High Plains within a modestly moist environment. Dry sub-cloud layers will support the potential for stronger downdrafts and the possibility of some severe-caliber wind gusts. Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0203 PM CDT Wed Sep 11 2024 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHEAST... ...SUMMARY... There is a marginal risk of severe thunderstorms across portions of the Southeast on Friday. ...Synopsis... A mid-level trough will de-amplify as it moves into the Canadian Prairies on Friday. At the surface, a cold front will move across the northern/central Plains. The remnants of Hurricane Francine will likely be extratropical and vertically stacked, somewhere near eastern Arkansas Friday morning. This system will slowly drift east through the day Friday. ...Southeast... A belt of stronger mid-level flow will be persistent south and southeast of a mid-level closed-low in the Tennessee Valley which will overspread moderate shear across a moist and moderately unstable surface airmass across eastern Alabama and western Georgia. 850mb flow will be quite weak and thus, low-level shear and the tornado threat will likely be somewhat limited. However, 1500 to 2000 J/kg MLCAPE and effective shear of 30 to 40 knots will support isolated stronger storms capable of damaging wind gusts. ...Central and Northern High Plains... Some forced convection may develop along a cold front as it moves through the northern Plains on Friday. However, limited moisture and instability should mitigate the severe weather threat with this activity. ..Bentley.. 09/11/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0155 PM CDT Wed Sep 11 2024 Valid 121200Z - 131200Z ...CRITICAL FIRE WEATHER AREA FOR MUCH OF THE CENTRAL INTO THE NORTHERN HIGH PLAINS... The forecast remains unchanged. Strong surface winds are still expected into eastern portions of the Dakotas into eastern Nebraska. Fuel receptiveness and RH trends will continue to be monitored in these areas, but current guidance continues to suggest lesser concerns with eastern extent. ..Wendt.. 09/11/2024 .PREV DISCUSSION... /ISSUED 0205 AM CDT Wed Sep 11 2024/ ...Synopsis... Mid-level troughing will continue to intensify as it crosses the Intermountain West and overspreads the northern/central Rockies Thursday. Strong flow aloft will approach the central High Plains as a lee low quickly deepens. A surface lee trough will trail south from the developing low, enhancing southerly winds over much of the Plains. With dry conditions in place, critical fire-weather concerns are likely. ...Central High Plains... Southerly surface winds will begin to increase overnight D1/Wednesday and into early D2/Thursday as upper-level forcing approaches from the west. Winds should continue to intensify through the day as the lee trough/low deepen considerably. South/southwesterly gusts of 20-30 mph are possible along with RH values below 25%. RH will be less favorable farther east, though winds will still be strong. Area fine fuels are dry, but should dry further over the next 24-36 hours, reaching critical levels. With the potent combination of strong winds and low RH likely over several hours D2/Thursday, widespread elevated to critical fire-weather conditions are likely. ...Intermountain West... Across parts of western CO/WY, strong southwesterly winds are expected ahead of the cold front moving out of the eastern Great Basin. Aided by the strong flow aloft, wind gusts of 25-30 mph are likely. Dry southwesterly flow and warm temperatures will support afternoon RH values below 20%. Meteorological conditions are quite conducive to fire spread. However, area fuels are much less favorable after recent rainfall. Given the magnitude of the wind and relatively dry conditions, several hours of elevated to near-critical fire-weather conditions still appear likely before the front passes through. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 2052 CONCERNING SEVERE POTENTIAL...TORNADO WATCH LIKELY FOR PORTIONS OF SOUTHERN AND EASTERN LOUISIANA INTO SOUTHERN MISSISSIPPI
Mesoscale Discussion 2052 NWS Storm Prediction Center Norman OK 1228 PM CDT Wed Sep 11 2024 Areas affected...portions of southern and eastern Louisiana into southern Mississippi Concerning...Severe potential...Tornado Watch likely Valid 111728Z - 111900Z Probability of Watch Issuance...95 percent SUMMARY...The threat for at least a few tornadoes is increasing across portions of southern LA into far southern MS. A Tornado Watch issuance will be needed soon. DISCUSSION...MRMS mosaic radar imagery has shown a gradual increase in the intensity of convective cells embedded within the broader rainbands associated with Hurricane Francine, which are attempting to move ashore. Surface temperatures/dewpoints in southeastern LA are in the upper 70s/mid 70s F, which are contributing to 500+ J/kg MLCAPE. At the same time, low-level shear continues to increase along the Gulf Coast, with the HDC VAD profiler showing increasingly curved hodographs, with nearly 200 m2/s2 0-3 km SRH noted. Low-level shear should continue to increase through the afternoon, with a subsequent increase in tornado potential likely as well. Given the increasing severe risk, a Tornado Watch issuance will be needed soon. ..Squitieri/Guyer.. 09/11/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MOB...LIX...LCH... LAT...LON 29539220 30089172 30559106 30769022 30888930 30908867 30808839 30598827 30238832 29968878 29288907 29048912 29008966 29019042 29099128 29539220 Read more

WW 0667 Status Updates
STATUS FOR WATCH 0667 HAS NOT BEEN ISSUED YET Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1212 PM CDT Wed Sep 11 2024 Valid 121200Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE FLORIDA PANHANDLE TO CENTRAL ALABAMA AND IN EASTERN MONTANA... ...SUMMARY... On Thursday, a few tornadoes will be possible, mainly in the morning and afternoon from the Florida Panhandle to north-central Alabama. Scattered large hail and severe gusts will also be possible across the eastern Montana vicinity during the afternoon to early evening. ...Synopsis... A strong mid-level trough will become negatively tilted across the northern Rockies on Thursday afternoon as a moderately strong mid-level jet streak wraps around the southern periphery of the primary trough. At the same time, Hurricane Francine will undergo extratropical transition across portions of the Southeast. ...FL Panhandle to the TN Valley... Thursday morning, backed surface winds and favorable hodographs for low-level rotating updrafts will be present along the Florida/Alabama coastal region. In addition, a tropical airmass with upper 70s dewpoints will support MLCAPE of 2000+ J/kg during the morning hours. South-southeasterly surface winds during the late morning will veer to south-southwesterly by the early afternoon hours which will lessen low-level shear and also lead to some dry-air advection and weaker instability during the afternoon and evening. Therefore, the primary tornado threat across the Florida Panhandle and southern Alabama should be confined to the morning hours. By early-to-mid afternoon, guidance indicates at least some clearing of cloud-cover across central Alabama which may result in some surface heating and destabilization with MLCAPE of 1000 to 1500 J/kg possible. The potential for this increase in diurnal instability may overlap the period when the most favorable wind profile also exists across the same region. This could result in a threat for a few tornadic storms across central Alabama during the mid-to-late afternoon period. ...Eastern Montana vicinity... Strong forcing will overspread eastern Montana Thursday afternoon as a mid-level shortwave trough approaches the region. A well-mixed, relatively moisture-starved airmass will exist ahead of the cold front/surface low. However, in the immediate wake of the cold front, prior to the colder surface air, better moisture will wrap around the surface low. This will lead to a narrow corridor of weak to moderate instability and the potential for scattered thunderstorms. Strong effective shear (55+ knots) will exist in this post-frontal airmass where storms are anticipated. Therefore, supercells or a few bowing segments may be possible with a threat for severe wind gusts and large hail. ..Bentley.. 09/11/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1212 PM CDT Wed Sep 11 2024 Valid 121200Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE FLORIDA PANHANDLE TO CENTRAL ALABAMA AND IN EASTERN MONTANA... ...SUMMARY... On Thursday, a few tornadoes will be possible, mainly in the morning and afternoon from the Florida Panhandle to north-central Alabama. Scattered large hail and severe gusts will also be possible across the eastern Montana vicinity during the afternoon to early evening. ...Synopsis... A strong mid-level trough will become negatively tilted across the northern Rockies on Thursday afternoon as a moderately strong mid-level jet streak wraps around the southern periphery of the primary trough. At the same time, Hurricane Francine will undergo extratropical transition across portions of the Southeast. ...FL Panhandle to the TN Valley... Thursday morning, backed surface winds and favorable hodographs for low-level rotating updrafts will be present along the Florida/Alabama coastal region. In addition, a tropical airmass with upper 70s dewpoints will support MLCAPE of 2000+ J/kg during the morning hours. South-southeasterly surface winds during the late morning will veer to south-southwesterly by the early afternoon hours which will lessen low-level shear and also lead to some dry-air advection and weaker instability during the afternoon and evening. Therefore, the primary tornado threat across the Florida Panhandle and southern Alabama should be confined to the morning hours. By early-to-mid afternoon, guidance indicates at least some clearing of cloud-cover across central Alabama which may result in some surface heating and destabilization with MLCAPE of 1000 to 1500 J/kg possible. The potential for this increase in diurnal instability may overlap the period when the most favorable wind profile also exists across the same region. This could result in a threat for a few tornadic storms across central Alabama during the mid-to-late afternoon period. ...Eastern Montana vicinity... Strong forcing will overspread eastern Montana Thursday afternoon as a mid-level shortwave trough approaches the region. A well-mixed, relatively moisture-starved airmass will exist ahead of the cold front/surface low. However, in the immediate wake of the cold front, prior to the colder surface air, better moisture will wrap around the surface low. This will lead to a narrow corridor of weak to moderate instability and the potential for scattered thunderstorms. Strong effective shear (55+ knots) will exist in this post-frontal airmass where storms are anticipated. Therefore, supercells or a few bowing segments may be possible with a threat for severe wind gusts and large hail. ..Bentley.. 09/11/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1127 AM CDT Wed Sep 11 2024 Valid 111630Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE GULF COAST... ...SUMMARY... Hurricane Francine will pose a tornado threat through tonight across the middle Gulf Coast region. ...Gulf Coast - Hurricane Francine... Hurricane Francine will continue to generally move northeastward toward the southern Louisiana coast. Reference NHC for the latest forecast track and intensity details. As Francine approaches the coast later this afternoon into evening, a considerable strengthening of east-southeasterly winds on its east-northeast periphery will lead to an increasing near-shore/inland supercell risk. This will be in tandem with a northward shift of a maritime warm front and associated moisture-rich air, which will tend to stay with about 50-75 miles within the Gulf Coast spanning southeast Louisiana to the Florida Panhandle. The supercell/tornado risk is expected to steadily increase this afternoon across southeast Louisiana, transitioning northeastward toward southeast Mississippi, southern Alabama and the Florida Panhandle into this evening and overnight, with a few tornadoes possible regionally. ...Northern Rockies and northern High Plains... High-based thunderstorms are expected to pose an isolated severe risk late this afternoon into evening, with severe-caliber wind gusts a possibility, along with some hail possible as well across the northern Rockies including parts of Idaho and western Montana. This is influenced by the lead portion of a Pacific Northwest upper-level trough, with preceding height falls and the exit region of the upper jet overspreading the northern Rockies and northern High Plains through tonight. Thunderstorms should increase in coverage/intensity by late afternoon, especially from far southeast Oregon into southern Idaho, southern Montana and northwest Wyoming. Around 250-750 J/kg MLCAPE coincident with 25-35 kt of effective shear will support clusters and bands of storms capable of hail and stronger wind gusts. Additional widely scattered storms are expected across the northern High Plains within a modestly moist environment. Dry sub-cloud layers will support the potential for stronger downdrafts and the possibility of some severe-caliber wind gusts. ..Guyer/Jirak.. 09/11/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1127 AM CDT Wed Sep 11 2024 Valid 111630Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE GULF COAST... ...SUMMARY... Hurricane Francine will pose a tornado threat through tonight across the middle Gulf Coast region. ...Gulf Coast - Hurricane Francine... Hurricane Francine will continue to generally move northeastward toward the southern Louisiana coast. Reference NHC for the latest forecast track and intensity details. As Francine approaches the coast later this afternoon into evening, a considerable strengthening of east-southeasterly winds on its east-northeast periphery will lead to an increasing near-shore/inland supercell risk. This will be in tandem with a northward shift of a maritime warm front and associated moisture-rich air, which will tend to stay with about 50-75 miles within the Gulf Coast spanning southeast Louisiana to the Florida Panhandle. The supercell/tornado risk is expected to steadily increase this afternoon across southeast Louisiana, transitioning northeastward toward southeast Mississippi, southern Alabama and the Florida Panhandle into this evening and overnight, with a few tornadoes possible regionally. ...Northern Rockies and northern High Plains... High-based thunderstorms are expected to pose an isolated severe risk late this afternoon into evening, with severe-caliber wind gusts a possibility, along with some hail possible as well across the northern Rockies including parts of Idaho and western Montana. This is influenced by the lead portion of a Pacific Northwest upper-level trough, with preceding height falls and the exit region of the upper jet overspreading the northern Rockies and northern High Plains through tonight. Thunderstorms should increase in coverage/intensity by late afternoon, especially from far southeast Oregon into southern Idaho, southern Montana and northwest Wyoming. Around 250-750 J/kg MLCAPE coincident with 25-35 kt of effective shear will support clusters and bands of storms capable of hail and stronger wind gusts. Additional widely scattered storms are expected across the northern High Plains within a modestly moist environment. Dry sub-cloud layers will support the potential for stronger downdrafts and the possibility of some severe-caliber wind gusts. ..Guyer/Jirak.. 09/11/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1053 AM CDT Wed Sep 11 2024 Valid 111700Z - 121200Z ...CRITICAL FIRE WEATHER AREA FOR THE GREAT BASIN... No changes needed to the ongoing forecast. ..Wendt.. 09/11/2024 .PREV DISCUSSION... /ISSUED 0203 AM CDT Wed Sep 11 2024/ ...Synopsis... A strong upper-level trough over the western US is forecast to continue intensifying as it moves over the Northwest and northern Great Basin today and tonight. Mid-level flow over much of the West will increase as an attendant mid-level jet approaches. A surface low will deepen over the northern Great Basin, while a cold front moves in from the northwest. To the east, 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 concern today and tonight. ...Great Basin and Northwest... Ahead of the deepening trough, a potent mid-level jet streak will overspread the western Great Basin through tonight. A surface low over eastern NV will quickly deepen, supporting 20-25 mph winds over much of the Great Basin and Intermountain West. Widespread critical fire-weather conditions are likely over parts of the Great Basin. Augmented by downslope flow off the Sierra Front and the approaching cold front, a brief period of winds of 25-30+ mph will be possible, along with localized extremely critical fire-weather conditions. Fire-weather concerns should diminish behind the front, as cooler and more quiescent conditions are expected behind the front into early D2/Thursday. Across parts of the Northwest, strong lift from the trough and deepening moisture behind the cold front will promote scattered thunderstorms. Lightning may interact with areas of somewhat drier fuels over parts of the Northwest and northern Rockies despite higher RH. A few drier strikes will remain possible, but overall lightning concerns should be limited by the potential for wetting rainfall. ...Lee of the Rockies and High Plains... With the upper trough intensifying to the west, height falls and stronger flow aloft will overspread the Rockies and High Plains today and continuing into D2/Thursday. A surface low will quickly deepen 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 to near-critical fire weather concerns are expected over parts of the High Plains through this evening. A few high-based thunderstorms may also support gusty outflow winds across the central High Plains and Front range. Fire-weather concerns may continue overnight as a pronounced low-level jet supports southerly gusts to 25 mph amid only modest humidity recovery. ...Mid South... As Francine approaches the Gulf Coast today and tonight, offshore winds will increase over parts of the lower MS Valley and Mid South. Humidity values will not be overly low with the tropical air mass approaching. However, strong gusts are expected to overlap with areas of relatively dry fuels and little recent rainfall. Brief elevated fire-weather conditions are possible over parts of MS and northern LA before rain chances increase into early D2/Thursday. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Wed Sep 11 13:48:01 UTC 2024.

MD 2051 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR SOUTHEASTERN LOUISIANA COASTAL AREAS
Mesoscale Discussion 2051 NWS Storm Prediction Center Norman OK 0750 AM CDT Wed Sep 11 2024 Areas affected...southeastern Louisiana coastal areas Concerning...Severe potential...Watch possible Valid 111250Z - 111615Z Probability of Watch Issuance...60 percent SUMMARY...The risk for occasional tornadoes may begin to increase near southeastern Louisiana coastal areas by late morning (10 AM-Noon). Trends are being monitored for the possibility of a tornado watch. DISCUSSION...The center of Francine has been migrating across and northeast of the Gunnison Oil Platform vicinity of the northwestern Gulf of Mexico during the past hour or so, and is still roughly 170 miles from its forecast south central Louisiana coastal landfall later today. However, the leading edge of a broader convective precipitation shield preceding Francine is beginning to overspread coastal areas, accompanied by saturating thermodynamic profiles with lapse rates trending moist adiabatic in mid-levels. In the wake of this regime, and with the continued approach of Francine, model forecast soundings suggest that a subtle increase in boundary-layer temperatures and dew points may contribute to modest destabilization by midday along coastal areas from west of Boothville into the Vermilion Bay vicinity. It appears that this will coincide with more notable strengthening of low-level wind fields, which are forecast to contribute to enlarging low-level hodographs increasingly supportive of convection with embedded low-level mesocyclones potentially capable of producing tornadoes. ..Kerr/Edwards.. 09/11/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LIX...LCH... LAT...LON 29459176 29519097 29258988 28839012 28759117 29189143 29459176 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0742 AM CDT Wed Sep 11 2024 Valid 111300Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN THE CENTRAL GULF COAST VICINITY... ...SUMMARY... Hurricane Francine poses a tornado threat today and tonight in the central Gulf Coast vicinity. ...Synopsis... The midlatitude westerly belt will amplify somewhat in mid/upper levels, related somewhat to general height rises over the mid/upper Mississippi Valley, Great Lakes and Northeast. However, the main influence will be troughing related to a cyclone now closing off, just offshore from the Pacific Northwest Coast. The trough will move inland today and cross the interior Northwest, reaching an axis from southern BC across eastern parts of WA/OR to the Sierra south of RNO by 00Z. By 12Z, the trough should extend from the southernmost Canadian Rockies, across westernmost MT, through a 500-mb low over eastern ID, to near LAS, with associated cyclonic flow covering most of the CONUS west of 100W and north of 35N. Farther southeast, moisture-channel imagery indicates that a weak, cut-off, 500-mb low analyzed last night at 00Z over north-central TX has moved little since. However, the low is expected to drift/ redevelop northeastward through the period, reaching southeastern OK by 12Z tomorrow. In response, and as forecast by NHC, Hurricane Francine should move inland tonight across southeastern LA, and into southwestern MS before daybreak tomorrow. At the surface, 11Z analysis showed a quasistationary front from northern FL across the shelf waters of the FL Panhandle/AL/MS, becoming a diffuse warm front over the Mississippi River mouth and southern Terrebonne Parish, then just offshore again around the northern/northwestern rim of Francine's circulation. This boundary should move slowly northward/inland over the north-central Gulf Coast through the period, with the decaying center of Francine likely catching the front inland tonight. Elsewhere, a lee trough, with several weak lows attached, was drawn over eastern portions of MT/WY/CO, and should strengthen today amidst peripheral mass response to the major mid/upper trough moving into the northwestern CONUS. ...Gulf Coast: Hurricane Francine... Increasing southwesterly deep shear on the cyclone as a whole is expected, contributing to greater asymmetry in the overall precip/ convective pattern, with increasing supercell/tornado potential today northeast through east of center. The threat is expected to ramp up through the remainder of the morning, from south to north and west to east along the coast, with the greatest potential still appearing to be this afternoon into early evening, near and south of the I-10/I-12 corridor from southeastern LA eastward toward MOB, then overnight, spreading eastward into some of the western FL Panhandle. This should occur as: 1. Destabilization spreads somewhat inland -- both from theta-e advection along and south of the warm front, and weak diurnal heating; 2. Relatively large low-level hodographs spread over the region along and south of the warm front -- in the outer parts of the closed TC circulation; and 3. Both the greater instability and shear spread into a regime of developing, discrete to semi-discrete convection in bands that can organize to supercells. Overland penetration of the most favorable parameter space will occur overnight, but should be restricted in extent and magnitude by abundant inland precip and associated stability, as well as nocturnal/diabatically driven stability inland. See SPC Mesoscale Discussion 2051 for near-term assessments. Refer to NHC advisories for forecast track, intensity and tropical watch/ warning information on Francine. ...Northern Rockies to northern High Plains... Two main regimes are expected to contribute to high-based thunderstorms, atop well-mixed subcloud layers, with marginal hail/wind potential (western lobe) and mainly strong/isolated severe gusts (eastern lobe) in the outlook area, with a relative minimum but non-zero potential for a severe gust in between. In the western lobe, scattered afternoon thunderstorms in bands and clusters should develop as low/middle-level destabilization, combined with modest but adequate moisture, weakens MLCINH and strengthens buoyancy. Cooling aloft related to increasing large- scale lift from DCVA, and in the left-exit region of cyclonically curved upper-jet segment, will overlie surface heating to steepen tropospheric lapse rates, with pockets of 250-750 J/kg peak/ preconvective MLCAPE expected to develop. Though north of the strongest deep shear, the area still will lie under strong difluence aloft, and 25-35-kt effective-shear magnitudes contributing to some organization. Farther east over the northern High Plains, marginal low-level moisture, recycled from the last continental/polar air intrusion, will keep moisture weak (with post-mixing surface dewpoints in the 40s to low 50s F), yet still just enough to support isolated to widely scattered thunderstorms this afternoon into early evening. Activity may be relatively maximized near the intensifying lee trough, where low-level mass convergence and strong diurnal heating will combine to eradicate CINH. Deep subcloud layers with steep lapse rates will support downdraft accelerations, even with modest updraft buoyancy (MLCAPE generally 500-1000 J/kg). A moist axis near and parallel to the front will yield higher CAPE, but in a more strongly capped air mass where initiation and maintenance of surface-based convection is less certain. ..Edwards/Kerr.. 09/11/2024 Read more

No Mesoscale Discussions are in effect as of Wed Sep 11 12:06:02 UTC 2024.

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0344 AM CDT Wed Sep 11 2024 Valid 141200Z - 191200Z ...DISCUSSION... Severe potential appears low during much of the period, with an area of interest on D7/Tuesday in the northern Great Plains vicinity. Guidance consensus suggests a large-scale trough should approach the West Coast by about D5/Sunday. An embedded shortwave impulse is generally projected to move northeast across the central Rockies into the northern High Plains early next week. This may yield at least a low-probability severe threat, seemingly centered on D7/Tuesday, in parts of the Dakotas to eastern MT. Typical spread for this time frame and only modest run-to-run continuity suggest predictability is too low for a 15 percent severe area. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0344 AM CDT Wed Sep 11 2024 Valid 141200Z - 191200Z ...DISCUSSION... Severe potential appears low during much of the period, with an area of interest on D7/Tuesday in the northern Great Plains vicinity. Guidance consensus suggests a large-scale trough should approach the West Coast by about D5/Sunday. An embedded shortwave impulse is generally projected to move northeast across the central Rockies into the northern High Plains early next week. This may yield at least a low-probability severe threat, seemingly centered on D7/Tuesday, in parts of the Dakotas to eastern MT. Typical spread for this time frame and only modest run-to-run continuity suggest predictability is too low for a 15 percent severe area. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 AM CDT Wed Sep 11 2024 Valid 131200Z - 141200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not yet forecast on Friday. ...AL/GA/TN vicinity... The remnants of TC Francine are expected to decay in place near the AR/TN border vicinity on Friday, with greater weakening of low-level winds relative to Thursday. Still, a belt of adequate low-level southeasterlies may persist during the morning to afternoon over a portion of the southern Appalachians towards the Lower OH Valley. A mesoscale corridor of modest low-level SRH coincident with weak surface-based instability may develop during the day. This corridor will likely be narrow, with a drier air mass/veered low-level winds to its west and cooler temps/lower mean mixing ratios to its northeast. Confidence is not great enough yet to delineate a low-probability tornado threat. ...Central Dakotas to the central High Plains... As the primary shortwave impulse and attendant surface cyclone advance north-northeast over SK to western MB, its trailing Pacific cold front should move east towards the central Dakotas to central High Plains by Friday afternoon. Boundary-layer moisture will be limited ahead of the front to the west of decaying Francine, but may be adequate for isolated to widely scattered thunderstorms near the front during the late afternoon and early evening. Mid-level winds will be strongest over ND, but largely parallel to the front and instability appears weakest here. Greater boundary-layer heating and modestly enhanced moistening should occur in the central High Plains, but neutral to weak mid-level height rises and modest deep-layer shear will be limiting factors. While locally strong gusts are possible, this threat appears insufficient for a low-probability severe highlight. ..Grams.. 09/11/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 AM CDT Wed Sep 11 2024 Valid 131200Z - 141200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not yet forecast on Friday. ...AL/GA/TN vicinity... The remnants of TC Francine are expected to decay in place near the AR/TN border vicinity on Friday, with greater weakening of low-level winds relative to Thursday. Still, a belt of adequate low-level southeasterlies may persist during the morning to afternoon over a portion of the southern Appalachians towards the Lower OH Valley. A mesoscale corridor of modest low-level SRH coincident with weak surface-based instability may develop during the day. This corridor will likely be narrow, with a drier air mass/veered low-level winds to its west and cooler temps/lower mean mixing ratios to its northeast. Confidence is not great enough yet to delineate a low-probability tornado threat. ...Central Dakotas to the central High Plains... As the primary shortwave impulse and attendant surface cyclone advance north-northeast over SK to western MB, its trailing Pacific cold front should move east towards the central Dakotas to central High Plains by Friday afternoon. Boundary-layer moisture will be limited ahead of the front to the west of decaying Francine, but may be adequate for isolated to widely scattered thunderstorms near the front during the late afternoon and early evening. Mid-level winds will be strongest over ND, but largely parallel to the front and instability appears weakest here. Greater boundary-layer heating and modestly enhanced moistening should occur in the central High Plains, but neutral to weak mid-level height rises and modest deep-layer shear will be limiting factors. While locally strong gusts are possible, this threat appears insufficient for a low-probability severe highlight. ..Grams.. 09/11/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0205 AM CDT Wed Sep 11 2024 Valid 121200Z - 131200Z ...CRITICAL FIRE WEATHER AREA FOR MUCH OF THE CENTRAL HIGH PLAINS.... ...Synopsis... Mid-level troughing will continue to intensify as it crosses the Intermountain West and overspreads the northern/central Rockies Thursday. Strong flow aloft will approach the central High Plains as a lee low quickly deepens. A surface lee trough will trail south from the developing low, enhancing southerly winds over much of the Plains. With dry conditions in place, critical fire-weather concerns are likely. ...Central High Plains... Southerly surface winds will begin to increase overnight D1/Wednesday and into early D2/Thursday as upper-level forcing approaches from the west. Winds should continue to intensify through the day as the lee trough/low deepen considerably. South/southwesterly gusts of 20-30 mph are possible along with RH values below 25%. RH will be less favorable farther east, though winds will still be strong. Area fine fuels are dry, but should dry further over the next 24-36 hours, reaching critical levels. With the potent combination of strong winds and low RH likely over several hours D2/Thursday, widespread elevated to critical fire-weather conditions are likely. ...Intermountain West... Across parts of western CO/WY, strong southwesterly winds are expected ahead of the cold front moving out of the eastern Great Basin. Aided by the strong flow aloft, wind gusts of 25-30 mph are likely. Dry southwesterly flow and warm temperatures will support afternoon RH values below 20%. Meteorological conditions are quite conducive to fire spread. However, area fuels are much less favorable after recent rainfall. Given the magnitude of the wind and relatively dry conditions, several hours of elevated to near-critical fire-weather conditions still appear likely before the front passes through. ..Lyons.. 09/11/2024 ...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 0203 AM CDT Wed Sep 11 2024 Valid 111200Z - 121200Z ...CRITICAL FIRE WEATHER AREA FOR THE GREAT BASIN... ...Synopsis... A strong upper-level trough over the western US is forecast to continue intensifying as it moves over the Northwest and northern Great Basin today and tonight. Mid-level flow over much of the West will increase as an attendant mid-level jet approaches. A surface low will deepen over the northern Great Basin, while a cold front moves in from the northwest. To the east, 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 concern today and tonight. ...Great Basin and Northwest... Ahead of the deepening trough, a potent mid-level jet streak will overspread the western Great Basin through tonight. A surface low over eastern NV will quickly deepen, supporting 20-25 mph winds over much of the Great Basin and Intermountain West. Widespread critical fire-weather conditions are likely over parts of the Great Basin. Augmented by downslope flow off the Sierra Front and the approaching cold front, a brief period of winds of 25-30+ mph will be possible, along with localized extremely critical fire-weather conditions. Fire-weather concerns should diminish behind the front, as cooler and more quiescent conditions are expected behind the front into early D2/Thursday. Across parts of the Northwest, strong lift from the trough and deepening moisture behind the cold front will promote scattered thunderstorms. Lightning may interact with areas of somewhat drier fuels over parts of the Northwest and northern Rockies despite higher RH. A few drier strikes will remain possible, but overall lightning concerns should be limited by the potential for wetting rainfall. ...Lee of the Rockies and High Plains... With the upper trough intensifying to the west, height falls and stronger flow aloft will overspread the Rockies and High Plains today and continuing into D2/Thursday. A surface low will quickly deepen 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 to near-critical fire weather concerns are expected over parts of the High Plains through this evening. A few high-based thunderstorms may also support gusty outflow winds across the central High Plains and Front range. Fire-weather concerns may continue overnight as a pronounced low-level jet supports southerly gusts to 25 mph amid only modest humidity recovery. ...Mid South... As Francine approaches the Gulf Coast today and tonight, offshore winds will increase over parts of the lower MS Valley and Mid South. Humidity values will not be overly low with the tropical air mass approaching. However, strong gusts are expected to overlap with areas of relatively dry fuels and little recent rainfall. Brief elevated fire-weather conditions are possible over parts of MS and northern LA before rain chances increase into early D2/Thursday. ..Lyons.. 09/11/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more