SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Tue Sep 24 2024 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST ALABAMA INTO THE WESTERN FLORIDA PANHANDLE...AND ACROSS MUCH OF THE FLORIDA PENINSULA... ...SUMMARY... Isolated severe thunderstorms capable of damaging gusts and/or brief tornadoes are possible from southeast Alabama into the western Florida Panhandle, and across much of the Florida Peninsula. ...Synopsis... An amplified upper pattern, featuring a ridge extended from northern Mexico through the northern High Plains and a trough extended from Ontario into the Lower MS Valley, will cover the CONUS early Wednesday. Bifurcation of the upper trough is anticipated throughout the period, with a northern shortwave trough remaining progressive as it moves across eastern Ontario into southern Quebec, and a southern upper low stalling over the Mid-South vicinity. The stalling of the southern upper low will occur as subtropical ridging builds across the western Atlantic and a tropical cyclone enters the eastern Gulf of Mexico. Latest forecast guidance from NHC for this tropical cyclone, which was recently upgraded to Tropical Storm Helene, suggests the storm will reach hurricane strength during the day Wednesday, with additional strengthening to major hurricane strength by early Thursday morning. Farther west, a progressive shortwave trough is forecast to move quickly across southern British Columbia and the Pacific Northwest, ending the period over the northern Rockies. At the surface, a weak front will likely extend from a low over the Lake Huron vicinity southward through middle TN before arcing more southwestward to another low in southeast TX. Western portion of this front over TX and LA is forecast to remain progressive, pushing southeastward to the western Gulf Coast by Wednesday evening. Eastern portion of the front will stall, maintaining a more north-south orientation from northern AL through southern Lower MI. ...Upper OH Valley through the southern Appalachians into AL, GA, and FL Panhandle Wednesday morning into the evening... A belt of enhanced southwesterly flow aloft is forecast to extend through the eastern periphery of the upper low developing over the Mid-South from the FL Panhandle northward into the Upper OH Valley. Widespread showers and thunderstorms are anticipated within this warm conveyor, reaching as far north as western A. However, poor lapse rates and limited destabilization should mitigate the overall severe potential across the majority of this region. An area of locally higher severe potential is anticipated within a spatially constrained corridor from southeast AL into far southwest GA and the western FL Panhandle, just west of the primary axis of precipitation anticipated within the warm conveyor. Here, a mix of low 70s dewpoints, modest heating, and moderate mid-level flow could result in a few thunderstorms capable of damaging gusts and/or a brief tornado or two. ...Much of the FL Peninsula... Rainbands associated with tropical cyclone Helene are forecast to move across the FL Peninsula throughout the period. At the same time, low to mid-level flow attendant to the cyclone will increase as the cyclone and its expansive wind field spread northward. As a result, vertical shear will be strong enough to support organized storm structure. Primary mitigating factor is warm, poor lapse rate profiles that limit buoyancy. Brief tornadoes will be possible within any updrafts that are able to mature/persist. ..Mosier.. 09/24/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Tue Sep 24 2024 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST ALABAMA INTO THE WESTERN FLORIDA PANHANDLE...AND ACROSS MUCH OF THE FLORIDA PENINSULA... ...SUMMARY... Isolated severe thunderstorms capable of damaging gusts and/or brief tornadoes are possible from southeast Alabama into the western Florida Panhandle, and across much of the Florida Peninsula. ...Synopsis... An amplified upper pattern, featuring a ridge extended from northern Mexico through the northern High Plains and a trough extended from Ontario into the Lower MS Valley, will cover the CONUS early Wednesday. Bifurcation of the upper trough is anticipated throughout the period, with a northern shortwave trough remaining progressive as it moves across eastern Ontario into southern Quebec, and a southern upper low stalling over the Mid-South vicinity. The stalling of the southern upper low will occur as subtropical ridging builds across the western Atlantic and a tropical cyclone enters the eastern Gulf of Mexico. Latest forecast guidance from NHC for this tropical cyclone, which was recently upgraded to Tropical Storm Helene, suggests the storm will reach hurricane strength during the day Wednesday, with additional strengthening to major hurricane strength by early Thursday morning. Farther west, a progressive shortwave trough is forecast to move quickly across southern British Columbia and the Pacific Northwest, ending the period over the northern Rockies. At the surface, a weak front will likely extend from a low over the Lake Huron vicinity southward through middle TN before arcing more southwestward to another low in southeast TX. Western portion of this front over TX and LA is forecast to remain progressive, pushing southeastward to the western Gulf Coast by Wednesday evening. Eastern portion of the front will stall, maintaining a more north-south orientation from northern AL through southern Lower MI. ...Upper OH Valley through the southern Appalachians into AL, GA, and FL Panhandle Wednesday morning into the evening... A belt of enhanced southwesterly flow aloft is forecast to extend through the eastern periphery of the upper low developing over the Mid-South from the FL Panhandle northward into the Upper OH Valley. Widespread showers and thunderstorms are anticipated within this warm conveyor, reaching as far north as western A. However, poor lapse rates and limited destabilization should mitigate the overall severe potential across the majority of this region. An area of locally higher severe potential is anticipated within a spatially constrained corridor from southeast AL into far southwest GA and the western FL Panhandle, just west of the primary axis of precipitation anticipated within the warm conveyor. Here, a mix of low 70s dewpoints, modest heating, and moderate mid-level flow could result in a few thunderstorms capable of damaging gusts and/or a brief tornado or two. ...Much of the FL Peninsula... Rainbands associated with tropical cyclone Helene are forecast to move across the FL Peninsula throughout the period. At the same time, low to mid-level flow attendant to the cyclone will increase as the cyclone and its expansive wind field spread northward. As a result, vertical shear will be strong enough to support organized storm structure. Primary mitigating factor is warm, poor lapse rate profiles that limit buoyancy. Brief tornadoes will be possible within any updrafts that are able to mature/persist. ..Mosier.. 09/24/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1147 AM CDT Tue Sep 24 2024 Valid 241700Z - 251200Z ...NO CRITICAL AREAS... No changes. See previous discussion below. ..Bentley.. 09/24/2024 .PREV DISCUSSION... /ISSUED 0153 AM CDT Tue Sep 24 2024/ ...Synopsis... Fire weather concerns will remain low today across the CONUS. A ridge will build in across the western US, with dry and warming conditions amid generally light winds. Longwave troughing will deepen across the Plains, with some post-frontal northwesterly breezes across the High Plains. Overall, cool conditions will keep relative humidity values high and there is potential for wetting rainfall. ...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 1147 AM CDT Tue Sep 24 2024 Valid 241700Z - 251200Z ...NO CRITICAL AREAS... No changes. See previous discussion below. ..Bentley.. 09/24/2024 .PREV DISCUSSION... /ISSUED 0153 AM CDT Tue Sep 24 2024/ ...Synopsis... Fire weather concerns will remain low today across the CONUS. A ridge will build in across the western US, with dry and warming conditions amid generally light winds. Longwave troughing will deepen across the Plains, with some post-frontal northwesterly breezes across the High Plains. Overall, cool conditions will keep relative humidity values high and there is potential for wetting rainfall. ...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 1145 AM CDT Tue Sep 24 2024 Valid 241630Z - 251200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF TN/KY/OH/WV AND CENTRAL OK... ...SUMMARY... Isolated to scattered severe thunderstorms are possible mainly this afternoon across portions of the Ohio and Tennessee Valleys into the central/southern Appalachians. Severe storms will also be possible across portions of Oklahoma. ...Ohio and Tennessee Valleys to southern Appalachians... Have spatially adjusted/expanded the Slight Risk based on observational trends and somewhat stronger destabilization across areas such as northern/middle Tennessee. Water-vapor imagery shows a mid-level vorticity maximum moving across the middle Mississippi Valley and into the Ohio Valley. A belt of moderate to strong southwesterly 500-mb flow (25-50 kt) will overspread Kentucky and the surrounding states. A surface low will migrate east-northeast into southern Lower Michigan by early evening, where isolated severe storms are possible, with a frontal zone extending south-southwest from this low into the Mid South. In the wake of early morning convection, modest cloud breaks/destabilization is forecast with upwards of 750-2000 J/kg MLCAPE from the southern Great Lakes into the southern Appalachians, with the strongest destabilization expected across Tennessee into southern Kentucky and possibly the western Carolinas pending the timing/abatement of lingering cloud cover. Regionally, ample deep-layer speed shear will aid in storm organization into organized multicells and probably several supercells. Damaging winds will be the most common hazard, but isolated large hail will be possible, and some tornado risk may exist as well. ...Oklahoma/North Texas... Have upgraded portions of central Oklahoma for what is expected to be a semi-focused regional corridor of large hail potential late this afternoon and early evening. The region will be influenced by the immediate backside of a southeastward-moving upper-level trough centered over the Lower Missouri Valley. A considerably strengthening cyclonically curved belt of westerlies aloft will influence Oklahoma, overspreading a relatively moist air mass, with lower to some middle 60s F surface dewpoints likely to persist through the diurnal heating/mixing cycle. Near a deepening surface low and nearby triple point/warm front, at least isolated storms are expected to develop as early as mid-afternoon (3-4pm), becoming more probable with a greater coverage through sunset. Overall buoyancy will not be robust, with MLCAPE generally not expected to exceed 1000 J/kg later this afternoon. However, this buoyancy, along with steep lapse rates and robustly vertically veering wind profiles, accentuated by 35-45 kt northwesterly mid/upper-level flow, should support initial supercells capable of large hail (potentially golfball size), along with some potential for damaging wind gusts. These storms will persist generally southeastward through the evening into southern/southeast Oklahoma, and probably north Texas overnight. Overall intensity will tend to wane nocturnally after sunset, but some severe hail/wind potential will probably linger, particularly on the west/southwest flank of any evolving clusters of storms, which will be increasingly elevated to the east of the warm front. ..Guyer/Lyons.. 09/24/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1145 AM CDT Tue Sep 24 2024 Valid 241630Z - 251200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF TN/KY/OH/WV AND CENTRAL OK... ...SUMMARY... Isolated to scattered severe thunderstorms are possible mainly this afternoon across portions of the Ohio and Tennessee Valleys into the central/southern Appalachians. Severe storms will also be possible across portions of Oklahoma. ...Ohio and Tennessee Valleys to southern Appalachians... Have spatially adjusted/expanded the Slight Risk based on observational trends and somewhat stronger destabilization across areas such as northern/middle Tennessee. Water-vapor imagery shows a mid-level vorticity maximum moving across the middle Mississippi Valley and into the Ohio Valley. A belt of moderate to strong southwesterly 500-mb flow (25-50 kt) will overspread Kentucky and the surrounding states. A surface low will migrate east-northeast into southern Lower Michigan by early evening, where isolated severe storms are possible, with a frontal zone extending south-southwest from this low into the Mid South. In the wake of early morning convection, modest cloud breaks/destabilization is forecast with upwards of 750-2000 J/kg MLCAPE from the southern Great Lakes into the southern Appalachians, with the strongest destabilization expected across Tennessee into southern Kentucky and possibly the western Carolinas pending the timing/abatement of lingering cloud cover. Regionally, ample deep-layer speed shear will aid in storm organization into organized multicells and probably several supercells. Damaging winds will be the most common hazard, but isolated large hail will be possible, and some tornado risk may exist as well. ...Oklahoma/North Texas... Have upgraded portions of central Oklahoma for what is expected to be a semi-focused regional corridor of large hail potential late this afternoon and early evening. The region will be influenced by the immediate backside of a southeastward-moving upper-level trough centered over the Lower Missouri Valley. A considerably strengthening cyclonically curved belt of westerlies aloft will influence Oklahoma, overspreading a relatively moist air mass, with lower to some middle 60s F surface dewpoints likely to persist through the diurnal heating/mixing cycle. Near a deepening surface low and nearby triple point/warm front, at least isolated storms are expected to develop as early as mid-afternoon (3-4pm), becoming more probable with a greater coverage through sunset. Overall buoyancy will not be robust, with MLCAPE generally not expected to exceed 1000 J/kg later this afternoon. However, this buoyancy, along with steep lapse rates and robustly vertically veering wind profiles, accentuated by 35-45 kt northwesterly mid/upper-level flow, should support initial supercells capable of large hail (potentially golfball size), along with some potential for damaging wind gusts. These storms will persist generally southeastward through the evening into southern/southeast Oklahoma, and probably north Texas overnight. Overall intensity will tend to wane nocturnally after sunset, but some severe hail/wind potential will probably linger, particularly on the west/southwest flank of any evolving clusters of storms, which will be increasingly elevated to the east of the warm front. ..Guyer/Lyons.. 09/24/2024 Read more

No watches are valid as of Tue Sep 24 12:54:02 UTC 2024.

No Mesoscale Discussions are in effect as of Tue Sep 24 12:54:02 UTC 2024.

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0742 AM CDT Tue Sep 24 2024 Valid 241300Z - 251200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL KENTUCKY INTO SOUTHERN OHIO AND WEST VIRGINIA... ...SUMMARY... Isolated to scattered severe thunderstorms are possible mainly this afternoon across portions of the Ohio and Tennessee Valleys into the central/southern Appalachians. A few strong/severe storms are also possible across portions of the southern Plains. ...Ohio and Tennessee Valleys to southern Appalachians... Water-vapor imagery this morning shows a mid-level vorticity maximum moving across the middle MS Valley and into the OH Valley. A belt of moderate to strong southwesterly 500-mb flow (25-50 kt) will overspread KY and the surrounding states, with the strongest flow generally within the Slight Risk bounds. Bands of showers/weak thunderstorms are ongoing this morning from middle TN into OH, and in a separate area over eastern IL immediately ahead of the surface low. This low will migrate east-northeast into southern Lower MI by early evening with a frontal zone extending south-southwest into the Mid South. In wake of the early morning convection, some cloud breaks/destabilization is forecast with upwards of 750-2000 J/kg MLCAPE from the southern Great Lakes into the southern Appalachian states. Ample deep-layer speed shear (via mostly southwesterly flow through the troposphere) will aid in storm organization into organized multicells and probably several supercells. Only notable change this outlook update was to include portions of the southern Great Lakes in low-severe probabilities for potential activity near/ahead of the surface low. The primary concern across the general region will likely be damaging winds with the stronger storms. ...OK vicinity... An amplifying large-scale trough over the MS Valley will feature a 60-kt 500mb speed max moving southward into the central Great Plains by early evening on the backside of the upper trough. Left exit region of this feature will encourage large-scale ascent, and a weak surface wave/low should evolve over southwest KS/northwest OK by early afternoon. Strong heating will contribute to 750-1250 J/kg MLCAPE by mid afternoon across OK with flow veering and strengthening with height. Elongated hodographs will support the potential for hail growth with a few of the stronger/sustained updrafts that evolve. An isolated threat for large hail (1 to 1.75 inches in diameter) and/or severe gusts (60-70 mph) will probably peak during the 23z-03z period before storms weaken during the late evening. ..Smith/Broyles.. 09/24/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0250 AM CDT Tue Sep 24 2024 Valid 271200Z - 021200Z ...DISCUSSION... A low-end tropical cyclone related tornado risk may continue into Day 4/Fri from parts of the Southeast toward the central Appalachian vicinity. However, spread among medium range guidance is quite large at this time frame regarding the position of the remnant tropical cyclone. Beyond Day 4/Fri, medium range guidance generally maintains an closed upper cyclone across the broader Mid-South and Ohio Valley vicinity through Day 6/Sun before this feature weakens and an open wave trough evolves and progresses east toward the Atlantic coast through early next week. Meanwhile, upper ridging will persist across much of the western half of the CONUS. Overall, severe potential beyond Day 4/Fri appears low given areas of widespread precipitation and cloudiness, along with limited instability and weakening deep-layer flow with time. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0250 AM CDT Tue Sep 24 2024 Valid 271200Z - 021200Z ...DISCUSSION... A low-end tropical cyclone related tornado risk may continue into Day 4/Fri from parts of the Southeast toward the central Appalachian vicinity. However, spread among medium range guidance is quite large at this time frame regarding the position of the remnant tropical cyclone. Beyond Day 4/Fri, medium range guidance generally maintains an closed upper cyclone across the broader Mid-South and Ohio Valley vicinity through Day 6/Sun before this feature weakens and an open wave trough evolves and progresses east toward the Atlantic coast through early next week. Meanwhile, upper ridging will persist across much of the western half of the CONUS. Overall, severe potential beyond Day 4/Fri appears low given areas of widespread precipitation and cloudiness, along with limited instability and weakening deep-layer flow with time. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0207 AM CDT Tue Sep 24 2024 Valid 261200Z - 271200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF NORTHERN FLORIDA INTO GEORGIA... ...SUMMARY... A tropical cyclone is forecast to move inland across northern Florida and Georgia on Thursday. A risk for tropical cyclone related tornadoes will accompany convection within the outer bands. ...FL/GA vicinity... A broad Marginal risk (level 1 of 5) has been delineated for parts of northern FL into GA as a tropical cyclone is forecast by the National Hurricane Center to move inland Thursday evening into early Friday. Southeasterly flow will increase over the region in response to the northerly moving hurricane. While exact track, size, and intensity of the storm is still somewhat uncertain, the favored eastern semi-circle of the storm should bring some risk for tornadoes to portions of the area. Forecast soundings indicated low to mid 70s F dewpoints amid strong low-level shear and sufficient instability to support rotation within low-top supercells associated with the outer bands of the tropical system. The outlook area may need to be refined in subsequent forecasts as storm track and evolution of convective bands becomes more certain, but inclusion of low-end probabilities appears prudent based on trends the past few model cycles. Reference the National Hurricane Center forecast for further details related to this potential tropical cyclone. ..Leitman.. 09/24/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0207 AM CDT Tue Sep 24 2024 Valid 261200Z - 271200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF NORTHERN FLORIDA INTO GEORGIA... ...SUMMARY... A tropical cyclone is forecast to move inland across northern Florida and Georgia on Thursday. A risk for tropical cyclone related tornadoes will accompany convection within the outer bands. ...FL/GA vicinity... A broad Marginal risk (level 1 of 5) has been delineated for parts of northern FL into GA as a tropical cyclone is forecast by the National Hurricane Center to move inland Thursday evening into early Friday. Southeasterly flow will increase over the region in response to the northerly moving hurricane. While exact track, size, and intensity of the storm is still somewhat uncertain, the favored eastern semi-circle of the storm should bring some risk for tornadoes to portions of the area. Forecast soundings indicated low to mid 70s F dewpoints amid strong low-level shear and sufficient instability to support rotation within low-top supercells associated with the outer bands of the tropical system. The outlook area may need to be refined in subsequent forecasts as storm track and evolution of convective bands becomes more certain, but inclusion of low-end probabilities appears prudent based on trends the past few model cycles. Reference the National Hurricane Center forecast for further details related to this potential tropical cyclone. ..Leitman.. 09/24/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0155 AM CDT Tue Sep 24 2024 Valid 251200Z - 261200Z ...NO CRITICAL AREAS... ...Synopsis... A trough will transverse eastward across the northern portion of a western US ridge on Wednesday, bringing enhanced mid-level flow over the Cascades into western Washington and Oregon. Across southwestern Oregon, sustained winds around 15-20 mph will overlap relative humidity reductions to around 20-25 percent. Elevated fire weather conditions will be possible. Receptive fuels in this region are spotty, which leads to low confidence in including an area at this time. ..Thornton.. 09/24/2024 ...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 0153 AM CDT Tue Sep 24 2024 Valid 241200Z - 251200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns will remain low today across the CONUS. A ridge will build in across the western US, with dry and warming conditions amid generally light winds. Longwave troughing will deepen across the Plains, with some post-frontal northwesterly breezes across the High Plains. Overall, cool conditions will keep relative humidity values high and there is potential for wetting rainfall. ..Thornton.. 09/24/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 2099 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR KENTUCKY...FAR SOUTHEAST ILLINOIS...FAR SOUTHERN INDIANA
Mesoscale Discussion 2099 NWS Storm Prediction Center Norman OK 1256 AM CDT Tue Sep 24 2024 Areas affected...Kentucky...Far Southeast Illinois...Far Southern Indiana Concerning...Severe potential...Watch unlikely Valid 240556Z - 240830Z Probability of Watch Issuance...5 percent SUMMARY...An isolated severe threat will continue across the Ohio Valley over the next several hours. A severe wind gust, or a brief tornado will be possible. The severe threat is expected to remain marginal, and watch issuance appears unlikely. DISCUSSION...The latest water vapor imagery shows a mid-level shortwave trough moving into the Ozarks. A distinct vorticity max is evident on mosaic radar as an MCV in far southeast Missouri. Thunderstorms are ongoing from near the MCV extending northeastward into southern Illinois and southern Indiana, near a maximum in warm air advection. Surface dewpoints in the lower Ohio Valley are in the upper 60s F, and the RAP has MLCAPE up to 750 J/kg in the vicinity of Evansville, Indiana. The WSR-88D VWP at Louisville has 0-6 km shear around 45 knots, with 0-3 km storm-relative helicity around 175 m2/s2. Directional shear is confined mostly to the lowest 1 kilometer. This wind profile should be enough for transient supercell structure. Any tornado that forms would likely be brief. An isolated severe gust will also be possible, especially if any of the cells can obtain a bowing structure. ..Broyles/Smith.. 09/24/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ILN...LMK...IND...PAH... LAT...LON 38588746 37968858 37498899 37138902 36918858 36898743 36918552 37288477 38038439 38578496 38708635 38588746 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1213 AM CDT Tue Sep 24 2024 Valid 251200Z - 261200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorm potential is low on Wednesday. ...Synopsis... An upper low within the base of the larger-scale upper trough extending from the Great Lakes to the Lower MS Valley will become cut-off from northern stream flow on Wednesday. As this occurs, the northern shortwave trough will progress east across the Great Lakes and southern Ontario. The developing upper cyclone over the Mid-South/Lower MS Valley will not move much through the period. However, moderately enhanced southerly deep-layer flow on the eastern flank of the cut-off low will persist over the Southeast. Meanwhile, latest forecast guidance and NHC forecasts show a strengthening tropical cyclone emerging across the eastern Gulf of Mexico. This system is forecast to remain well offshore from the southwest FL coast through 12z Thursday. ...Southeast... A stalled surface boundary/inverted trough will extend from near coastal MS/AL northeast across the central Appalachians. Near and east of this boundary, south/southeasterly low-level flow will maintain a very moist airmass with dewpoints from the mid 60s to low 70s F. Potentially widespread convection may be ongoing Wednesday morning across portions of this area, limiting destabilization. Despite vertical shear that may otherwise support organized convection, weak instability and poor lapse rates will limit severe potential, though the strongest cells may produce locally gusty winds. Further south across the FL Peninsula, southeasterly low to midlevel flow will increase, especially after 00z, as the developing tropical cyclone emerges into the eastern Gulf. Forecast soundings show enlarged, favorably curved low-level hodographs developing late in the period. However, instability across the Peninsula is expected to remain weak through early Thursday morning. At this time, tropical cyclone related tornado potential appears limited through 12z Thursday. ...Upper OH Valley/Lower Great Lakes vicinity... A cold front will move east/southeast across the Lower Great Lakes during the afternoon and into the overnight hours. Ahead of this feature, a corridor of 60s F dewpoints will be in place. However, surface heating is expected to be muted by cloud cover and showers. As a result, instability will be weak and lapse rates will remain poor, precluding severe thunderstorm potential. ..Leitman.. 09/24/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1213 AM CDT Tue Sep 24 2024 Valid 251200Z - 261200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorm potential is low on Wednesday. ...Synopsis... An upper low within the base of the larger-scale upper trough extending from the Great Lakes to the Lower MS Valley will become cut-off from northern stream flow on Wednesday. As this occurs, the northern shortwave trough will progress east across the Great Lakes and southern Ontario. The developing upper cyclone over the Mid-South/Lower MS Valley will not move much through the period. However, moderately enhanced southerly deep-layer flow on the eastern flank of the cut-off low will persist over the Southeast. Meanwhile, latest forecast guidance and NHC forecasts show a strengthening tropical cyclone emerging across the eastern Gulf of Mexico. This system is forecast to remain well offshore from the southwest FL coast through 12z Thursday. ...Southeast... A stalled surface boundary/inverted trough will extend from near coastal MS/AL northeast across the central Appalachians. Near and east of this boundary, south/southeasterly low-level flow will maintain a very moist airmass with dewpoints from the mid 60s to low 70s F. Potentially widespread convection may be ongoing Wednesday morning across portions of this area, limiting destabilization. Despite vertical shear that may otherwise support organized convection, weak instability and poor lapse rates will limit severe potential, though the strongest cells may produce locally gusty winds. Further south across the FL Peninsula, southeasterly low to midlevel flow will increase, especially after 00z, as the developing tropical cyclone emerges into the eastern Gulf. Forecast soundings show enlarged, favorably curved low-level hodographs developing late in the period. However, instability across the Peninsula is expected to remain weak through early Thursday morning. At this time, tropical cyclone related tornado potential appears limited through 12z Thursday. ...Upper OH Valley/Lower Great Lakes vicinity... A cold front will move east/southeast across the Lower Great Lakes during the afternoon and into the overnight hours. Ahead of this feature, a corridor of 60s F dewpoints will be in place. However, surface heating is expected to be muted by cloud cover and showers. As a result, instability will be weak and lapse rates will remain poor, precluding severe thunderstorm potential. ..Leitman.. 09/24/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1232 AM CDT Tue Sep 24 2024 Valid 241200Z - 251200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE TENNESSEE AND OHIO VALLEYS INTO THE SOUTHERN APPALACHIANS. A FEW STRONG/SEVERE STORMS ARE ALSO POSSIBLE OVER THE SOUTHERN PLAINS.... ...SUMMARY... Isolated to scattered severe thunderstorms are possible today across portions of the Ohio and Tennessee Valleys into the central/southern Appalachians. A few strong/severe storms are also possible across portions of the southern Plains. ...Ohio and Tennessee Valleys to southern Appalachians... Positive-tilt short-wave trough is ejecting east across the mid MS Valley early this morning. This feature is gradually deamplifying as it's kicked downstream in advance of an upstream short-wave trough that's digging across the Plains. As a result, 500mb flow should increase across the TN/OH Valley region, and high-level flow will become increasingly diffluent. Early this morning, an elongated corridor of convection continues ahead of this feature, extending from southwest IN into southeast MO. Some form of this activity will likely be ongoing at the start of the period, immediately ahead of the front. While the early-day convection should not be particularly robust, boundary-layer heating should aid destabilization, especially south of the OH River where 0-3km lapse rates should steepen by 18z allowing MLCAPE values to increase to 1000-2000 J/kg. While deep-layer flow will be decidedly southwesterly, effective shear will be more than adequate for sustaining longer-lived clusters and even a few supercells. Forecast soundings suggest convection should develop fairly early in the period as mid-level lapse rates are poor, but convective temperatures will be breached quickly with temperatures rising through the 70s to near 80F. Primary concern with these storms will be damaging winds. ...Southern Plains... Upper ridge is forecast to build east into the Rockies during the day1 period, but this will allow a strong upper trough to dig south-southeast across the Plains as a 500mb speed max translates down the back side into western KS by 25/00z. Left exit region of this feature will encourage large-scale ascent, and a weak surface wave/low should evolve over southwest KS/northwest OK by early afternoon. This evolution will result in strong boundary-layer heating across the TX South Plains into northwest OK. Forecast soundings suggest 0-3km lapse rates will approach dry adiabatic by 21z, and convective temperatures will be breached in the upper 80s to near 90F. While LLJ is not expected to be particularly noteworthy, profiles across northwest into central OK will favor supercells as low-level flow will be decidedly southeasterly through 1km, and effective shear will be strong (50kt). Additionally, MLCAPE values in excess of 1000 J/kg should support robust updrafts. Will introduce low severe probabilities for hail/wind for supercells that evolve during the mid-late afternoon. This activity will spread south-southeast during the evening hours in advance of the digging short wave. Will continue to monitor this region, but at this time coverage of severe may not warrant higher probabilities. ..Darrow/Thornton.. 09/24/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1232 AM CDT Tue Sep 24 2024 Valid 241200Z - 251200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE TENNESSEE AND OHIO VALLEYS INTO THE SOUTHERN APPALACHIANS. A FEW STRONG/SEVERE STORMS ARE ALSO POSSIBLE OVER THE SOUTHERN PLAINS.... ...SUMMARY... Isolated to scattered severe thunderstorms are possible today across portions of the Ohio and Tennessee Valleys into the central/southern Appalachians. A few strong/severe storms are also possible across portions of the southern Plains. ...Ohio and Tennessee Valleys to southern Appalachians... Positive-tilt short-wave trough is ejecting east across the mid MS Valley early this morning. This feature is gradually deamplifying as it's kicked downstream in advance of an upstream short-wave trough that's digging across the Plains. As a result, 500mb flow should increase across the TN/OH Valley region, and high-level flow will become increasingly diffluent. Early this morning, an elongated corridor of convection continues ahead of this feature, extending from southwest IN into southeast MO. Some form of this activity will likely be ongoing at the start of the period, immediately ahead of the front. While the early-day convection should not be particularly robust, boundary-layer heating should aid destabilization, especially south of the OH River where 0-3km lapse rates should steepen by 18z allowing MLCAPE values to increase to 1000-2000 J/kg. While deep-layer flow will be decidedly southwesterly, effective shear will be more than adequate for sustaining longer-lived clusters and even a few supercells. Forecast soundings suggest convection should develop fairly early in the period as mid-level lapse rates are poor, but convective temperatures will be breached quickly with temperatures rising through the 70s to near 80F. Primary concern with these storms will be damaging winds. ...Southern Plains... Upper ridge is forecast to build east into the Rockies during the day1 period, but this will allow a strong upper trough to dig south-southeast across the Plains as a 500mb speed max translates down the back side into western KS by 25/00z. Left exit region of this feature will encourage large-scale ascent, and a weak surface wave/low should evolve over southwest KS/northwest OK by early afternoon. This evolution will result in strong boundary-layer heating across the TX South Plains into northwest OK. Forecast soundings suggest 0-3km lapse rates will approach dry adiabatic by 21z, and convective temperatures will be breached in the upper 80s to near 90F. While LLJ is not expected to be particularly noteworthy, profiles across northwest into central OK will favor supercells as low-level flow will be decidedly southeasterly through 1km, and effective shear will be strong (50kt). Additionally, MLCAPE values in excess of 1000 J/kg should support robust updrafts. Will introduce low severe probabilities for hail/wind for supercells that evolve during the mid-late afternoon. This activity will spread south-southeast during the evening hours in advance of the digging short wave. Will continue to monitor this region, but at this time coverage of severe may not warrant higher probabilities. ..Darrow/Thornton.. 09/24/2024 Read more