Severe Storms

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1021 AM CST Mon Feb 19 2024 Valid 191630Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE SACRAMENTO VALLEY IN CENTRAL INTO NORTHERN CALIFORNIA... ...SUMMARY... A tornado or two may occur in the Sacramento Valley region of California today. ...Synopsis... A pronounced mid-level trough and associated surface low continue to impinge on the West Coast, supporting a continued northward transport of moisture over California into southern portions of the Pacific Northwest. 12Z observed soundings for sites along the California coast already show cooler mid-level temperatures overspreading inland, suggesting that marginal buoyancy should already be present across central into northern CA. With time, insolation will support locally higher amounts of buoyancy amid a highly sheared environment to support low-topped but organized thunderstorms capable of producing severe hazards over portions of central into northern CA this afternoon. ...Portions of central into northern CA... Low-level warm-air advection has encouraged surface temperatures to warm into the mid 50s F across southern portions of the Sacramento Valley prior to diurnal heating. By afternoon, 52-54 F surface dewpoints beneath 7.5+ C/km mid-level lapse rates will boost tall but thin SBCAPE to the 500-750 J/kg range. The BBX VAD currently depicts a sizable, curved low-level hodograph, with over 300 m2/s2 of 0-3 km SRH, and these favorable low-level shear trends are expected to persist through the day as the surface low continues to meander just offshore. Modifying RAP forecast soundings suggest that surface dewpoints need to rise at least into the 53-54F range to support efficient ingesting of SRH for tornadogenesis. It is unclear how widespread 53-54 F dewpoints will become by afternoon, with the tornado threat more conditional on these dewpoints being realized. Nonetheless, a couple of low-topped supercells are possible this afternoon, likely accompanied by at least a marginal severe hail/wind threat. ..Squitieri.. 02/19/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1021 AM CST Mon Feb 19 2024 Valid 191630Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE SACRAMENTO VALLEY IN CENTRAL INTO NORTHERN CALIFORNIA... ...SUMMARY... A tornado or two may occur in the Sacramento Valley region of California today. ...Synopsis... A pronounced mid-level trough and associated surface low continue to impinge on the West Coast, supporting a continued northward transport of moisture over California into southern portions of the Pacific Northwest. 12Z observed soundings for sites along the California coast already show cooler mid-level temperatures overspreading inland, suggesting that marginal buoyancy should already be present across central into northern CA. With time, insolation will support locally higher amounts of buoyancy amid a highly sheared environment to support low-topped but organized thunderstorms capable of producing severe hazards over portions of central into northern CA this afternoon. ...Portions of central into northern CA... Low-level warm-air advection has encouraged surface temperatures to warm into the mid 50s F across southern portions of the Sacramento Valley prior to diurnal heating. By afternoon, 52-54 F surface dewpoints beneath 7.5+ C/km mid-level lapse rates will boost tall but thin SBCAPE to the 500-750 J/kg range. The BBX VAD currently depicts a sizable, curved low-level hodograph, with over 300 m2/s2 of 0-3 km SRH, and these favorable low-level shear trends are expected to persist through the day as the surface low continues to meander just offshore. Modifying RAP forecast soundings suggest that surface dewpoints need to rise at least into the 53-54F range to support efficient ingesting of SRH for tornadogenesis. It is unclear how widespread 53-54 F dewpoints will become by afternoon, with the tornado threat more conditional on these dewpoints being realized. Nonetheless, a couple of low-topped supercells are possible this afternoon, likely accompanied by at least a marginal severe hail/wind threat. ..Squitieri.. 02/19/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1021 AM CST Mon Feb 19 2024 Valid 191630Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE SACRAMENTO VALLEY IN CENTRAL INTO NORTHERN CALIFORNIA... ...SUMMARY... A tornado or two may occur in the Sacramento Valley region of California today. ...Synopsis... A pronounced mid-level trough and associated surface low continue to impinge on the West Coast, supporting a continued northward transport of moisture over California into southern portions of the Pacific Northwest. 12Z observed soundings for sites along the California coast already show cooler mid-level temperatures overspreading inland, suggesting that marginal buoyancy should already be present across central into northern CA. With time, insolation will support locally higher amounts of buoyancy amid a highly sheared environment to support low-topped but organized thunderstorms capable of producing severe hazards over portions of central into northern CA this afternoon. ...Portions of central into northern CA... Low-level warm-air advection has encouraged surface temperatures to warm into the mid 50s F across southern portions of the Sacramento Valley prior to diurnal heating. By afternoon, 52-54 F surface dewpoints beneath 7.5+ C/km mid-level lapse rates will boost tall but thin SBCAPE to the 500-750 J/kg range. The BBX VAD currently depicts a sizable, curved low-level hodograph, with over 300 m2/s2 of 0-3 km SRH, and these favorable low-level shear trends are expected to persist through the day as the surface low continues to meander just offshore. Modifying RAP forecast soundings suggest that surface dewpoints need to rise at least into the 53-54F range to support efficient ingesting of SRH for tornadogenesis. It is unclear how widespread 53-54 F dewpoints will become by afternoon, with the tornado threat more conditional on these dewpoints being realized. Nonetheless, a couple of low-topped supercells are possible this afternoon, likely accompanied by at least a marginal severe hail/wind threat. ..Squitieri.. 02/19/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1021 AM CST Mon Feb 19 2024 Valid 191630Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE SACRAMENTO VALLEY IN CENTRAL INTO NORTHERN CALIFORNIA... ...SUMMARY... A tornado or two may occur in the Sacramento Valley region of California today. ...Synopsis... A pronounced mid-level trough and associated surface low continue to impinge on the West Coast, supporting a continued northward transport of moisture over California into southern portions of the Pacific Northwest. 12Z observed soundings for sites along the California coast already show cooler mid-level temperatures overspreading inland, suggesting that marginal buoyancy should already be present across central into northern CA. With time, insolation will support locally higher amounts of buoyancy amid a highly sheared environment to support low-topped but organized thunderstorms capable of producing severe hazards over portions of central into northern CA this afternoon. ...Portions of central into northern CA... Low-level warm-air advection has encouraged surface temperatures to warm into the mid 50s F across southern portions of the Sacramento Valley prior to diurnal heating. By afternoon, 52-54 F surface dewpoints beneath 7.5+ C/km mid-level lapse rates will boost tall but thin SBCAPE to the 500-750 J/kg range. The BBX VAD currently depicts a sizable, curved low-level hodograph, with over 300 m2/s2 of 0-3 km SRH, and these favorable low-level shear trends are expected to persist through the day as the surface low continues to meander just offshore. Modifying RAP forecast soundings suggest that surface dewpoints need to rise at least into the 53-54F range to support efficient ingesting of SRH for tornadogenesis. It is unclear how widespread 53-54 F dewpoints will become by afternoon, with the tornado threat more conditional on these dewpoints being realized. Nonetheless, a couple of low-topped supercells are possible this afternoon, likely accompanied by at least a marginal severe hail/wind threat. ..Squitieri.. 02/19/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1021 AM CST Mon Feb 19 2024 Valid 191630Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE SACRAMENTO VALLEY IN CENTRAL INTO NORTHERN CALIFORNIA... ...SUMMARY... A tornado or two may occur in the Sacramento Valley region of California today. ...Synopsis... A pronounced mid-level trough and associated surface low continue to impinge on the West Coast, supporting a continued northward transport of moisture over California into southern portions of the Pacific Northwest. 12Z observed soundings for sites along the California coast already show cooler mid-level temperatures overspreading inland, suggesting that marginal buoyancy should already be present across central into northern CA. With time, insolation will support locally higher amounts of buoyancy amid a highly sheared environment to support low-topped but organized thunderstorms capable of producing severe hazards over portions of central into northern CA this afternoon. ...Portions of central into northern CA... Low-level warm-air advection has encouraged surface temperatures to warm into the mid 50s F across southern portions of the Sacramento Valley prior to diurnal heating. By afternoon, 52-54 F surface dewpoints beneath 7.5+ C/km mid-level lapse rates will boost tall but thin SBCAPE to the 500-750 J/kg range. The BBX VAD currently depicts a sizable, curved low-level hodograph, with over 300 m2/s2 of 0-3 km SRH, and these favorable low-level shear trends are expected to persist through the day as the surface low continues to meander just offshore. Modifying RAP forecast soundings suggest that surface dewpoints need to rise at least into the 53-54F range to support efficient ingesting of SRH for tornadogenesis. It is unclear how widespread 53-54 F dewpoints will become by afternoon, with the tornado threat more conditional on these dewpoints being realized. Nonetheless, a couple of low-topped supercells are possible this afternoon, likely accompanied by at least a marginal severe hail/wind threat. ..Squitieri.. 02/19/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0648 AM CST Mon Feb 19 2024 Valid 191300Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF INLAND NORTHERN CALIFORNIA.... ...SUMMARY... A tornado or two may occur in the Sacramento Valley region of California today. ...Synopsis... The large-scale pattern will continue to be characterized by a longwave trough just off the West Coast, ridging over the Rockies and High Plains, and a trough over parts of the eastern CONUS and eastern Gulf. Progressive, well-developed shortwave troughs -- now apparent in moisture-channel imagery over GA and the central High Plains -- will move through the broader-scale cyclonic-flow field of the eastern longwave trough. Conditions should remain too stable in low levels to support a thunder threat over land from the Intermountain West eastward to the Atlantic Coast. Upstream, a large cyclone off northern CA and the Pacific Northwest will weaken gradually and shift northward through the period, devolving into an open wave synoptic trough. However, the broader- scale troughing will be maintained, as a strong shortwave perturbation now in the cyclone's northwestern quadrant digs southward then southeastward, approaching 130W west of southern CA and northern Baja by 12Z. These processes will maintain a fetch of southwest flow aloft across CA. A weaker shortwave trough is moving inland over north-central CA, and should cross northwestern NV today before reaching parts of ID around 00Z. ...CA... Scattered showers and isolated to widely scattered thunderstorms are expected this afternoon into early evening. Isolated supercells are possible, with a threat for a tornado or two. Mostly subsevere hail and convective winds are expected, through the largest hail and gusts may briefly reach severe limits. As noted above, the initial shortwave trough is crossing the area, preceded by a precip plume with isolated embedded thunderstorms over the central/northern Sierra and San Joaquin Valley. In the weak subsidence following that perturbation, a few hours of relatively tranquil conditions are expected. Thereafter, upper-level forcing will be nearly neutral, but with diurnal/diabatic heating contributing to low-level destabilization over the Sacramento Valley/Delta region and perhaps northernmost parts of the San Joaquin Valley, beneath favorable low/middle-level lapse rates and weakening of MLCINH. Episodic, isolated to scattered convection and a few thunderstorms are possible again this afternoon into evening, in an environment characterized by favorably veering/increasing winds with height. Orographically forced backing of surface flow in the valley likely will be slightly greater than most models indicate as well, further enlarging already favorable hodographs progged for supercells. Any quasi-linear modes also may contain LEWP/bow features with embedded mesocirculations. Effective SRH of 150-300 J/kg and 40-55-kt effective-shear magnitudes are possible. With surface dewpoints holding generally in the low/mid 50s F, the preconvective/inflow sector may attain 250-700 J/kg peak MLCAPE, based on modifications to the 12Z OAK RAOB and model soundings. A combination of nocturnal surface cooling/stabilization and outflow air should reduce severe potential after dark. Isolated storm-scale rotation also is possible with cells mainly over the Pacific marine layer off the northwestern CA coastline, with waterspout/tornado potential nonzero but too low/conditional over land for an outlook area at this time. ..Edwards/Mosier.. 02/19/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0648 AM CST Mon Feb 19 2024 Valid 191300Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF INLAND NORTHERN CALIFORNIA.... ...SUMMARY... A tornado or two may occur in the Sacramento Valley region of California today. ...Synopsis... The large-scale pattern will continue to be characterized by a longwave trough just off the West Coast, ridging over the Rockies and High Plains, and a trough over parts of the eastern CONUS and eastern Gulf. Progressive, well-developed shortwave troughs -- now apparent in moisture-channel imagery over GA and the central High Plains -- will move through the broader-scale cyclonic-flow field of the eastern longwave trough. Conditions should remain too stable in low levels to support a thunder threat over land from the Intermountain West eastward to the Atlantic Coast. Upstream, a large cyclone off northern CA and the Pacific Northwest will weaken gradually and shift northward through the period, devolving into an open wave synoptic trough. However, the broader- scale troughing will be maintained, as a strong shortwave perturbation now in the cyclone's northwestern quadrant digs southward then southeastward, approaching 130W west of southern CA and northern Baja by 12Z. These processes will maintain a fetch of southwest flow aloft across CA. A weaker shortwave trough is moving inland over north-central CA, and should cross northwestern NV today before reaching parts of ID around 00Z. ...CA... Scattered showers and isolated to widely scattered thunderstorms are expected this afternoon into early evening. Isolated supercells are possible, with a threat for a tornado or two. Mostly subsevere hail and convective winds are expected, through the largest hail and gusts may briefly reach severe limits. As noted above, the initial shortwave trough is crossing the area, preceded by a precip plume with isolated embedded thunderstorms over the central/northern Sierra and San Joaquin Valley. In the weak subsidence following that perturbation, a few hours of relatively tranquil conditions are expected. Thereafter, upper-level forcing will be nearly neutral, but with diurnal/diabatic heating contributing to low-level destabilization over the Sacramento Valley/Delta region and perhaps northernmost parts of the San Joaquin Valley, beneath favorable low/middle-level lapse rates and weakening of MLCINH. Episodic, isolated to scattered convection and a few thunderstorms are possible again this afternoon into evening, in an environment characterized by favorably veering/increasing winds with height. Orographically forced backing of surface flow in the valley likely will be slightly greater than most models indicate as well, further enlarging already favorable hodographs progged for supercells. Any quasi-linear modes also may contain LEWP/bow features with embedded mesocirculations. Effective SRH of 150-300 J/kg and 40-55-kt effective-shear magnitudes are possible. With surface dewpoints holding generally in the low/mid 50s F, the preconvective/inflow sector may attain 250-700 J/kg peak MLCAPE, based on modifications to the 12Z OAK RAOB and model soundings. A combination of nocturnal surface cooling/stabilization and outflow air should reduce severe potential after dark. Isolated storm-scale rotation also is possible with cells mainly over the Pacific marine layer off the northwestern CA coastline, with waterspout/tornado potential nonzero but too low/conditional over land for an outlook area at this time. ..Edwards/Mosier.. 02/19/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0648 AM CST Mon Feb 19 2024 Valid 191300Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF INLAND NORTHERN CALIFORNIA.... ...SUMMARY... A tornado or two may occur in the Sacramento Valley region of California today. ...Synopsis... The large-scale pattern will continue to be characterized by a longwave trough just off the West Coast, ridging over the Rockies and High Plains, and a trough over parts of the eastern CONUS and eastern Gulf. Progressive, well-developed shortwave troughs -- now apparent in moisture-channel imagery over GA and the central High Plains -- will move through the broader-scale cyclonic-flow field of the eastern longwave trough. Conditions should remain too stable in low levels to support a thunder threat over land from the Intermountain West eastward to the Atlantic Coast. Upstream, a large cyclone off northern CA and the Pacific Northwest will weaken gradually and shift northward through the period, devolving into an open wave synoptic trough. However, the broader- scale troughing will be maintained, as a strong shortwave perturbation now in the cyclone's northwestern quadrant digs southward then southeastward, approaching 130W west of southern CA and northern Baja by 12Z. These processes will maintain a fetch of southwest flow aloft across CA. A weaker shortwave trough is moving inland over north-central CA, and should cross northwestern NV today before reaching parts of ID around 00Z. ...CA... Scattered showers and isolated to widely scattered thunderstorms are expected this afternoon into early evening. Isolated supercells are possible, with a threat for a tornado or two. Mostly subsevere hail and convective winds are expected, through the largest hail and gusts may briefly reach severe limits. As noted above, the initial shortwave trough is crossing the area, preceded by a precip plume with isolated embedded thunderstorms over the central/northern Sierra and San Joaquin Valley. In the weak subsidence following that perturbation, a few hours of relatively tranquil conditions are expected. Thereafter, upper-level forcing will be nearly neutral, but with diurnal/diabatic heating contributing to low-level destabilization over the Sacramento Valley/Delta region and perhaps northernmost parts of the San Joaquin Valley, beneath favorable low/middle-level lapse rates and weakening of MLCINH. Episodic, isolated to scattered convection and a few thunderstorms are possible again this afternoon into evening, in an environment characterized by favorably veering/increasing winds with height. Orographically forced backing of surface flow in the valley likely will be slightly greater than most models indicate as well, further enlarging already favorable hodographs progged for supercells. Any quasi-linear modes also may contain LEWP/bow features with embedded mesocirculations. Effective SRH of 150-300 J/kg and 40-55-kt effective-shear magnitudes are possible. With surface dewpoints holding generally in the low/mid 50s F, the preconvective/inflow sector may attain 250-700 J/kg peak MLCAPE, based on modifications to the 12Z OAK RAOB and model soundings. A combination of nocturnal surface cooling/stabilization and outflow air should reduce severe potential after dark. Isolated storm-scale rotation also is possible with cells mainly over the Pacific marine layer off the northwestern CA coastline, with waterspout/tornado potential nonzero but too low/conditional over land for an outlook area at this time. ..Edwards/Mosier.. 02/19/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0648 AM CST Mon Feb 19 2024 Valid 191300Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF INLAND NORTHERN CALIFORNIA.... ...SUMMARY... A tornado or two may occur in the Sacramento Valley region of California today. ...Synopsis... The large-scale pattern will continue to be characterized by a longwave trough just off the West Coast, ridging over the Rockies and High Plains, and a trough over parts of the eastern CONUS and eastern Gulf. Progressive, well-developed shortwave troughs -- now apparent in moisture-channel imagery over GA and the central High Plains -- will move through the broader-scale cyclonic-flow field of the eastern longwave trough. Conditions should remain too stable in low levels to support a thunder threat over land from the Intermountain West eastward to the Atlantic Coast. Upstream, a large cyclone off northern CA and the Pacific Northwest will weaken gradually and shift northward through the period, devolving into an open wave synoptic trough. However, the broader- scale troughing will be maintained, as a strong shortwave perturbation now in the cyclone's northwestern quadrant digs southward then southeastward, approaching 130W west of southern CA and northern Baja by 12Z. These processes will maintain a fetch of southwest flow aloft across CA. A weaker shortwave trough is moving inland over north-central CA, and should cross northwestern NV today before reaching parts of ID around 00Z. ...CA... Scattered showers and isolated to widely scattered thunderstorms are expected this afternoon into early evening. Isolated supercells are possible, with a threat for a tornado or two. Mostly subsevere hail and convective winds are expected, through the largest hail and gusts may briefly reach severe limits. As noted above, the initial shortwave trough is crossing the area, preceded by a precip plume with isolated embedded thunderstorms over the central/northern Sierra and San Joaquin Valley. In the weak subsidence following that perturbation, a few hours of relatively tranquil conditions are expected. Thereafter, upper-level forcing will be nearly neutral, but with diurnal/diabatic heating contributing to low-level destabilization over the Sacramento Valley/Delta region and perhaps northernmost parts of the San Joaquin Valley, beneath favorable low/middle-level lapse rates and weakening of MLCINH. Episodic, isolated to scattered convection and a few thunderstorms are possible again this afternoon into evening, in an environment characterized by favorably veering/increasing winds with height. Orographically forced backing of surface flow in the valley likely will be slightly greater than most models indicate as well, further enlarging already favorable hodographs progged for supercells. Any quasi-linear modes also may contain LEWP/bow features with embedded mesocirculations. Effective SRH of 150-300 J/kg and 40-55-kt effective-shear magnitudes are possible. With surface dewpoints holding generally in the low/mid 50s F, the preconvective/inflow sector may attain 250-700 J/kg peak MLCAPE, based on modifications to the 12Z OAK RAOB and model soundings. A combination of nocturnal surface cooling/stabilization and outflow air should reduce severe potential after dark. Isolated storm-scale rotation also is possible with cells mainly over the Pacific marine layer off the northwestern CA coastline, with waterspout/tornado potential nonzero but too low/conditional over land for an outlook area at this time. ..Edwards/Mosier.. 02/19/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0648 AM CST Mon Feb 19 2024 Valid 191300Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF INLAND NORTHERN CALIFORNIA.... ...SUMMARY... A tornado or two may occur in the Sacramento Valley region of California today. ...Synopsis... The large-scale pattern will continue to be characterized by a longwave trough just off the West Coast, ridging over the Rockies and High Plains, and a trough over parts of the eastern CONUS and eastern Gulf. Progressive, well-developed shortwave troughs -- now apparent in moisture-channel imagery over GA and the central High Plains -- will move through the broader-scale cyclonic-flow field of the eastern longwave trough. Conditions should remain too stable in low levels to support a thunder threat over land from the Intermountain West eastward to the Atlantic Coast. Upstream, a large cyclone off northern CA and the Pacific Northwest will weaken gradually and shift northward through the period, devolving into an open wave synoptic trough. However, the broader- scale troughing will be maintained, as a strong shortwave perturbation now in the cyclone's northwestern quadrant digs southward then southeastward, approaching 130W west of southern CA and northern Baja by 12Z. These processes will maintain a fetch of southwest flow aloft across CA. A weaker shortwave trough is moving inland over north-central CA, and should cross northwestern NV today before reaching parts of ID around 00Z. ...CA... Scattered showers and isolated to widely scattered thunderstorms are expected this afternoon into early evening. Isolated supercells are possible, with a threat for a tornado or two. Mostly subsevere hail and convective winds are expected, through the largest hail and gusts may briefly reach severe limits. As noted above, the initial shortwave trough is crossing the area, preceded by a precip plume with isolated embedded thunderstorms over the central/northern Sierra and San Joaquin Valley. In the weak subsidence following that perturbation, a few hours of relatively tranquil conditions are expected. Thereafter, upper-level forcing will be nearly neutral, but with diurnal/diabatic heating contributing to low-level destabilization over the Sacramento Valley/Delta region and perhaps northernmost parts of the San Joaquin Valley, beneath favorable low/middle-level lapse rates and weakening of MLCINH. Episodic, isolated to scattered convection and a few thunderstorms are possible again this afternoon into evening, in an environment characterized by favorably veering/increasing winds with height. Orographically forced backing of surface flow in the valley likely will be slightly greater than most models indicate as well, further enlarging already favorable hodographs progged for supercells. Any quasi-linear modes also may contain LEWP/bow features with embedded mesocirculations. Effective SRH of 150-300 J/kg and 40-55-kt effective-shear magnitudes are possible. With surface dewpoints holding generally in the low/mid 50s F, the preconvective/inflow sector may attain 250-700 J/kg peak MLCAPE, based on modifications to the 12Z OAK RAOB and model soundings. A combination of nocturnal surface cooling/stabilization and outflow air should reduce severe potential after dark. Isolated storm-scale rotation also is possible with cells mainly over the Pacific marine layer off the northwestern CA coastline, with waterspout/tornado potential nonzero but too low/conditional over land for an outlook area at this time. ..Edwards/Mosier.. 02/19/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0648 AM CST Mon Feb 19 2024 Valid 191300Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF INLAND NORTHERN CALIFORNIA.... ...SUMMARY... A tornado or two may occur in the Sacramento Valley region of California today. ...Synopsis... The large-scale pattern will continue to be characterized by a longwave trough just off the West Coast, ridging over the Rockies and High Plains, and a trough over parts of the eastern CONUS and eastern Gulf. Progressive, well-developed shortwave troughs -- now apparent in moisture-channel imagery over GA and the central High Plains -- will move through the broader-scale cyclonic-flow field of the eastern longwave trough. Conditions should remain too stable in low levels to support a thunder threat over land from the Intermountain West eastward to the Atlantic Coast. Upstream, a large cyclone off northern CA and the Pacific Northwest will weaken gradually and shift northward through the period, devolving into an open wave synoptic trough. However, the broader- scale troughing will be maintained, as a strong shortwave perturbation now in the cyclone's northwestern quadrant digs southward then southeastward, approaching 130W west of southern CA and northern Baja by 12Z. These processes will maintain a fetch of southwest flow aloft across CA. A weaker shortwave trough is moving inland over north-central CA, and should cross northwestern NV today before reaching parts of ID around 00Z. ...CA... Scattered showers and isolated to widely scattered thunderstorms are expected this afternoon into early evening. Isolated supercells are possible, with a threat for a tornado or two. Mostly subsevere hail and convective winds are expected, through the largest hail and gusts may briefly reach severe limits. As noted above, the initial shortwave trough is crossing the area, preceded by a precip plume with isolated embedded thunderstorms over the central/northern Sierra and San Joaquin Valley. In the weak subsidence following that perturbation, a few hours of relatively tranquil conditions are expected. Thereafter, upper-level forcing will be nearly neutral, but with diurnal/diabatic heating contributing to low-level destabilization over the Sacramento Valley/Delta region and perhaps northernmost parts of the San Joaquin Valley, beneath favorable low/middle-level lapse rates and weakening of MLCINH. Episodic, isolated to scattered convection and a few thunderstorms are possible again this afternoon into evening, in an environment characterized by favorably veering/increasing winds with height. Orographically forced backing of surface flow in the valley likely will be slightly greater than most models indicate as well, further enlarging already favorable hodographs progged for supercells. Any quasi-linear modes also may contain LEWP/bow features with embedded mesocirculations. Effective SRH of 150-300 J/kg and 40-55-kt effective-shear magnitudes are possible. With surface dewpoints holding generally in the low/mid 50s F, the preconvective/inflow sector may attain 250-700 J/kg peak MLCAPE, based on modifications to the 12Z OAK RAOB and model soundings. A combination of nocturnal surface cooling/stabilization and outflow air should reduce severe potential after dark. Isolated storm-scale rotation also is possible with cells mainly over the Pacific marine layer off the northwestern CA coastline, with waterspout/tornado potential nonzero but too low/conditional over land for an outlook area at this time. ..Edwards/Mosier.. 02/19/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CST Mon Feb 19 2024 Valid 221200Z - 271200Z ...DISCUSSION... Medium-range model guidance exhibits reasonable agreement in showing a strong mid-level speed max moving quickly east across the Southeast on Thursday. Models have shown some consistency in showing limited moisture return north into parts of the lower MS Valley/Mid South on Thursday, and areas farther east prior to a front moving offshore into the western Atlantic on Friday. Given the potential for lower CAPE/strong shear setup and inherent uncertainties involved, will refrain from a highlighted area on Thursday across the Mid South for this outlook update. A progressive flow regime will continue on Saturday across the CONUS with climatologically below-average severe-weather potential likely through Sunday. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CST Mon Feb 19 2024 Valid 221200Z - 271200Z ...DISCUSSION... Medium-range model guidance exhibits reasonable agreement in showing a strong mid-level speed max moving quickly east across the Southeast on Thursday. Models have shown some consistency in showing limited moisture return north into parts of the lower MS Valley/Mid South on Thursday, and areas farther east prior to a front moving offshore into the western Atlantic on Friday. Given the potential for lower CAPE/strong shear setup and inherent uncertainties involved, will refrain from a highlighted area on Thursday across the Mid South for this outlook update. A progressive flow regime will continue on Saturday across the CONUS with climatologically below-average severe-weather potential likely through Sunday. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CST Mon Feb 19 2024 Valid 221200Z - 271200Z ...DISCUSSION... Medium-range model guidance exhibits reasonable agreement in showing a strong mid-level speed max moving quickly east across the Southeast on Thursday. Models have shown some consistency in showing limited moisture return north into parts of the lower MS Valley/Mid South on Thursday, and areas farther east prior to a front moving offshore into the western Atlantic on Friday. Given the potential for lower CAPE/strong shear setup and inherent uncertainties involved, will refrain from a highlighted area on Thursday across the Mid South for this outlook update. A progressive flow regime will continue on Saturday across the CONUS with climatologically below-average severe-weather potential likely through Sunday. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CST Mon Feb 19 2024 Valid 221200Z - 271200Z ...DISCUSSION... Medium-range model guidance exhibits reasonable agreement in showing a strong mid-level speed max moving quickly east across the Southeast on Thursday. Models have shown some consistency in showing limited moisture return north into parts of the lower MS Valley/Mid South on Thursday, and areas farther east prior to a front moving offshore into the western Atlantic on Friday. Given the potential for lower CAPE/strong shear setup and inherent uncertainties involved, will refrain from a highlighted area on Thursday across the Mid South for this outlook update. A progressive flow regime will continue on Saturday across the CONUS with climatologically below-average severe-weather potential likely through Sunday. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CST Mon Feb 19 2024 Valid 221200Z - 271200Z ...DISCUSSION... Medium-range model guidance exhibits reasonable agreement in showing a strong mid-level speed max moving quickly east across the Southeast on Thursday. Models have shown some consistency in showing limited moisture return north into parts of the lower MS Valley/Mid South on Thursday, and areas farther east prior to a front moving offshore into the western Atlantic on Friday. Given the potential for lower CAPE/strong shear setup and inherent uncertainties involved, will refrain from a highlighted area on Thursday across the Mid South for this outlook update. A progressive flow regime will continue on Saturday across the CONUS with climatologically below-average severe-weather potential likely through Sunday. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CST Mon Feb 19 2024 Valid 221200Z - 271200Z ...DISCUSSION... Medium-range model guidance exhibits reasonable agreement in showing a strong mid-level speed max moving quickly east across the Southeast on Thursday. Models have shown some consistency in showing limited moisture return north into parts of the lower MS Valley/Mid South on Thursday, and areas farther east prior to a front moving offshore into the western Atlantic on Friday. Given the potential for lower CAPE/strong shear setup and inherent uncertainties involved, will refrain from a highlighted area on Thursday across the Mid South for this outlook update. A progressive flow regime will continue on Saturday across the CONUS with climatologically below-average severe-weather potential likely through Sunday. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CST Mon Feb 19 2024 Valid 221200Z - 271200Z ...DISCUSSION... Medium-range model guidance exhibits reasonable agreement in showing a strong mid-level speed max moving quickly east across the Southeast on Thursday. Models have shown some consistency in showing limited moisture return north into parts of the lower MS Valley/Mid South on Thursday, and areas farther east prior to a front moving offshore into the western Atlantic on Friday. Given the potential for lower CAPE/strong shear setup and inherent uncertainties involved, will refrain from a highlighted area on Thursday across the Mid South for this outlook update. A progressive flow regime will continue on Saturday across the CONUS with climatologically below-average severe-weather potential likely through Sunday. Read more

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0240 AM CST Mon Feb 19 2024 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OZARKS... ...SUMMARY... Isolated thunderstorms potentially capable of severe hail are possible Wednesday night over the Ozarks. ...Synopsis... A potent mid-level trough initially west of Baja California will quickly move east reaching OK/TX by early Thursday morning. A cyclone is forecast to develop over the south-central High Plains by early evening and move across northern OK overnight Wednesday. Southerly low-level flow will strengthen across the southern Great Plains during the day with the initial stage of moisture return into the south-central U.S. ...Ozarks vicinity... An intensifying southern Great Plains LLJ Wednesday evening will favor strong low-level warm air advection/isentropic lift over eastern OK/AR northward into KS/MO. An EML is forecast to overspread the OK/TX into the Ozarks during the day with a plume of 8 deg C/km 700-500 mb lapse rates. Cold temperatures in the mid levels (-20 to -22 deg C at 500 mb) over the Ozarks coupled with lower 50s dewpoints spreading into the area, will yield 500-1000 J/kg MUCAPE. Isolated to scattered storms will probably develop within the warm conveyer east of the cyclone, on the periphery of the stronger capping inversion (04-12z). Model forecast soundings suggest potential for severe hail with the stronger storms that manage to develop. ..Smith.. 02/19/2024 Read more

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0240 AM CST Mon Feb 19 2024 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OZARKS... ...SUMMARY... Isolated thunderstorms potentially capable of severe hail are possible Wednesday night over the Ozarks. ...Synopsis... A potent mid-level trough initially west of Baja California will quickly move east reaching OK/TX by early Thursday morning. A cyclone is forecast to develop over the south-central High Plains by early evening and move across northern OK overnight Wednesday. Southerly low-level flow will strengthen across the southern Great Plains during the day with the initial stage of moisture return into the south-central U.S. ...Ozarks vicinity... An intensifying southern Great Plains LLJ Wednesday evening will favor strong low-level warm air advection/isentropic lift over eastern OK/AR northward into KS/MO. An EML is forecast to overspread the OK/TX into the Ozarks during the day with a plume of 8 deg C/km 700-500 mb lapse rates. Cold temperatures in the mid levels (-20 to -22 deg C at 500 mb) over the Ozarks coupled with lower 50s dewpoints spreading into the area, will yield 500-1000 J/kg MUCAPE. Isolated to scattered storms will probably develop within the warm conveyer east of the cyclone, on the periphery of the stronger capping inversion (04-12z). Model forecast soundings suggest potential for severe hail with the stronger storms that manage to develop. ..Smith.. 02/19/2024 Read more