SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Sat Sep 07 2024 Valid 081200Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible on Sunday in parts of the Southeast, western states and Great Lakes. No severe weather is expected. ...DISCUSSION... An upper-level trough will move eastward across the Ohio and Tennessee Valleys on Sunday. In the wake of the trough, northwest mid-level flow will be in place over the Great Lakes. Strong large-scale ascent and cold temperatures aloft, associated with the trough, will be favorable for isolated thunderstorms. Additional thunderstorms will be possible in the central and eastern Gulf Coast states near and to the south of a front. In the western U.S., scattered thunderstorms are expected to the west of an upper-level ridge, over much of the Intermountain West. No severe threat is expected in the U.S. on Sunday or Sunday night. ..Broyles.. 09/07/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Sat Sep 07 2024 Valid 081200Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible on Sunday in parts of the Southeast, western states and Great Lakes. No severe weather is expected. ...DISCUSSION... An upper-level trough will move eastward across the Ohio and Tennessee Valleys on Sunday. In the wake of the trough, northwest mid-level flow will be in place over the Great Lakes. Strong large-scale ascent and cold temperatures aloft, associated with the trough, will be favorable for isolated thunderstorms. Additional thunderstorms will be possible in the central and eastern Gulf Coast states near and to the south of a front. In the western U.S., scattered thunderstorms are expected to the west of an upper-level ridge, over much of the Intermountain West. No severe threat is expected in the U.S. on Sunday or Sunday night. ..Broyles.. 09/07/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1247 AM CDT Sat Sep 07 2024 Valid 071200Z - 081200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not forecast today; although, a few strong gusts could accompany the most robust convection. ...Northeast... Seasonally strong upper trough will shift across the lower Great Lakes later this afternoon, along with 60-120m, 12hr 500mb height falls. Latest guidance suggests a 70kt 500mb speed max will translate through the base of the trough across eastern PA into southern New England after 08/00z. This feature should encourage scattered convection along the synoptic front, though mid-level lapse rates are forecast to be quite weak, and this will limit buoyancy across the Hudson Valley into northern NJ. Forecast soundings ahead of the front suggest MLCAPE values will remain less than 1000 J/kg, with only modest shear in the lowest 3km. While weak frontal convection may exhibit some organization, given the large-scale support, weak lapse rates and only modest lower-tropospheric flow do not favor severe thunderstorms. ...Central High Plains... Late-evening water-vapor imagery depicts a weak, but well-defined short-wave trough over eastern MT, digging south-southeast toward the Black Hills region. This feature will ensure a focused lee trough holds across the central High Plains, and should encourage a strengthening LLJ this evening across western KS into western NE. Latest model guidance suggests strong boundary-layer heating will occur across eastern CO into the NE Panhandle. While convective temperatures should be breached by late afternoon, PW values will likely remain generally less than 1 inch across this region. Even so, forecast soundings support high-based convection that will be strongly sheared. Some consideration has been given for adding a MRGL risk to portions of the NE Panhandle into northeast CO to account for a few strong gusts, or perhaps marginally severe hail. Will continue to monitor this region. ..Darrow/Lyons.. 09/07/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1247 AM CDT Sat Sep 07 2024 Valid 071200Z - 081200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not forecast today; although, a few strong gusts could accompany the most robust convection. ...Northeast... Seasonally strong upper trough will shift across the lower Great Lakes later this afternoon, along with 60-120m, 12hr 500mb height falls. Latest guidance suggests a 70kt 500mb speed max will translate through the base of the trough across eastern PA into southern New England after 08/00z. This feature should encourage scattered convection along the synoptic front, though mid-level lapse rates are forecast to be quite weak, and this will limit buoyancy across the Hudson Valley into northern NJ. Forecast soundings ahead of the front suggest MLCAPE values will remain less than 1000 J/kg, with only modest shear in the lowest 3km. While weak frontal convection may exhibit some organization, given the large-scale support, weak lapse rates and only modest lower-tropospheric flow do not favor severe thunderstorms. ...Central High Plains... Late-evening water-vapor imagery depicts a weak, but well-defined short-wave trough over eastern MT, digging south-southeast toward the Black Hills region. This feature will ensure a focused lee trough holds across the central High Plains, and should encourage a strengthening LLJ this evening across western KS into western NE. Latest model guidance suggests strong boundary-layer heating will occur across eastern CO into the NE Panhandle. While convective temperatures should be breached by late afternoon, PW values will likely remain generally less than 1 inch across this region. Even so, forecast soundings support high-based convection that will be strongly sheared. Some consideration has been given for adding a MRGL risk to portions of the NE Panhandle into northeast CO to account for a few strong gusts, or perhaps marginally severe hail. Will continue to monitor this region. ..Darrow/Lyons.. 09/07/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0742 PM CDT Fri Sep 06 2024 Valid 070100Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe threat should be negligible the rest of tonight across the Ohio Valley. ...01z Update... Strong short-wave trough is digging southeast across the Great Lakes early this evening. Large-scale ascent is spreading downstream ahead of this feature, and this appears partly responsible for scattered convection that developed along the associated cold front that currently stretches from western NY-western PA-KY. Some of this activity was briefly severe with gusts and some hail. However, frontal convection is now spreading east of the primary instability corridor where it will quickly encounter less favorable buoyancy. Additionally, boundary-layer cooling will only lead to less instability by mid evening. While gusty winds may continue with the most robust storms for the next 1-2 hours, the overall severe threat appears too limited to warrant MRGL risk overnight. ..Darrow.. 09/07/2024 Read more

No watches are valid as of Fri Sep 6 21:32:01 UTC 2024.

No Mesoscale Discussions are in effect as of Fri Sep 6 21:32:01 UTC 2024.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0343 PM CDT Fri Sep 06 2024 Valid 081200Z - 141200Z Fire weather concerns will be focused in the Northwest and northern parts of the Great Basin this weekend into early next week. Some concerns for dry thunderstorms may also be present in the northern Great Basin into the northern Rockies this weekend as well. The greatest potential for critical fire weather currently appears to be in the Great Basin early to mid next week as a seasonably strong trough digs into the Western U.S. ...Great Basin... Fire weather concerns will begin to increase on Sunday as modest influence of the shortwave in the Northwest will increase surface winds in northern Nevada into parts of southern Idaho. A similar scenario will unfold on Monday as well. Greater fire weather concerns will develop on Tuesday into Wednesday as the stronger West Coast trough digs into the region. There will be potential for areas of critical fire weather both days. Greater probabilities may be needed depending on trends in guidance in the coming days. ...Northwest... As the shortwave trough continues slowly eastward this weekend, there will be at least low potential for isolated thunderstorms on Sunday. Confidence in coverage is too low for highlights. With the trough approaching the area, westerly winds are expected to increase on Monday. This will lead to an increase in fire weather concerns considering the ongoing fires and thunderstorm potential in preceding days. Some humidity recovery will eventually occur as marine influence will increase with time. However, at least elevated conditions can be expected east of the Cascades. ...Idaho/Southwest Montana... Isolated thunderstorms are possible on Sunday as the subtle shortwave trough moves through the area. Forecast soundings suggest mid/high-level cloud cover and there is also potential for smoke in the region given ongoing fires locally and to the west. Highlights will be withheld for now given the uncertainty in coverage. As the second trough approaches the Northwest, some subtle forcing may promote thunderstorm development in Southwest Montana on Tuesday as well. Coverage still appears too isolated for highlights. ...Central/Northern Plains... As the trough moves into the Great Basin Wednesday/Thursday, some increase in southerly winds can be expected in the Plains. While moisture return will occur, a zone of drier air will remain in portions of the central/northern Plains. Given pockets of dry fuels in eastern Kansas into Nebraska and perhaps southern South Dakota, some potential for elevated fire weather will exist as the surface low deepens and surface winds increase. Placement and strength of the surface low differs in guidance to a degree that reduces confidence below 40%. ..Wendt.. 09/06/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0343 PM CDT Fri Sep 06 2024 Valid 081200Z - 141200Z Fire weather concerns will be focused in the Northwest and northern parts of the Great Basin this weekend into early next week. Some concerns for dry thunderstorms may also be present in the northern Great Basin into the northern Rockies this weekend as well. The greatest potential for critical fire weather currently appears to be in the Great Basin early to mid next week as a seasonably strong trough digs into the Western U.S. ...Great Basin... Fire weather concerns will begin to increase on Sunday as modest influence of the shortwave in the Northwest will increase surface winds in northern Nevada into parts of southern Idaho. A similar scenario will unfold on Monday as well. Greater fire weather concerns will develop on Tuesday into Wednesday as the stronger West Coast trough digs into the region. There will be potential for areas of critical fire weather both days. Greater probabilities may be needed depending on trends in guidance in the coming days. ...Northwest... As the shortwave trough continues slowly eastward this weekend, there will be at least low potential for isolated thunderstorms on Sunday. Confidence in coverage is too low for highlights. With the trough approaching the area, westerly winds are expected to increase on Monday. This will lead to an increase in fire weather concerns considering the ongoing fires and thunderstorm potential in preceding days. Some humidity recovery will eventually occur as marine influence will increase with time. However, at least elevated conditions can be expected east of the Cascades. ...Idaho/Southwest Montana... Isolated thunderstorms are possible on Sunday as the subtle shortwave trough moves through the area. Forecast soundings suggest mid/high-level cloud cover and there is also potential for smoke in the region given ongoing fires locally and to the west. Highlights will be withheld for now given the uncertainty in coverage. As the second trough approaches the Northwest, some subtle forcing may promote thunderstorm development in Southwest Montana on Tuesday as well. Coverage still appears too isolated for highlights. ...Central/Northern Plains... As the trough moves into the Great Basin Wednesday/Thursday, some increase in southerly winds can be expected in the Plains. While moisture return will occur, a zone of drier air will remain in portions of the central/northern Plains. Given pockets of dry fuels in eastern Kansas into Nebraska and perhaps southern South Dakota, some potential for elevated fire weather will exist as the surface low deepens and surface winds increase. Placement and strength of the surface low differs in guidance to a degree that reduces confidence below 40%. ..Wendt.. 09/06/2024 ...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 0259 PM CDT Fri Sep 06 2024 Valid 062000Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM LAKE ERIE ACROSS MUCH OF OHIO AND INTO SOUTHEAST INDIANA AND NORTHERN KENTUCKY... ...SUMMARY... Strong to locally severe storms are possible this afternoon from Lake Erie across much of Ohio and into southeast Indiana and northern Kentucky. ...20Z Update... Minimal changes were made to the outlook, as the previous forecast remains on track. Along the front/wind shift in OH, a couple small, loosely organized clusters (with transient supercell characteristics) will be capable of producing strong to locally damaging wind gusts through the afternoon, aided by diurnally steepened low-level lapse rates. Isolated small to marginally severe hail will also be possible with this activity. Farther southwest into southeast IN, additional small clusters and weak/transient left-movers are evolving behind the wind shift. Here, slightly stronger deep-layer shear (per the latest IND VWP) could support sporadic hail and isolated strong to severe gusts. Overall, the severe threat still appears too marginal/localized for an upgrade. For additional details on the near-term severe risk, see MCD #2049. ..Weinman.. 09/06/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Sep 06 2024/ ...Lower Great Lakes into the OH Valley... Morning satellite imagery shows a well-defined shortwave trough moving through the Upper Midwest and into the Mid MS/Lower OH Valley. This shortwave trough is expected to continue eastward/southeastward through OH Valley during the day, progressing through the base of the parent upper trough over Ontario. Recent surface analysis places the low associated with this wave over southwestern Ontario. A cold front extends southwestward from this low across the middle/lower OH Valley and the Ozark Plateau before continuing through central and southwest OK. Low-level airmass ahead of this front across much of the OH Valley is characterized by mid 60s dewpoints. This low-level moisture is forecast to advect northeastward into the Upper OH Valley in a fairly narrow corridor ahead of the front throughout the day, although boundary-layer mixing could drop dewpoints into the upper 50s by the afternoon. This low-level moisture will help support modest buoyancy as the airmass diurnally warms, although the overall buoyancy will be limited by both the boundary-layer mixing and persistence of warm mid-level temperatures. There should still be enough buoyancy to support thunderstorm development along the front during the afternoon. The stronger mid-level flow, and resultant stronger vertical shear, will lag behind the front, while also having a more front-parallel structure. This orientation, coupled with the modest buoyancy and weak pre-frontal convergence, could result in quick undercutting of any updrafts, leading to a more anafrontal character to the storms. Even so, isolated thunderstorms may remain in the warm sector long enough to produce a few damaging gusts. Isolated hail is possible as well, even as storms become displaced behind the front. Activity should weaken this evening as it moves eastward out of the most favorable moisture, and into a nocturnally cooling/stabilizing boundary layer. ...Elsewhere... Isolated to widely scattered thunderstorms are possible along the front from Mid-South vicinity across AR into northwest TX. Weak buoyancy and shear should mitigate storm intensity, keeping the severe potential low. Numerous thunderstorms are anticipated from the Gulf Coast into FL, amid the tropical airmass in place. A few water-loaded downbursts capable of damaging gusts are possible, particularly across the FL Peninsula. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Fri Sep 06 2024 Valid 062000Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM LAKE ERIE ACROSS MUCH OF OHIO AND INTO SOUTHEAST INDIANA AND NORTHERN KENTUCKY... ...SUMMARY... Strong to locally severe storms are possible this afternoon from Lake Erie across much of Ohio and into southeast Indiana and northern Kentucky. ...20Z Update... Minimal changes were made to the outlook, as the previous forecast remains on track. Along the front/wind shift in OH, a couple small, loosely organized clusters (with transient supercell characteristics) will be capable of producing strong to locally damaging wind gusts through the afternoon, aided by diurnally steepened low-level lapse rates. Isolated small to marginally severe hail will also be possible with this activity. Farther southwest into southeast IN, additional small clusters and weak/transient left-movers are evolving behind the wind shift. Here, slightly stronger deep-layer shear (per the latest IND VWP) could support sporadic hail and isolated strong to severe gusts. Overall, the severe threat still appears too marginal/localized for an upgrade. For additional details on the near-term severe risk, see MCD #2049. ..Weinman.. 09/06/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Sep 06 2024/ ...Lower Great Lakes into the OH Valley... Morning satellite imagery shows a well-defined shortwave trough moving through the Upper Midwest and into the Mid MS/Lower OH Valley. This shortwave trough is expected to continue eastward/southeastward through OH Valley during the day, progressing through the base of the parent upper trough over Ontario. Recent surface analysis places the low associated with this wave over southwestern Ontario. A cold front extends southwestward from this low across the middle/lower OH Valley and the Ozark Plateau before continuing through central and southwest OK. Low-level airmass ahead of this front across much of the OH Valley is characterized by mid 60s dewpoints. This low-level moisture is forecast to advect northeastward into the Upper OH Valley in a fairly narrow corridor ahead of the front throughout the day, although boundary-layer mixing could drop dewpoints into the upper 50s by the afternoon. This low-level moisture will help support modest buoyancy as the airmass diurnally warms, although the overall buoyancy will be limited by both the boundary-layer mixing and persistence of warm mid-level temperatures. There should still be enough buoyancy to support thunderstorm development along the front during the afternoon. The stronger mid-level flow, and resultant stronger vertical shear, will lag behind the front, while also having a more front-parallel structure. This orientation, coupled with the modest buoyancy and weak pre-frontal convergence, could result in quick undercutting of any updrafts, leading to a more anafrontal character to the storms. Even so, isolated thunderstorms may remain in the warm sector long enough to produce a few damaging gusts. Isolated hail is possible as well, even as storms become displaced behind the front. Activity should weaken this evening as it moves eastward out of the most favorable moisture, and into a nocturnally cooling/stabilizing boundary layer. ...Elsewhere... Isolated to widely scattered thunderstorms are possible along the front from Mid-South vicinity across AR into northwest TX. Weak buoyancy and shear should mitigate storm intensity, keeping the severe potential low. Numerous thunderstorms are anticipated from the Gulf Coast into FL, amid the tropical airmass in place. A few water-loaded downbursts capable of damaging gusts are possible, particularly across the FL Peninsula. Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0222 PM CDT Fri Sep 06 2024 Valid 081200Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible on Sunday in parts of the Southeast, western states and Great Lakes. No severe weather is expected. ...Synopsis... A deep upper low will move northward across Quebec with a large area of cyclonic flow aloft encompassing much of the northeastern states. Meanwhile, an upper ridge will remain over much of the Rockies, with a weak shortwave trough affecting the Pacific Northwest. High pressure will provide relatively cool and stable conditions to much of the CONUS on Sunday. This high will be centered over the mid MS/Lower OH Valleys, and will shunt any appreciable moisture and instability southward over the Gulf of Mexico. However, a moist and unstable air mass will remain over the FL Peninsula, well south of the upper trough. A few daytime thunderstorms are likely there. Elsewhere, moisture beneath the upper ridge will lead to scattered daytime thunderstorms over much of the Four Corners states, with weak wind fields aloft. ..Jewell.. 09/06/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0155 PM CDT Fri Sep 06 2024 Valid 071200Z - 081200Z The forecast remains unchanged. There is potential for thunderstorms to form on the Blue Mountains and more elevated activity into eastern Washington very late in the period. Confidence in either of those scenarios is too low for highlights, however. ..Wendt.. 09/06/2024 .PREV DISCUSSION... /ISSUED 0153 AM CDT Fri Sep 06 2024/ ...Synopsis... As the weak Pacific trough continues inland, additional mid-level moisture will advect onshore over portions of the northern Sierra and Cascades through the weekend. The upper ridge will continue to slowly weaken, allowing for isolated thunderstorms over the Northwest. Thunderstorms are likely across portions of the Cascades in OR and southern WA, across the Sierra, and into portions of southern CA. Hot and well-mixed boundary-layer profiles will likely support low precipitation efficiency, especially with storm motions greater than 20 kt. Confidence in dry thunderstorm coverage is greatest across portions of the central Cascades, though drier storms will also be possible, albeit less certain, across the northern Sierra and parts of southern CA. Given the risk for lightning atop dry fuels, an IsoDryT area has been added where storm coverage and confidence in lightning atop dry fuels is highest. In addition to the risk for lightning, increasingly strong southwesterly flow aloft is expected to support gusty downslope winds over parts of northern CA and northwest NV. Gusty winds of 15-20 mph in the lee of the Sierra are likely to overlap with afternoon RH values below 20%. With receptive fuels and at least a few hours of dry and breezy conditions possible, elevated fire-weather conditions are likely. ...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 1223 PM CDT Fri Sep 06 2024 Valid 071200Z - 081200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible Saturday over parts of the Northeast and Mid Atlantic, the central Rockies/High Plains, Florida, and across parts of the Southwest. No severe weather is expected. ...Synopsis and Discussion... A deep upper low/trough will move eastward across the Great Lakes and toward the Northeast, becoming negatively tilted and resulting in substantial cooling aloft. At the surface, a cold front will extend south from a low over southern Quebec, roughly from the Hudson Valley into the Piedmont around 18Z. While dewpoints in the 60s F will exist ahead of the cold front, instability will be minimal and generally less than 500 J/kg due to a shallow/cool boundary layer. In addition, low-level shear will not be particularly strong, with modest warm advection around 850 mb. As such, severe weather is not anticipated with this system despite the strong upper trough. Elsewhere, northwest flow will exist across the central High Plains east of the upper ridge, with around 1000 J/kg MUCAPE developing. Dewpoints may struggle to reach 50 F, though isolated thunderstorms are expected with locally gusty winds or small hail over northeast CO into western NE during the late afternoon. ..Jewell.. 09/06/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1223 PM CDT Fri Sep 06 2024 Valid 071200Z - 081200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible Saturday over parts of the Northeast and Mid Atlantic, the central Rockies/High Plains, Florida, and across parts of the Southwest. No severe weather is expected. ...Synopsis and Discussion... A deep upper low/trough will move eastward across the Great Lakes and toward the Northeast, becoming negatively tilted and resulting in substantial cooling aloft. At the surface, a cold front will extend south from a low over southern Quebec, roughly from the Hudson Valley into the Piedmont around 18Z. While dewpoints in the 60s F will exist ahead of the cold front, instability will be minimal and generally less than 500 J/kg due to a shallow/cool boundary layer. In addition, low-level shear will not be particularly strong, with modest warm advection around 850 mb. As such, severe weather is not anticipated with this system despite the strong upper trough. Elsewhere, northwest flow will exist across the central High Plains east of the upper ridge, with around 1000 J/kg MUCAPE developing. Dewpoints may struggle to reach 50 F, though isolated thunderstorms are expected with locally gusty winds or small hail over northeast CO into western NE during the late afternoon. ..Jewell.. 09/06/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1127 AM CDT Fri Sep 06 2024 Valid 061630Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM LAKE ERIE ACROSS MUCH OF OHIO AND INTO SOUTHEAST INDIANA AND NORTHERN KENTUCKY... ...SUMMARY... Strong to locally severe storms are possible this afternoon from Lake Erie across much of Ohio and into southeast Indiana and northern Kentucky. ...Lower Great Lakes into the OH Valley... Morning satellite imagery shows a well-defined shortwave trough moving through the Upper Midwest and into the Mid MS/Lower OH Valley. This shortwave trough is expected to continue eastward/southeastward through OH Valley during the day, progressing through the base of the parent upper trough over Ontario. Recent surface analysis places the low associated with this wave over southwestern Ontario. A cold front extends southwestward from this low across the middle/lower OH Valley and the Ozark Plateau before continuing through central and southwest OK. Low-level airmass ahead of this front across much of the OH Valley is characterized by mid 60s dewpoints. This low-level moisture is forecast to advect northeastward into the Upper OH Valley in a fairly narrow corridor ahead of the front throughout the day, although boundary-layer mixing could drop dewpoints into the upper 50s by the afternoon. This low-level moisture will help support modest buoyancy as the airmass diurnally warms, although the overall buoyancy will be limited by both the boundary-layer mixing and persistence of warm mid-level temperatures. There should still be enough buoyancy to support thunderstorm development along the front during the afternoon. The stronger mid-level flow, and resultant stronger vertical shear, will lag behind the front, while also having a more front-parallel structure. This orientation, coupled with the modest buoyancy and weak pre-frontal convergence, could result in quick undercutting of any updrafts, leading to a more anafrontal character to the storms. Even so, isolated thunderstorms may remain in the warm sector long enough to produce a few damaging gusts. Isolated hail is possible as well, even as storms become displaced behind the front. Activity should weaken this evening as it moves eastward out of the most favorable moisture, and into a nocturnally cooling/stabilizing boundary layer. ...Elsewhere... Isolated to widely scattered thunderstorms are possible along the front from Mid-South vicinity across AR into northwest TX. Weak buoyancy and shear should mitigate storm intensity, keeping the severe potential low. Numerous thunderstorms are anticipated from the Gulf Coast into FL, amid the tropical airmass in place. A few water-loaded downbursts capable of damaging gusts are possible, particularly across the FL Peninsula. ..Mosier/Dean.. 09/06/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1127 AM CDT Fri Sep 06 2024 Valid 061700Z - 071200Z The dry thunderstorm area from the northern Sierra into the Northwest was adjusted to account for the most recent guidance. Thunderstorms also appear likely in parts of the southern Sierra, but diminishing mid/upper-level winds should keep storm motions slow and potential for greater wetting rainfall higher. ..Wendt.. 09/06/2024 .PREV DISCUSSION... /ISSUED 0151 AM CDT Fri Sep 06 2024/ ...Synopsis... Mid-level ridging centered over the Great Basin is forecast to slowly decay today as a weak upper trough approaches the Pacific Coast. Ahead of the weak trough, a modest influx of mid-level moisture and ascent will overspread the northern Sierra and southern Cascades. Adequate buoyancy will develop with daytime heating supporting isolated thunderstorms through the evening hours. Beneath the advancing mid-level moisture, dry boundary-layer profiles and storm motions of 20-25 kt will favor low to very low rainfall efficiency with these storms. With thunderstorms expected atop areas of receptive fuels, dry lightning appears probable. Additionally, strengthening southwesterly mid-level flow should enhance downslope winds and low relative humidity across northern CA into northwest NV. Areas of brief elevated fire weather conditions are possible, though the duration and coverage should remain limited. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 AM CDT Fri Sep 06 2024 Valid 061300Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF OHIO TO THE OHIO VALLEY... ...SUMMARY... Strong to locally severe storms are possible this afternoon from Lake Erie across much of Ohio to the Ohio Valley. ...Synopsis... A highly amplified mid/upper-level pattern will persist across the CONUS, but with some weakening of the western mean ridge and intensification of troughing over the Great Lakes/Ohio Valley regions. The latter will occur in relation to a synoptic-scale trough with several accompanying vorticity maxima and broad cyclonic flow -- apparent in moisture-channel imagery over much of northern ON and the Lake Superior vicinity. Phasing of accompanying shortwaves/ vorticity lobes will contribute to both amplification and wavelength shortening through the period. A closed 500-mb low should develop around 00Z near the eastern end of Upper MI, with trough near an MKG-ORD-MVN line. By 12Z, a fully developed cyclone should cover much of ON from the southern end of James Bay to Lake Erie, with 500-mb trough extending southwestward near a CVG-BNA line. Associated cyclonic flow at that time will cover most of the CONUS over and east of the mid/upper Mississippi Valley. At the surface, a cold front related to the ON trough was drawn at 11Z near a DTW-FDY-IND-ICT line. This front should proceed eastward/southeastward across the Ohio Valley, Lower Great Lakes and into the central/northern Appalachians through the period, ahead of the mid/upper trough. By 00Z, the front should extend from Lake Ontario across western parts of NY/PA to southeastern OH, northern middle to western TN, and AR, becoming diffuse amidst northeast flow on both sides over OK. Northeasterlies over the southern Plains south of the cold front will be largely in isallobaric response to a deepening surface frontal-wave low over the northwestern Gulf, initially drawn about 100 nm south of GLS, and forecast to drift erratically eastward through tonight. Strong/organized convection related to the Gulf cyclone is expected to remain over water through the period. ...OH, Ohio Valley... Damaging to isolated, marginally severe gusts, as well as marginal hail, will be possible with thunderstorms moving eastward across the outlook area today. A broken line of convection -- including widely scattered non-severe thunderstorms -- is apparent this morning from northwestern OH to western MO approximately along the low-level cold front. This activity, or succeeding/newer development after a short time gap later this morning -- should become better organized between Lake Erie and the Ohio Valley around midday as the foregoing boundary layer (and prospective inflow) destabilizes. This will occur in response to a combination of warm advection and diurnal heating/ mixing, whose mixing-related moisture-reduction effects will be counterbalanced to some extent by moist advection. Activity should move into a narrow corridor of 50s to mid 60s F surface dewpoints, combining with diurnal heating to support patchy, highly variable MLCAPE in the 500-1500 J/kg range. Substantial westerly component to prefrontal near-surface flow will limit both convergence and vertical shear, though weak MLCINH will permit frontal development/maintenance of thunderstorms, regardless. Around 30-35 kt effective-shear magnitudes will support mainly multicells, though some intermittent/transient supercell character will be possible for longer-lived, discrete cells. Activity should weaken this evening as it moves eastward out of the most favorable moisture, and into a nocturnally cooling/stabilizing boundary layer. ..Edwards/Kerr.. 09/06/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0352 AM CDT Fri Sep 06 2024 Valid 091200Z - 141200Z ...DISCUSSION... ...Monday/Day 4 to Wednesday/Day 6... An upper-level trough is forecast to move from the Northeast into the Atlantic early in the week, as a shortwave ridge moves through the Great Lakes. Another shortwave trough is forecast to move through the north-central U.S. At the surface, a large area of high pressure is forecast to remain over the eastern third of the U.S. This will likely impede moisture return over the southern U.S. through midweek. While thunderstorms will be possible near the Gulf Coast each day, deep-layer shear is forecast to be too weak for severe storms. Isolated thunderstorms may also develop each afternoon in parts of the north-central states, but limited large-scale ascent and relatively weak deep-layer shear should be unfavorable for organized storms. ...Thursday/Day 7 and Friday/Day 8... Low-level moisture is forecast to return northward into the Arklatex on Thursday, as a shortwave trough moves through the south-central U.S. Thunderstorm development, with some potentially severe, will be possible within the moist airmass from the southern Plains eastward into the lower to mid Mississippi Valley. There is considerable uncertainty concerning the timing of the shortwave trough and instability. For this reason, the area with the greatest threat is unclear at this time. On Friday, moisture advection is forecast to continue across the central U.S. as the western U.S. upper-level trough approaches the central and northern Plains. Isolated severe thunderstorms will be possible ahead of the trough in the north-central states. Uncertainty on Friday is again substantial due to the relatively wide dispersion among the model solutions. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 AM CDT Fri Sep 06 2024 Valid 081200Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible on Sunday in parts of the Southeast, western states and Great Lakes. No severe weather is expected. ...DISCUSSION... An upper-level trough is forecast to move through the Ohio and Tennessee Valleys on Sunday, as a front remains located over the central and eastern Gulf Coast states. Thunderstorms will be possible on Sunday near and to the south of the front. Thunderstorms will also be possible within southwest mid-level flow to the west of a ridge in the western U.S. Isolated thunderstorms may also occur in north-northwesterly mid-level flow over parts of the Great Lakes. No severe threat is expected across the U.S. on Sunday or Sunday night. ..Broyles.. 09/06/2024 Read more