Severe Storms

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1059 AM CDT Thu Aug 08 2019 Valid 081700Z - 091200Z The forecast remains on track. Minor modifications have been made to the ISODRYT area based on latest observations and model guidance. Two shortwave troughs are evident in satellite water vapor imagery in northern Nevada and near the southern California coast. These features are already promoting thunderstorm activity and are expected to continue doing so into the afternoon/evening. Thunderstorm coverage may approach 40% within portions of Oregon, but GPS satellite and forecast soundings show increasing PWAT values which will help to mitigate some of the threat for ignitions. ..Wendt.. 08/08/2019 .PREV DISCUSSION... /ISSUED 0110 AM CDT Thu Aug 08 2019/ ...Synopsis... Deep southerly flow between a longwave trough over the northeastern Pacific and a longwave ridge centered over the Great Basin will maintain mid-level moisture in a corridor from Nevada northward to northern Washington State today. Heating beneath this moist plume will promote areas of isolated to scattered thunderstorms, which will serve as the main focus for fire weather threats across the West. ...Nevada, Idaho, southwestern Montana, central and eastern Oregon, and central and eastern Washington State... The aforementioned synoptic pattern and surface heating will foster development and gradual expansion of convective coverage - likely beginning around mid-morning across Nevada and expanding northward through the afternoon and evening. These storms will occur atop widespread areas of dry fuels, favoring lightning-related fire ignition and spread. Additionally, gusty/erratic downburst winds will complicate fire suppression efforts near ongoing fires in the region. The greatest coverage of storms is expected to occur across portions of Nevada during the afternoon, where 40%+ coverage of lightning strikes are expected. The primary limiting factor for a greater fire-weather threat in this area will be wetting thunderstorm cores and the likelihood of upscale growth of convection into bands/linear segments. The wetting rainfall should keep dry lightning relatively isolated in this area. Likewise, slow-moving convection across Idaho/southwestern Montana should also limit the extent of dry lightning and also result in heavy rainfall in localized areas. The extent of isolated dry lightning strikes will eventually reach Washington State later in the day (late afternoon through early evening). ...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 1059 AM CDT Thu Aug 08 2019 Valid 081700Z - 091200Z The forecast remains on track. Minor modifications have been made to the ISODRYT area based on latest observations and model guidance. Two shortwave troughs are evident in satellite water vapor imagery in northern Nevada and near the southern California coast. These features are already promoting thunderstorm activity and are expected to continue doing so into the afternoon/evening. Thunderstorm coverage may approach 40% within portions of Oregon, but GPS satellite and forecast soundings show increasing PWAT values which will help to mitigate some of the threat for ignitions. ..Wendt.. 08/08/2019 .PREV DISCUSSION... /ISSUED 0110 AM CDT Thu Aug 08 2019/ ...Synopsis... Deep southerly flow between a longwave trough over the northeastern Pacific and a longwave ridge centered over the Great Basin will maintain mid-level moisture in a corridor from Nevada northward to northern Washington State today. Heating beneath this moist plume will promote areas of isolated to scattered thunderstorms, which will serve as the main focus for fire weather threats across the West. ...Nevada, Idaho, southwestern Montana, central and eastern Oregon, and central and eastern Washington State... The aforementioned synoptic pattern and surface heating will foster development and gradual expansion of convective coverage - likely beginning around mid-morning across Nevada and expanding northward through the afternoon and evening. These storms will occur atop widespread areas of dry fuels, favoring lightning-related fire ignition and spread. Additionally, gusty/erratic downburst winds will complicate fire suppression efforts near ongoing fires in the region. The greatest coverage of storms is expected to occur across portions of Nevada during the afternoon, where 40%+ coverage of lightning strikes are expected. The primary limiting factor for a greater fire-weather threat in this area will be wetting thunderstorm cores and the likelihood of upscale growth of convection into bands/linear segments. The wetting rainfall should keep dry lightning relatively isolated in this area. Likewise, slow-moving convection across Idaho/southwestern Montana should also limit the extent of dry lightning and also result in heavy rainfall in localized areas. The extent of isolated dry lightning strikes will eventually reach Washington State later in the day (late afternoon through early evening). ...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 1059 AM CDT Thu Aug 08 2019 Valid 081700Z - 091200Z The forecast remains on track. Minor modifications have been made to the ISODRYT area based on latest observations and model guidance. Two shortwave troughs are evident in satellite water vapor imagery in northern Nevada and near the southern California coast. These features are already promoting thunderstorm activity and are expected to continue doing so into the afternoon/evening. Thunderstorm coverage may approach 40% within portions of Oregon, but GPS satellite and forecast soundings show increasing PWAT values which will help to mitigate some of the threat for ignitions. ..Wendt.. 08/08/2019 .PREV DISCUSSION... /ISSUED 0110 AM CDT Thu Aug 08 2019/ ...Synopsis... Deep southerly flow between a longwave trough over the northeastern Pacific and a longwave ridge centered over the Great Basin will maintain mid-level moisture in a corridor from Nevada northward to northern Washington State today. Heating beneath this moist plume will promote areas of isolated to scattered thunderstorms, which will serve as the main focus for fire weather threats across the West. ...Nevada, Idaho, southwestern Montana, central and eastern Oregon, and central and eastern Washington State... The aforementioned synoptic pattern and surface heating will foster development and gradual expansion of convective coverage - likely beginning around mid-morning across Nevada and expanding northward through the afternoon and evening. These storms will occur atop widespread areas of dry fuels, favoring lightning-related fire ignition and spread. Additionally, gusty/erratic downburst winds will complicate fire suppression efforts near ongoing fires in the region. The greatest coverage of storms is expected to occur across portions of Nevada during the afternoon, where 40%+ coverage of lightning strikes are expected. The primary limiting factor for a greater fire-weather threat in this area will be wetting thunderstorm cores and the likelihood of upscale growth of convection into bands/linear segments. The wetting rainfall should keep dry lightning relatively isolated in this area. Likewise, slow-moving convection across Idaho/southwestern Montana should also limit the extent of dry lightning and also result in heavy rainfall in localized areas. The extent of isolated dry lightning strikes will eventually reach Washington State later in the day (late afternoon through early evening). ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Thu Aug 8 16:02:02 UTC 2019.

MD 1674 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR CENTRAL AND NORTHERN NY...NORTH-CENTRAL PA
Mesoscale Discussion 1674 NWS Storm Prediction Center Norman OK 1058 AM CDT Thu Aug 08 2019 Areas affected...central and northern NY...north-central PA Concerning...Severe potential...Watch possible Valid 081558Z - 081730Z Probability of Watch Issuance...60 percent SUMMARY...The potential for strong to locally severe gusts (45-60mph) will probably increase through midday and into the early afternoon as a squall line moves from western into central and northern NY. DISCUSSION...Radar mosaic shows a squall line over western NY as of 1150am EDT. The 7am Buffalo raob showed meager buoyancy and relatively weak westerly flow from just above the surface through 300mb. Surface heating has occurred this morning with temperatures on the NY Mesonet rising into the upper 70 to lower 80s degrees F immediately east of the squall line. KIAG measured a 40kt gust at 1039am. The NY Mesonet has up until recently only observed 33mph at 3 sites thus far. However, the NY Mesonet Batavia site very recently observed a measured gust of 47mph. RAP forecast soundings show several hundred J/kg MLCAPE developing by early afternoon across central NY. As the mid-level shortwave trough over Ontario and the lower Great Lakes progresses eastward, storm intensity is forecast to increase aided in part by the associated forcing for ascent and diurnal destabilization. Isolated wind damage owing to gusts ranging from 45-55mph (locally up to 60mph) is possible. ..Smith/Goss.. 08/08/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BTV...ALY...BGM...BUF...CTP...PBZ... LAT...LON 41337933 42517802 43417715 44647615 45047477 44377401 43217406 42047485 41397611 41337933 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Thu Aug 08 2019 Valid 081300Z - 091200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE LOWER GREAT LAKES AND NORTH-CENTRAL APPALACHIANS TO THE MID/UPPER OHIO VALLEY... ...SUMMARY... The greatest concentration of potentially severe storms today should be from the lower Great Lakes and north-central Appalachians to the mid/upper Ohio Valley. ...Synopsis... In mid/upper levels, the CONUS subset of the large-scale pattern will continue to feature a mean ridge in the West, from a TX anticyclone to the northern Rockies, and troughing from eastern Canada down the Appalachians. However, some breakdown of the ridging will occur as a series of variably amplified shortwave impinges on its northwestern parts. Two of those perturbations follow each other in quick succession and are evident in moisture channel imagery: the first from over northwestern NV to southwestern UT, the second over the Pacific, approaching the CA Channel Islands. Both of these features will move northeastward across the Great Basin through the period, with the leading one reaching the northern Rockies by 12Z. A series of shortwaves also will traverse the extensive cyclonic- flow field over the Great Lakes and Northeast regions, anchored by a large cyclone over far northern ON and Hudson Bay. Among those is a convectively enhanced vorticity lobe, now apparent in satellite and composited radar imagery from Lake Huron to northern/eastern IN. This perturbation will pivot across the Lower Great Lakes and adjoining states through tonight, following a leading shortwave now ejecting across New England. Meanwhile, in a zone of weaker, difluent flow aloft, convectively induced vorticity lobes will move slowly southeastward over a corridor from KS to the Mid-South. At the surface, 11Z analysis showed a cold front from northwestern Lake Huron across central Lake Michigan, central IA and northern NE, becoming a warm front over southeastern MT to a low near GTF. The eastern portion of this front should proceed eastward across the lower Great Lakes, much of New England, and parts of the Mid- Atlantic through the period. An outflow-reinforced baroclinic zone was evident over northern MS, northern AR, and northern OK, quasistationary except for a southward shunting by convective processes over OK and parts of northern AR. ...Lower Great Lakes to Ohio Valley... Widely scattered to scattered thunderstorms will develop from late morning through the afternoon over western parts of the outlook area, moving somewhat southeastward across the central Appalachians region and eastward to east-northeastward over NY, in close accordance with the cyclonic ambient-flow pattern. Convection should increase in coverage/intensity as it moves into a favorably moist and destabilizing boundary layer. Occasional large hail and damaging to severe gusts will be the main concerns. Activity may form along but mainly ahead of the surface cold front, in areas of weak pre-frontal surface troughing and low-level convergence/heating where MLCINH is locally minimized. Sever hours of strong, direct heating of the near-surface layer with 60s F dew points should occur over most of the area, given the lack of clouds evident in satellite imagery. Meanwhile, the large-scale lift/DCVA field of the shortwave trough should provide supportive destabilization aloft. This should permit a patchy prefrontal corridor of 1000-1500 J/kg MLCAPE to develop, atop steep boundary- layer lapse rates and a well-mixed subcloud layer. Lack of stronger shear area-wide will be a limiting factor for an even better- organized event, though pockets of 30-40 kt effective-shear magnitudes appear possible. Severe potential should weaken with eastward extent and time this evening, into a stabilizing thermodynamic regime. ...Eastern Rockies to central/southern Plains... Two physically distinct regimes will contribute to strong/severe thunderstorm potential today into this evening, with activity moving generally eastward to southeastward around the upper high/ridge. These areas have been split up spatially due to convective/precip trends since the prior outlook: 1. A large area of precip and embedded, non-severe thunderstorms in evident initially from central KS across northeastern OK to the Ozarks of northern AR, supported by warm advection and related lift to LFC northeast of the surface front. A brief/isolated severe-hail event cannot be ruled out in this regime for a few more hours. Additional, widely scattered to scattered thunderstorms are expected to form this afternoon along associated outflow/differential-heating boundaries, offering the threat for isolated large hail and damaging to severe gusts. MCVs now apparent over the northeastern TX Panhandle and west-central KS may provide mesoscale mass-response enhancement in support of storm organization as they shift east-southeastward to southeastward. More-sustained diurnal heating of the favorably moist boundary layer over eastern OK and AR will yield 2000-3000 J/kg MLCAPE, transitioning to 1000-2000 J/kg under more cloud cover to the west. Weak low/middle-level winds and lack of stronger shear should limit overall organization, though localized clustering of damaging gusts may occur where driven by aggregation of multicellular cold pools. 2. Farther west, scattered thunderstorms should develop this afternoon over the eastern WY mountains southward over the CO Front Range and Sangre de Cristos, as well as adjoining foothills and eastward-extending topographic ridges. Sporadic/isolated damaging gusts and severe hail will be possible from the most intense cores. Formation of one or two small MCSs with locally maximized wind-corridor potential also cannot be ruled out as convection moves onto the adjoining High Plains, and into a well-heated/mixed boundary layer supporting a transition from mixed hail/wind threat to mostly wind. In the absence of substantial upper forcing or LLJ activity, convection generally should weaken this evening in keeping with stabilization of the nocturnal boundary layer. ...Great Basin to extreme southern ID... Isolated thunderstorms already have been noted over the southern Sierra and northwest of LAS during the pre-dawn hours, beneath the leading shortwave perturbation. Episodic, widely scattered to scattered thunderstorms are possible across a large part of the Great Basin today in association with both mid/upper level troughs. At least marginal unconditional risk for strong/locally severe gusts is apparent from midday through afternoon -- mainly over areas of western UT and eastern NV that can diabatically destabilize through pre-existing cloud cover, ahead of the densest cloud/precip areas. Thermodynamic support also will be provided by a plume of low-level monsoonal moisture. Preconvective, lower-elevation surface dew points commonly in the 40s over western parts of the outlook area 50s in UT will support MLCAPE mainly in the 500-1000 J/kg range, locally a bit lower or higher. Slight enhancement to the ambient southwest flow is possible in mid/upper levels near each trough, leading to modest but sufficient deep shear for storm organization. Some clustering and cold-pool aggregation may occur as well in support of a more-concentrated wind swath within this broader area, but this depends on mesoscale to storm-scale processes still unresolved. The overall threat should diminish with time this evening int ID and central UT as nocturnal/diabatic stabilization and outflow stabilize the boundary layer. ..Edwards/Broyles.. 08/08/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Thu Aug 08 2019 Valid 081300Z - 091200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE LOWER GREAT LAKES AND NORTH-CENTRAL APPALACHIANS TO THE MID/UPPER OHIO VALLEY... ...SUMMARY... The greatest concentration of potentially severe storms today should be from the lower Great Lakes and north-central Appalachians to the mid/upper Ohio Valley. ...Synopsis... In mid/upper levels, the CONUS subset of the large-scale pattern will continue to feature a mean ridge in the West, from a TX anticyclone to the northern Rockies, and troughing from eastern Canada down the Appalachians. However, some breakdown of the ridging will occur as a series of variably amplified shortwave impinges on its northwestern parts. Two of those perturbations follow each other in quick succession and are evident in moisture channel imagery: the first from over northwestern NV to southwestern UT, the second over the Pacific, approaching the CA Channel Islands. Both of these features will move northeastward across the Great Basin through the period, with the leading one reaching the northern Rockies by 12Z. A series of shortwaves also will traverse the extensive cyclonic- flow field over the Great Lakes and Northeast regions, anchored by a large cyclone over far northern ON and Hudson Bay. Among those is a convectively enhanced vorticity lobe, now apparent in satellite and composited radar imagery from Lake Huron to northern/eastern IN. This perturbation will pivot across the Lower Great Lakes and adjoining states through tonight, following a leading shortwave now ejecting across New England. Meanwhile, in a zone of weaker, difluent flow aloft, convectively induced vorticity lobes will move slowly southeastward over a corridor from KS to the Mid-South. At the surface, 11Z analysis showed a cold front from northwestern Lake Huron across central Lake Michigan, central IA and northern NE, becoming a warm front over southeastern MT to a low near GTF. The eastern portion of this front should proceed eastward across the lower Great Lakes, much of New England, and parts of the Mid- Atlantic through the period. An outflow-reinforced baroclinic zone was evident over northern MS, northern AR, and northern OK, quasistationary except for a southward shunting by convective processes over OK and parts of northern AR. ...Lower Great Lakes to Ohio Valley... Widely scattered to scattered thunderstorms will develop from late morning through the afternoon over western parts of the outlook area, moving somewhat southeastward across the central Appalachians region and eastward to east-northeastward over NY, in close accordance with the cyclonic ambient-flow pattern. Convection should increase in coverage/intensity as it moves into a favorably moist and destabilizing boundary layer. Occasional large hail and damaging to severe gusts will be the main concerns. Activity may form along but mainly ahead of the surface cold front, in areas of weak pre-frontal surface troughing and low-level convergence/heating where MLCINH is locally minimized. Sever hours of strong, direct heating of the near-surface layer with 60s F dew points should occur over most of the area, given the lack of clouds evident in satellite imagery. Meanwhile, the large-scale lift/DCVA field of the shortwave trough should provide supportive destabilization aloft. This should permit a patchy prefrontal corridor of 1000-1500 J/kg MLCAPE to develop, atop steep boundary- layer lapse rates and a well-mixed subcloud layer. Lack of stronger shear area-wide will be a limiting factor for an even better- organized event, though pockets of 30-40 kt effective-shear magnitudes appear possible. Severe potential should weaken with eastward extent and time this evening, into a stabilizing thermodynamic regime. ...Eastern Rockies to central/southern Plains... Two physically distinct regimes will contribute to strong/severe thunderstorm potential today into this evening, with activity moving generally eastward to southeastward around the upper high/ridge. These areas have been split up spatially due to convective/precip trends since the prior outlook: 1. A large area of precip and embedded, non-severe thunderstorms in evident initially from central KS across northeastern OK to the Ozarks of northern AR, supported by warm advection and related lift to LFC northeast of the surface front. A brief/isolated severe-hail event cannot be ruled out in this regime for a few more hours. Additional, widely scattered to scattered thunderstorms are expected to form this afternoon along associated outflow/differential-heating boundaries, offering the threat for isolated large hail and damaging to severe gusts. MCVs now apparent over the northeastern TX Panhandle and west-central KS may provide mesoscale mass-response enhancement in support of storm organization as they shift east-southeastward to southeastward. More-sustained diurnal heating of the favorably moist boundary layer over eastern OK and AR will yield 2000-3000 J/kg MLCAPE, transitioning to 1000-2000 J/kg under more cloud cover to the west. Weak low/middle-level winds and lack of stronger shear should limit overall organization, though localized clustering of damaging gusts may occur where driven by aggregation of multicellular cold pools. 2. Farther west, scattered thunderstorms should develop this afternoon over the eastern WY mountains southward over the CO Front Range and Sangre de Cristos, as well as adjoining foothills and eastward-extending topographic ridges. Sporadic/isolated damaging gusts and severe hail will be possible from the most intense cores. Formation of one or two small MCSs with locally maximized wind-corridor potential also cannot be ruled out as convection moves onto the adjoining High Plains, and into a well-heated/mixed boundary layer supporting a transition from mixed hail/wind threat to mostly wind. In the absence of substantial upper forcing or LLJ activity, convection generally should weaken this evening in keeping with stabilization of the nocturnal boundary layer. ...Great Basin to extreme southern ID... Isolated thunderstorms already have been noted over the southern Sierra and northwest of LAS during the pre-dawn hours, beneath the leading shortwave perturbation. Episodic, widely scattered to scattered thunderstorms are possible across a large part of the Great Basin today in association with both mid/upper level troughs. At least marginal unconditional risk for strong/locally severe gusts is apparent from midday through afternoon -- mainly over areas of western UT and eastern NV that can diabatically destabilize through pre-existing cloud cover, ahead of the densest cloud/precip areas. Thermodynamic support also will be provided by a plume of low-level monsoonal moisture. Preconvective, lower-elevation surface dew points commonly in the 40s over western parts of the outlook area 50s in UT will support MLCAPE mainly in the 500-1000 J/kg range, locally a bit lower or higher. Slight enhancement to the ambient southwest flow is possible in mid/upper levels near each trough, leading to modest but sufficient deep shear for storm organization. Some clustering and cold-pool aggregation may occur as well in support of a more-concentrated wind swath within this broader area, but this depends on mesoscale to storm-scale processes still unresolved. The overall threat should diminish with time this evening int ID and central UT as nocturnal/diabatic stabilization and outflow stabilize the boundary layer. ..Edwards/Broyles.. 08/08/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Thu Aug 08 2019 Valid 081300Z - 091200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE LOWER GREAT LAKES AND NORTH-CENTRAL APPALACHIANS TO THE MID/UPPER OHIO VALLEY... ...SUMMARY... The greatest concentration of potentially severe storms today should be from the lower Great Lakes and north-central Appalachians to the mid/upper Ohio Valley. ...Synopsis... In mid/upper levels, the CONUS subset of the large-scale pattern will continue to feature a mean ridge in the West, from a TX anticyclone to the northern Rockies, and troughing from eastern Canada down the Appalachians. However, some breakdown of the ridging will occur as a series of variably amplified shortwave impinges on its northwestern parts. Two of those perturbations follow each other in quick succession and are evident in moisture channel imagery: the first from over northwestern NV to southwestern UT, the second over the Pacific, approaching the CA Channel Islands. Both of these features will move northeastward across the Great Basin through the period, with the leading one reaching the northern Rockies by 12Z. A series of shortwaves also will traverse the extensive cyclonic- flow field over the Great Lakes and Northeast regions, anchored by a large cyclone over far northern ON and Hudson Bay. Among those is a convectively enhanced vorticity lobe, now apparent in satellite and composited radar imagery from Lake Huron to northern/eastern IN. This perturbation will pivot across the Lower Great Lakes and adjoining states through tonight, following a leading shortwave now ejecting across New England. Meanwhile, in a zone of weaker, difluent flow aloft, convectively induced vorticity lobes will move slowly southeastward over a corridor from KS to the Mid-South. At the surface, 11Z analysis showed a cold front from northwestern Lake Huron across central Lake Michigan, central IA and northern NE, becoming a warm front over southeastern MT to a low near GTF. The eastern portion of this front should proceed eastward across the lower Great Lakes, much of New England, and parts of the Mid- Atlantic through the period. An outflow-reinforced baroclinic zone was evident over northern MS, northern AR, and northern OK, quasistationary except for a southward shunting by convective processes over OK and parts of northern AR. ...Lower Great Lakes to Ohio Valley... Widely scattered to scattered thunderstorms will develop from late morning through the afternoon over western parts of the outlook area, moving somewhat southeastward across the central Appalachians region and eastward to east-northeastward over NY, in close accordance with the cyclonic ambient-flow pattern. Convection should increase in coverage/intensity as it moves into a favorably moist and destabilizing boundary layer. Occasional large hail and damaging to severe gusts will be the main concerns. Activity may form along but mainly ahead of the surface cold front, in areas of weak pre-frontal surface troughing and low-level convergence/heating where MLCINH is locally minimized. Sever hours of strong, direct heating of the near-surface layer with 60s F dew points should occur over most of the area, given the lack of clouds evident in satellite imagery. Meanwhile, the large-scale lift/DCVA field of the shortwave trough should provide supportive destabilization aloft. This should permit a patchy prefrontal corridor of 1000-1500 J/kg MLCAPE to develop, atop steep boundary- layer lapse rates and a well-mixed subcloud layer. Lack of stronger shear area-wide will be a limiting factor for an even better- organized event, though pockets of 30-40 kt effective-shear magnitudes appear possible. Severe potential should weaken with eastward extent and time this evening, into a stabilizing thermodynamic regime. ...Eastern Rockies to central/southern Plains... Two physically distinct regimes will contribute to strong/severe thunderstorm potential today into this evening, with activity moving generally eastward to southeastward around the upper high/ridge. These areas have been split up spatially due to convective/precip trends since the prior outlook: 1. A large area of precip and embedded, non-severe thunderstorms in evident initially from central KS across northeastern OK to the Ozarks of northern AR, supported by warm advection and related lift to LFC northeast of the surface front. A brief/isolated severe-hail event cannot be ruled out in this regime for a few more hours. Additional, widely scattered to scattered thunderstorms are expected to form this afternoon along associated outflow/differential-heating boundaries, offering the threat for isolated large hail and damaging to severe gusts. MCVs now apparent over the northeastern TX Panhandle and west-central KS may provide mesoscale mass-response enhancement in support of storm organization as they shift east-southeastward to southeastward. More-sustained diurnal heating of the favorably moist boundary layer over eastern OK and AR will yield 2000-3000 J/kg MLCAPE, transitioning to 1000-2000 J/kg under more cloud cover to the west. Weak low/middle-level winds and lack of stronger shear should limit overall organization, though localized clustering of damaging gusts may occur where driven by aggregation of multicellular cold pools. 2. Farther west, scattered thunderstorms should develop this afternoon over the eastern WY mountains southward over the CO Front Range and Sangre de Cristos, as well as adjoining foothills and eastward-extending topographic ridges. Sporadic/isolated damaging gusts and severe hail will be possible from the most intense cores. Formation of one or two small MCSs with locally maximized wind-corridor potential also cannot be ruled out as convection moves onto the adjoining High Plains, and into a well-heated/mixed boundary layer supporting a transition from mixed hail/wind threat to mostly wind. In the absence of substantial upper forcing or LLJ activity, convection generally should weaken this evening in keeping with stabilization of the nocturnal boundary layer. ...Great Basin to extreme southern ID... Isolated thunderstorms already have been noted over the southern Sierra and northwest of LAS during the pre-dawn hours, beneath the leading shortwave perturbation. Episodic, widely scattered to scattered thunderstorms are possible across a large part of the Great Basin today in association with both mid/upper level troughs. At least marginal unconditional risk for strong/locally severe gusts is apparent from midday through afternoon -- mainly over areas of western UT and eastern NV that can diabatically destabilize through pre-existing cloud cover, ahead of the densest cloud/precip areas. Thermodynamic support also will be provided by a plume of low-level monsoonal moisture. Preconvective, lower-elevation surface dew points commonly in the 40s over western parts of the outlook area 50s in UT will support MLCAPE mainly in the 500-1000 J/kg range, locally a bit lower or higher. Slight enhancement to the ambient southwest flow is possible in mid/upper levels near each trough, leading to modest but sufficient deep shear for storm organization. Some clustering and cold-pool aggregation may occur as well in support of a more-concentrated wind swath within this broader area, but this depends on mesoscale to storm-scale processes still unresolved. The overall threat should diminish with time this evening int ID and central UT as nocturnal/diabatic stabilization and outflow stabilize the boundary layer. ..Edwards/Broyles.. 08/08/2019 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0335 AM CDT Thu Aug 08 2019 Valid 111200Z - 161200Z ...DISCUSSION... Forecast guidance generally maintains a strong upper anticyclone over the south-central U.S. Meanwhile, less-amplified, but still progressive northern-stream flow will bring several shortwave impulses across the northern Plains, Great Lakes and Northeast during the forecast period, though timing of these features and any mesoscale influences from multiple days of convection over the next week is uncertain. This is in part due to inconsistency between forecast models and also poor resolution of finer-scale features at these timescales. As a result, predictability is too low to include severe probabilities at this time. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0335 AM CDT Thu Aug 08 2019 Valid 111200Z - 161200Z ...DISCUSSION... Forecast guidance generally maintains a strong upper anticyclone over the south-central U.S. Meanwhile, less-amplified, but still progressive northern-stream flow will bring several shortwave impulses across the northern Plains, Great Lakes and Northeast during the forecast period, though timing of these features and any mesoscale influences from multiple days of convection over the next week is uncertain. This is in part due to inconsistency between forecast models and also poor resolution of finer-scale features at these timescales. As a result, predictability is too low to include severe probabilities at this time. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0335 AM CDT Thu Aug 08 2019 Valid 111200Z - 161200Z ...DISCUSSION... Forecast guidance generally maintains a strong upper anticyclone over the south-central U.S. Meanwhile, less-amplified, but still progressive northern-stream flow will bring several shortwave impulses across the northern Plains, Great Lakes and Northeast during the forecast period, though timing of these features and any mesoscale influences from multiple days of convection over the next week is uncertain. This is in part due to inconsistency between forecast models and also poor resolution of finer-scale features at these timescales. As a result, predictability is too low to include severe probabilities at this time. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0335 AM CDT Thu Aug 08 2019 Valid 111200Z - 161200Z ...DISCUSSION... Forecast guidance generally maintains a strong upper anticyclone over the south-central U.S. Meanwhile, less-amplified, but still progressive northern-stream flow will bring several shortwave impulses across the northern Plains, Great Lakes and Northeast during the forecast period, though timing of these features and any mesoscale influences from multiple days of convection over the next week is uncertain. This is in part due to inconsistency between forecast models and also poor resolution of finer-scale features at these timescales. As a result, predictability is too low to include severe probabilities at this time. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CDT Thu Aug 08 2019 Valid 101200Z - 111200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN ROCKIES SATURDAY AFTERNOON AND EVENING... ...SUMMARY... Isolated strong thunderstorms are expected across parts of the northern Rockies Saturday afternoon and early evening. Hail and strong gusts are possible with these storms. ...Northern Rockies... An upper low near the OR/CA coast will lift northeast across OR/WA on Saturday. A belt of strong southwesterly deep-layer flow will overspread the northern Rockies in conjunction with height falls as the upper ridge is shunted eastward toward the northern Plains. A weak surface low/trough will extend from northeast WA toward western MT during the afternoon and strong east/southeasterly low level flow will maintain an unseasonably moist boundary-layer, in which surface dewpoints in the 50s are forecast to extend westward across much of MT into northern ID and eastern WA. Cooling aloft will result in steepening midlevel lapse rates and MLCAPE as high as 1500 J/kg is possible from northeast OR into parts of northern/central ID and western MT. Some uncertainty exists due to impact of cloud cover across the region, though moist guidance supports at least isolated thunderstorm development during the afternoon in this corridor. In addition to favorable thermodynamic profiles, strong effective shear should support organized cells capable of large hail and strong wind gusts. ...Portions of the Northern/Central Plains toward the Mid-MO Valley Vicinity... A more conditional severe threat will exist across parts of northern and central High Plains eastward to the Mid-MO Valley. Convection may be ongoing Saturday morning across parts of eastern SD in association with a midlevel impulse shifting east/southeast across the eastern Dakotas toward MN/IA. It is uncertain at this time if this ongoing convection will be severe. However, guidance suggests intensification of this feature is possible as the downstream airmass destabilizes by early afternoon, when a weak surface boundary/outflow is forecast to drop south/southeast from southern MN into eastern NE. While severe potential is possible, uncertainty remains too great to introduce severe probabilities at this time as the threat will be driven by surface features and mesoscale processes influenced by previous day's convection. Additional isolated strong to severe storms will be possible on continued moist, upslope flow regime across the High Plains from eastern CO/WY into eastern MT. However, as the upper ridge shifts east from the northern Rockies, confidence in storm coverage and intensity is too low to include severe probs at this time. ..Leitman.. 08/08/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CDT Thu Aug 08 2019 Valid 101200Z - 111200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN ROCKIES SATURDAY AFTERNOON AND EVENING... ...SUMMARY... Isolated strong thunderstorms are expected across parts of the northern Rockies Saturday afternoon and early evening. Hail and strong gusts are possible with these storms. ...Northern Rockies... An upper low near the OR/CA coast will lift northeast across OR/WA on Saturday. A belt of strong southwesterly deep-layer flow will overspread the northern Rockies in conjunction with height falls as the upper ridge is shunted eastward toward the northern Plains. A weak surface low/trough will extend from northeast WA toward western MT during the afternoon and strong east/southeasterly low level flow will maintain an unseasonably moist boundary-layer, in which surface dewpoints in the 50s are forecast to extend westward across much of MT into northern ID and eastern WA. Cooling aloft will result in steepening midlevel lapse rates and MLCAPE as high as 1500 J/kg is possible from northeast OR into parts of northern/central ID and western MT. Some uncertainty exists due to impact of cloud cover across the region, though moist guidance supports at least isolated thunderstorm development during the afternoon in this corridor. In addition to favorable thermodynamic profiles, strong effective shear should support organized cells capable of large hail and strong wind gusts. ...Portions of the Northern/Central Plains toward the Mid-MO Valley Vicinity... A more conditional severe threat will exist across parts of northern and central High Plains eastward to the Mid-MO Valley. Convection may be ongoing Saturday morning across parts of eastern SD in association with a midlevel impulse shifting east/southeast across the eastern Dakotas toward MN/IA. It is uncertain at this time if this ongoing convection will be severe. However, guidance suggests intensification of this feature is possible as the downstream airmass destabilizes by early afternoon, when a weak surface boundary/outflow is forecast to drop south/southeast from southern MN into eastern NE. While severe potential is possible, uncertainty remains too great to introduce severe probabilities at this time as the threat will be driven by surface features and mesoscale processes influenced by previous day's convection. Additional isolated strong to severe storms will be possible on continued moist, upslope flow regime across the High Plains from eastern CO/WY into eastern MT. However, as the upper ridge shifts east from the northern Rockies, confidence in storm coverage and intensity is too low to include severe probs at this time. ..Leitman.. 08/08/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CDT Thu Aug 08 2019 Valid 101200Z - 111200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN ROCKIES SATURDAY AFTERNOON AND EVENING... ...SUMMARY... Isolated strong thunderstorms are expected across parts of the northern Rockies Saturday afternoon and early evening. Hail and strong gusts are possible with these storms. ...Northern Rockies... An upper low near the OR/CA coast will lift northeast across OR/WA on Saturday. A belt of strong southwesterly deep-layer flow will overspread the northern Rockies in conjunction with height falls as the upper ridge is shunted eastward toward the northern Plains. A weak surface low/trough will extend from northeast WA toward western MT during the afternoon and strong east/southeasterly low level flow will maintain an unseasonably moist boundary-layer, in which surface dewpoints in the 50s are forecast to extend westward across much of MT into northern ID and eastern WA. Cooling aloft will result in steepening midlevel lapse rates and MLCAPE as high as 1500 J/kg is possible from northeast OR into parts of northern/central ID and western MT. Some uncertainty exists due to impact of cloud cover across the region, though moist guidance supports at least isolated thunderstorm development during the afternoon in this corridor. In addition to favorable thermodynamic profiles, strong effective shear should support organized cells capable of large hail and strong wind gusts. ...Portions of the Northern/Central Plains toward the Mid-MO Valley Vicinity... A more conditional severe threat will exist across parts of northern and central High Plains eastward to the Mid-MO Valley. Convection may be ongoing Saturday morning across parts of eastern SD in association with a midlevel impulse shifting east/southeast across the eastern Dakotas toward MN/IA. It is uncertain at this time if this ongoing convection will be severe. However, guidance suggests intensification of this feature is possible as the downstream airmass destabilizes by early afternoon, when a weak surface boundary/outflow is forecast to drop south/southeast from southern MN into eastern NE. While severe potential is possible, uncertainty remains too great to introduce severe probabilities at this time as the threat will be driven by surface features and mesoscale processes influenced by previous day's convection. Additional isolated strong to severe storms will be possible on continued moist, upslope flow regime across the High Plains from eastern CO/WY into eastern MT. However, as the upper ridge shifts east from the northern Rockies, confidence in storm coverage and intensity is too low to include severe probs at this time. ..Leitman.. 08/08/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CDT Thu Aug 08 2019 Valid 101200Z - 111200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN ROCKIES SATURDAY AFTERNOON AND EVENING... ...SUMMARY... Isolated strong thunderstorms are expected across parts of the northern Rockies Saturday afternoon and early evening. Hail and strong gusts are possible with these storms. ...Northern Rockies... An upper low near the OR/CA coast will lift northeast across OR/WA on Saturday. A belt of strong southwesterly deep-layer flow will overspread the northern Rockies in conjunction with height falls as the upper ridge is shunted eastward toward the northern Plains. A weak surface low/trough will extend from northeast WA toward western MT during the afternoon and strong east/southeasterly low level flow will maintain an unseasonably moist boundary-layer, in which surface dewpoints in the 50s are forecast to extend westward across much of MT into northern ID and eastern WA. Cooling aloft will result in steepening midlevel lapse rates and MLCAPE as high as 1500 J/kg is possible from northeast OR into parts of northern/central ID and western MT. Some uncertainty exists due to impact of cloud cover across the region, though moist guidance supports at least isolated thunderstorm development during the afternoon in this corridor. In addition to favorable thermodynamic profiles, strong effective shear should support organized cells capable of large hail and strong wind gusts. ...Portions of the Northern/Central Plains toward the Mid-MO Valley Vicinity... A more conditional severe threat will exist across parts of northern and central High Plains eastward to the Mid-MO Valley. Convection may be ongoing Saturday morning across parts of eastern SD in association with a midlevel impulse shifting east/southeast across the eastern Dakotas toward MN/IA. It is uncertain at this time if this ongoing convection will be severe. However, guidance suggests intensification of this feature is possible as the downstream airmass destabilizes by early afternoon, when a weak surface boundary/outflow is forecast to drop south/southeast from southern MN into eastern NE. While severe potential is possible, uncertainty remains too great to introduce severe probabilities at this time as the threat will be driven by surface features and mesoscale processes influenced by previous day's convection. Additional isolated strong to severe storms will be possible on continued moist, upslope flow regime across the High Plains from eastern CO/WY into eastern MT. However, as the upper ridge shifts east from the northern Rockies, confidence in storm coverage and intensity is too low to include severe probs at this time. ..Leitman.. 08/08/2019 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0142 AM CDT Thu Aug 08 2019 Valid 091200Z - 101200Z ...Synopsis... The overall synoptic pattern should remain similar throughout the D2/Thu forecast period. A longwave trough will begin to make eastward progression toward Oregon and northern California, resulting in strengthening mid-level flow from Nevada northward through western Idaho as a mid-level ridge keeps hold over the central Rockies and vicinity. Lift from the approaching trough and maintenance of mid-level moisture should promote a few thunderstorms during the afternoon and evening, while strengthening wind fields will result in elevated to locally critical fire weather in the western Great Basin. ...Much of Nevada and far northeastern California for dry/windy conditions... Vertical mixing processes beneath strengthening flow aloft and a strengthening surface trough across the region will result in areas of 20+ mph surface winds from afternoon onward, especially from southern and central Nevada northwestward through the lee of the Sierras. While critical wind fields will be exceeded in a few areas, RH values will be borderline critical based on latest forecast guidance. Furthermore, areas of thunderstorm development should also temper boundary-layer RH values in a few areas, with any critical fire weather conditions being brief and localized. Fuels are dry, however, and fire spread may occur with any ongoing fires especially where critical thresholds can be met for any length of time. ...Much of Oregon, far northern California, northern/central Nevada, and western Idaho for thunderstorms... Isolated to scattered thunderstorms are expected to develop from afternoon onward and should move north fairly quickly (25-35 kts) given the enhanced mid-level wind fields across the region. Cores should be wetter than in the previous day, however, given higher tropospheric moisture content and greater lift/ascent associated with the approach of the mid-level trough. Still, scattered, northward-moving clusters of storms should be most concentrated across southern/central Oregon and northeast Nevada/southwest Idaho and will be capable of isolated dry lightning strikes that will cause a few fire starts given dry fuels. ..Cook.. 08/08/2019 ...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 0142 AM CDT Thu Aug 08 2019 Valid 091200Z - 101200Z ...Synopsis... The overall synoptic pattern should remain similar throughout the D2/Thu forecast period. A longwave trough will begin to make eastward progression toward Oregon and northern California, resulting in strengthening mid-level flow from Nevada northward through western Idaho as a mid-level ridge keeps hold over the central Rockies and vicinity. Lift from the approaching trough and maintenance of mid-level moisture should promote a few thunderstorms during the afternoon and evening, while strengthening wind fields will result in elevated to locally critical fire weather in the western Great Basin. ...Much of Nevada and far northeastern California for dry/windy conditions... Vertical mixing processes beneath strengthening flow aloft and a strengthening surface trough across the region will result in areas of 20+ mph surface winds from afternoon onward, especially from southern and central Nevada northwestward through the lee of the Sierras. While critical wind fields will be exceeded in a few areas, RH values will be borderline critical based on latest forecast guidance. Furthermore, areas of thunderstorm development should also temper boundary-layer RH values in a few areas, with any critical fire weather conditions being brief and localized. Fuels are dry, however, and fire spread may occur with any ongoing fires especially where critical thresholds can be met for any length of time. ...Much of Oregon, far northern California, northern/central Nevada, and western Idaho for thunderstorms... Isolated to scattered thunderstorms are expected to develop from afternoon onward and should move north fairly quickly (25-35 kts) given the enhanced mid-level wind fields across the region. Cores should be wetter than in the previous day, however, given higher tropospheric moisture content and greater lift/ascent associated with the approach of the mid-level trough. Still, scattered, northward-moving clusters of storms should be most concentrated across southern/central Oregon and northeast Nevada/southwest Idaho and will be capable of isolated dry lightning strikes that will cause a few fire starts given dry fuels. ..Cook.. 08/08/2019 ...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 0142 AM CDT Thu Aug 08 2019 Valid 091200Z - 101200Z ...Synopsis... The overall synoptic pattern should remain similar throughout the D2/Thu forecast period. A longwave trough will begin to make eastward progression toward Oregon and northern California, resulting in strengthening mid-level flow from Nevada northward through western Idaho as a mid-level ridge keeps hold over the central Rockies and vicinity. Lift from the approaching trough and maintenance of mid-level moisture should promote a few thunderstorms during the afternoon and evening, while strengthening wind fields will result in elevated to locally critical fire weather in the western Great Basin. ...Much of Nevada and far northeastern California for dry/windy conditions... Vertical mixing processes beneath strengthening flow aloft and a strengthening surface trough across the region will result in areas of 20+ mph surface winds from afternoon onward, especially from southern and central Nevada northwestward through the lee of the Sierras. While critical wind fields will be exceeded in a few areas, RH values will be borderline critical based on latest forecast guidance. Furthermore, areas of thunderstorm development should also temper boundary-layer RH values in a few areas, with any critical fire weather conditions being brief and localized. Fuels are dry, however, and fire spread may occur with any ongoing fires especially where critical thresholds can be met for any length of time. ...Much of Oregon, far northern California, northern/central Nevada, and western Idaho for thunderstorms... Isolated to scattered thunderstorms are expected to develop from afternoon onward and should move north fairly quickly (25-35 kts) given the enhanced mid-level wind fields across the region. Cores should be wetter than in the previous day, however, given higher tropospheric moisture content and greater lift/ascent associated with the approach of the mid-level trough. Still, scattered, northward-moving clusters of storms should be most concentrated across southern/central Oregon and northeast Nevada/southwest Idaho and will be capable of isolated dry lightning strikes that will cause a few fire starts given dry fuels. ..Cook.. 08/08/2019 ...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 0142 AM CDT Thu Aug 08 2019 Valid 091200Z - 101200Z ...Synopsis... The overall synoptic pattern should remain similar throughout the D2/Thu forecast period. A longwave trough will begin to make eastward progression toward Oregon and northern California, resulting in strengthening mid-level flow from Nevada northward through western Idaho as a mid-level ridge keeps hold over the central Rockies and vicinity. Lift from the approaching trough and maintenance of mid-level moisture should promote a few thunderstorms during the afternoon and evening, while strengthening wind fields will result in elevated to locally critical fire weather in the western Great Basin. ...Much of Nevada and far northeastern California for dry/windy conditions... Vertical mixing processes beneath strengthening flow aloft and a strengthening surface trough across the region will result in areas of 20+ mph surface winds from afternoon onward, especially from southern and central Nevada northwestward through the lee of the Sierras. While critical wind fields will be exceeded in a few areas, RH values will be borderline critical based on latest forecast guidance. Furthermore, areas of thunderstorm development should also temper boundary-layer RH values in a few areas, with any critical fire weather conditions being brief and localized. Fuels are dry, however, and fire spread may occur with any ongoing fires especially where critical thresholds can be met for any length of time. ...Much of Oregon, far northern California, northern/central Nevada, and western Idaho for thunderstorms... Isolated to scattered thunderstorms are expected to develop from afternoon onward and should move north fairly quickly (25-35 kts) given the enhanced mid-level wind fields across the region. Cores should be wetter than in the previous day, however, given higher tropospheric moisture content and greater lift/ascent associated with the approach of the mid-level trough. Still, scattered, northward-moving clusters of storms should be most concentrated across southern/central Oregon and northeast Nevada/southwest Idaho and will be capable of isolated dry lightning strikes that will cause a few fire starts given dry fuels. ..Cook.. 08/08/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more