Severe Storms

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0747 AM CDT Wed Aug 07 2024 Valid 071300Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE CENTRAL GREAT PLAINS AND COASTAL CAROLINAS... ...SUMMARY... Marginal severe-weather potential is apparent over parts of the central Great Plains and coastal Carolinas. ...Synopsis... The persistent western CONUS anticyclone will contract through the period and shift westward across the southern Great Basin, in response to both infusions of positive vorticity in its eastern semicircle, and more strongly, amplification/progression of a northern-stream synoptic trough over western/central Canada. That trough -- evident in moisture-channel imagery from a low over north-central MB west-southwestward across the Canadian Rockies -- will move southward through the period. By 12Z tomorrow, the 500-mb low should cross the remainder of central/southern MB to near the eastern ND/MB border. Associated height falls and cyclonic flow aloft will spread southward over the northern Plains today, to the central Plains late tonight. Downstream, the northern-stream flow will flatten to a more-zonal configuration through the period, across the Upper Great Lakes, the St. Lawrence Valley and northern New England. This temporarily maintains a dearth of steering flow near T.S. Debby, with weak poleward/inland motion forecast by NHC through 12Z tomorrow. See latest NHC advisories for track/intensity forecasts for Debby, as well as tropical watches/warnings. At the surface, 11Z analysis showed a wavy, quasistationary to slowly moving cold front from southern New England coastal waters westward over northeastern PA, then southwestward through a low near HTS, becoming a cold front over central KY to northeastern OK, through a low near LTS, then quasistationary again northwestward to a weak low over southeastern CO. The boundary should continue southward across parts of KY, TN, northern MS and AR, amidst broader northerlies extending westward from the circulation of T.S. Debby. A separate cold front -- related to the northern-stream perturbation over Canada -- was drawn from southeastern MB to near a BIS-RAP-RWL line. By 00Z, this front should extend from western parts of northwestern ON southwestward over northern MN, eastern SD, central NE, and northeastern CO. By 12Z tomorrow, the front should reach western parts of Lake Superior and WI, then southwestward over western IA, southeastern NE, southwestern KS, and northeastern NM. ...Central Great Plains... Widely scattered to scattered thunderstorms are forecast to form this afternoon and evening -- mainly on the cold front over NE and southeastern SD, and over higher elevations of southeastern WY and north-central/northeastern CO behind the front. Activity will pose a threat for isolated large hail and severe gusts before weakening overnight. Once an area of clouds and precip now over southern SD and northern NE exits the area, afternoon destabilization should reduce EML-related CINH ahead of the front through the afternoon, with frontal lift expected to be strong enough to break the cap in a few spots by late afternoon. Surface dewpoints in the upper 50s to low 60s F (locally higher) will contribute to a prefrontal plume of 1000-1500 J/kg MLCAPE that will narrow with northeastward extent into lower antecedent theta-e. The southern fringe of falls and a tightening gradient of heights aloft will extend across parts of this area from late afternoon onward as well, contributing to favorable deep shear for some storm organization and isolated supercell potential -- with effective-shear magnitudes generally 35-45 kt. Stronger veering with height -- but somewhat weaker mid/upper flow -- will characterize the post-frontal upslope regime, with elongated, nearly straight hodographs and similar bulk-shear values. Well-mixed subcloud layers will support gust potential, which may become concentrated on the mesobeta scale where any upscale clustering and cold-pool development can occur (most probable with activity initiated in the higher elevations). ...T.S. Debby -- Coastal Carolinas... As Debby gradually turns and moves northward to northwestward, only a slow corresponding shift of the tornado potential will occur. Inland destabilization is expected to be minimal, owing to extensive cloud cover and areas of precip north of center, and acting as a northern/northwestern limiter to the threat. Meanwhile the skeletal to almost nonexistent core convective structure and weaker shear will minimize potential closer to center. This leaves a segment of eastern NC near the sounds and Outer Banks today and tonight, as well as perhaps a small part of the adjoining SC coastal areas today, with potential for isolated, mainly short-lived supercells in the middle/outer bands. While hodographs are not forecast to be especially large, compared to many TC-tornado events, 150-250 J/kg effective SRH for northwestward-moving cells has been present in VWP hodographs and 6-hourly RAOBs, and should continue. This will overlap favorable buoyancy within roughly 75-100 nm inland of the beaches in NC. If a relatively concentrated area of sustained, multiple supercell development or potential appears for a particular band, a smaller area of greater probabilities may be added in a subsequent outlook. ..Edwards/Dean.. 08/07/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0747 AM CDT Wed Aug 07 2024 Valid 071300Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE CENTRAL GREAT PLAINS AND COASTAL CAROLINAS... ...SUMMARY... Marginal severe-weather potential is apparent over parts of the central Great Plains and coastal Carolinas. ...Synopsis... The persistent western CONUS anticyclone will contract through the period and shift westward across the southern Great Basin, in response to both infusions of positive vorticity in its eastern semicircle, and more strongly, amplification/progression of a northern-stream synoptic trough over western/central Canada. That trough -- evident in moisture-channel imagery from a low over north-central MB west-southwestward across the Canadian Rockies -- will move southward through the period. By 12Z tomorrow, the 500-mb low should cross the remainder of central/southern MB to near the eastern ND/MB border. Associated height falls and cyclonic flow aloft will spread southward over the northern Plains today, to the central Plains late tonight. Downstream, the northern-stream flow will flatten to a more-zonal configuration through the period, across the Upper Great Lakes, the St. Lawrence Valley and northern New England. This temporarily maintains a dearth of steering flow near T.S. Debby, with weak poleward/inland motion forecast by NHC through 12Z tomorrow. See latest NHC advisories for track/intensity forecasts for Debby, as well as tropical watches/warnings. At the surface, 11Z analysis showed a wavy, quasistationary to slowly moving cold front from southern New England coastal waters westward over northeastern PA, then southwestward through a low near HTS, becoming a cold front over central KY to northeastern OK, through a low near LTS, then quasistationary again northwestward to a weak low over southeastern CO. The boundary should continue southward across parts of KY, TN, northern MS and AR, amidst broader northerlies extending westward from the circulation of T.S. Debby. A separate cold front -- related to the northern-stream perturbation over Canada -- was drawn from southeastern MB to near a BIS-RAP-RWL line. By 00Z, this front should extend from western parts of northwestern ON southwestward over northern MN, eastern SD, central NE, and northeastern CO. By 12Z tomorrow, the front should reach western parts of Lake Superior and WI, then southwestward over western IA, southeastern NE, southwestern KS, and northeastern NM. ...Central Great Plains... Widely scattered to scattered thunderstorms are forecast to form this afternoon and evening -- mainly on the cold front over NE and southeastern SD, and over higher elevations of southeastern WY and north-central/northeastern CO behind the front. Activity will pose a threat for isolated large hail and severe gusts before weakening overnight. Once an area of clouds and precip now over southern SD and northern NE exits the area, afternoon destabilization should reduce EML-related CINH ahead of the front through the afternoon, with frontal lift expected to be strong enough to break the cap in a few spots by late afternoon. Surface dewpoints in the upper 50s to low 60s F (locally higher) will contribute to a prefrontal plume of 1000-1500 J/kg MLCAPE that will narrow with northeastward extent into lower antecedent theta-e. The southern fringe of falls and a tightening gradient of heights aloft will extend across parts of this area from late afternoon onward as well, contributing to favorable deep shear for some storm organization and isolated supercell potential -- with effective-shear magnitudes generally 35-45 kt. Stronger veering with height -- but somewhat weaker mid/upper flow -- will characterize the post-frontal upslope regime, with elongated, nearly straight hodographs and similar bulk-shear values. Well-mixed subcloud layers will support gust potential, which may become concentrated on the mesobeta scale where any upscale clustering and cold-pool development can occur (most probable with activity initiated in the higher elevations). ...T.S. Debby -- Coastal Carolinas... As Debby gradually turns and moves northward to northwestward, only a slow corresponding shift of the tornado potential will occur. Inland destabilization is expected to be minimal, owing to extensive cloud cover and areas of precip north of center, and acting as a northern/northwestern limiter to the threat. Meanwhile the skeletal to almost nonexistent core convective structure and weaker shear will minimize potential closer to center. This leaves a segment of eastern NC near the sounds and Outer Banks today and tonight, as well as perhaps a small part of the adjoining SC coastal areas today, with potential for isolated, mainly short-lived supercells in the middle/outer bands. While hodographs are not forecast to be especially large, compared to many TC-tornado events, 150-250 J/kg effective SRH for northwestward-moving cells has been present in VWP hodographs and 6-hourly RAOBs, and should continue. This will overlap favorable buoyancy within roughly 75-100 nm inland of the beaches in NC. If a relatively concentrated area of sustained, multiple supercell development or potential appears for a particular band, a smaller area of greater probabilities may be added in a subsequent outlook. ..Edwards/Dean.. 08/07/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0747 AM CDT Wed Aug 07 2024 Valid 071300Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE CENTRAL GREAT PLAINS AND COASTAL CAROLINAS... ...SUMMARY... Marginal severe-weather potential is apparent over parts of the central Great Plains and coastal Carolinas. ...Synopsis... The persistent western CONUS anticyclone will contract through the period and shift westward across the southern Great Basin, in response to both infusions of positive vorticity in its eastern semicircle, and more strongly, amplification/progression of a northern-stream synoptic trough over western/central Canada. That trough -- evident in moisture-channel imagery from a low over north-central MB west-southwestward across the Canadian Rockies -- will move southward through the period. By 12Z tomorrow, the 500-mb low should cross the remainder of central/southern MB to near the eastern ND/MB border. Associated height falls and cyclonic flow aloft will spread southward over the northern Plains today, to the central Plains late tonight. Downstream, the northern-stream flow will flatten to a more-zonal configuration through the period, across the Upper Great Lakes, the St. Lawrence Valley and northern New England. This temporarily maintains a dearth of steering flow near T.S. Debby, with weak poleward/inland motion forecast by NHC through 12Z tomorrow. See latest NHC advisories for track/intensity forecasts for Debby, as well as tropical watches/warnings. At the surface, 11Z analysis showed a wavy, quasistationary to slowly moving cold front from southern New England coastal waters westward over northeastern PA, then southwestward through a low near HTS, becoming a cold front over central KY to northeastern OK, through a low near LTS, then quasistationary again northwestward to a weak low over southeastern CO. The boundary should continue southward across parts of KY, TN, northern MS and AR, amidst broader northerlies extending westward from the circulation of T.S. Debby. A separate cold front -- related to the northern-stream perturbation over Canada -- was drawn from southeastern MB to near a BIS-RAP-RWL line. By 00Z, this front should extend from western parts of northwestern ON southwestward over northern MN, eastern SD, central NE, and northeastern CO. By 12Z tomorrow, the front should reach western parts of Lake Superior and WI, then southwestward over western IA, southeastern NE, southwestern KS, and northeastern NM. ...Central Great Plains... Widely scattered to scattered thunderstorms are forecast to form this afternoon and evening -- mainly on the cold front over NE and southeastern SD, and over higher elevations of southeastern WY and north-central/northeastern CO behind the front. Activity will pose a threat for isolated large hail and severe gusts before weakening overnight. Once an area of clouds and precip now over southern SD and northern NE exits the area, afternoon destabilization should reduce EML-related CINH ahead of the front through the afternoon, with frontal lift expected to be strong enough to break the cap in a few spots by late afternoon. Surface dewpoints in the upper 50s to low 60s F (locally higher) will contribute to a prefrontal plume of 1000-1500 J/kg MLCAPE that will narrow with northeastward extent into lower antecedent theta-e. The southern fringe of falls and a tightening gradient of heights aloft will extend across parts of this area from late afternoon onward as well, contributing to favorable deep shear for some storm organization and isolated supercell potential -- with effective-shear magnitudes generally 35-45 kt. Stronger veering with height -- but somewhat weaker mid/upper flow -- will characterize the post-frontal upslope regime, with elongated, nearly straight hodographs and similar bulk-shear values. Well-mixed subcloud layers will support gust potential, which may become concentrated on the mesobeta scale where any upscale clustering and cold-pool development can occur (most probable with activity initiated in the higher elevations). ...T.S. Debby -- Coastal Carolinas... As Debby gradually turns and moves northward to northwestward, only a slow corresponding shift of the tornado potential will occur. Inland destabilization is expected to be minimal, owing to extensive cloud cover and areas of precip north of center, and acting as a northern/northwestern limiter to the threat. Meanwhile the skeletal to almost nonexistent core convective structure and weaker shear will minimize potential closer to center. This leaves a segment of eastern NC near the sounds and Outer Banks today and tonight, as well as perhaps a small part of the adjoining SC coastal areas today, with potential for isolated, mainly short-lived supercells in the middle/outer bands. While hodographs are not forecast to be especially large, compared to many TC-tornado events, 150-250 J/kg effective SRH for northwestward-moving cells has been present in VWP hodographs and 6-hourly RAOBs, and should continue. This will overlap favorable buoyancy within roughly 75-100 nm inland of the beaches in NC. If a relatively concentrated area of sustained, multiple supercell development or potential appears for a particular band, a smaller area of greater probabilities may be added in a subsequent outlook. ..Edwards/Dean.. 08/07/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0747 AM CDT Wed Aug 07 2024 Valid 071300Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE CENTRAL GREAT PLAINS AND COASTAL CAROLINAS... ...SUMMARY... Marginal severe-weather potential is apparent over parts of the central Great Plains and coastal Carolinas. ...Synopsis... The persistent western CONUS anticyclone will contract through the period and shift westward across the southern Great Basin, in response to both infusions of positive vorticity in its eastern semicircle, and more strongly, amplification/progression of a northern-stream synoptic trough over western/central Canada. That trough -- evident in moisture-channel imagery from a low over north-central MB west-southwestward across the Canadian Rockies -- will move southward through the period. By 12Z tomorrow, the 500-mb low should cross the remainder of central/southern MB to near the eastern ND/MB border. Associated height falls and cyclonic flow aloft will spread southward over the northern Plains today, to the central Plains late tonight. Downstream, the northern-stream flow will flatten to a more-zonal configuration through the period, across the Upper Great Lakes, the St. Lawrence Valley and northern New England. This temporarily maintains a dearth of steering flow near T.S. Debby, with weak poleward/inland motion forecast by NHC through 12Z tomorrow. See latest NHC advisories for track/intensity forecasts for Debby, as well as tropical watches/warnings. At the surface, 11Z analysis showed a wavy, quasistationary to slowly moving cold front from southern New England coastal waters westward over northeastern PA, then southwestward through a low near HTS, becoming a cold front over central KY to northeastern OK, through a low near LTS, then quasistationary again northwestward to a weak low over southeastern CO. The boundary should continue southward across parts of KY, TN, northern MS and AR, amidst broader northerlies extending westward from the circulation of T.S. Debby. A separate cold front -- related to the northern-stream perturbation over Canada -- was drawn from southeastern MB to near a BIS-RAP-RWL line. By 00Z, this front should extend from western parts of northwestern ON southwestward over northern MN, eastern SD, central NE, and northeastern CO. By 12Z tomorrow, the front should reach western parts of Lake Superior and WI, then southwestward over western IA, southeastern NE, southwestern KS, and northeastern NM. ...Central Great Plains... Widely scattered to scattered thunderstorms are forecast to form this afternoon and evening -- mainly on the cold front over NE and southeastern SD, and over higher elevations of southeastern WY and north-central/northeastern CO behind the front. Activity will pose a threat for isolated large hail and severe gusts before weakening overnight. Once an area of clouds and precip now over southern SD and northern NE exits the area, afternoon destabilization should reduce EML-related CINH ahead of the front through the afternoon, with frontal lift expected to be strong enough to break the cap in a few spots by late afternoon. Surface dewpoints in the upper 50s to low 60s F (locally higher) will contribute to a prefrontal plume of 1000-1500 J/kg MLCAPE that will narrow with northeastward extent into lower antecedent theta-e. The southern fringe of falls and a tightening gradient of heights aloft will extend across parts of this area from late afternoon onward as well, contributing to favorable deep shear for some storm organization and isolated supercell potential -- with effective-shear magnitudes generally 35-45 kt. Stronger veering with height -- but somewhat weaker mid/upper flow -- will characterize the post-frontal upslope regime, with elongated, nearly straight hodographs and similar bulk-shear values. Well-mixed subcloud layers will support gust potential, which may become concentrated on the mesobeta scale where any upscale clustering and cold-pool development can occur (most probable with activity initiated in the higher elevations). ...T.S. Debby -- Coastal Carolinas... As Debby gradually turns and moves northward to northwestward, only a slow corresponding shift of the tornado potential will occur. Inland destabilization is expected to be minimal, owing to extensive cloud cover and areas of precip north of center, and acting as a northern/northwestern limiter to the threat. Meanwhile the skeletal to almost nonexistent core convective structure and weaker shear will minimize potential closer to center. This leaves a segment of eastern NC near the sounds and Outer Banks today and tonight, as well as perhaps a small part of the adjoining SC coastal areas today, with potential for isolated, mainly short-lived supercells in the middle/outer bands. While hodographs are not forecast to be especially large, compared to many TC-tornado events, 150-250 J/kg effective SRH for northwestward-moving cells has been present in VWP hodographs and 6-hourly RAOBs, and should continue. This will overlap favorable buoyancy within roughly 75-100 nm inland of the beaches in NC. If a relatively concentrated area of sustained, multiple supercell development or potential appears for a particular band, a smaller area of greater probabilities may be added in a subsequent outlook. ..Edwards/Dean.. 08/07/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0747 AM CDT Wed Aug 07 2024 Valid 071300Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE CENTRAL GREAT PLAINS AND COASTAL CAROLINAS... ...SUMMARY... Marginal severe-weather potential is apparent over parts of the central Great Plains and coastal Carolinas. ...Synopsis... The persistent western CONUS anticyclone will contract through the period and shift westward across the southern Great Basin, in response to both infusions of positive vorticity in its eastern semicircle, and more strongly, amplification/progression of a northern-stream synoptic trough over western/central Canada. That trough -- evident in moisture-channel imagery from a low over north-central MB west-southwestward across the Canadian Rockies -- will move southward through the period. By 12Z tomorrow, the 500-mb low should cross the remainder of central/southern MB to near the eastern ND/MB border. Associated height falls and cyclonic flow aloft will spread southward over the northern Plains today, to the central Plains late tonight. Downstream, the northern-stream flow will flatten to a more-zonal configuration through the period, across the Upper Great Lakes, the St. Lawrence Valley and northern New England. This temporarily maintains a dearth of steering flow near T.S. Debby, with weak poleward/inland motion forecast by NHC through 12Z tomorrow. See latest NHC advisories for track/intensity forecasts for Debby, as well as tropical watches/warnings. At the surface, 11Z analysis showed a wavy, quasistationary to slowly moving cold front from southern New England coastal waters westward over northeastern PA, then southwestward through a low near HTS, becoming a cold front over central KY to northeastern OK, through a low near LTS, then quasistationary again northwestward to a weak low over southeastern CO. The boundary should continue southward across parts of KY, TN, northern MS and AR, amidst broader northerlies extending westward from the circulation of T.S. Debby. A separate cold front -- related to the northern-stream perturbation over Canada -- was drawn from southeastern MB to near a BIS-RAP-RWL line. By 00Z, this front should extend from western parts of northwestern ON southwestward over northern MN, eastern SD, central NE, and northeastern CO. By 12Z tomorrow, the front should reach western parts of Lake Superior and WI, then southwestward over western IA, southeastern NE, southwestern KS, and northeastern NM. ...Central Great Plains... Widely scattered to scattered thunderstorms are forecast to form this afternoon and evening -- mainly on the cold front over NE and southeastern SD, and over higher elevations of southeastern WY and north-central/northeastern CO behind the front. Activity will pose a threat for isolated large hail and severe gusts before weakening overnight. Once an area of clouds and precip now over southern SD and northern NE exits the area, afternoon destabilization should reduce EML-related CINH ahead of the front through the afternoon, with frontal lift expected to be strong enough to break the cap in a few spots by late afternoon. Surface dewpoints in the upper 50s to low 60s F (locally higher) will contribute to a prefrontal plume of 1000-1500 J/kg MLCAPE that will narrow with northeastward extent into lower antecedent theta-e. The southern fringe of falls and a tightening gradient of heights aloft will extend across parts of this area from late afternoon onward as well, contributing to favorable deep shear for some storm organization and isolated supercell potential -- with effective-shear magnitudes generally 35-45 kt. Stronger veering with height -- but somewhat weaker mid/upper flow -- will characterize the post-frontal upslope regime, with elongated, nearly straight hodographs and similar bulk-shear values. Well-mixed subcloud layers will support gust potential, which may become concentrated on the mesobeta scale where any upscale clustering and cold-pool development can occur (most probable with activity initiated in the higher elevations). ...T.S. Debby -- Coastal Carolinas... As Debby gradually turns and moves northward to northwestward, only a slow corresponding shift of the tornado potential will occur. Inland destabilization is expected to be minimal, owing to extensive cloud cover and areas of precip north of center, and acting as a northern/northwestern limiter to the threat. Meanwhile the skeletal to almost nonexistent core convective structure and weaker shear will minimize potential closer to center. This leaves a segment of eastern NC near the sounds and Outer Banks today and tonight, as well as perhaps a small part of the adjoining SC coastal areas today, with potential for isolated, mainly short-lived supercells in the middle/outer bands. While hodographs are not forecast to be especially large, compared to many TC-tornado events, 150-250 J/kg effective SRH for northwestward-moving cells has been present in VWP hodographs and 6-hourly RAOBs, and should continue. This will overlap favorable buoyancy within roughly 75-100 nm inland of the beaches in NC. If a relatively concentrated area of sustained, multiple supercell development or potential appears for a particular band, a smaller area of greater probabilities may be added in a subsequent outlook. ..Edwards/Dean.. 08/07/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0747 AM CDT Wed Aug 07 2024 Valid 071300Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE CENTRAL GREAT PLAINS AND COASTAL CAROLINAS... ...SUMMARY... Marginal severe-weather potential is apparent over parts of the central Great Plains and coastal Carolinas. ...Synopsis... The persistent western CONUS anticyclone will contract through the period and shift westward across the southern Great Basin, in response to both infusions of positive vorticity in its eastern semicircle, and more strongly, amplification/progression of a northern-stream synoptic trough over western/central Canada. That trough -- evident in moisture-channel imagery from a low over north-central MB west-southwestward across the Canadian Rockies -- will move southward through the period. By 12Z tomorrow, the 500-mb low should cross the remainder of central/southern MB to near the eastern ND/MB border. Associated height falls and cyclonic flow aloft will spread southward over the northern Plains today, to the central Plains late tonight. Downstream, the northern-stream flow will flatten to a more-zonal configuration through the period, across the Upper Great Lakes, the St. Lawrence Valley and northern New England. This temporarily maintains a dearth of steering flow near T.S. Debby, with weak poleward/inland motion forecast by NHC through 12Z tomorrow. See latest NHC advisories for track/intensity forecasts for Debby, as well as tropical watches/warnings. At the surface, 11Z analysis showed a wavy, quasistationary to slowly moving cold front from southern New England coastal waters westward over northeastern PA, then southwestward through a low near HTS, becoming a cold front over central KY to northeastern OK, through a low near LTS, then quasistationary again northwestward to a weak low over southeastern CO. The boundary should continue southward across parts of KY, TN, northern MS and AR, amidst broader northerlies extending westward from the circulation of T.S. Debby. A separate cold front -- related to the northern-stream perturbation over Canada -- was drawn from southeastern MB to near a BIS-RAP-RWL line. By 00Z, this front should extend from western parts of northwestern ON southwestward over northern MN, eastern SD, central NE, and northeastern CO. By 12Z tomorrow, the front should reach western parts of Lake Superior and WI, then southwestward over western IA, southeastern NE, southwestern KS, and northeastern NM. ...Central Great Plains... Widely scattered to scattered thunderstorms are forecast to form this afternoon and evening -- mainly on the cold front over NE and southeastern SD, and over higher elevations of southeastern WY and north-central/northeastern CO behind the front. Activity will pose a threat for isolated large hail and severe gusts before weakening overnight. Once an area of clouds and precip now over southern SD and northern NE exits the area, afternoon destabilization should reduce EML-related CINH ahead of the front through the afternoon, with frontal lift expected to be strong enough to break the cap in a few spots by late afternoon. Surface dewpoints in the upper 50s to low 60s F (locally higher) will contribute to a prefrontal plume of 1000-1500 J/kg MLCAPE that will narrow with northeastward extent into lower antecedent theta-e. The southern fringe of falls and a tightening gradient of heights aloft will extend across parts of this area from late afternoon onward as well, contributing to favorable deep shear for some storm organization and isolated supercell potential -- with effective-shear magnitudes generally 35-45 kt. Stronger veering with height -- but somewhat weaker mid/upper flow -- will characterize the post-frontal upslope regime, with elongated, nearly straight hodographs and similar bulk-shear values. Well-mixed subcloud layers will support gust potential, which may become concentrated on the mesobeta scale where any upscale clustering and cold-pool development can occur (most probable with activity initiated in the higher elevations). ...T.S. Debby -- Coastal Carolinas... As Debby gradually turns and moves northward to northwestward, only a slow corresponding shift of the tornado potential will occur. Inland destabilization is expected to be minimal, owing to extensive cloud cover and areas of precip north of center, and acting as a northern/northwestern limiter to the threat. Meanwhile the skeletal to almost nonexistent core convective structure and weaker shear will minimize potential closer to center. This leaves a segment of eastern NC near the sounds and Outer Banks today and tonight, as well as perhaps a small part of the adjoining SC coastal areas today, with potential for isolated, mainly short-lived supercells in the middle/outer bands. While hodographs are not forecast to be especially large, compared to many TC-tornado events, 150-250 J/kg effective SRH for northwestward-moving cells has been present in VWP hodographs and 6-hourly RAOBs, and should continue. This will overlap favorable buoyancy within roughly 75-100 nm inland of the beaches in NC. If a relatively concentrated area of sustained, multiple supercell development or potential appears for a particular band, a smaller area of greater probabilities may be added in a subsequent outlook. ..Edwards/Dean.. 08/07/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0747 AM CDT Wed Aug 07 2024 Valid 071300Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE CENTRAL GREAT PLAINS AND COASTAL CAROLINAS... ...SUMMARY... Marginal severe-weather potential is apparent over parts of the central Great Plains and coastal Carolinas. ...Synopsis... The persistent western CONUS anticyclone will contract through the period and shift westward across the southern Great Basin, in response to both infusions of positive vorticity in its eastern semicircle, and more strongly, amplification/progression of a northern-stream synoptic trough over western/central Canada. That trough -- evident in moisture-channel imagery from a low over north-central MB west-southwestward across the Canadian Rockies -- will move southward through the period. By 12Z tomorrow, the 500-mb low should cross the remainder of central/southern MB to near the eastern ND/MB border. Associated height falls and cyclonic flow aloft will spread southward over the northern Plains today, to the central Plains late tonight. Downstream, the northern-stream flow will flatten to a more-zonal configuration through the period, across the Upper Great Lakes, the St. Lawrence Valley and northern New England. This temporarily maintains a dearth of steering flow near T.S. Debby, with weak poleward/inland motion forecast by NHC through 12Z tomorrow. See latest NHC advisories for track/intensity forecasts for Debby, as well as tropical watches/warnings. At the surface, 11Z analysis showed a wavy, quasistationary to slowly moving cold front from southern New England coastal waters westward over northeastern PA, then southwestward through a low near HTS, becoming a cold front over central KY to northeastern OK, through a low near LTS, then quasistationary again northwestward to a weak low over southeastern CO. The boundary should continue southward across parts of KY, TN, northern MS and AR, amidst broader northerlies extending westward from the circulation of T.S. Debby. A separate cold front -- related to the northern-stream perturbation over Canada -- was drawn from southeastern MB to near a BIS-RAP-RWL line. By 00Z, this front should extend from western parts of northwestern ON southwestward over northern MN, eastern SD, central NE, and northeastern CO. By 12Z tomorrow, the front should reach western parts of Lake Superior and WI, then southwestward over western IA, southeastern NE, southwestern KS, and northeastern NM. ...Central Great Plains... Widely scattered to scattered thunderstorms are forecast to form this afternoon and evening -- mainly on the cold front over NE and southeastern SD, and over higher elevations of southeastern WY and north-central/northeastern CO behind the front. Activity will pose a threat for isolated large hail and severe gusts before weakening overnight. Once an area of clouds and precip now over southern SD and northern NE exits the area, afternoon destabilization should reduce EML-related CINH ahead of the front through the afternoon, with frontal lift expected to be strong enough to break the cap in a few spots by late afternoon. Surface dewpoints in the upper 50s to low 60s F (locally higher) will contribute to a prefrontal plume of 1000-1500 J/kg MLCAPE that will narrow with northeastward extent into lower antecedent theta-e. The southern fringe of falls and a tightening gradient of heights aloft will extend across parts of this area from late afternoon onward as well, contributing to favorable deep shear for some storm organization and isolated supercell potential -- with effective-shear magnitudes generally 35-45 kt. Stronger veering with height -- but somewhat weaker mid/upper flow -- will characterize the post-frontal upslope regime, with elongated, nearly straight hodographs and similar bulk-shear values. Well-mixed subcloud layers will support gust potential, which may become concentrated on the mesobeta scale where any upscale clustering and cold-pool development can occur (most probable with activity initiated in the higher elevations). ...T.S. Debby -- Coastal Carolinas... As Debby gradually turns and moves northward to northwestward, only a slow corresponding shift of the tornado potential will occur. Inland destabilization is expected to be minimal, owing to extensive cloud cover and areas of precip north of center, and acting as a northern/northwestern limiter to the threat. Meanwhile the skeletal to almost nonexistent core convective structure and weaker shear will minimize potential closer to center. This leaves a segment of eastern NC near the sounds and Outer Banks today and tonight, as well as perhaps a small part of the adjoining SC coastal areas today, with potential for isolated, mainly short-lived supercells in the middle/outer bands. While hodographs are not forecast to be especially large, compared to many TC-tornado events, 150-250 J/kg effective SRH for northwestward-moving cells has been present in VWP hodographs and 6-hourly RAOBs, and should continue. This will overlap favorable buoyancy within roughly 75-100 nm inland of the beaches in NC. If a relatively concentrated area of sustained, multiple supercell development or potential appears for a particular band, a smaller area of greater probabilities may be added in a subsequent outlook. ..Edwards/Dean.. 08/07/2024 Read more

MD 1855 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR SOUTHEAST NC INTO EXTREME NORTHEAST SC
Mesoscale Discussion 1855 NWS Storm Prediction Center Norman OK 0155 AM CDT Wed Aug 07 2024 Areas affected...Southeast NC into extreme northeast SC Concerning...Severe potential...Watch unlikely Valid 070655Z - 071000Z Probability of Watch Issuance...20 percent SUMMARY...A brief tornado or two will be possible overnight. DISCUSSION...A band of convection along the east/northeast periphery of Tropical Storm Debby's circulation has become somewhat more well-defined early this morning. A theta-e/instability gradient persists near the coast, with a narrow inland zone of MLCAPE near 1000 J/kg noted (per recent objective mesoanalyses and a modified 06Z sounding from KMHX) where temperatures remain near 80 F. The 06Z MHX sounding and recent VWPs from KMHX/KLTX depict 0-1 km SRH of around 150-200 m2/s2 for observed cell motions, which is sufficient to support at least transient low-level rotation with the strongest cells. While ongoing convection has generally struggled to become organized, a brief tornado or two cannot be ruled out overnight as stronger embedded cells within the primary convective band move inland and cross the near-coastal baroclinic zone. ..Dean/Edwards.. 08/07/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MHX...ILM... LAT...LON 34147884 34387852 35037745 35037690 34857667 34427693 33847770 33627823 33527882 33797896 34147884 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Wed Aug 07 2024 Valid 101200Z - 151200Z ...DISCUSSION... Medium-range guidance indicates that the initially prominent higher-latitude mid-level ridging emerging from the Canadian Northwest Territories will gradually become suppressed through this period. Although there is notable spread concerning the downstream acceleration of the initially significant mid-level low to its southeast, it appears that larger-scale mid-level troughing will slowly shift eastward in positively tilted fashion, through the St. Lawrence Valley and lower Great Lakes region by late this coming weekend, through the Northeast and Canadian Maritimes by the middle of next week. In advance of the troughing, Debby's remnant surface low may interact with a surface cold front advancing to the east of the lower Great Lakes/upper Ohio Valley, before perhaps merging into the primary surface cyclone across southern Quebec by Saturday. Models have varied concerning these developments, but tropical pre-frontal moistening in the presence of intensifying deep-layer southerly wind fields might be accompanied by an evolving low-topped convective band with potential to produce damaging wind gusts near/east of the Hudson/Champlain Valleys through New England. Due to lingering uncertainties severe probabilities are begin maintained at less than 15 percent, but this could change in later outlooks for Saturday. Otherwise, the potential for severe weather elsewhere across the U.S. late this coming weekend into the middle of next week appears likely to be remain limited by the lack of stronger boundary-layer destabilization. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Wed Aug 07 2024 Valid 101200Z - 151200Z ...DISCUSSION... Medium-range guidance indicates that the initially prominent higher-latitude mid-level ridging emerging from the Canadian Northwest Territories will gradually become suppressed through this period. Although there is notable spread concerning the downstream acceleration of the initially significant mid-level low to its southeast, it appears that larger-scale mid-level troughing will slowly shift eastward in positively tilted fashion, through the St. Lawrence Valley and lower Great Lakes region by late this coming weekend, through the Northeast and Canadian Maritimes by the middle of next week. In advance of the troughing, Debby's remnant surface low may interact with a surface cold front advancing to the east of the lower Great Lakes/upper Ohio Valley, before perhaps merging into the primary surface cyclone across southern Quebec by Saturday. Models have varied concerning these developments, but tropical pre-frontal moistening in the presence of intensifying deep-layer southerly wind fields might be accompanied by an evolving low-topped convective band with potential to produce damaging wind gusts near/east of the Hudson/Champlain Valleys through New England. Due to lingering uncertainties severe probabilities are begin maintained at less than 15 percent, but this could change in later outlooks for Saturday. Otherwise, the potential for severe weather elsewhere across the U.S. late this coming weekend into the middle of next week appears likely to be remain limited by the lack of stronger boundary-layer destabilization. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Wed Aug 07 2024 Valid 101200Z - 151200Z ...DISCUSSION... Medium-range guidance indicates that the initially prominent higher-latitude mid-level ridging emerging from the Canadian Northwest Territories will gradually become suppressed through this period. Although there is notable spread concerning the downstream acceleration of the initially significant mid-level low to its southeast, it appears that larger-scale mid-level troughing will slowly shift eastward in positively tilted fashion, through the St. Lawrence Valley and lower Great Lakes region by late this coming weekend, through the Northeast and Canadian Maritimes by the middle of next week. In advance of the troughing, Debby's remnant surface low may interact with a surface cold front advancing to the east of the lower Great Lakes/upper Ohio Valley, before perhaps merging into the primary surface cyclone across southern Quebec by Saturday. Models have varied concerning these developments, but tropical pre-frontal moistening in the presence of intensifying deep-layer southerly wind fields might be accompanied by an evolving low-topped convective band with potential to produce damaging wind gusts near/east of the Hudson/Champlain Valleys through New England. Due to lingering uncertainties severe probabilities are begin maintained at less than 15 percent, but this could change in later outlooks for Saturday. Otherwise, the potential for severe weather elsewhere across the U.S. late this coming weekend into the middle of next week appears likely to be remain limited by the lack of stronger boundary-layer destabilization. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Wed Aug 07 2024 Valid 101200Z - 151200Z ...DISCUSSION... Medium-range guidance indicates that the initially prominent higher-latitude mid-level ridging emerging from the Canadian Northwest Territories will gradually become suppressed through this period. Although there is notable spread concerning the downstream acceleration of the initially significant mid-level low to its southeast, it appears that larger-scale mid-level troughing will slowly shift eastward in positively tilted fashion, through the St. Lawrence Valley and lower Great Lakes region by late this coming weekend, through the Northeast and Canadian Maritimes by the middle of next week. In advance of the troughing, Debby's remnant surface low may interact with a surface cold front advancing to the east of the lower Great Lakes/upper Ohio Valley, before perhaps merging into the primary surface cyclone across southern Quebec by Saturday. Models have varied concerning these developments, but tropical pre-frontal moistening in the presence of intensifying deep-layer southerly wind fields might be accompanied by an evolving low-topped convective band with potential to produce damaging wind gusts near/east of the Hudson/Champlain Valleys through New England. Due to lingering uncertainties severe probabilities are begin maintained at less than 15 percent, but this could change in later outlooks for Saturday. Otherwise, the potential for severe weather elsewhere across the U.S. late this coming weekend into the middle of next week appears likely to be remain limited by the lack of stronger boundary-layer destabilization. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Wed Aug 07 2024 Valid 101200Z - 151200Z ...DISCUSSION... Medium-range guidance indicates that the initially prominent higher-latitude mid-level ridging emerging from the Canadian Northwest Territories will gradually become suppressed through this period. Although there is notable spread concerning the downstream acceleration of the initially significant mid-level low to its southeast, it appears that larger-scale mid-level troughing will slowly shift eastward in positively tilted fashion, through the St. Lawrence Valley and lower Great Lakes region by late this coming weekend, through the Northeast and Canadian Maritimes by the middle of next week. In advance of the troughing, Debby's remnant surface low may interact with a surface cold front advancing to the east of the lower Great Lakes/upper Ohio Valley, before perhaps merging into the primary surface cyclone across southern Quebec by Saturday. Models have varied concerning these developments, but tropical pre-frontal moistening in the presence of intensifying deep-layer southerly wind fields might be accompanied by an evolving low-topped convective band with potential to produce damaging wind gusts near/east of the Hudson/Champlain Valleys through New England. Due to lingering uncertainties severe probabilities are begin maintained at less than 15 percent, but this could change in later outlooks for Saturday. Otherwise, the potential for severe weather elsewhere across the U.S. late this coming weekend into the middle of next week appears likely to be remain limited by the lack of stronger boundary-layer destabilization. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Wed Aug 07 2024 Valid 101200Z - 151200Z ...DISCUSSION... Medium-range guidance indicates that the initially prominent higher-latitude mid-level ridging emerging from the Canadian Northwest Territories will gradually become suppressed through this period. Although there is notable spread concerning the downstream acceleration of the initially significant mid-level low to its southeast, it appears that larger-scale mid-level troughing will slowly shift eastward in positively tilted fashion, through the St. Lawrence Valley and lower Great Lakes region by late this coming weekend, through the Northeast and Canadian Maritimes by the middle of next week. In advance of the troughing, Debby's remnant surface low may interact with a surface cold front advancing to the east of the lower Great Lakes/upper Ohio Valley, before perhaps merging into the primary surface cyclone across southern Quebec by Saturday. Models have varied concerning these developments, but tropical pre-frontal moistening in the presence of intensifying deep-layer southerly wind fields might be accompanied by an evolving low-topped convective band with potential to produce damaging wind gusts near/east of the Hudson/Champlain Valleys through New England. Due to lingering uncertainties severe probabilities are begin maintained at less than 15 percent, but this could change in later outlooks for Saturday. Otherwise, the potential for severe weather elsewhere across the U.S. late this coming weekend into the middle of next week appears likely to be remain limited by the lack of stronger boundary-layer destabilization. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Wed Aug 07 2024 Valid 101200Z - 151200Z ...DISCUSSION... Medium-range guidance indicates that the initially prominent higher-latitude mid-level ridging emerging from the Canadian Northwest Territories will gradually become suppressed through this period. Although there is notable spread concerning the downstream acceleration of the initially significant mid-level low to its southeast, it appears that larger-scale mid-level troughing will slowly shift eastward in positively tilted fashion, through the St. Lawrence Valley and lower Great Lakes region by late this coming weekend, through the Northeast and Canadian Maritimes by the middle of next week. In advance of the troughing, Debby's remnant surface low may interact with a surface cold front advancing to the east of the lower Great Lakes/upper Ohio Valley, before perhaps merging into the primary surface cyclone across southern Quebec by Saturday. Models have varied concerning these developments, but tropical pre-frontal moistening in the presence of intensifying deep-layer southerly wind fields might be accompanied by an evolving low-topped convective band with potential to produce damaging wind gusts near/east of the Hudson/Champlain Valleys through New England. Due to lingering uncertainties severe probabilities are begin maintained at less than 15 percent, but this could change in later outlooks for Saturday. Otherwise, the potential for severe weather elsewhere across the U.S. late this coming weekend into the middle of next week appears likely to be remain limited by the lack of stronger boundary-layer destabilization. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Wed Aug 07 2024 Valid 101200Z - 151200Z ...DISCUSSION... Medium-range guidance indicates that the initially prominent higher-latitude mid-level ridging emerging from the Canadian Northwest Territories will gradually become suppressed through this period. Although there is notable spread concerning the downstream acceleration of the initially significant mid-level low to its southeast, it appears that larger-scale mid-level troughing will slowly shift eastward in positively tilted fashion, through the St. Lawrence Valley and lower Great Lakes region by late this coming weekend, through the Northeast and Canadian Maritimes by the middle of next week. In advance of the troughing, Debby's remnant surface low may interact with a surface cold front advancing to the east of the lower Great Lakes/upper Ohio Valley, before perhaps merging into the primary surface cyclone across southern Quebec by Saturday. Models have varied concerning these developments, but tropical pre-frontal moistening in the presence of intensifying deep-layer southerly wind fields might be accompanied by an evolving low-topped convective band with potential to produce damaging wind gusts near/east of the Hudson/Champlain Valleys through New England. Due to lingering uncertainties severe probabilities are begin maintained at less than 15 percent, but this could change in later outlooks for Saturday. Otherwise, the potential for severe weather elsewhere across the U.S. late this coming weekend into the middle of next week appears likely to be remain limited by the lack of stronger boundary-layer destabilization. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0225 AM CDT Wed Aug 07 2024 Valid 091200Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FRIDAY ACROSS PARTS OF NORTHEASTERN VIRGINIA...THE DISTRICT OF COLUMBIA...CENTRAL MARYLAND AND THE EASTERN SHORE OF MARYLAND...DELAWARE...SOUTHEASTERN PENNSYLVANIA...MUCH OF NEW JERSEY...ADJACENT SOUTHEASTERN NEW YORK AND WESTERN LONG ISLAND... ...SUMMARY... There may be at least some continuing risk for tornadoes in advance of the remnant low of Debby, spreading across the northern Mid Atlantic region on Friday. ...Synopsis... Models indicate that an initially prominent higher-latitude ridge will generally be maintained through this period, with its mid-level height center perhaps slowly shifting east of the Canadian Northwest Territories. Some eastward redevelopment of a significant low evolving to its southeast may also commence, as a couple of embedded perturbations pivot around its circulation center near the upper Great Lakes region. This may be accompanied by modest secondary surface cyclogenesis, along an occluding surface front across the lower Great Lakes into upper St. Lawrence Valley vicinity, with a trailing cold front advancing through the remainder of the Ohio Valley, into and across the Appalachians. Through the day, Debby's remnant circulation, forecast to weaken to a depression by 12Z Friday and a remnant low by early Friday evening, appears likely to continue a gradual north-northeastward acceleration ahead of the front, to the lee of the Blue Ridge, before continuing toward the Catskill/lower Hudson Valley vicinity Friday night. ...Northern Mid Atlantic... Despite the weakening trends to Debby, models suggest that the evolution of sizable clockwise-curved low-level hodographs and appreciable boundary-layer buoyancy may be maintained into at least Friday afternoon, focused in a sector to the northeast of the accelerating surface low. It appears that this may be in the process of overspreading the Chesapeake/Delmarva vicinity as daytime heating contributes to boundary-layer destabilization, before spreading northward through the northern Mid Atlantic in advance of the more inhibiting mid-level warm core. Within this environment, the evolution of a few supercell structures posing a risk for tornadoes appears possible, before this threat wanes with the loss of daytime heating Friday evening. ..Kerr.. 08/07/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0225 AM CDT Wed Aug 07 2024 Valid 091200Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FRIDAY ACROSS PARTS OF NORTHEASTERN VIRGINIA...THE DISTRICT OF COLUMBIA...CENTRAL MARYLAND AND THE EASTERN SHORE OF MARYLAND...DELAWARE...SOUTHEASTERN PENNSYLVANIA...MUCH OF NEW JERSEY...ADJACENT SOUTHEASTERN NEW YORK AND WESTERN LONG ISLAND... ...SUMMARY... There may be at least some continuing risk for tornadoes in advance of the remnant low of Debby, spreading across the northern Mid Atlantic region on Friday. ...Synopsis... Models indicate that an initially prominent higher-latitude ridge will generally be maintained through this period, with its mid-level height center perhaps slowly shifting east of the Canadian Northwest Territories. Some eastward redevelopment of a significant low evolving to its southeast may also commence, as a couple of embedded perturbations pivot around its circulation center near the upper Great Lakes region. This may be accompanied by modest secondary surface cyclogenesis, along an occluding surface front across the lower Great Lakes into upper St. Lawrence Valley vicinity, with a trailing cold front advancing through the remainder of the Ohio Valley, into and across the Appalachians. Through the day, Debby's remnant circulation, forecast to weaken to a depression by 12Z Friday and a remnant low by early Friday evening, appears likely to continue a gradual north-northeastward acceleration ahead of the front, to the lee of the Blue Ridge, before continuing toward the Catskill/lower Hudson Valley vicinity Friday night. ...Northern Mid Atlantic... Despite the weakening trends to Debby, models suggest that the evolution of sizable clockwise-curved low-level hodographs and appreciable boundary-layer buoyancy may be maintained into at least Friday afternoon, focused in a sector to the northeast of the accelerating surface low. It appears that this may be in the process of overspreading the Chesapeake/Delmarva vicinity as daytime heating contributes to boundary-layer destabilization, before spreading northward through the northern Mid Atlantic in advance of the more inhibiting mid-level warm core. Within this environment, the evolution of a few supercell structures posing a risk for tornadoes appears possible, before this threat wanes with the loss of daytime heating Friday evening. ..Kerr.. 08/07/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0225 AM CDT Wed Aug 07 2024 Valid 091200Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FRIDAY ACROSS PARTS OF NORTHEASTERN VIRGINIA...THE DISTRICT OF COLUMBIA...CENTRAL MARYLAND AND THE EASTERN SHORE OF MARYLAND...DELAWARE...SOUTHEASTERN PENNSYLVANIA...MUCH OF NEW JERSEY...ADJACENT SOUTHEASTERN NEW YORK AND WESTERN LONG ISLAND... ...SUMMARY... There may be at least some continuing risk for tornadoes in advance of the remnant low of Debby, spreading across the northern Mid Atlantic region on Friday. ...Synopsis... Models indicate that an initially prominent higher-latitude ridge will generally be maintained through this period, with its mid-level height center perhaps slowly shifting east of the Canadian Northwest Territories. Some eastward redevelopment of a significant low evolving to its southeast may also commence, as a couple of embedded perturbations pivot around its circulation center near the upper Great Lakes region. This may be accompanied by modest secondary surface cyclogenesis, along an occluding surface front across the lower Great Lakes into upper St. Lawrence Valley vicinity, with a trailing cold front advancing through the remainder of the Ohio Valley, into and across the Appalachians. Through the day, Debby's remnant circulation, forecast to weaken to a depression by 12Z Friday and a remnant low by early Friday evening, appears likely to continue a gradual north-northeastward acceleration ahead of the front, to the lee of the Blue Ridge, before continuing toward the Catskill/lower Hudson Valley vicinity Friday night. ...Northern Mid Atlantic... Despite the weakening trends to Debby, models suggest that the evolution of sizable clockwise-curved low-level hodographs and appreciable boundary-layer buoyancy may be maintained into at least Friday afternoon, focused in a sector to the northeast of the accelerating surface low. It appears that this may be in the process of overspreading the Chesapeake/Delmarva vicinity as daytime heating contributes to boundary-layer destabilization, before spreading northward through the northern Mid Atlantic in advance of the more inhibiting mid-level warm core. Within this environment, the evolution of a few supercell structures posing a risk for tornadoes appears possible, before this threat wanes with the loss of daytime heating Friday evening. ..Kerr.. 08/07/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0225 AM CDT Wed Aug 07 2024 Valid 091200Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FRIDAY ACROSS PARTS OF NORTHEASTERN VIRGINIA...THE DISTRICT OF COLUMBIA...CENTRAL MARYLAND AND THE EASTERN SHORE OF MARYLAND...DELAWARE...SOUTHEASTERN PENNSYLVANIA...MUCH OF NEW JERSEY...ADJACENT SOUTHEASTERN NEW YORK AND WESTERN LONG ISLAND... ...SUMMARY... There may be at least some continuing risk for tornadoes in advance of the remnant low of Debby, spreading across the northern Mid Atlantic region on Friday. ...Synopsis... Models indicate that an initially prominent higher-latitude ridge will generally be maintained through this period, with its mid-level height center perhaps slowly shifting east of the Canadian Northwest Territories. Some eastward redevelopment of a significant low evolving to its southeast may also commence, as a couple of embedded perturbations pivot around its circulation center near the upper Great Lakes region. This may be accompanied by modest secondary surface cyclogenesis, along an occluding surface front across the lower Great Lakes into upper St. Lawrence Valley vicinity, with a trailing cold front advancing through the remainder of the Ohio Valley, into and across the Appalachians. Through the day, Debby's remnant circulation, forecast to weaken to a depression by 12Z Friday and a remnant low by early Friday evening, appears likely to continue a gradual north-northeastward acceleration ahead of the front, to the lee of the Blue Ridge, before continuing toward the Catskill/lower Hudson Valley vicinity Friday night. ...Northern Mid Atlantic... Despite the weakening trends to Debby, models suggest that the evolution of sizable clockwise-curved low-level hodographs and appreciable boundary-layer buoyancy may be maintained into at least Friday afternoon, focused in a sector to the northeast of the accelerating surface low. It appears that this may be in the process of overspreading the Chesapeake/Delmarva vicinity as daytime heating contributes to boundary-layer destabilization, before spreading northward through the northern Mid Atlantic in advance of the more inhibiting mid-level warm core. Within this environment, the evolution of a few supercell structures posing a risk for tornadoes appears possible, before this threat wanes with the loss of daytime heating Friday evening. ..Kerr.. 08/07/2024 Read more