Severe Storms

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0355 AM CDT Fri Aug 09 2019 Valid 121200Z - 171200Z ...DISCUSSION... Day 4 (Monday) Western U.S. upper trough will deamplify as it moves through the ridge position over the northern Plains. Widespread rain and thunderstorms will likely be ongoing in a warm advection regime across the central and northern Plains. While some severe threat could evolve along a cold front in wake of this activity, confidence is low regarding evolution of morning storms and its impact on subsequent destabilization potential. Days 5-8 model consensus is that upper pattern will trend to a quasi-zonal regime over the northern tier states. While there will undoubtedly be severe threats at times mainly over the northern Plains and northeast states, timing of low-amplitude shortwave troughs and uncertainty regarding where corridors of greater destabilization will be, lowers overall predictability at this range. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0355 AM CDT Fri Aug 09 2019 Valid 121200Z - 171200Z ...DISCUSSION... Day 4 (Monday) Western U.S. upper trough will deamplify as it moves through the ridge position over the northern Plains. Widespread rain and thunderstorms will likely be ongoing in a warm advection regime across the central and northern Plains. While some severe threat could evolve along a cold front in wake of this activity, confidence is low regarding evolution of morning storms and its impact on subsequent destabilization potential. Days 5-8 model consensus is that upper pattern will trend to a quasi-zonal regime over the northern tier states. While there will undoubtedly be severe threats at times mainly over the northern Plains and northeast states, timing of low-amplitude shortwave troughs and uncertainty regarding where corridors of greater destabilization will be, lowers overall predictability at this range. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0234 AM CDT Fri Aug 09 2019 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE CENTRAL THROUGH NORTHERN HIGH PLAINS... ...SUMMARY... Isolated strong to severe storms are expected over portions of the northern through central High Plains Sunday. ...Northern through central High Plains... Upper trough now off the west U.S. coast will move east northeast through the northern Rockies and northern High Plains Sunday, cresting an upper ridge centered over the southern Plains. A plume of steeper mid-level lapse rates will overspread a moist axis that will be in place east of the higher terrain with surface dewpoints generally in the low 60s F resulting in moderate instability as the boundary layer destabilizes. Storms are expected to develop over the higher terrain and spread east into the High Plains during the afternoon and evening. A belt of stronger mid-upper flow will evolve in the gradient zone between the progressive upper trough and the ridge over the southern Plains. This will contribute to sufficient vertical shear for organized storms including supercells capable of isolated damaging wind and large hail from late afternoon into the evening. ..Dial.. 08/09/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0234 AM CDT Fri Aug 09 2019 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE CENTRAL THROUGH NORTHERN HIGH PLAINS... ...SUMMARY... Isolated strong to severe storms are expected over portions of the northern through central High Plains Sunday. ...Northern through central High Plains... Upper trough now off the west U.S. coast will move east northeast through the northern Rockies and northern High Plains Sunday, cresting an upper ridge centered over the southern Plains. A plume of steeper mid-level lapse rates will overspread a moist axis that will be in place east of the higher terrain with surface dewpoints generally in the low 60s F resulting in moderate instability as the boundary layer destabilizes. Storms are expected to develop over the higher terrain and spread east into the High Plains during the afternoon and evening. A belt of stronger mid-upper flow will evolve in the gradient zone between the progressive upper trough and the ridge over the southern Plains. This will contribute to sufficient vertical shear for organized storms including supercells capable of isolated damaging wind and large hail from late afternoon into the evening. ..Dial.. 08/09/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0234 AM CDT Fri Aug 09 2019 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE CENTRAL THROUGH NORTHERN HIGH PLAINS... ...SUMMARY... Isolated strong to severe storms are expected over portions of the northern through central High Plains Sunday. ...Northern through central High Plains... Upper trough now off the west U.S. coast will move east northeast through the northern Rockies and northern High Plains Sunday, cresting an upper ridge centered over the southern Plains. A plume of steeper mid-level lapse rates will overspread a moist axis that will be in place east of the higher terrain with surface dewpoints generally in the low 60s F resulting in moderate instability as the boundary layer destabilizes. Storms are expected to develop over the higher terrain and spread east into the High Plains during the afternoon and evening. A belt of stronger mid-upper flow will evolve in the gradient zone between the progressive upper trough and the ridge over the southern Plains. This will contribute to sufficient vertical shear for organized storms including supercells capable of isolated damaging wind and large hail from late afternoon into the evening. ..Dial.. 08/09/2019 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0126 AM CDT Fri Aug 09 2019 Valid 101200Z - 111200Z ...Synopsis... The mid-level trough responsible for D1 fire weather concerns in the West will take on a negative tilt while slowly migrating northeastward over Oregon and vicinity. As this occurs, a belt of enhanced mid-level flow will shift eastward toward eastern Nevada and eastern Idaho. Meanwhile, areas of scattered to widespread thunderstorm activity will once again migrate over inland portions of the Pacific Northwest and northern California. ...Eastern Nevada, far western Utah, and eastern Idaho... Vertical mixing processes beneath the mid-level jet core will encourage development of a belt of relatively strong (15-25 mph) south-southwesterly surface winds during peak heating periods across the region. This region also resides on the western fringe of much of the rainfall over the past month or so, with dry fuels supporting ongoing fires across the region. One lingering uncertainty with regard to the extent of the fire-weather threat in this area will be potential for wetting rainfall over the region on D1/Fri, which may temper fuels in a few areas. However, elevated to locally critical fire weather will likely exist given near-critical RH values expected during the afternoon. Some portions of this region may need a critical upgrade in later outlook updates. ...Washington, Oregon, and northern California for thunderstorms... The continued presence of mid-level moisture and a nearby trough will again foster areas of northeastward-moving clusters of storms across the region. However, the extent of dry thunder potential is a bit less clear compared to prior days due to 1) expected areas of wetting rainfall on D1/Fri, which should temper fuel states on at least a localized basis and 2) the coverage of wetting rainfall during the afternoon and evening, which should further temper fuel states over a much broader area especially in Oregon. CAMS/high-res guidance even depicts upscale growth into linear complex(es) during peak heating hours. Nevertheless, areas that can remain dry will be susceptible to isolated dry lightning strikes outside of heavier thunderstorm cores, and gusty/erratic winds near downdrafts are expected. ..Cook.. 08/09/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0126 AM CDT Fri Aug 09 2019 Valid 101200Z - 111200Z ...Synopsis... The mid-level trough responsible for D1 fire weather concerns in the West will take on a negative tilt while slowly migrating northeastward over Oregon and vicinity. As this occurs, a belt of enhanced mid-level flow will shift eastward toward eastern Nevada and eastern Idaho. Meanwhile, areas of scattered to widespread thunderstorm activity will once again migrate over inland portions of the Pacific Northwest and northern California. ...Eastern Nevada, far western Utah, and eastern Idaho... Vertical mixing processes beneath the mid-level jet core will encourage development of a belt of relatively strong (15-25 mph) south-southwesterly surface winds during peak heating periods across the region. This region also resides on the western fringe of much of the rainfall over the past month or so, with dry fuels supporting ongoing fires across the region. One lingering uncertainty with regard to the extent of the fire-weather threat in this area will be potential for wetting rainfall over the region on D1/Fri, which may temper fuels in a few areas. However, elevated to locally critical fire weather will likely exist given near-critical RH values expected during the afternoon. Some portions of this region may need a critical upgrade in later outlook updates. ...Washington, Oregon, and northern California for thunderstorms... The continued presence of mid-level moisture and a nearby trough will again foster areas of northeastward-moving clusters of storms across the region. However, the extent of dry thunder potential is a bit less clear compared to prior days due to 1) expected areas of wetting rainfall on D1/Fri, which should temper fuel states on at least a localized basis and 2) the coverage of wetting rainfall during the afternoon and evening, which should further temper fuel states over a much broader area especially in Oregon. CAMS/high-res guidance even depicts upscale growth into linear complex(es) during peak heating hours. Nevertheless, areas that can remain dry will be susceptible to isolated dry lightning strikes outside of heavier thunderstorm cores, and gusty/erratic winds near downdrafts are expected. ..Cook.. 08/09/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0126 AM CDT Fri Aug 09 2019 Valid 101200Z - 111200Z ...Synopsis... The mid-level trough responsible for D1 fire weather concerns in the West will take on a negative tilt while slowly migrating northeastward over Oregon and vicinity. As this occurs, a belt of enhanced mid-level flow will shift eastward toward eastern Nevada and eastern Idaho. Meanwhile, areas of scattered to widespread thunderstorm activity will once again migrate over inland portions of the Pacific Northwest and northern California. ...Eastern Nevada, far western Utah, and eastern Idaho... Vertical mixing processes beneath the mid-level jet core will encourage development of a belt of relatively strong (15-25 mph) south-southwesterly surface winds during peak heating periods across the region. This region also resides on the western fringe of much of the rainfall over the past month or so, with dry fuels supporting ongoing fires across the region. One lingering uncertainty with regard to the extent of the fire-weather threat in this area will be potential for wetting rainfall over the region on D1/Fri, which may temper fuels in a few areas. However, elevated to locally critical fire weather will likely exist given near-critical RH values expected during the afternoon. Some portions of this region may need a critical upgrade in later outlook updates. ...Washington, Oregon, and northern California for thunderstorms... The continued presence of mid-level moisture and a nearby trough will again foster areas of northeastward-moving clusters of storms across the region. However, the extent of dry thunder potential is a bit less clear compared to prior days due to 1) expected areas of wetting rainfall on D1/Fri, which should temper fuel states on at least a localized basis and 2) the coverage of wetting rainfall during the afternoon and evening, which should further temper fuel states over a much broader area especially in Oregon. CAMS/high-res guidance even depicts upscale growth into linear complex(es) during peak heating hours. Nevertheless, areas that can remain dry will be susceptible to isolated dry lightning strikes outside of heavier thunderstorm cores, and gusty/erratic winds near downdrafts are expected. ..Cook.. 08/09/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0104 AM CDT Fri Aug 09 2019 Valid 091200Z - 101200Z ...Synopsis... A longwave trough centered just west of the northern California coast will continue its slow trek eastward toward the West Coast throughout the day. As this occurs, mid-level flow will increase in a corridor from southern California northward to Idaho. The deep southerly flow will maintain moist mid-level profiles in much of the western third of the CONUS, and lift associated with the approaching trough and surface heating should foster several areas of thunderstorms. Additionally, a favorable pressure gradient and terrain-related forcing should foster areas of windy conditions across Nevada and vicinity through the evening. ...Central Nevada northward into Washington for thunderstorms... The aforementioned synoptic pattern will foster scattered areas of thunderstorms as early as mid-day while gradually increasing in coverage and intensity through the afternoon and evening hours. These storms should provide wetting rains to several areas, with isolated dry lightning strikes occurring on the periphery of wetting thunderstorm cores. Coverage will increase with northward extent into Oregon and southwestern Idaho throughout the day, with widespread areas of gusty outflow winds amidst areas of dry fuels suggestive of erratic fire behavior and complicated suppression efforts. A few of these wind gusts may exceed severe limits - refer to SPC Day 1 Convective Outlooks for more updates on this threat. At least pockets of dry fuels will exist as far east as eastern Idaho, and isolated dry thunderstorm potential has been highlighted in this area with storms expected through early evening. Storms will continue to lift northward and persist in many areas of Washington and Oregon overnight. ...Much of Nevada and far northeast California for elevated fire weather conditions... Surface troughing and vertical mixing processes will foster areas of 20-25 mph surface winds that will be strongest in a couple of corridors - one in the immediate lee of the Sierras and another along an axis from southeastern into east-central Nevada. Areas of critically low RH values will also exist for a few hours during peak heating, though clouds and areas of precipitation may hinder the degree of mixing/lowered RH in several areas as well. The overall scenario appears to be consistent with elevated fire weather thresholds, though locally critical fire weather will probably develop over southeastern Nevada for at least an hour or two. ..Cook.. 08/09/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0104 AM CDT Fri Aug 09 2019 Valid 091200Z - 101200Z ...Synopsis... A longwave trough centered just west of the northern California coast will continue its slow trek eastward toward the West Coast throughout the day. As this occurs, mid-level flow will increase in a corridor from southern California northward to Idaho. The deep southerly flow will maintain moist mid-level profiles in much of the western third of the CONUS, and lift associated with the approaching trough and surface heating should foster several areas of thunderstorms. Additionally, a favorable pressure gradient and terrain-related forcing should foster areas of windy conditions across Nevada and vicinity through the evening. ...Central Nevada northward into Washington for thunderstorms... The aforementioned synoptic pattern will foster scattered areas of thunderstorms as early as mid-day while gradually increasing in coverage and intensity through the afternoon and evening hours. These storms should provide wetting rains to several areas, with isolated dry lightning strikes occurring on the periphery of wetting thunderstorm cores. Coverage will increase with northward extent into Oregon and southwestern Idaho throughout the day, with widespread areas of gusty outflow winds amidst areas of dry fuels suggestive of erratic fire behavior and complicated suppression efforts. A few of these wind gusts may exceed severe limits - refer to SPC Day 1 Convective Outlooks for more updates on this threat. At least pockets of dry fuels will exist as far east as eastern Idaho, and isolated dry thunderstorm potential has been highlighted in this area with storms expected through early evening. Storms will continue to lift northward and persist in many areas of Washington and Oregon overnight. ...Much of Nevada and far northeast California for elevated fire weather conditions... Surface troughing and vertical mixing processes will foster areas of 20-25 mph surface winds that will be strongest in a couple of corridors - one in the immediate lee of the Sierras and another along an axis from southeastern into east-central Nevada. Areas of critically low RH values will also exist for a few hours during peak heating, though clouds and areas of precipitation may hinder the degree of mixing/lowered RH in several areas as well. The overall scenario appears to be consistent with elevated fire weather thresholds, though locally critical fire weather will probably develop over southeastern Nevada for at least an hour or two. ..Cook.. 08/09/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0104 AM CDT Fri Aug 09 2019 Valid 091200Z - 101200Z ...Synopsis... A longwave trough centered just west of the northern California coast will continue its slow trek eastward toward the West Coast throughout the day. As this occurs, mid-level flow will increase in a corridor from southern California northward to Idaho. The deep southerly flow will maintain moist mid-level profiles in much of the western third of the CONUS, and lift associated with the approaching trough and surface heating should foster several areas of thunderstorms. Additionally, a favorable pressure gradient and terrain-related forcing should foster areas of windy conditions across Nevada and vicinity through the evening. ...Central Nevada northward into Washington for thunderstorms... The aforementioned synoptic pattern will foster scattered areas of thunderstorms as early as mid-day while gradually increasing in coverage and intensity through the afternoon and evening hours. These storms should provide wetting rains to several areas, with isolated dry lightning strikes occurring on the periphery of wetting thunderstorm cores. Coverage will increase with northward extent into Oregon and southwestern Idaho throughout the day, with widespread areas of gusty outflow winds amidst areas of dry fuels suggestive of erratic fire behavior and complicated suppression efforts. A few of these wind gusts may exceed severe limits - refer to SPC Day 1 Convective Outlooks for more updates on this threat. At least pockets of dry fuels will exist as far east as eastern Idaho, and isolated dry thunderstorm potential has been highlighted in this area with storms expected through early evening. Storms will continue to lift northward and persist in many areas of Washington and Oregon overnight. ...Much of Nevada and far northeast California for elevated fire weather conditions... Surface troughing and vertical mixing processes will foster areas of 20-25 mph surface winds that will be strongest in a couple of corridors - one in the immediate lee of the Sierras and another along an axis from southeastern into east-central Nevada. Areas of critically low RH values will also exist for a few hours during peak heating, though clouds and areas of precipitation may hinder the degree of mixing/lowered RH in several areas as well. The overall scenario appears to be consistent with elevated fire weather thresholds, though locally critical fire weather will probably develop over southeastern Nevada for at least an hour or two. ..Cook.. 08/09/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Fri Aug 09 2019 Valid 101200Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE NORTHERN ROCKIES... ...SUMMARY... Isolated strong to severe storms are expected Saturday afternoon and evening mainly over the northern Rockies with large hail and damaging wind the main threats. Other strong to severe storms are possible over the central High Plains and coastal North Carolina. ...Synopsis... An omega blocking pattern will prevail over the U.S. Saturday with an upper ridge situated over the southern Plains flanked by upper troughs over the western and eastern states. At the surface a cold front should extend from a weak surface low over eastern SD southwest into northwest NE and move slowly southeast during the day. A quasi-stationary front will extend southeast from the low through the middle MS and into the TN Valley regions. Farther north another cold front will move southward into the northern Plains. A quasi-stationary front will reside across the eastern Carolinas. ...Northern Rockies... Steep mid-level lapse rates will reside over the northern Rockies with a belt of stronger southwesterly winds aloft downstream from an approaching upper trough. Diabatic heating over the higher terrain should promote moderate instability with 1000-1500 J/kg MLCAPE possible during the afternoon and evening. Storms are expected to develop over the mountains and within corridor of deeper ascent associated with the upper trough. Effective bulk shear from 35-40 kt will support some organized structures including a few supercells with isolated large hail and damaging wind possible from late afternoon through mid evening. ...Central High Plains... An easterly upslope component is expected over a portion of the central Rockies Saturday afternoon, and storms are expected to develop over the higher terrain and spread east into the High Plains where dewpoints in the upper 50s to low 60s F will promote moderate instability (2000-2500 J/kg MLCAPE). Potential will exist for vorticity maxima to move along northern periphery of upper ridge and into the central High Plains. A risk for hail and downburst winds may accompany the storms as they move into the High Plains. However, vertical wind profiles and storm coverage will be modulated by the timing and strength of these impulses which remains somewhat uncertain at this time. Will therefore introduce a MRGL risk this update will possible SLGT risk in later outlooks. ...Coastal North Carolina... Storms may develop across the eastern Carolinas along and ahead of the aforementioned front where richer low-level moisture will support moderate instability. This region will also reside within belt of 30-40 kt mid-level winds within base of an upper trough. This environment will be conditionally favorable for a few strong to severe storms during the afternoon and have therefore introduced a MRGL risk category this update. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Dial.. 08/09/2019 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Fri Aug 09 2019 Valid 101200Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE NORTHERN ROCKIES... ...SUMMARY... Isolated strong to severe storms are expected Saturday afternoon and evening mainly over the northern Rockies with large hail and damaging wind the main threats. Other strong to severe storms are possible over the central High Plains and coastal North Carolina. ...Synopsis... An omega blocking pattern will prevail over the U.S. Saturday with an upper ridge situated over the southern Plains flanked by upper troughs over the western and eastern states. At the surface a cold front should extend from a weak surface low over eastern SD southwest into northwest NE and move slowly southeast during the day. A quasi-stationary front will extend southeast from the low through the middle MS and into the TN Valley regions. Farther north another cold front will move southward into the northern Plains. A quasi-stationary front will reside across the eastern Carolinas. ...Northern Rockies... Steep mid-level lapse rates will reside over the northern Rockies with a belt of stronger southwesterly winds aloft downstream from an approaching upper trough. Diabatic heating over the higher terrain should promote moderate instability with 1000-1500 J/kg MLCAPE possible during the afternoon and evening. Storms are expected to develop over the mountains and within corridor of deeper ascent associated with the upper trough. Effective bulk shear from 35-40 kt will support some organized structures including a few supercells with isolated large hail and damaging wind possible from late afternoon through mid evening. ...Central High Plains... An easterly upslope component is expected over a portion of the central Rockies Saturday afternoon, and storms are expected to develop over the higher terrain and spread east into the High Plains where dewpoints in the upper 50s to low 60s F will promote moderate instability (2000-2500 J/kg MLCAPE). Potential will exist for vorticity maxima to move along northern periphery of upper ridge and into the central High Plains. A risk for hail and downburst winds may accompany the storms as they move into the High Plains. However, vertical wind profiles and storm coverage will be modulated by the timing and strength of these impulses which remains somewhat uncertain at this time. Will therefore introduce a MRGL risk this update will possible SLGT risk in later outlooks. ...Coastal North Carolina... Storms may develop across the eastern Carolinas along and ahead of the aforementioned front where richer low-level moisture will support moderate instability. This region will also reside within belt of 30-40 kt mid-level winds within base of an upper trough. This environment will be conditionally favorable for a few strong to severe storms during the afternoon and have therefore introduced a MRGL risk category this update. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Dial.. 08/09/2019 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Fri Aug 09 2019 Valid 101200Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE NORTHERN ROCKIES... ...SUMMARY... Isolated strong to severe storms are expected Saturday afternoon and evening mainly over the northern Rockies with large hail and damaging wind the main threats. Other strong to severe storms are possible over the central High Plains and coastal North Carolina. ...Synopsis... An omega blocking pattern will prevail over the U.S. Saturday with an upper ridge situated over the southern Plains flanked by upper troughs over the western and eastern states. At the surface a cold front should extend from a weak surface low over eastern SD southwest into northwest NE and move slowly southeast during the day. A quasi-stationary front will extend southeast from the low through the middle MS and into the TN Valley regions. Farther north another cold front will move southward into the northern Plains. A quasi-stationary front will reside across the eastern Carolinas. ...Northern Rockies... Steep mid-level lapse rates will reside over the northern Rockies with a belt of stronger southwesterly winds aloft downstream from an approaching upper trough. Diabatic heating over the higher terrain should promote moderate instability with 1000-1500 J/kg MLCAPE possible during the afternoon and evening. Storms are expected to develop over the mountains and within corridor of deeper ascent associated with the upper trough. Effective bulk shear from 35-40 kt will support some organized structures including a few supercells with isolated large hail and damaging wind possible from late afternoon through mid evening. ...Central High Plains... An easterly upslope component is expected over a portion of the central Rockies Saturday afternoon, and storms are expected to develop over the higher terrain and spread east into the High Plains where dewpoints in the upper 50s to low 60s F will promote moderate instability (2000-2500 J/kg MLCAPE). Potential will exist for vorticity maxima to move along northern periphery of upper ridge and into the central High Plains. A risk for hail and downburst winds may accompany the storms as they move into the High Plains. However, vertical wind profiles and storm coverage will be modulated by the timing and strength of these impulses which remains somewhat uncertain at this time. Will therefore introduce a MRGL risk this update will possible SLGT risk in later outlooks. ...Coastal North Carolina... Storms may develop across the eastern Carolinas along and ahead of the aforementioned front where richer low-level moisture will support moderate instability. This region will also reside within belt of 30-40 kt mid-level winds within base of an upper trough. This environment will be conditionally favorable for a few strong to severe storms during the afternoon and have therefore introduced a MRGL risk category this update. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Dial.. 08/09/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1257 AM CDT Fri Aug 09 2019 Valid 091200Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER CENTRAL SOUTH DAKOTA AND FAR NORTH-CENTRAL NEBRASKA...AND CENTRAL OREGON... ...SUMMARY... Severe storms are likely over parts of the Northern Plains and over parts of Oregon. A few strong to severe storms are also possible over parts of the Mid Atlantic and central High Plains. ...Synopsis... An upper high will remain centered over the southern Plains, with upper troughs over the West Coast and from the Great Lakes into Northeast. A surface low will develop from SD southward across the High Plains, with a stationary front extending east from the SD low across the MO and OH Valleys. A moist air mass will remain over much of the Plains, and will result in unstable conditions especially over SD and NE where minor disturbances will round the upper ridge, enhancing shear and lift. Farther east, the primary synoptic boundary will move east as a cold front across VA and the Delmarva, providing a focus for storms. To the west, cooling aloft will aid destabilization over OR and western ID, with increasing winds aloft aiding in severe potential during the afternoon and evening. ...Northern Plains... A few storms are possible early in the day moving from west to east across SD in a zone of low-level warm advection with 30 kt southerly winds at 850 mb. In the wake of this activity, strong heating will occur across WY and western NE, with the low-level lapse rate plume extending into southwest SD. Heating combined with a plume of mid 60s F dewpoints will lead to areas of strong instability, beneath modest westerly midlevel winds. Storms are expected to initiate by 21Z along a line from west-central SD into parts of the NE Panhandle, and few could be supercells. Lapse rates aloft will not be particularly steep due to warming aloft but large hail is still likely given cellular storm mode. A brief tornado or two cannot be ruled out as effective SRH increases to 200-400 m2/s2 east of where storms initiate. ...Oregon... Strong heating beneath cooling profiles aloft will lead to very steep lapse rates through a deep layer, while winds aloft also increase with the approaching upper trough. Storms are expected to initiate over southern OR by afternoon in a zone of increasing differential divergence, and will spread northward across the state, and possibly into western ID as well. A few storms may contain small hail but the main threat is expected to be damaging outflow winds. ...Mid Atlantic... Relatively strong northwest flow aloft will remain over the region with the main upper trough over the Northeast. Strong heating will occur ahead of the cold front, with storms initiating after 18Z over central VA, spreading southeastward during the afternoon. Although storm coverage may remain isolated, any storms will have both hail and wind potential given favorable time of day, and sufficient deep-layer shear to sustain storms for several hours. ..Jewell/Cook.. 08/09/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1257 AM CDT Fri Aug 09 2019 Valid 091200Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER CENTRAL SOUTH DAKOTA AND FAR NORTH-CENTRAL NEBRASKA...AND CENTRAL OREGON... ...SUMMARY... Severe storms are likely over parts of the Northern Plains and over parts of Oregon. A few strong to severe storms are also possible over parts of the Mid Atlantic and central High Plains. ...Synopsis... An upper high will remain centered over the southern Plains, with upper troughs over the West Coast and from the Great Lakes into Northeast. A surface low will develop from SD southward across the High Plains, with a stationary front extending east from the SD low across the MO and OH Valleys. A moist air mass will remain over much of the Plains, and will result in unstable conditions especially over SD and NE where minor disturbances will round the upper ridge, enhancing shear and lift. Farther east, the primary synoptic boundary will move east as a cold front across VA and the Delmarva, providing a focus for storms. To the west, cooling aloft will aid destabilization over OR and western ID, with increasing winds aloft aiding in severe potential during the afternoon and evening. ...Northern Plains... A few storms are possible early in the day moving from west to east across SD in a zone of low-level warm advection with 30 kt southerly winds at 850 mb. In the wake of this activity, strong heating will occur across WY and western NE, with the low-level lapse rate plume extending into southwest SD. Heating combined with a plume of mid 60s F dewpoints will lead to areas of strong instability, beneath modest westerly midlevel winds. Storms are expected to initiate by 21Z along a line from west-central SD into parts of the NE Panhandle, and few could be supercells. Lapse rates aloft will not be particularly steep due to warming aloft but large hail is still likely given cellular storm mode. A brief tornado or two cannot be ruled out as effective SRH increases to 200-400 m2/s2 east of where storms initiate. ...Oregon... Strong heating beneath cooling profiles aloft will lead to very steep lapse rates through a deep layer, while winds aloft also increase with the approaching upper trough. Storms are expected to initiate over southern OR by afternoon in a zone of increasing differential divergence, and will spread northward across the state, and possibly into western ID as well. A few storms may contain small hail but the main threat is expected to be damaging outflow winds. ...Mid Atlantic... Relatively strong northwest flow aloft will remain over the region with the main upper trough over the Northeast. Strong heating will occur ahead of the cold front, with storms initiating after 18Z over central VA, spreading southeastward during the afternoon. Although storm coverage may remain isolated, any storms will have both hail and wind potential given favorable time of day, and sufficient deep-layer shear to sustain storms for several hours. ..Jewell/Cook.. 08/09/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1257 AM CDT Fri Aug 09 2019 Valid 091200Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER CENTRAL SOUTH DAKOTA AND FAR NORTH-CENTRAL NEBRASKA...AND CENTRAL OREGON... ...SUMMARY... Severe storms are likely over parts of the Northern Plains and over parts of Oregon. A few strong to severe storms are also possible over parts of the Mid Atlantic and central High Plains. ...Synopsis... An upper high will remain centered over the southern Plains, with upper troughs over the West Coast and from the Great Lakes into Northeast. A surface low will develop from SD southward across the High Plains, with a stationary front extending east from the SD low across the MO and OH Valleys. A moist air mass will remain over much of the Plains, and will result in unstable conditions especially over SD and NE where minor disturbances will round the upper ridge, enhancing shear and lift. Farther east, the primary synoptic boundary will move east as a cold front across VA and the Delmarva, providing a focus for storms. To the west, cooling aloft will aid destabilization over OR and western ID, with increasing winds aloft aiding in severe potential during the afternoon and evening. ...Northern Plains... A few storms are possible early in the day moving from west to east across SD in a zone of low-level warm advection with 30 kt southerly winds at 850 mb. In the wake of this activity, strong heating will occur across WY and western NE, with the low-level lapse rate plume extending into southwest SD. Heating combined with a plume of mid 60s F dewpoints will lead to areas of strong instability, beneath modest westerly midlevel winds. Storms are expected to initiate by 21Z along a line from west-central SD into parts of the NE Panhandle, and few could be supercells. Lapse rates aloft will not be particularly steep due to warming aloft but large hail is still likely given cellular storm mode. A brief tornado or two cannot be ruled out as effective SRH increases to 200-400 m2/s2 east of where storms initiate. ...Oregon... Strong heating beneath cooling profiles aloft will lead to very steep lapse rates through a deep layer, while winds aloft also increase with the approaching upper trough. Storms are expected to initiate over southern OR by afternoon in a zone of increasing differential divergence, and will spread northward across the state, and possibly into western ID as well. A few storms may contain small hail but the main threat is expected to be damaging outflow winds. ...Mid Atlantic... Relatively strong northwest flow aloft will remain over the region with the main upper trough over the Northeast. Strong heating will occur ahead of the cold front, with storms initiating after 18Z over central VA, spreading southeastward during the afternoon. Although storm coverage may remain isolated, any storms will have both hail and wind potential given favorable time of day, and sufficient deep-layer shear to sustain storms for several hours. ..Jewell/Cook.. 08/09/2019 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0752 PM CDT Thu Aug 08 2019 Valid 090100Z - 091200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE OHIO VALLEY AND CENTRAL HIGH PLAINS... ...SUMMARY... A few severe storms remain possible across parts of the Ohio Valley, and over parts of the Central Plains through evening. ...Ohio Valley... Scattered storms persist near the cold front, from southern IN across central OH and into WV. These cells may produce marginally severe hail, with storm longevity aided by long, straight hodographs. Ample moisture and instability remains mainly north of the OH River, in part due to cool temperatures aloft, and will support strong storms for a few hours before the boundary layer cools and stabilizes. ...Central Plains... Widely spaced storms persist across the central High Plains, along with isolated cells into central NE and eastern OK. Given that the area is beneath the upper ridge, the loss of heating should result in a downward trend in storm strength. Marginal hail or wind gusts are possible with the strongest storms through early evening. Additional storms are possible this evening and overnight near an east-west stationary front extending from the TX Panhandle across OK and into AR. While shear will remain weak, MLCAPE of 1500-2000 J/kg along with nocturnal warm advection with southwesterly 850 mb flow will support scattered storms through early morning. A few strong wind gusts cannot be ruled out with rather disorganized convection. ..Jewell.. 08/09/2019 Read more

No Mesoscale Discussions are in effect as of Thu Aug 8 23:30:06 UTC 2019.

WW 0563 Status Updates
STATUS REPORT ON WW 563 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 15 ENE ABE TO 30 N EWR TO 35 E POU TO 20 NNE BAF TO 20 N EEN. ..COOK..08/08/19 ATTN...WFO...OKX...BOX...ALY...PHI... STATUS REPORT FOR WS 563 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS CTC001-003-007-009-013-090040- CT . CONNECTICUT COUNTIES INCLUDED ARE FAIRFIELD HARTFORD MIDDLESEX NEW HAVEN TOLLAND MAC011-013-015-090040- MA . MASSACHUSETTS COUNTIES INCLUDED ARE FRANKLIN HAMPDEN HAMPSHIRE NJC003-031-090040- NJ . NEW JERSEY COUNTIES INCLUDED ARE BERGEN PASSAIC Read more