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SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1008 AM CST Sun Feb 18 2024 Valid 181630Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON OVER PARTS OF SOUTH FLORIDA... ...SUMMARY... Isolated to scattered thunderstorms, associated with a marginal wind/tornado threat, will be possible across part of south Florida and the Keys this afternoon. ...South Florida... Current radar imagery shows a line of thunderstorms approaching the lower FL Keys. This line has multiple embedded weak circulations, which should continue through the day as it tracks east-northeastward at 25 knots. Meanwhile, a surface boundary extends across the southern tip of FL and Keys, which should provide some enhancement to low-level shear and convergence. Despite the very small areal nature of the risk, there is some potential for a tornado or damaging winds as these storms track across parts of Monroe, Miami-Dade, and Broward counties FL this afternoon from 18-21z. Please refer to SPC Mesoscale Discussion #151 for further details. ..Hart/Jewell.. 02/18/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1008 AM CST Sun Feb 18 2024 Valid 181630Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON OVER PARTS OF SOUTH FLORIDA... ...SUMMARY... Isolated to scattered thunderstorms, associated with a marginal wind/tornado threat, will be possible across part of south Florida and the Keys this afternoon. ...South Florida... Current radar imagery shows a line of thunderstorms approaching the lower FL Keys. This line has multiple embedded weak circulations, which should continue through the day as it tracks east-northeastward at 25 knots. Meanwhile, a surface boundary extends across the southern tip of FL and Keys, which should provide some enhancement to low-level shear and convergence. Despite the very small areal nature of the risk, there is some potential for a tornado or damaging winds as these storms track across parts of Monroe, Miami-Dade, and Broward counties FL this afternoon from 18-21z. Please refer to SPC Mesoscale Discussion #151 for further details. ..Hart/Jewell.. 02/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0630 AM CST Sun Feb 18 2024 Valid 181300Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE FLORIDA KEYS AND A SMALL PART OF SOUTH FLORIDA... ...SUMMARY... Isolated to scattered thunderstorms, associated with a marginal wind/tornado threat, will be possible across part of south Florida and the Keys today. ...Synopsis... A generally progressive shortwave pattern is expected across most of the CONUS. A northeastern Pacific cyclone -- initially centered near 38N137W -- is forecast to approach (but stay offshore from) the West Coast this period. Associated frontal forcing and large-scale DCVA/cooling aloft should contribute to increasing general- thunderstorm potential from mid/late afternoon into tonight across portions of northern/central CA. Meanwhile, a downstream/midlatitiude shortwave trough was evident in moisture-channel imagery over the Mid-South and Arklatex regions, while a southern-stream perturbation was fairly prominent in the same imagery over the western Gulf. By 00Z, the midlatitude trough is expected to amplify and pivot from strongly positively tilted initially to only slightly positive over MS and the Tennessee Valley region. Overnight, this perturbation should develop a closed 500-mb low , reaching northern GA by 12Z, with trough south-southwestward across the FL Panhandle to the northeastern Gulf. As this occurs, the southern-stream/Gulf perturbation will eject east-northeastward and deamplify, reaching the extreme eastern Gulf just west of the FL Peninsula by 00Z. This perturbation should cross the peninsula and move over Atlantic waters by 06Z. In response to those developments, a slow-moving/wavy surface frontal zone -- analyzed at 11Z from near TMB to about 35 nm N of EYW -- may oscillate northward on mesobeta to local scales while remaining over extreme southern mainland FL for much of the day. With the approach of the Gulf shortwave trough aloft, a weak/ frontal-wave low now drawn about 200 nm west of EYW should ripple along the front and across south FL by 00Z, to a position just offshore from the FLL-PBI corridor. As that low proceeds east- northeastward just north of the Bahamas, the cold front should move southeastward past mainland FL and the Keys by 09Z. ...South FL/Keys... A band of convection, with isolated to scattered embedded thunderstorms, is apparent in satellite, distant radar and lightning data over the extreme eastern Gulf west of the Dry Tortugas. This activity is expected to be maintained and perhaps intensify somewhat while move east-northeastward, affecting parts of the southern mainland either side of the front, as well as the Keys, from midday into part of the afternoon. This activity may be preceded by more isolated thunderstorms developing in the warm sector and crossing the front. Marginal potential exists for supercells or embedded LEWP/bow formations, offering a damaging-gust or brief tornado risk. A richly moist boundary layer will persist south of the front, characterized by surface dewpoints from the upper 60s to the low 70s F. Even then, buoyancy will be weak due to poor mid/upper-level lapse rates, including a couple prominent stable layers noted in the 12Z KEY sounding, which will keep peak/preconvective MLCAPE values generally in the 400-800 J/kg range. The lack of more-robust instability/buoyancy will be a limiting factor for severe potential amid favorable deep shear, and potentially favorable localized low-level shear. Strong mid/upper-level winds will persist, with flow commonly 60-75 kt in the 500-250-mb layer. This will contribute to 45-55-kt effective-shear magnitudes. Low-level hodographs should be long but not particularly enlarged, with the possible exception of localized boundary influences, such as the front just east of the low. ..Edwards/Mosier.. 02/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0630 AM CST Sun Feb 18 2024 Valid 181300Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE FLORIDA KEYS AND A SMALL PART OF SOUTH FLORIDA... ...SUMMARY... Isolated to scattered thunderstorms, associated with a marginal wind/tornado threat, will be possible across part of south Florida and the Keys today. ...Synopsis... A generally progressive shortwave pattern is expected across most of the CONUS. A northeastern Pacific cyclone -- initially centered near 38N137W -- is forecast to approach (but stay offshore from) the West Coast this period. Associated frontal forcing and large-scale DCVA/cooling aloft should contribute to increasing general- thunderstorm potential from mid/late afternoon into tonight across portions of northern/central CA. Meanwhile, a downstream/midlatitiude shortwave trough was evident in moisture-channel imagery over the Mid-South and Arklatex regions, while a southern-stream perturbation was fairly prominent in the same imagery over the western Gulf. By 00Z, the midlatitude trough is expected to amplify and pivot from strongly positively tilted initially to only slightly positive over MS and the Tennessee Valley region. Overnight, this perturbation should develop a closed 500-mb low , reaching northern GA by 12Z, with trough south-southwestward across the FL Panhandle to the northeastern Gulf. As this occurs, the southern-stream/Gulf perturbation will eject east-northeastward and deamplify, reaching the extreme eastern Gulf just west of the FL Peninsula by 00Z. This perturbation should cross the peninsula and move over Atlantic waters by 06Z. In response to those developments, a slow-moving/wavy surface frontal zone -- analyzed at 11Z from near TMB to about 35 nm N of EYW -- may oscillate northward on mesobeta to local scales while remaining over extreme southern mainland FL for much of the day. With the approach of the Gulf shortwave trough aloft, a weak/ frontal-wave low now drawn about 200 nm west of EYW should ripple along the front and across south FL by 00Z, to a position just offshore from the FLL-PBI corridor. As that low proceeds east- northeastward just north of the Bahamas, the cold front should move southeastward past mainland FL and the Keys by 09Z. ...South FL/Keys... A band of convection, with isolated to scattered embedded thunderstorms, is apparent in satellite, distant radar and lightning data over the extreme eastern Gulf west of the Dry Tortugas. This activity is expected to be maintained and perhaps intensify somewhat while move east-northeastward, affecting parts of the southern mainland either side of the front, as well as the Keys, from midday into part of the afternoon. This activity may be preceded by more isolated thunderstorms developing in the warm sector and crossing the front. Marginal potential exists for supercells or embedded LEWP/bow formations, offering a damaging-gust or brief tornado risk. A richly moist boundary layer will persist south of the front, characterized by surface dewpoints from the upper 60s to the low 70s F. Even then, buoyancy will be weak due to poor mid/upper-level lapse rates, including a couple prominent stable layers noted in the 12Z KEY sounding, which will keep peak/preconvective MLCAPE values generally in the 400-800 J/kg range. The lack of more-robust instability/buoyancy will be a limiting factor for severe potential amid favorable deep shear, and potentially favorable localized low-level shear. Strong mid/upper-level winds will persist, with flow commonly 60-75 kt in the 500-250-mb layer. This will contribute to 45-55-kt effective-shear magnitudes. Low-level hodographs should be long but not particularly enlarged, with the possible exception of localized boundary influences, such as the front just east of the low. ..Edwards/Mosier.. 02/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0630 AM CST Sun Feb 18 2024 Valid 181300Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE FLORIDA KEYS AND A SMALL PART OF SOUTH FLORIDA... ...SUMMARY... Isolated to scattered thunderstorms, associated with a marginal wind/tornado threat, will be possible across part of south Florida and the Keys today. ...Synopsis... A generally progressive shortwave pattern is expected across most of the CONUS. A northeastern Pacific cyclone -- initially centered near 38N137W -- is forecast to approach (but stay offshore from) the West Coast this period. Associated frontal forcing and large-scale DCVA/cooling aloft should contribute to increasing general- thunderstorm potential from mid/late afternoon into tonight across portions of northern/central CA. Meanwhile, a downstream/midlatitiude shortwave trough was evident in moisture-channel imagery over the Mid-South and Arklatex regions, while a southern-stream perturbation was fairly prominent in the same imagery over the western Gulf. By 00Z, the midlatitude trough is expected to amplify and pivot from strongly positively tilted initially to only slightly positive over MS and the Tennessee Valley region. Overnight, this perturbation should develop a closed 500-mb low , reaching northern GA by 12Z, with trough south-southwestward across the FL Panhandle to the northeastern Gulf. As this occurs, the southern-stream/Gulf perturbation will eject east-northeastward and deamplify, reaching the extreme eastern Gulf just west of the FL Peninsula by 00Z. This perturbation should cross the peninsula and move over Atlantic waters by 06Z. In response to those developments, a slow-moving/wavy surface frontal zone -- analyzed at 11Z from near TMB to about 35 nm N of EYW -- may oscillate northward on mesobeta to local scales while remaining over extreme southern mainland FL for much of the day. With the approach of the Gulf shortwave trough aloft, a weak/ frontal-wave low now drawn about 200 nm west of EYW should ripple along the front and across south FL by 00Z, to a position just offshore from the FLL-PBI corridor. As that low proceeds east- northeastward just north of the Bahamas, the cold front should move southeastward past mainland FL and the Keys by 09Z. ...South FL/Keys... A band of convection, with isolated to scattered embedded thunderstorms, is apparent in satellite, distant radar and lightning data over the extreme eastern Gulf west of the Dry Tortugas. This activity is expected to be maintained and perhaps intensify somewhat while move east-northeastward, affecting parts of the southern mainland either side of the front, as well as the Keys, from midday into part of the afternoon. This activity may be preceded by more isolated thunderstorms developing in the warm sector and crossing the front. Marginal potential exists for supercells or embedded LEWP/bow formations, offering a damaging-gust or brief tornado risk. A richly moist boundary layer will persist south of the front, characterized by surface dewpoints from the upper 60s to the low 70s F. Even then, buoyancy will be weak due to poor mid/upper-level lapse rates, including a couple prominent stable layers noted in the 12Z KEY sounding, which will keep peak/preconvective MLCAPE values generally in the 400-800 J/kg range. The lack of more-robust instability/buoyancy will be a limiting factor for severe potential amid favorable deep shear, and potentially favorable localized low-level shear. Strong mid/upper-level winds will persist, with flow commonly 60-75 kt in the 500-250-mb layer. This will contribute to 45-55-kt effective-shear magnitudes. Low-level hodographs should be long but not particularly enlarged, with the possible exception of localized boundary influences, such as the front just east of the low. ..Edwards/Mosier.. 02/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0630 AM CST Sun Feb 18 2024 Valid 181300Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE FLORIDA KEYS AND A SMALL PART OF SOUTH FLORIDA... ...SUMMARY... Isolated to scattered thunderstorms, associated with a marginal wind/tornado threat, will be possible across part of south Florida and the Keys today. ...Synopsis... A generally progressive shortwave pattern is expected across most of the CONUS. A northeastern Pacific cyclone -- initially centered near 38N137W -- is forecast to approach (but stay offshore from) the West Coast this period. Associated frontal forcing and large-scale DCVA/cooling aloft should contribute to increasing general- thunderstorm potential from mid/late afternoon into tonight across portions of northern/central CA. Meanwhile, a downstream/midlatitiude shortwave trough was evident in moisture-channel imagery over the Mid-South and Arklatex regions, while a southern-stream perturbation was fairly prominent in the same imagery over the western Gulf. By 00Z, the midlatitude trough is expected to amplify and pivot from strongly positively tilted initially to only slightly positive over MS and the Tennessee Valley region. Overnight, this perturbation should develop a closed 500-mb low , reaching northern GA by 12Z, with trough south-southwestward across the FL Panhandle to the northeastern Gulf. As this occurs, the southern-stream/Gulf perturbation will eject east-northeastward and deamplify, reaching the extreme eastern Gulf just west of the FL Peninsula by 00Z. This perturbation should cross the peninsula and move over Atlantic waters by 06Z. In response to those developments, a slow-moving/wavy surface frontal zone -- analyzed at 11Z from near TMB to about 35 nm N of EYW -- may oscillate northward on mesobeta to local scales while remaining over extreme southern mainland FL for much of the day. With the approach of the Gulf shortwave trough aloft, a weak/ frontal-wave low now drawn about 200 nm west of EYW should ripple along the front and across south FL by 00Z, to a position just offshore from the FLL-PBI corridor. As that low proceeds east- northeastward just north of the Bahamas, the cold front should move southeastward past mainland FL and the Keys by 09Z. ...South FL/Keys... A band of convection, with isolated to scattered embedded thunderstorms, is apparent in satellite, distant radar and lightning data over the extreme eastern Gulf west of the Dry Tortugas. This activity is expected to be maintained and perhaps intensify somewhat while move east-northeastward, affecting parts of the southern mainland either side of the front, as well as the Keys, from midday into part of the afternoon. This activity may be preceded by more isolated thunderstorms developing in the warm sector and crossing the front. Marginal potential exists for supercells or embedded LEWP/bow formations, offering a damaging-gust or brief tornado risk. A richly moist boundary layer will persist south of the front, characterized by surface dewpoints from the upper 60s to the low 70s F. Even then, buoyancy will be weak due to poor mid/upper-level lapse rates, including a couple prominent stable layers noted in the 12Z KEY sounding, which will keep peak/preconvective MLCAPE values generally in the 400-800 J/kg range. The lack of more-robust instability/buoyancy will be a limiting factor for severe potential amid favorable deep shear, and potentially favorable localized low-level shear. Strong mid/upper-level winds will persist, with flow commonly 60-75 kt in the 500-250-mb layer. This will contribute to 45-55-kt effective-shear magnitudes. Low-level hodographs should be long but not particularly enlarged, with the possible exception of localized boundary influences, such as the front just east of the low. ..Edwards/Mosier.. 02/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0630 AM CST Sun Feb 18 2024 Valid 181300Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE FLORIDA KEYS AND A SMALL PART OF SOUTH FLORIDA... ...SUMMARY... Isolated to scattered thunderstorms, associated with a marginal wind/tornado threat, will be possible across part of south Florida and the Keys today. ...Synopsis... A generally progressive shortwave pattern is expected across most of the CONUS. A northeastern Pacific cyclone -- initially centered near 38N137W -- is forecast to approach (but stay offshore from) the West Coast this period. Associated frontal forcing and large-scale DCVA/cooling aloft should contribute to increasing general- thunderstorm potential from mid/late afternoon into tonight across portions of northern/central CA. Meanwhile, a downstream/midlatitiude shortwave trough was evident in moisture-channel imagery over the Mid-South and Arklatex regions, while a southern-stream perturbation was fairly prominent in the same imagery over the western Gulf. By 00Z, the midlatitude trough is expected to amplify and pivot from strongly positively tilted initially to only slightly positive over MS and the Tennessee Valley region. Overnight, this perturbation should develop a closed 500-mb low , reaching northern GA by 12Z, with trough south-southwestward across the FL Panhandle to the northeastern Gulf. As this occurs, the southern-stream/Gulf perturbation will eject east-northeastward and deamplify, reaching the extreme eastern Gulf just west of the FL Peninsula by 00Z. This perturbation should cross the peninsula and move over Atlantic waters by 06Z. In response to those developments, a slow-moving/wavy surface frontal zone -- analyzed at 11Z from near TMB to about 35 nm N of EYW -- may oscillate northward on mesobeta to local scales while remaining over extreme southern mainland FL for much of the day. With the approach of the Gulf shortwave trough aloft, a weak/ frontal-wave low now drawn about 200 nm west of EYW should ripple along the front and across south FL by 00Z, to a position just offshore from the FLL-PBI corridor. As that low proceeds east- northeastward just north of the Bahamas, the cold front should move southeastward past mainland FL and the Keys by 09Z. ...South FL/Keys... A band of convection, with isolated to scattered embedded thunderstorms, is apparent in satellite, distant radar and lightning data over the extreme eastern Gulf west of the Dry Tortugas. This activity is expected to be maintained and perhaps intensify somewhat while move east-northeastward, affecting parts of the southern mainland either side of the front, as well as the Keys, from midday into part of the afternoon. This activity may be preceded by more isolated thunderstorms developing in the warm sector and crossing the front. Marginal potential exists for supercells or embedded LEWP/bow formations, offering a damaging-gust or brief tornado risk. A richly moist boundary layer will persist south of the front, characterized by surface dewpoints from the upper 60s to the low 70s F. Even then, buoyancy will be weak due to poor mid/upper-level lapse rates, including a couple prominent stable layers noted in the 12Z KEY sounding, which will keep peak/preconvective MLCAPE values generally in the 400-800 J/kg range. The lack of more-robust instability/buoyancy will be a limiting factor for severe potential amid favorable deep shear, and potentially favorable localized low-level shear. Strong mid/upper-level winds will persist, with flow commonly 60-75 kt in the 500-250-mb layer. This will contribute to 45-55-kt effective-shear magnitudes. Low-level hodographs should be long but not particularly enlarged, with the possible exception of localized boundary influences, such as the front just east of the low. ..Edwards/Mosier.. 02/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0630 AM CST Sun Feb 18 2024 Valid 181300Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE FLORIDA KEYS AND A SMALL PART OF SOUTH FLORIDA... ...SUMMARY... Isolated to scattered thunderstorms, associated with a marginal wind/tornado threat, will be possible across part of south Florida and the Keys today. ...Synopsis... A generally progressive shortwave pattern is expected across most of the CONUS. A northeastern Pacific cyclone -- initially centered near 38N137W -- is forecast to approach (but stay offshore from) the West Coast this period. Associated frontal forcing and large-scale DCVA/cooling aloft should contribute to increasing general- thunderstorm potential from mid/late afternoon into tonight across portions of northern/central CA. Meanwhile, a downstream/midlatitiude shortwave trough was evident in moisture-channel imagery over the Mid-South and Arklatex regions, while a southern-stream perturbation was fairly prominent in the same imagery over the western Gulf. By 00Z, the midlatitude trough is expected to amplify and pivot from strongly positively tilted initially to only slightly positive over MS and the Tennessee Valley region. Overnight, this perturbation should develop a closed 500-mb low , reaching northern GA by 12Z, with trough south-southwestward across the FL Panhandle to the northeastern Gulf. As this occurs, the southern-stream/Gulf perturbation will eject east-northeastward and deamplify, reaching the extreme eastern Gulf just west of the FL Peninsula by 00Z. This perturbation should cross the peninsula and move over Atlantic waters by 06Z. In response to those developments, a slow-moving/wavy surface frontal zone -- analyzed at 11Z from near TMB to about 35 nm N of EYW -- may oscillate northward on mesobeta to local scales while remaining over extreme southern mainland FL for much of the day. With the approach of the Gulf shortwave trough aloft, a weak/ frontal-wave low now drawn about 200 nm west of EYW should ripple along the front and across south FL by 00Z, to a position just offshore from the FLL-PBI corridor. As that low proceeds east- northeastward just north of the Bahamas, the cold front should move southeastward past mainland FL and the Keys by 09Z. ...South FL/Keys... A band of convection, with isolated to scattered embedded thunderstorms, is apparent in satellite, distant radar and lightning data over the extreme eastern Gulf west of the Dry Tortugas. This activity is expected to be maintained and perhaps intensify somewhat while move east-northeastward, affecting parts of the southern mainland either side of the front, as well as the Keys, from midday into part of the afternoon. This activity may be preceded by more isolated thunderstorms developing in the warm sector and crossing the front. Marginal potential exists for supercells or embedded LEWP/bow formations, offering a damaging-gust or brief tornado risk. A richly moist boundary layer will persist south of the front, characterized by surface dewpoints from the upper 60s to the low 70s F. Even then, buoyancy will be weak due to poor mid/upper-level lapse rates, including a couple prominent stable layers noted in the 12Z KEY sounding, which will keep peak/preconvective MLCAPE values generally in the 400-800 J/kg range. The lack of more-robust instability/buoyancy will be a limiting factor for severe potential amid favorable deep shear, and potentially favorable localized low-level shear. Strong mid/upper-level winds will persist, with flow commonly 60-75 kt in the 500-250-mb layer. This will contribute to 45-55-kt effective-shear magnitudes. Low-level hodographs should be long but not particularly enlarged, with the possible exception of localized boundary influences, such as the front just east of the low. ..Edwards/Mosier.. 02/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0630 AM CST Sun Feb 18 2024 Valid 181300Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE FLORIDA KEYS AND A SMALL PART OF SOUTH FLORIDA... ...SUMMARY... Isolated to scattered thunderstorms, associated with a marginal wind/tornado threat, will be possible across part of south Florida and the Keys today. ...Synopsis... A generally progressive shortwave pattern is expected across most of the CONUS. A northeastern Pacific cyclone -- initially centered near 38N137W -- is forecast to approach (but stay offshore from) the West Coast this period. Associated frontal forcing and large-scale DCVA/cooling aloft should contribute to increasing general- thunderstorm potential from mid/late afternoon into tonight across portions of northern/central CA. Meanwhile, a downstream/midlatitiude shortwave trough was evident in moisture-channel imagery over the Mid-South and Arklatex regions, while a southern-stream perturbation was fairly prominent in the same imagery over the western Gulf. By 00Z, the midlatitude trough is expected to amplify and pivot from strongly positively tilted initially to only slightly positive over MS and the Tennessee Valley region. Overnight, this perturbation should develop a closed 500-mb low , reaching northern GA by 12Z, with trough south-southwestward across the FL Panhandle to the northeastern Gulf. As this occurs, the southern-stream/Gulf perturbation will eject east-northeastward and deamplify, reaching the extreme eastern Gulf just west of the FL Peninsula by 00Z. This perturbation should cross the peninsula and move over Atlantic waters by 06Z. In response to those developments, a slow-moving/wavy surface frontal zone -- analyzed at 11Z from near TMB to about 35 nm N of EYW -- may oscillate northward on mesobeta to local scales while remaining over extreme southern mainland FL for much of the day. With the approach of the Gulf shortwave trough aloft, a weak/ frontal-wave low now drawn about 200 nm west of EYW should ripple along the front and across south FL by 00Z, to a position just offshore from the FLL-PBI corridor. As that low proceeds east- northeastward just north of the Bahamas, the cold front should move southeastward past mainland FL and the Keys by 09Z. ...South FL/Keys... A band of convection, with isolated to scattered embedded thunderstorms, is apparent in satellite, distant radar and lightning data over the extreme eastern Gulf west of the Dry Tortugas. This activity is expected to be maintained and perhaps intensify somewhat while move east-northeastward, affecting parts of the southern mainland either side of the front, as well as the Keys, from midday into part of the afternoon. This activity may be preceded by more isolated thunderstorms developing in the warm sector and crossing the front. Marginal potential exists for supercells or embedded LEWP/bow formations, offering a damaging-gust or brief tornado risk. A richly moist boundary layer will persist south of the front, characterized by surface dewpoints from the upper 60s to the low 70s F. Even then, buoyancy will be weak due to poor mid/upper-level lapse rates, including a couple prominent stable layers noted in the 12Z KEY sounding, which will keep peak/preconvective MLCAPE values generally in the 400-800 J/kg range. The lack of more-robust instability/buoyancy will be a limiting factor for severe potential amid favorable deep shear, and potentially favorable localized low-level shear. Strong mid/upper-level winds will persist, with flow commonly 60-75 kt in the 500-250-mb layer. This will contribute to 45-55-kt effective-shear magnitudes. Low-level hodographs should be long but not particularly enlarged, with the possible exception of localized boundary influences, such as the front just east of the low. ..Edwards/Mosier.. 02/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0630 AM CST Sun Feb 18 2024 Valid 181300Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE FLORIDA KEYS AND A SMALL PART OF SOUTH FLORIDA... ...SUMMARY... Isolated to scattered thunderstorms, associated with a marginal wind/tornado threat, will be possible across part of south Florida and the Keys today. ...Synopsis... A generally progressive shortwave pattern is expected across most of the CONUS. A northeastern Pacific cyclone -- initially centered near 38N137W -- is forecast to approach (but stay offshore from) the West Coast this period. Associated frontal forcing and large-scale DCVA/cooling aloft should contribute to increasing general- thunderstorm potential from mid/late afternoon into tonight across portions of northern/central CA. Meanwhile, a downstream/midlatitiude shortwave trough was evident in moisture-channel imagery over the Mid-South and Arklatex regions, while a southern-stream perturbation was fairly prominent in the same imagery over the western Gulf. By 00Z, the midlatitude trough is expected to amplify and pivot from strongly positively tilted initially to only slightly positive over MS and the Tennessee Valley region. Overnight, this perturbation should develop a closed 500-mb low , reaching northern GA by 12Z, with trough south-southwestward across the FL Panhandle to the northeastern Gulf. As this occurs, the southern-stream/Gulf perturbation will eject east-northeastward and deamplify, reaching the extreme eastern Gulf just west of the FL Peninsula by 00Z. This perturbation should cross the peninsula and move over Atlantic waters by 06Z. In response to those developments, a slow-moving/wavy surface frontal zone -- analyzed at 11Z from near TMB to about 35 nm N of EYW -- may oscillate northward on mesobeta to local scales while remaining over extreme southern mainland FL for much of the day. With the approach of the Gulf shortwave trough aloft, a weak/ frontal-wave low now drawn about 200 nm west of EYW should ripple along the front and across south FL by 00Z, to a position just offshore from the FLL-PBI corridor. As that low proceeds east- northeastward just north of the Bahamas, the cold front should move southeastward past mainland FL and the Keys by 09Z. ...South FL/Keys... A band of convection, with isolated to scattered embedded thunderstorms, is apparent in satellite, distant radar and lightning data over the extreme eastern Gulf west of the Dry Tortugas. This activity is expected to be maintained and perhaps intensify somewhat while move east-northeastward, affecting parts of the southern mainland either side of the front, as well as the Keys, from midday into part of the afternoon. This activity may be preceded by more isolated thunderstorms developing in the warm sector and crossing the front. Marginal potential exists for supercells or embedded LEWP/bow formations, offering a damaging-gust or brief tornado risk. A richly moist boundary layer will persist south of the front, characterized by surface dewpoints from the upper 60s to the low 70s F. Even then, buoyancy will be weak due to poor mid/upper-level lapse rates, including a couple prominent stable layers noted in the 12Z KEY sounding, which will keep peak/preconvective MLCAPE values generally in the 400-800 J/kg range. The lack of more-robust instability/buoyancy will be a limiting factor for severe potential amid favorable deep shear, and potentially favorable localized low-level shear. Strong mid/upper-level winds will persist, with flow commonly 60-75 kt in the 500-250-mb layer. This will contribute to 45-55-kt effective-shear magnitudes. Low-level hodographs should be long but not particularly enlarged, with the possible exception of localized boundary influences, such as the front just east of the low. ..Edwards/Mosier.. 02/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0630 AM CST Sun Feb 18 2024 Valid 181300Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE FLORIDA KEYS AND A SMALL PART OF SOUTH FLORIDA... ...SUMMARY... Isolated to scattered thunderstorms, associated with a marginal wind/tornado threat, will be possible across part of south Florida and the Keys today. ...Synopsis... A generally progressive shortwave pattern is expected across most of the CONUS. A northeastern Pacific cyclone -- initially centered near 38N137W -- is forecast to approach (but stay offshore from) the West Coast this period. Associated frontal forcing and large-scale DCVA/cooling aloft should contribute to increasing general- thunderstorm potential from mid/late afternoon into tonight across portions of northern/central CA. Meanwhile, a downstream/midlatitiude shortwave trough was evident in moisture-channel imagery over the Mid-South and Arklatex regions, while a southern-stream perturbation was fairly prominent in the same imagery over the western Gulf. By 00Z, the midlatitude trough is expected to amplify and pivot from strongly positively tilted initially to only slightly positive over MS and the Tennessee Valley region. Overnight, this perturbation should develop a closed 500-mb low , reaching northern GA by 12Z, with trough south-southwestward across the FL Panhandle to the northeastern Gulf. As this occurs, the southern-stream/Gulf perturbation will eject east-northeastward and deamplify, reaching the extreme eastern Gulf just west of the FL Peninsula by 00Z. This perturbation should cross the peninsula and move over Atlantic waters by 06Z. In response to those developments, a slow-moving/wavy surface frontal zone -- analyzed at 11Z from near TMB to about 35 nm N of EYW -- may oscillate northward on mesobeta to local scales while remaining over extreme southern mainland FL for much of the day. With the approach of the Gulf shortwave trough aloft, a weak/ frontal-wave low now drawn about 200 nm west of EYW should ripple along the front and across south FL by 00Z, to a position just offshore from the FLL-PBI corridor. As that low proceeds east- northeastward just north of the Bahamas, the cold front should move southeastward past mainland FL and the Keys by 09Z. ...South FL/Keys... A band of convection, with isolated to scattered embedded thunderstorms, is apparent in satellite, distant radar and lightning data over the extreme eastern Gulf west of the Dry Tortugas. This activity is expected to be maintained and perhaps intensify somewhat while move east-northeastward, affecting parts of the southern mainland either side of the front, as well as the Keys, from midday into part of the afternoon. This activity may be preceded by more isolated thunderstorms developing in the warm sector and crossing the front. Marginal potential exists for supercells or embedded LEWP/bow formations, offering a damaging-gust or brief tornado risk. A richly moist boundary layer will persist south of the front, characterized by surface dewpoints from the upper 60s to the low 70s F. Even then, buoyancy will be weak due to poor mid/upper-level lapse rates, including a couple prominent stable layers noted in the 12Z KEY sounding, which will keep peak/preconvective MLCAPE values generally in the 400-800 J/kg range. The lack of more-robust instability/buoyancy will be a limiting factor for severe potential amid favorable deep shear, and potentially favorable localized low-level shear. Strong mid/upper-level winds will persist, with flow commonly 60-75 kt in the 500-250-mb layer. This will contribute to 45-55-kt effective-shear magnitudes. Low-level hodographs should be long but not particularly enlarged, with the possible exception of localized boundary influences, such as the front just east of the low. ..Edwards/Mosier.. 02/18/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CST Sun Feb 18 2024 Valid 211200Z - 261200Z ...DISCUSSION... The initial stage of moisture return is progged by medium-range model guidance on Wednesday into the southern Great Plains/Ozark Plateau regions. Models agree on the depiction of a speed max/mid-level shortwave trough moving quickly east from the Desert Southwest into the Southeast during the Wednesday-Thursday period. More in question is the quality of low-level moisture in advance of the disturbance across the Ozark Plateau eastward across the lower MS Valley and Southeast during the late Wednesday through early Friday timeframe. After the disturbance quickly exits the East Coast late in the work week, offshore flow in the Gulf of Mexico region and tranquil conditions over much of the remaining Lower 48 states will result in seasonably below-average severe potential for late February. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CST Sun Feb 18 2024 Valid 211200Z - 261200Z ...DISCUSSION... The initial stage of moisture return is progged by medium-range model guidance on Wednesday into the southern Great Plains/Ozark Plateau regions. Models agree on the depiction of a speed max/mid-level shortwave trough moving quickly east from the Desert Southwest into the Southeast during the Wednesday-Thursday period. More in question is the quality of low-level moisture in advance of the disturbance across the Ozark Plateau eastward across the lower MS Valley and Southeast during the late Wednesday through early Friday timeframe. After the disturbance quickly exits the East Coast late in the work week, offshore flow in the Gulf of Mexico region and tranquil conditions over much of the remaining Lower 48 states will result in seasonably below-average severe potential for late February. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CST Sun Feb 18 2024 Valid 211200Z - 261200Z ...DISCUSSION... The initial stage of moisture return is progged by medium-range model guidance on Wednesday into the southern Great Plains/Ozark Plateau regions. Models agree on the depiction of a speed max/mid-level shortwave trough moving quickly east from the Desert Southwest into the Southeast during the Wednesday-Thursday period. More in question is the quality of low-level moisture in advance of the disturbance across the Ozark Plateau eastward across the lower MS Valley and Southeast during the late Wednesday through early Friday timeframe. After the disturbance quickly exits the East Coast late in the work week, offshore flow in the Gulf of Mexico region and tranquil conditions over much of the remaining Lower 48 states will result in seasonably below-average severe potential for late February. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CST Sun Feb 18 2024 Valid 211200Z - 261200Z ...DISCUSSION... The initial stage of moisture return is progged by medium-range model guidance on Wednesday into the southern Great Plains/Ozark Plateau regions. Models agree on the depiction of a speed max/mid-level shortwave trough moving quickly east from the Desert Southwest into the Southeast during the Wednesday-Thursday period. More in question is the quality of low-level moisture in advance of the disturbance across the Ozark Plateau eastward across the lower MS Valley and Southeast during the late Wednesday through early Friday timeframe. After the disturbance quickly exits the East Coast late in the work week, offshore flow in the Gulf of Mexico region and tranquil conditions over much of the remaining Lower 48 states will result in seasonably below-average severe potential for late February. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CST Sun Feb 18 2024 Valid 211200Z - 261200Z ...DISCUSSION... The initial stage of moisture return is progged by medium-range model guidance on Wednesday into the southern Great Plains/Ozark Plateau regions. Models agree on the depiction of a speed max/mid-level shortwave trough moving quickly east from the Desert Southwest into the Southeast during the Wednesday-Thursday period. More in question is the quality of low-level moisture in advance of the disturbance across the Ozark Plateau eastward across the lower MS Valley and Southeast during the late Wednesday through early Friday timeframe. After the disturbance quickly exits the East Coast late in the work week, offshore flow in the Gulf of Mexico region and tranquil conditions over much of the remaining Lower 48 states will result in seasonably below-average severe potential for late February. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CST Sun Feb 18 2024 Valid 211200Z - 261200Z ...DISCUSSION... The initial stage of moisture return is progged by medium-range model guidance on Wednesday into the southern Great Plains/Ozark Plateau regions. Models agree on the depiction of a speed max/mid-level shortwave trough moving quickly east from the Desert Southwest into the Southeast during the Wednesday-Thursday period. More in question is the quality of low-level moisture in advance of the disturbance across the Ozark Plateau eastward across the lower MS Valley and Southeast during the late Wednesday through early Friday timeframe. After the disturbance quickly exits the East Coast late in the work week, offshore flow in the Gulf of Mexico region and tranquil conditions over much of the remaining Lower 48 states will result in seasonably below-average severe potential for late February. Read more

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0215 AM CST Sun Feb 18 2024 Valid 201200Z - 211200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not forecast across the contiguous United States on Tuesday. ...Synopsis... A large-scale mid-level trough will remain situated along the West Coast while a downstream ridge resides over the High Plains. Farther east, mean troughing due to two mid-level troughs will encompass much of the East. Isolated to scattered showers will continue over parts of the West Coast in association with the mid-level trough. Pockets of weak instability will likely develop and may result in isolated thunderstorms over mainly CA, but perhaps on a much more localized/widely spaced basis in NV and ID. Tranquil weather conditions are forecast over the central and eastern states. ..Smith.. 02/18/2024 Read more

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0215 AM CST Sun Feb 18 2024 Valid 201200Z - 211200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not forecast across the contiguous United States on Tuesday. ...Synopsis... A large-scale mid-level trough will remain situated along the West Coast while a downstream ridge resides over the High Plains. Farther east, mean troughing due to two mid-level troughs will encompass much of the East. Isolated to scattered showers will continue over parts of the West Coast in association with the mid-level trough. Pockets of weak instability will likely develop and may result in isolated thunderstorms over mainly CA, but perhaps on a much more localized/widely spaced basis in NV and ID. Tranquil weather conditions are forecast over the central and eastern states. ..Smith.. 02/18/2024 Read more

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0215 AM CST Sun Feb 18 2024 Valid 201200Z - 211200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not forecast across the contiguous United States on Tuesday. ...Synopsis... A large-scale mid-level trough will remain situated along the West Coast while a downstream ridge resides over the High Plains. Farther east, mean troughing due to two mid-level troughs will encompass much of the East. Isolated to scattered showers will continue over parts of the West Coast in association with the mid-level trough. Pockets of weak instability will likely develop and may result in isolated thunderstorms over mainly CA, but perhaps on a much more localized/widely spaced basis in NV and ID. Tranquil weather conditions are forecast over the central and eastern states. ..Smith.. 02/18/2024 Read more