Severe Storms

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0629 AM CST Mon Dec 11 2023 Valid 111300Z - 121200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not expected in the U.S. through tonight. ...Synopsis/Discussion... In mid/upper levels, cyclonic flow will remain over the East, but will lose amplitude in response to two processes: 1. The eastward ejection of a substantial trough now over the Lower Great Lakes and Mid-Atlantic region. The associated low-level cold front is in the process of clearing the New England Coast, with the surface-based buoyancy well south of the area, and another couple hours of 100-300 J/kg MUCAPE largely confined to between the top of a stable boundary layer and the -20 deg C thermal level. While a rogue flash cannot be ruled out around Cape Cod, lightning potential appears too low and isolated to introduce a general-thunder area. 2. Amplification and slow eastward shift of initially weak troughing now over the Pacific Coast vicinity, reaching interior OR/western ID, northwestern NV, and east-central/southwestern CA by the end of the period. Associated strengthening DCVA/cooling aloft should remain too displaced from enough elevated moisture to support a thunderstorm area until day 2. ..Edwards/Gleason.. 12/11/2023 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0629 AM CST Mon Dec 11 2023 Valid 111300Z - 121200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not expected in the U.S. through tonight. ...Synopsis/Discussion... In mid/upper levels, cyclonic flow will remain over the East, but will lose amplitude in response to two processes: 1. The eastward ejection of a substantial trough now over the Lower Great Lakes and Mid-Atlantic region. The associated low-level cold front is in the process of clearing the New England Coast, with the surface-based buoyancy well south of the area, and another couple hours of 100-300 J/kg MUCAPE largely confined to between the top of a stable boundary layer and the -20 deg C thermal level. While a rogue flash cannot be ruled out around Cape Cod, lightning potential appears too low and isolated to introduce a general-thunder area. 2. Amplification and slow eastward shift of initially weak troughing now over the Pacific Coast vicinity, reaching interior OR/western ID, northwestern NV, and east-central/southwestern CA by the end of the period. Associated strengthening DCVA/cooling aloft should remain too displaced from enough elevated moisture to support a thunderstorm area until day 2. ..Edwards/Gleason.. 12/11/2023 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0629 AM CST Mon Dec 11 2023 Valid 111300Z - 121200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not expected in the U.S. through tonight. ...Synopsis/Discussion... In mid/upper levels, cyclonic flow will remain over the East, but will lose amplitude in response to two processes: 1. The eastward ejection of a substantial trough now over the Lower Great Lakes and Mid-Atlantic region. The associated low-level cold front is in the process of clearing the New England Coast, with the surface-based buoyancy well south of the area, and another couple hours of 100-300 J/kg MUCAPE largely confined to between the top of a stable boundary layer and the -20 deg C thermal level. While a rogue flash cannot be ruled out around Cape Cod, lightning potential appears too low and isolated to introduce a general-thunder area. 2. Amplification and slow eastward shift of initially weak troughing now over the Pacific Coast vicinity, reaching interior OR/western ID, northwestern NV, and east-central/southwestern CA by the end of the period. Associated strengthening DCVA/cooling aloft should remain too displaced from enough elevated moisture to support a thunderstorm area until day 2. ..Edwards/Gleason.. 12/11/2023 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0629 AM CST Mon Dec 11 2023 Valid 111300Z - 121200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not expected in the U.S. through tonight. ...Synopsis/Discussion... In mid/upper levels, cyclonic flow will remain over the East, but will lose amplitude in response to two processes: 1. The eastward ejection of a substantial trough now over the Lower Great Lakes and Mid-Atlantic region. The associated low-level cold front is in the process of clearing the New England Coast, with the surface-based buoyancy well south of the area, and another couple hours of 100-300 J/kg MUCAPE largely confined to between the top of a stable boundary layer and the -20 deg C thermal level. While a rogue flash cannot be ruled out around Cape Cod, lightning potential appears too low and isolated to introduce a general-thunder area. 2. Amplification and slow eastward shift of initially weak troughing now over the Pacific Coast vicinity, reaching interior OR/western ID, northwestern NV, and east-central/southwestern CA by the end of the period. Associated strengthening DCVA/cooling aloft should remain too displaced from enough elevated moisture to support a thunderstorm area until day 2. ..Edwards/Gleason.. 12/11/2023 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0629 AM CST Mon Dec 11 2023 Valid 111300Z - 121200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not expected in the U.S. through tonight. ...Synopsis/Discussion... In mid/upper levels, cyclonic flow will remain over the East, but will lose amplitude in response to two processes: 1. The eastward ejection of a substantial trough now over the Lower Great Lakes and Mid-Atlantic region. The associated low-level cold front is in the process of clearing the New England Coast, with the surface-based buoyancy well south of the area, and another couple hours of 100-300 J/kg MUCAPE largely confined to between the top of a stable boundary layer and the -20 deg C thermal level. While a rogue flash cannot be ruled out around Cape Cod, lightning potential appears too low and isolated to introduce a general-thunder area. 2. Amplification and slow eastward shift of initially weak troughing now over the Pacific Coast vicinity, reaching interior OR/western ID, northwestern NV, and east-central/southwestern CA by the end of the period. Associated strengthening DCVA/cooling aloft should remain too displaced from enough elevated moisture to support a thunderstorm area until day 2. ..Edwards/Gleason.. 12/11/2023 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0335 AM CST Mon Dec 11 2023 Valid 141200Z - 191200Z ...DISCUSSION... Severe probabilities appear negligible through D5. An area-of-interest for increasing severe potential during D6-8 continues across the eastern Gulf to south Atlantic Coasts. An initially stout surface anticyclone will weaken heading into the weekend over the OH Valley to central Appalachians. A remnant continental polar airmass will largely remain entrenched across the Southeast outside of the FL Peninsula. Deterministic 00Z guidance has trended towards increasing agreement with slow eastward progression of an upper low over the Southwest across the southern Great Plains into the Gulf this weekend. This will likely support cyclogenesis over the predominately offshore (outside of the FL Peninsula) baroclinic zone, which ECMWF ensemble and GEFS members have increasingly trended towards supporting their parent deterministic runs. But the degree of cyclone amplification remains quite varied, which has related impacts on timing/location of a potentially favorable warm-sector environment. This renders low predictability for a 15 percent severe weather area. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0335 AM CST Mon Dec 11 2023 Valid 141200Z - 191200Z ...DISCUSSION... Severe probabilities appear negligible through D5. An area-of-interest for increasing severe potential during D6-8 continues across the eastern Gulf to south Atlantic Coasts. An initially stout surface anticyclone will weaken heading into the weekend over the OH Valley to central Appalachians. A remnant continental polar airmass will largely remain entrenched across the Southeast outside of the FL Peninsula. Deterministic 00Z guidance has trended towards increasing agreement with slow eastward progression of an upper low over the Southwest across the southern Great Plains into the Gulf this weekend. This will likely support cyclogenesis over the predominately offshore (outside of the FL Peninsula) baroclinic zone, which ECMWF ensemble and GEFS members have increasingly trended towards supporting their parent deterministic runs. But the degree of cyclone amplification remains quite varied, which has related impacts on timing/location of a potentially favorable warm-sector environment. This renders low predictability for a 15 percent severe weather area. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0335 AM CST Mon Dec 11 2023 Valid 141200Z - 191200Z ...DISCUSSION... Severe probabilities appear negligible through D5. An area-of-interest for increasing severe potential during D6-8 continues across the eastern Gulf to south Atlantic Coasts. An initially stout surface anticyclone will weaken heading into the weekend over the OH Valley to central Appalachians. A remnant continental polar airmass will largely remain entrenched across the Southeast outside of the FL Peninsula. Deterministic 00Z guidance has trended towards increasing agreement with slow eastward progression of an upper low over the Southwest across the southern Great Plains into the Gulf this weekend. This will likely support cyclogenesis over the predominately offshore (outside of the FL Peninsula) baroclinic zone, which ECMWF ensemble and GEFS members have increasingly trended towards supporting their parent deterministic runs. But the degree of cyclone amplification remains quite varied, which has related impacts on timing/location of a potentially favorable warm-sector environment. This renders low predictability for a 15 percent severe weather area. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0335 AM CST Mon Dec 11 2023 Valid 141200Z - 191200Z ...DISCUSSION... Severe probabilities appear negligible through D5. An area-of-interest for increasing severe potential during D6-8 continues across the eastern Gulf to south Atlantic Coasts. An initially stout surface anticyclone will weaken heading into the weekend over the OH Valley to central Appalachians. A remnant continental polar airmass will largely remain entrenched across the Southeast outside of the FL Peninsula. Deterministic 00Z guidance has trended towards increasing agreement with slow eastward progression of an upper low over the Southwest across the southern Great Plains into the Gulf this weekend. This will likely support cyclogenesis over the predominately offshore (outside of the FL Peninsula) baroclinic zone, which ECMWF ensemble and GEFS members have increasingly trended towards supporting their parent deterministic runs. But the degree of cyclone amplification remains quite varied, which has related impacts on timing/location of a potentially favorable warm-sector environment. This renders low predictability for a 15 percent severe weather area. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0335 AM CST Mon Dec 11 2023 Valid 141200Z - 191200Z ...DISCUSSION... Severe probabilities appear negligible through D5. An area-of-interest for increasing severe potential during D6-8 continues across the eastern Gulf to south Atlantic Coasts. An initially stout surface anticyclone will weaken heading into the weekend over the OH Valley to central Appalachians. A remnant continental polar airmass will largely remain entrenched across the Southeast outside of the FL Peninsula. Deterministic 00Z guidance has trended towards increasing agreement with slow eastward progression of an upper low over the Southwest across the southern Great Plains into the Gulf this weekend. This will likely support cyclogenesis over the predominately offshore (outside of the FL Peninsula) baroclinic zone, which ECMWF ensemble and GEFS members have increasingly trended towards supporting their parent deterministic runs. But the degree of cyclone amplification remains quite varied, which has related impacts on timing/location of a potentially favorable warm-sector environment. This renders low predictability for a 15 percent severe weather area. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0335 AM CST Mon Dec 11 2023 Valid 141200Z - 191200Z ...DISCUSSION... Severe probabilities appear negligible through D5. An area-of-interest for increasing severe potential during D6-8 continues across the eastern Gulf to south Atlantic Coasts. An initially stout surface anticyclone will weaken heading into the weekend over the OH Valley to central Appalachians. A remnant continental polar airmass will largely remain entrenched across the Southeast outside of the FL Peninsula. Deterministic 00Z guidance has trended towards increasing agreement with slow eastward progression of an upper low over the Southwest across the southern Great Plains into the Gulf this weekend. This will likely support cyclogenesis over the predominately offshore (outside of the FL Peninsula) baroclinic zone, which ECMWF ensemble and GEFS members have increasingly trended towards supporting their parent deterministic runs. But the degree of cyclone amplification remains quite varied, which has related impacts on timing/location of a potentially favorable warm-sector environment. This renders low predictability for a 15 percent severe weather area. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0335 AM CST Mon Dec 11 2023 Valid 141200Z - 191200Z ...DISCUSSION... Severe probabilities appear negligible through D5. An area-of-interest for increasing severe potential during D6-8 continues across the eastern Gulf to south Atlantic Coasts. An initially stout surface anticyclone will weaken heading into the weekend over the OH Valley to central Appalachians. A remnant continental polar airmass will largely remain entrenched across the Southeast outside of the FL Peninsula. Deterministic 00Z guidance has trended towards increasing agreement with slow eastward progression of an upper low over the Southwest across the southern Great Plains into the Gulf this weekend. This will likely support cyclogenesis over the predominately offshore (outside of the FL Peninsula) baroclinic zone, which ECMWF ensemble and GEFS members have increasingly trended towards supporting their parent deterministic runs. But the degree of cyclone amplification remains quite varied, which has related impacts on timing/location of a potentially favorable warm-sector environment. This renders low predictability for a 15 percent severe weather area. Read more

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0217 AM CST Mon Dec 11 2023 Valid 131200Z - 141200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected on Wednesday. ...Southwest... A mid-level low over the Lower CO Valley should pivot and drift east across AZ through the period. Scant to meager elevated buoyancy will become increasingly pervasive downstream of this low. Sporadic lightning flashes should be favored in the first half of the period within a modest but persistent low-level warm theta-e advection regime. Convective coverage should increase Wednesday evening into the night as the cold-core region of the mid-level low shifts east, with an attendant corridor of steeper lapse rates overspreading the marginal moisture plume. The bulk of strong mid-level flow should remain confined to Sonora/Chihuahua, but small hail might occur overnight across south NM. ...South FL... Above-average agreement exists across guidance with the depiction of a stout 1040+ mb anticyclone centered on IL/IN Wednesday afternoon. This will influence persistent east-northeasterly low-level flow across FL, with gradual moistening anticipated. More prominent model differences occur with the depth of this low-level moistening and the erosion of a relatively warm/dry layer centered on 700 mb. In addition, weak lapse rates centered on 400 mb, near the -20 C level, further lowers confidence in whether lower-topped convection can acquire charge separation outside of the FL Straits. Still, enough signal exists to warrant a low thunderstorm probability. ..Grams.. 12/11/2023 Read more

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0217 AM CST Mon Dec 11 2023 Valid 131200Z - 141200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected on Wednesday. ...Southwest... A mid-level low over the Lower CO Valley should pivot and drift east across AZ through the period. Scant to meager elevated buoyancy will become increasingly pervasive downstream of this low. Sporadic lightning flashes should be favored in the first half of the period within a modest but persistent low-level warm theta-e advection regime. Convective coverage should increase Wednesday evening into the night as the cold-core region of the mid-level low shifts east, with an attendant corridor of steeper lapse rates overspreading the marginal moisture plume. The bulk of strong mid-level flow should remain confined to Sonora/Chihuahua, but small hail might occur overnight across south NM. ...South FL... Above-average agreement exists across guidance with the depiction of a stout 1040+ mb anticyclone centered on IL/IN Wednesday afternoon. This will influence persistent east-northeasterly low-level flow across FL, with gradual moistening anticipated. More prominent model differences occur with the depth of this low-level moistening and the erosion of a relatively warm/dry layer centered on 700 mb. In addition, weak lapse rates centered on 400 mb, near the -20 C level, further lowers confidence in whether lower-topped convection can acquire charge separation outside of the FL Straits. Still, enough signal exists to warrant a low thunderstorm probability. ..Grams.. 12/11/2023 Read more

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0217 AM CST Mon Dec 11 2023 Valid 131200Z - 141200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected on Wednesday. ...Southwest... A mid-level low over the Lower CO Valley should pivot and drift east across AZ through the period. Scant to meager elevated buoyancy will become increasingly pervasive downstream of this low. Sporadic lightning flashes should be favored in the first half of the period within a modest but persistent low-level warm theta-e advection regime. Convective coverage should increase Wednesday evening into the night as the cold-core region of the mid-level low shifts east, with an attendant corridor of steeper lapse rates overspreading the marginal moisture plume. The bulk of strong mid-level flow should remain confined to Sonora/Chihuahua, but small hail might occur overnight across south NM. ...South FL... Above-average agreement exists across guidance with the depiction of a stout 1040+ mb anticyclone centered on IL/IN Wednesday afternoon. This will influence persistent east-northeasterly low-level flow across FL, with gradual moistening anticipated. More prominent model differences occur with the depth of this low-level moistening and the erosion of a relatively warm/dry layer centered on 700 mb. In addition, weak lapse rates centered on 400 mb, near the -20 C level, further lowers confidence in whether lower-topped convection can acquire charge separation outside of the FL Straits. Still, enough signal exists to warrant a low thunderstorm probability. ..Grams.. 12/11/2023 Read more

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0217 AM CST Mon Dec 11 2023 Valid 131200Z - 141200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected on Wednesday. ...Southwest... A mid-level low over the Lower CO Valley should pivot and drift east across AZ through the period. Scant to meager elevated buoyancy will become increasingly pervasive downstream of this low. Sporadic lightning flashes should be favored in the first half of the period within a modest but persistent low-level warm theta-e advection regime. Convective coverage should increase Wednesday evening into the night as the cold-core region of the mid-level low shifts east, with an attendant corridor of steeper lapse rates overspreading the marginal moisture plume. The bulk of strong mid-level flow should remain confined to Sonora/Chihuahua, but small hail might occur overnight across south NM. ...South FL... Above-average agreement exists across guidance with the depiction of a stout 1040+ mb anticyclone centered on IL/IN Wednesday afternoon. This will influence persistent east-northeasterly low-level flow across FL, with gradual moistening anticipated. More prominent model differences occur with the depth of this low-level moistening and the erosion of a relatively warm/dry layer centered on 700 mb. In addition, weak lapse rates centered on 400 mb, near the -20 C level, further lowers confidence in whether lower-topped convection can acquire charge separation outside of the FL Straits. Still, enough signal exists to warrant a low thunderstorm probability. ..Grams.. 12/11/2023 Read more

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0217 AM CST Mon Dec 11 2023 Valid 131200Z - 141200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected on Wednesday. ...Southwest... A mid-level low over the Lower CO Valley should pivot and drift east across AZ through the period. Scant to meager elevated buoyancy will become increasingly pervasive downstream of this low. Sporadic lightning flashes should be favored in the first half of the period within a modest but persistent low-level warm theta-e advection regime. Convective coverage should increase Wednesday evening into the night as the cold-core region of the mid-level low shifts east, with an attendant corridor of steeper lapse rates overspreading the marginal moisture plume. The bulk of strong mid-level flow should remain confined to Sonora/Chihuahua, but small hail might occur overnight across south NM. ...South FL... Above-average agreement exists across guidance with the depiction of a stout 1040+ mb anticyclone centered on IL/IN Wednesday afternoon. This will influence persistent east-northeasterly low-level flow across FL, with gradual moistening anticipated. More prominent model differences occur with the depth of this low-level moistening and the erosion of a relatively warm/dry layer centered on 700 mb. In addition, weak lapse rates centered on 400 mb, near the -20 C level, further lowers confidence in whether lower-topped convection can acquire charge separation outside of the FL Straits. Still, enough signal exists to warrant a low thunderstorm probability. ..Grams.. 12/11/2023 Read more

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0217 AM CST Mon Dec 11 2023 Valid 131200Z - 141200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected on Wednesday. ...Southwest... A mid-level low over the Lower CO Valley should pivot and drift east across AZ through the period. Scant to meager elevated buoyancy will become increasingly pervasive downstream of this low. Sporadic lightning flashes should be favored in the first half of the period within a modest but persistent low-level warm theta-e advection regime. Convective coverage should increase Wednesday evening into the night as the cold-core region of the mid-level low shifts east, with an attendant corridor of steeper lapse rates overspreading the marginal moisture plume. The bulk of strong mid-level flow should remain confined to Sonora/Chihuahua, but small hail might occur overnight across south NM. ...South FL... Above-average agreement exists across guidance with the depiction of a stout 1040+ mb anticyclone centered on IL/IN Wednesday afternoon. This will influence persistent east-northeasterly low-level flow across FL, with gradual moistening anticipated. More prominent model differences occur with the depth of this low-level moistening and the erosion of a relatively warm/dry layer centered on 700 mb. In addition, weak lapse rates centered on 400 mb, near the -20 C level, further lowers confidence in whether lower-topped convection can acquire charge separation outside of the FL Straits. Still, enough signal exists to warrant a low thunderstorm probability. ..Grams.. 12/11/2023 Read more

SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1257 AM CST Mon Dec 11 2023 Valid 121200Z - 131200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected on Tuesday. ...Discussion... A dearth of buoyancy adequate for thunderstorm potential will persist across much of the CONUS on Tuesday. One exception will be over the TX Trans-Pecos into southeast NM. Moistening around 700 mb should gradually occur downstream of a shortwave impulse digging from the Sierra Nevada to the Lower CO Valley. Guidance has trended faster with indicating scant elevated buoyancy by Tuesday night. The RRFS and parent 03Z RAP environment support isolated thunderstorm potential, despite neutral mid-level height change. Even so, most 00Z non-CAM and both available HREF members in the 48-60 hour time frame indicate minimal convective signal prior to 12Z Wednesday. ..Grams.. 12/11/2023 Read more

SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1257 AM CST Mon Dec 11 2023 Valid 121200Z - 131200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected on Tuesday. ...Discussion... A dearth of buoyancy adequate for thunderstorm potential will persist across much of the CONUS on Tuesday. One exception will be over the TX Trans-Pecos into southeast NM. Moistening around 700 mb should gradually occur downstream of a shortwave impulse digging from the Sierra Nevada to the Lower CO Valley. Guidance has trended faster with indicating scant elevated buoyancy by Tuesday night. The RRFS and parent 03Z RAP environment support isolated thunderstorm potential, despite neutral mid-level height change. Even so, most 00Z non-CAM and both available HREF members in the 48-60 hour time frame indicate minimal convective signal prior to 12Z Wednesday. ..Grams.. 12/11/2023 Read more