Severe Storms

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0346 AM CDT Thu Sep 04 2025 Valid 071200Z - 121200Z ...DISCUSSION... A seasonally cool and dry continental airmass will be in place across much of the eastern US at the start of the forecast period, resulting in low severe potential. By Monday/Day-5, the surface high pressure responsible for this airmass will have begun to move east allowing return flow to become established across the Plains. At the same time, lee troughing in response to a western US longwave trough will reinforce the return flow regime. As the moisture is drawn northward into the Plains, steep lapse rates will advect out into the Plains from the higher elevations to the west. This combination of moistening low-levels and steep midlevel lapse rates will support increasing buoyancy profiles through the week. Any subtle shortwave trough that ejects out of the western trough and emerges into the central and northern Plains will have an opportunity to tap into this moist, buoyant atmosphere. The result would be at least some potential for thunderstorms, some of which could be severe. However predictability of these kinds of subtle features is too poor at these lead times to attempt to highlight favored days or corridors, thus predictability remains too low for unconditional probabilities. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0346 AM CDT Thu Sep 04 2025 Valid 071200Z - 121200Z ...DISCUSSION... A seasonally cool and dry continental airmass will be in place across much of the eastern US at the start of the forecast period, resulting in low severe potential. By Monday/Day-5, the surface high pressure responsible for this airmass will have begun to move east allowing return flow to become established across the Plains. At the same time, lee troughing in response to a western US longwave trough will reinforce the return flow regime. As the moisture is drawn northward into the Plains, steep lapse rates will advect out into the Plains from the higher elevations to the west. This combination of moistening low-levels and steep midlevel lapse rates will support increasing buoyancy profiles through the week. Any subtle shortwave trough that ejects out of the western trough and emerges into the central and northern Plains will have an opportunity to tap into this moist, buoyant atmosphere. The result would be at least some potential for thunderstorms, some of which could be severe. However predictability of these kinds of subtle features is too poor at these lead times to attempt to highlight favored days or corridors, thus predictability remains too low for unconditional probabilities. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0215 AM CDT Thu Sep 04 2025 Valid 061200Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHERN NORTH CAROLINA NORTHWARD INTO SOUTHERN PENNSYLVANIA... ...SUMMARY... Strong thunderstorms are expected from northern North Carolina into southern Pennsylvania on Saturday. The strongest storms may pose a threat for damaging winds. ... Discussion ... A surface cold front will slowly move east across the eastern US on Saturday. Along and ahead of this front, surface temperatures should warm into the upper-80Fs to low-90Fs from the Mid-Atlantic region southward into the Carolinas, with surface dewpoint temperatures in the upper-60Fs to low-70Fs. As a result a corridor of instability perhaps as great as 2000 J/kg will develop from North Carolina northward into the Mid-Atlantic area. Isolated to scattered thunderstorms should develop during the afternoon along the slow moving front across the Carolinas into the Mid Atlantic. Despite deep layer shear on the order of 40 knots and 2000 J/kg CAPE, poor mid-level lapse rates and precipitable water values around 1.75 inches should limit the overall severe threat to the potential for isolated damaging thunderstorm winds. ..Marsh.. 09/04/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0215 AM CDT Thu Sep 04 2025 Valid 061200Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHERN NORTH CAROLINA NORTHWARD INTO SOUTHERN PENNSYLVANIA... ...SUMMARY... Strong thunderstorms are expected from northern North Carolina into southern Pennsylvania on Saturday. The strongest storms may pose a threat for damaging winds. ... Discussion ... A surface cold front will slowly move east across the eastern US on Saturday. Along and ahead of this front, surface temperatures should warm into the upper-80Fs to low-90Fs from the Mid-Atlantic region southward into the Carolinas, with surface dewpoint temperatures in the upper-60Fs to low-70Fs. As a result a corridor of instability perhaps as great as 2000 J/kg will develop from North Carolina northward into the Mid-Atlantic area. Isolated to scattered thunderstorms should develop during the afternoon along the slow moving front across the Carolinas into the Mid Atlantic. Despite deep layer shear on the order of 40 knots and 2000 J/kg CAPE, poor mid-level lapse rates and precipitable water values around 1.75 inches should limit the overall severe threat to the potential for isolated damaging thunderstorm winds. ..Marsh.. 09/04/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0215 AM CDT Thu Sep 04 2025 Valid 061200Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHERN NORTH CAROLINA NORTHWARD INTO SOUTHERN PENNSYLVANIA... ...SUMMARY... Strong thunderstorms are expected from northern North Carolina into southern Pennsylvania on Saturday. The strongest storms may pose a threat for damaging winds. ... Discussion ... A surface cold front will slowly move east across the eastern US on Saturday. Along and ahead of this front, surface temperatures should warm into the upper-80Fs to low-90Fs from the Mid-Atlantic region southward into the Carolinas, with surface dewpoint temperatures in the upper-60Fs to low-70Fs. As a result a corridor of instability perhaps as great as 2000 J/kg will develop from North Carolina northward into the Mid-Atlantic area. Isolated to scattered thunderstorms should develop during the afternoon along the slow moving front across the Carolinas into the Mid Atlantic. Despite deep layer shear on the order of 40 knots and 2000 J/kg CAPE, poor mid-level lapse rates and precipitable water values around 1.75 inches should limit the overall severe threat to the potential for isolated damaging thunderstorm winds. ..Marsh.. 09/04/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0215 AM CDT Thu Sep 04 2025 Valid 061200Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHERN NORTH CAROLINA NORTHWARD INTO SOUTHERN PENNSYLVANIA... ...SUMMARY... Strong thunderstorms are expected from northern North Carolina into southern Pennsylvania on Saturday. The strongest storms may pose a threat for damaging winds. ... Discussion ... A surface cold front will slowly move east across the eastern US on Saturday. Along and ahead of this front, surface temperatures should warm into the upper-80Fs to low-90Fs from the Mid-Atlantic region southward into the Carolinas, with surface dewpoint temperatures in the upper-60Fs to low-70Fs. As a result a corridor of instability perhaps as great as 2000 J/kg will develop from North Carolina northward into the Mid-Atlantic area. Isolated to scattered thunderstorms should develop during the afternoon along the slow moving front across the Carolinas into the Mid Atlantic. Despite deep layer shear on the order of 40 knots and 2000 J/kg CAPE, poor mid-level lapse rates and precipitable water values around 1.75 inches should limit the overall severe threat to the potential for isolated damaging thunderstorm winds. ..Marsh.. 09/04/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Thu Sep 04 2025 Valid 051200Z - 061200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS STRETCHING FROM NORTHERN TEXAS NORTHEAST INTO SOUTHERN OHIO... ...SUMMARY... Strong thunderstorms will be possible from the southern Plains into the Ohio and Tennessee Valleys during the afternoon into the overnight hours. Isolated large hail and damaging winds may be possible with the strongest storms. ... Synopsis ... A seasonably strong/cold midlevel low will persist across Ontario, with an attendant larger-scale trough persisting across much of the eastern United States. A potent midlevel shortwave trough will be across the Upper Great Lakes at the start of the period and will quickly rotate around the upper low into Quebec through the period. In its wake a midlevel ribbon of higher vorticity will be left behind from Iowa northeast across Michigan. Upstream from this, the midlevel height field will begin to respond to another shortwave trough rotating around the Ontario low. At the surface, a surface low will quickly lift northeast from northern Michigan through Ontario and into Quebec through the forecast period. A cold from will extend southwest from this low and will push south and east as the surface low lifts northeast. Although somewhat diffuse initially, the temperature gradient across the cold front will rapidly strengthen through the day. ... Ohio and Tennessee Valleys ... Diurnal heating should allow afternoon temperatures to warm into the 80Fs and 90Fs across the region. Given surface dewpoint temperatures in the mid 60Fs perhaps as far north as southern Ohio, this heating will result in most-unstable CAPE values in excess of 2000 J/kg across the area. The region will also be on the periphery of the stronger midlevel flow, yield effective shear of around 40 knots. Thunderstorms should develop by late afternoon in response to increasing large-scale ascent associated with both differential vorticity advection and frontal circulations. Given the degree of instability and effective layer shear, initial thunderstorms may exhibit supercellular structures. However, given the temperature-dewpoint spreads on the order of 20F+ the expectation is that thunderstorms should tend to favor upscale growth toward linear segments. As such, thunderstorms may initially pose a hail threat, especially across western Kentucky and Tennessee, but should transition to more of a wind threat with eastward extent. Across portions of Kentucky and southern Ohio, a short-window, conditional tornado threat may evolve as thunderstorms develop in the vicinity of the surface boundary. As thunderstorms interact with or cross over the boundary, strong northeasterly surface winds will enlarge low-level hodographs supporting at least some tornado threat. ... Greater Arklatex Region ... The surface cold front across the region is expected to strengthen during the day as it slowly moves south. During the evening into the overnight hours, strong warm-air advection on the nose of a strengthening low-level jet may support thunderstorm development on the cool side of the cold front. Despite surface temperatures in the 60Fs and low 70Fs, steep mid-level lapse rates atop the colder surface layer may support isolated large hail. ..Marsh.. 09/04/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Thu Sep 04 2025 Valid 051200Z - 061200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS STRETCHING FROM NORTHERN TEXAS NORTHEAST INTO SOUTHERN OHIO... ...SUMMARY... Strong thunderstorms will be possible from the southern Plains into the Ohio and Tennessee Valleys during the afternoon into the overnight hours. Isolated large hail and damaging winds may be possible with the strongest storms. ... Synopsis ... A seasonably strong/cold midlevel low will persist across Ontario, with an attendant larger-scale trough persisting across much of the eastern United States. A potent midlevel shortwave trough will be across the Upper Great Lakes at the start of the period and will quickly rotate around the upper low into Quebec through the period. In its wake a midlevel ribbon of higher vorticity will be left behind from Iowa northeast across Michigan. Upstream from this, the midlevel height field will begin to respond to another shortwave trough rotating around the Ontario low. At the surface, a surface low will quickly lift northeast from northern Michigan through Ontario and into Quebec through the forecast period. A cold from will extend southwest from this low and will push south and east as the surface low lifts northeast. Although somewhat diffuse initially, the temperature gradient across the cold front will rapidly strengthen through the day. ... Ohio and Tennessee Valleys ... Diurnal heating should allow afternoon temperatures to warm into the 80Fs and 90Fs across the region. Given surface dewpoint temperatures in the mid 60Fs perhaps as far north as southern Ohio, this heating will result in most-unstable CAPE values in excess of 2000 J/kg across the area. The region will also be on the periphery of the stronger midlevel flow, yield effective shear of around 40 knots. Thunderstorms should develop by late afternoon in response to increasing large-scale ascent associated with both differential vorticity advection and frontal circulations. Given the degree of instability and effective layer shear, initial thunderstorms may exhibit supercellular structures. However, given the temperature-dewpoint spreads on the order of 20F+ the expectation is that thunderstorms should tend to favor upscale growth toward linear segments. As such, thunderstorms may initially pose a hail threat, especially across western Kentucky and Tennessee, but should transition to more of a wind threat with eastward extent. Across portions of Kentucky and southern Ohio, a short-window, conditional tornado threat may evolve as thunderstorms develop in the vicinity of the surface boundary. As thunderstorms interact with or cross over the boundary, strong northeasterly surface winds will enlarge low-level hodographs supporting at least some tornado threat. ... Greater Arklatex Region ... The surface cold front across the region is expected to strengthen during the day as it slowly moves south. During the evening into the overnight hours, strong warm-air advection on the nose of a strengthening low-level jet may support thunderstorm development on the cool side of the cold front. Despite surface temperatures in the 60Fs and low 70Fs, steep mid-level lapse rates atop the colder surface layer may support isolated large hail. ..Marsh.. 09/04/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Thu Sep 04 2025 Valid 051200Z - 061200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS STRETCHING FROM NORTHERN TEXAS NORTHEAST INTO SOUTHERN OHIO... ...SUMMARY... Strong thunderstorms will be possible from the southern Plains into the Ohio and Tennessee Valleys during the afternoon into the overnight hours. Isolated large hail and damaging winds may be possible with the strongest storms. ... Synopsis ... A seasonably strong/cold midlevel low will persist across Ontario, with an attendant larger-scale trough persisting across much of the eastern United States. A potent midlevel shortwave trough will be across the Upper Great Lakes at the start of the period and will quickly rotate around the upper low into Quebec through the period. In its wake a midlevel ribbon of higher vorticity will be left behind from Iowa northeast across Michigan. Upstream from this, the midlevel height field will begin to respond to another shortwave trough rotating around the Ontario low. At the surface, a surface low will quickly lift northeast from northern Michigan through Ontario and into Quebec through the forecast period. A cold from will extend southwest from this low and will push south and east as the surface low lifts northeast. Although somewhat diffuse initially, the temperature gradient across the cold front will rapidly strengthen through the day. ... Ohio and Tennessee Valleys ... Diurnal heating should allow afternoon temperatures to warm into the 80Fs and 90Fs across the region. Given surface dewpoint temperatures in the mid 60Fs perhaps as far north as southern Ohio, this heating will result in most-unstable CAPE values in excess of 2000 J/kg across the area. The region will also be on the periphery of the stronger midlevel flow, yield effective shear of around 40 knots. Thunderstorms should develop by late afternoon in response to increasing large-scale ascent associated with both differential vorticity advection and frontal circulations. Given the degree of instability and effective layer shear, initial thunderstorms may exhibit supercellular structures. However, given the temperature-dewpoint spreads on the order of 20F+ the expectation is that thunderstorms should tend to favor upscale growth toward linear segments. As such, thunderstorms may initially pose a hail threat, especially across western Kentucky and Tennessee, but should transition to more of a wind threat with eastward extent. Across portions of Kentucky and southern Ohio, a short-window, conditional tornado threat may evolve as thunderstorms develop in the vicinity of the surface boundary. As thunderstorms interact with or cross over the boundary, strong northeasterly surface winds will enlarge low-level hodographs supporting at least some tornado threat. ... Greater Arklatex Region ... The surface cold front across the region is expected to strengthen during the day as it slowly moves south. During the evening into the overnight hours, strong warm-air advection on the nose of a strengthening low-level jet may support thunderstorm development on the cool side of the cold front. Despite surface temperatures in the 60Fs and low 70Fs, steep mid-level lapse rates atop the colder surface layer may support isolated large hail. ..Marsh.. 09/04/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Thu Sep 04 2025 Valid 051200Z - 061200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS STRETCHING FROM NORTHERN TEXAS NORTHEAST INTO SOUTHERN OHIO... ...SUMMARY... Strong thunderstorms will be possible from the southern Plains into the Ohio and Tennessee Valleys during the afternoon into the overnight hours. Isolated large hail and damaging winds may be possible with the strongest storms. ... Synopsis ... A seasonably strong/cold midlevel low will persist across Ontario, with an attendant larger-scale trough persisting across much of the eastern United States. A potent midlevel shortwave trough will be across the Upper Great Lakes at the start of the period and will quickly rotate around the upper low into Quebec through the period. In its wake a midlevel ribbon of higher vorticity will be left behind from Iowa northeast across Michigan. Upstream from this, the midlevel height field will begin to respond to another shortwave trough rotating around the Ontario low. At the surface, a surface low will quickly lift northeast from northern Michigan through Ontario and into Quebec through the forecast period. A cold from will extend southwest from this low and will push south and east as the surface low lifts northeast. Although somewhat diffuse initially, the temperature gradient across the cold front will rapidly strengthen through the day. ... Ohio and Tennessee Valleys ... Diurnal heating should allow afternoon temperatures to warm into the 80Fs and 90Fs across the region. Given surface dewpoint temperatures in the mid 60Fs perhaps as far north as southern Ohio, this heating will result in most-unstable CAPE values in excess of 2000 J/kg across the area. The region will also be on the periphery of the stronger midlevel flow, yield effective shear of around 40 knots. Thunderstorms should develop by late afternoon in response to increasing large-scale ascent associated with both differential vorticity advection and frontal circulations. Given the degree of instability and effective layer shear, initial thunderstorms may exhibit supercellular structures. However, given the temperature-dewpoint spreads on the order of 20F+ the expectation is that thunderstorms should tend to favor upscale growth toward linear segments. As such, thunderstorms may initially pose a hail threat, especially across western Kentucky and Tennessee, but should transition to more of a wind threat with eastward extent. Across portions of Kentucky and southern Ohio, a short-window, conditional tornado threat may evolve as thunderstorms develop in the vicinity of the surface boundary. As thunderstorms interact with or cross over the boundary, strong northeasterly surface winds will enlarge low-level hodographs supporting at least some tornado threat. ... Greater Arklatex Region ... The surface cold front across the region is expected to strengthen during the day as it slowly moves south. During the evening into the overnight hours, strong warm-air advection on the nose of a strengthening low-level jet may support thunderstorm development on the cool side of the cold front. Despite surface temperatures in the 60Fs and low 70Fs, steep mid-level lapse rates atop the colder surface layer may support isolated large hail. ..Marsh.. 09/04/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1250 AM CDT Thu Sep 04 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE EAST... ...SUMMARY... Isolated damaging winds are possible across parts of the Northeast to the southern Appalachians and Tennessee Valley from late morning through the afternoon. ...Synopsis... A vertically stacked cyclone will drift north in northern ON, as an intense mid-level jetlet and shortwave trough amplifies from the southern Canadian Prairies across the Upper Midwest/Great Lakes. A leading cold front will progress east into the Northeast to TN Valley by this afternoon, with a separate lee trough diurnally sharpening from VA into NY. ...Southern Appalachians/TN Valley to the Northeast... Convection will likely be ongoing at 12Z along parts of the aforementioned cold front from the Lake Erie to northern KY vicinity. Despite weak mid-level lapse rates, diabatic surface heating ahead of this activity should yield diurnal increases in convective coverage/intensity by late morning across parts of the Cumberland Plateau. This will overlap the northern extent of moderate buoyancy across the TN Valley where low-level moisture is richer. Combined with a more westerly component to mid-level flow near the basal portion of the broad trough, a few semi-discrete and loosely organized cells should develop southward during the afternoon. Locally damaging winds and marginally severe hail are possible, centered on the eastern TN vicinity. Isolated to scattered multicell clusters and short-line segments may also evolve in the afternoon from convection along/ahead of the cold front and lee trough. Weak MLCAPE and poor mid-level lapse rates will temper convective vigor, with damaging wind potential locally augmented where pockets of deeper boundary-layer heating occur. ...Mid-MO Valley... The aforementioned shortwave trough and intense mid-level jetlet amplifying into the Upper Midwest could support a couple brief strong storms in the early evening. A narrow corridor of meager surface-based buoyancy may develop ahead of a sharpening cold front by late afternoon. Modified moisture return in the wake of a prior frontal passage will be limited and convection should remain low-topped given the flimsy buoyancy. Still, the background wind fields and strengthening forcing for ascent render concern for a few locally strong gusts and small hail. ...KS... An accelerating and sharpening cold front will sweep south across the central High/Great Plains tonight. Undercut/elevated convection should form to the cold side of this boundary early Friday morning. Locally strong surface gusts may accompany this activity amid robust low-level northerlies. ..Grams/Thornton.. 09/04/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1250 AM CDT Thu Sep 04 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE EAST... ...SUMMARY... Isolated damaging winds are possible across parts of the Northeast to the southern Appalachians and Tennessee Valley from late morning through the afternoon. ...Synopsis... A vertically stacked cyclone will drift north in northern ON, as an intense mid-level jetlet and shortwave trough amplifies from the southern Canadian Prairies across the Upper Midwest/Great Lakes. A leading cold front will progress east into the Northeast to TN Valley by this afternoon, with a separate lee trough diurnally sharpening from VA into NY. ...Southern Appalachians/TN Valley to the Northeast... Convection will likely be ongoing at 12Z along parts of the aforementioned cold front from the Lake Erie to northern KY vicinity. Despite weak mid-level lapse rates, diabatic surface heating ahead of this activity should yield diurnal increases in convective coverage/intensity by late morning across parts of the Cumberland Plateau. This will overlap the northern extent of moderate buoyancy across the TN Valley where low-level moisture is richer. Combined with a more westerly component to mid-level flow near the basal portion of the broad trough, a few semi-discrete and loosely organized cells should develop southward during the afternoon. Locally damaging winds and marginally severe hail are possible, centered on the eastern TN vicinity. Isolated to scattered multicell clusters and short-line segments may also evolve in the afternoon from convection along/ahead of the cold front and lee trough. Weak MLCAPE and poor mid-level lapse rates will temper convective vigor, with damaging wind potential locally augmented where pockets of deeper boundary-layer heating occur. ...Mid-MO Valley... The aforementioned shortwave trough and intense mid-level jetlet amplifying into the Upper Midwest could support a couple brief strong storms in the early evening. A narrow corridor of meager surface-based buoyancy may develop ahead of a sharpening cold front by late afternoon. Modified moisture return in the wake of a prior frontal passage will be limited and convection should remain low-topped given the flimsy buoyancy. Still, the background wind fields and strengthening forcing for ascent render concern for a few locally strong gusts and small hail. ...KS... An accelerating and sharpening cold front will sweep south across the central High/Great Plains tonight. Undercut/elevated convection should form to the cold side of this boundary early Friday morning. Locally strong surface gusts may accompany this activity amid robust low-level northerlies. ..Grams/Thornton.. 09/04/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1250 AM CDT Thu Sep 04 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE EAST... ...SUMMARY... Isolated damaging winds are possible across parts of the Northeast to the southern Appalachians and Tennessee Valley from late morning through the afternoon. ...Synopsis... A vertically stacked cyclone will drift north in northern ON, as an intense mid-level jetlet and shortwave trough amplifies from the southern Canadian Prairies across the Upper Midwest/Great Lakes. A leading cold front will progress east into the Northeast to TN Valley by this afternoon, with a separate lee trough diurnally sharpening from VA into NY. ...Southern Appalachians/TN Valley to the Northeast... Convection will likely be ongoing at 12Z along parts of the aforementioned cold front from the Lake Erie to northern KY vicinity. Despite weak mid-level lapse rates, diabatic surface heating ahead of this activity should yield diurnal increases in convective coverage/intensity by late morning across parts of the Cumberland Plateau. This will overlap the northern extent of moderate buoyancy across the TN Valley where low-level moisture is richer. Combined with a more westerly component to mid-level flow near the basal portion of the broad trough, a few semi-discrete and loosely organized cells should develop southward during the afternoon. Locally damaging winds and marginally severe hail are possible, centered on the eastern TN vicinity. Isolated to scattered multicell clusters and short-line segments may also evolve in the afternoon from convection along/ahead of the cold front and lee trough. Weak MLCAPE and poor mid-level lapse rates will temper convective vigor, with damaging wind potential locally augmented where pockets of deeper boundary-layer heating occur. ...Mid-MO Valley... The aforementioned shortwave trough and intense mid-level jetlet amplifying into the Upper Midwest could support a couple brief strong storms in the early evening. A narrow corridor of meager surface-based buoyancy may develop ahead of a sharpening cold front by late afternoon. Modified moisture return in the wake of a prior frontal passage will be limited and convection should remain low-topped given the flimsy buoyancy. Still, the background wind fields and strengthening forcing for ascent render concern for a few locally strong gusts and small hail. ...KS... An accelerating and sharpening cold front will sweep south across the central High/Great Plains tonight. Undercut/elevated convection should form to the cold side of this boundary early Friday morning. Locally strong surface gusts may accompany this activity amid robust low-level northerlies. ..Grams/Thornton.. 09/04/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1250 AM CDT Thu Sep 04 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE EAST... ...SUMMARY... Isolated damaging winds are possible across parts of the Northeast to the southern Appalachians and Tennessee Valley from late morning through the afternoon. ...Synopsis... A vertically stacked cyclone will drift north in northern ON, as an intense mid-level jetlet and shortwave trough amplifies from the southern Canadian Prairies across the Upper Midwest/Great Lakes. A leading cold front will progress east into the Northeast to TN Valley by this afternoon, with a separate lee trough diurnally sharpening from VA into NY. ...Southern Appalachians/TN Valley to the Northeast... Convection will likely be ongoing at 12Z along parts of the aforementioned cold front from the Lake Erie to northern KY vicinity. Despite weak mid-level lapse rates, diabatic surface heating ahead of this activity should yield diurnal increases in convective coverage/intensity by late morning across parts of the Cumberland Plateau. This will overlap the northern extent of moderate buoyancy across the TN Valley where low-level moisture is richer. Combined with a more westerly component to mid-level flow near the basal portion of the broad trough, a few semi-discrete and loosely organized cells should develop southward during the afternoon. Locally damaging winds and marginally severe hail are possible, centered on the eastern TN vicinity. Isolated to scattered multicell clusters and short-line segments may also evolve in the afternoon from convection along/ahead of the cold front and lee trough. Weak MLCAPE and poor mid-level lapse rates will temper convective vigor, with damaging wind potential locally augmented where pockets of deeper boundary-layer heating occur. ...Mid-MO Valley... The aforementioned shortwave trough and intense mid-level jetlet amplifying into the Upper Midwest could support a couple brief strong storms in the early evening. A narrow corridor of meager surface-based buoyancy may develop ahead of a sharpening cold front by late afternoon. Modified moisture return in the wake of a prior frontal passage will be limited and convection should remain low-topped given the flimsy buoyancy. Still, the background wind fields and strengthening forcing for ascent render concern for a few locally strong gusts and small hail. ...KS... An accelerating and sharpening cold front will sweep south across the central High/Great Plains tonight. Undercut/elevated convection should form to the cold side of this boundary early Friday morning. Locally strong surface gusts may accompany this activity amid robust low-level northerlies. ..Grams/Thornton.. 09/04/2025 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1249 AM CDT Thu Sep 04 2025 Valid 051200Z - 061200Z ...NO CRITICAL AREAS... ...Synopsis... A secondary mid-level wave will traverse the Pacific Northwest on D2/Friday. This wave will bring much cooler temperatures, higher relative humidity, and potential for more widespread thunderstorm activity. While lightning efficiency may increase, increase coverage of thunderstorms and better organization with increasing shear should promote heavier cores and wetting rainfall potential. As such, no isolated thunderstorm areas were included at this time. ..Thornton.. 09/04/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1249 AM CDT Thu Sep 04 2025 Valid 051200Z - 061200Z ...NO CRITICAL AREAS... ...Synopsis... A secondary mid-level wave will traverse the Pacific Northwest on D2/Friday. This wave will bring much cooler temperatures, higher relative humidity, and potential for more widespread thunderstorm activity. While lightning efficiency may increase, increase coverage of thunderstorms and better organization with increasing shear should promote heavier cores and wetting rainfall potential. As such, no isolated thunderstorm areas were included at this time. ..Thornton.. 09/04/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1249 AM CDT Thu Sep 04 2025 Valid 051200Z - 061200Z ...NO CRITICAL AREAS... ...Synopsis... A secondary mid-level wave will traverse the Pacific Northwest on D2/Friday. This wave will bring much cooler temperatures, higher relative humidity, and potential for more widespread thunderstorm activity. While lightning efficiency may increase, increase coverage of thunderstorms and better organization with increasing shear should promote heavier cores and wetting rainfall potential. As such, no isolated thunderstorm areas were included at this time. ..Thornton.. 09/04/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1249 AM CDT Thu Sep 04 2025 Valid 051200Z - 061200Z ...NO CRITICAL AREAS... ...Synopsis... A secondary mid-level wave will traverse the Pacific Northwest on D2/Friday. This wave will bring much cooler temperatures, higher relative humidity, and potential for more widespread thunderstorm activity. While lightning efficiency may increase, increase coverage of thunderstorms and better organization with increasing shear should promote heavier cores and wetting rainfall potential. As such, no isolated thunderstorm areas were included at this time. ..Thornton.. 09/04/2025 ...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 1247 AM CDT Thu Sep 04 2025 Valid 041200Z - 051200Z ...Synopsis... A departing mid-level wave will aid in thunderstorm development across portions of northern California into Washington this afternoon. Storm motions today will be slower than in recent days. A mix of wet/dry thunderstorms is expected. However, mainly mid-level moisture and dry sub-cloud layer should reduce rainfall amounts and increase potential for dry lightning strikes to occur. Activity over the last 24-48 hours has generally produced 0.25" of rain with several new fires detected. An area of isolated dry thunderstorm risk was maintained across portions of northern California into central Oregon with this outlook. A strike or two may extend as far north as the Washington Cascades. ..Thornton.. 09/04/2025 ...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 1247 AM CDT Thu Sep 04 2025 Valid 041200Z - 051200Z ...Synopsis... A departing mid-level wave will aid in thunderstorm development across portions of northern California into Washington this afternoon. Storm motions today will be slower than in recent days. A mix of wet/dry thunderstorms is expected. However, mainly mid-level moisture and dry sub-cloud layer should reduce rainfall amounts and increase potential for dry lightning strikes to occur. Activity over the last 24-48 hours has generally produced 0.25" of rain with several new fires detected. An area of isolated dry thunderstorm risk was maintained across portions of northern California into central Oregon with this outlook. A strike or two may extend as far north as the Washington Cascades. ..Thornton.. 09/04/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more