Severe Storms

WW 0570 Status Updates
STATUS FOR WATCH 0570 HAS NOT BEEN ISSUED YET Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0211 PM CDT Sun Aug 11 2019 Valid 121200Z - 131200Z ...NO CRITICAL AREAS... The previous forecast remains on track, with no changes made. Please see below for more details. ..Squitieri.. 08/11/2019 .PREV DISCUSSION... /ISSUED 1230 AM CDT Sun Aug 11 2019/ ...Synopsis... The northern Rockies mid-level trough responsible for heightened fire weather concerns the past few days will continue to weaken and lift northeastward toward the Plains/southern Canadian provinces. In the wake of this system, zonal mid-level flow will extend across the northern tier of the CONUS along with weaker mid-level flow compared to recent days. This pattern will translate to weaker low-level flow across dry areas of the West. Outside of locally elevated fire weather conditions across Wyoming and vicinity, the overall pattern will be quiet and no highlights are needed for this outlook. ...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 0211 PM CDT Sun Aug 11 2019 Valid 121200Z - 131200Z ...NO CRITICAL AREAS... The previous forecast remains on track, with no changes made. Please see below for more details. ..Squitieri.. 08/11/2019 .PREV DISCUSSION... /ISSUED 1230 AM CDT Sun Aug 11 2019/ ...Synopsis... The northern Rockies mid-level trough responsible for heightened fire weather concerns the past few days will continue to weaken and lift northeastward toward the Plains/southern Canadian provinces. In the wake of this system, zonal mid-level flow will extend across the northern tier of the CONUS along with weaker mid-level flow compared to recent days. This pattern will translate to weaker low-level flow across dry areas of the West. Outside of locally elevated fire weather conditions across Wyoming and vicinity, the overall pattern will be quiet and no highlights are needed for this outlook. ...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 0211 PM CDT Sun Aug 11 2019 Valid 121200Z - 131200Z ...NO CRITICAL AREAS... The previous forecast remains on track, with no changes made. Please see below for more details. ..Squitieri.. 08/11/2019 .PREV DISCUSSION... /ISSUED 1230 AM CDT Sun Aug 11 2019/ ...Synopsis... The northern Rockies mid-level trough responsible for heightened fire weather concerns the past few days will continue to weaken and lift northeastward toward the Plains/southern Canadian provinces. In the wake of this system, zonal mid-level flow will extend across the northern tier of the CONUS along with weaker mid-level flow compared to recent days. This pattern will translate to weaker low-level flow across dry areas of the West. Outside of locally elevated fire weather conditions across Wyoming and vicinity, the overall pattern will be quiet and no highlights are needed for this outlook. ...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 0211 PM CDT Sun Aug 11 2019 Valid 121200Z - 131200Z ...NO CRITICAL AREAS... The previous forecast remains on track, with no changes made. Please see below for more details. ..Squitieri.. 08/11/2019 .PREV DISCUSSION... /ISSUED 1230 AM CDT Sun Aug 11 2019/ ...Synopsis... The northern Rockies mid-level trough responsible for heightened fire weather concerns the past few days will continue to weaken and lift northeastward toward the Plains/southern Canadian provinces. In the wake of this system, zonal mid-level flow will extend across the northern tier of the CONUS along with weaker mid-level flow compared to recent days. This pattern will translate to weaker low-level flow across dry areas of the West. Outside of locally elevated fire weather conditions across Wyoming and vicinity, the overall pattern will be quiet and no highlights are needed for this outlook. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 1700 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR PORTIONS OF SOUTHEASTERN WY...THE NE PANHANDLE...AND NORTHEASTERN CO
Mesoscale Discussion 1700 NWS Storm Prediction Center Norman OK 0154 PM CDT Sun Aug 11 2019 Areas affected...Portions of southeastern WY...the NE Panhandle...and northeastern CO Concerning...Severe potential...Watch likely Valid 111854Z - 112100Z Probability of Watch Issuance...80 percent SUMMARY...Severe threat is expected to increase this afternoon, with both large hail and damaging winds possible. A tornado or two may also occur. Watch issuance is likely by 21Z (3 PM MDT). DISCUSSION...With weak surface lows analyzed over east-central CO and southeastern WY, persistent easterly low-level upslope flow will continue to encourage gradual convective development along the Laramie Mountains and Front Range in southeastern WY/northeastern CO, respectively. In addition, at least modest large-scale ascent associated with an upper low over the northern Rockies will continue to overspread the central Rockies this afternoon and evening. Mid-level southwesterly winds are forecast to only modestly strengthen to 25-35 kt through the remainder of the day, but a strongly veering wind profile from the surface through mid levels noted in RAP forecast soundings will contribute to around 30-40 kt of effective bulk shear. Continued boundary-layer heating will erode remaining convective inhibition over the next couple of hours to the north of a remnant outflow boundary extending across northern KS into northeastern CO. The presence of low to mid 60s dewpoints across much of this region in combination with steepening mid-level lapse rates emanating from the central Rockies will promote MLCAPE of generally 2500-3500 J/kg by peak afternoon heating. The expected combination of strong instability with sufficient shear will likely support a mix of supercells/multicells initially. Large hail would probably be the main threat with this semi-discrete development, although a tornado or two could also occur near the surface boundary in northeastern CO where backed low-level flow will locally augment effective SRH. Eventual storm mergers/clustering should occur with eastward extent into the NE Panhandle and northeastern CO as a low-level jet strengthens by early evening. Damaging wind potential would likewise increase if this occurred. With severe potential expected to continue increasing this afternoon, watch issuance is likely by 21Z (3 PM MDT). ..Gleason/Grams.. 08/11/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LBF...GLD...BOU...CYS... LAT...LON 39320473 41240520 42950513 42960211 40800206 39640209 39120305 39120391 39320473 Read more

WW 0569 Status Updates
STATUS FOR WATCH 0569 HAS NOT BEEN ISSUED YET Read more

MD 1699 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR SOUTHEAST MT...NORTHERN WY...NORTHWEST SD...SOUTHWEST ND
Mesoscale Discussion 1699 NWS Storm Prediction Center Norman OK 0115 PM CDT Sun Aug 11 2019 Areas affected...Southeast MT...Northern WY...Northwest SD...Southwest ND Concerning...Severe potential...Watch likely Valid 111815Z - 111945Z Probability of Watch Issuance...95 percent SUMMARY...Severe thunderstorm development is likely across some portion of the area this afternoon. Very large hail and severe wind gusts will be the primary hazards, though a tornado or two will also be possible. One or more watches are likely by 19-20Z. DISCUSSION...A strong thunderstorm has recently developed near Sheridan, WY, while a gradual intensification has been noted for embedded cells within an ongoing elevated cluster across southeast MT. Thunderstorms are expected to increase in coverage and intensity through the afternoon, as further destabilization occurs and a seasonably strong upper-level low/trough ejects across the northern Rockies. Evolution of the ongoing elevated cluster remains uncertain, but there is some potential for a transition to surface-based convection as the downstream airmass destabilizes into southwest ND/northwest SD. Meanwhile, additional thunderstorms are likely to develop across the higher terrain of northern/eastern WY later this afternoon. Moderate to locally strong buoyancy (MLCAPE 1500-3000 J/kg) is forecast to develop later this afternoon, as heating of a moist low-level environment occurs beneath steep midlevel lapse rates. Effective shear in the 35-45 kt range will favor supercell development with initial deep convection, with some cell mergers/upscale growth possible later in the convective evolution. Very large hail will the primary initial threat, along with isolated severe wind gusts. Any upscale growth later this afternoon would favor somewhat greater wind potential. A tornado or two will also be possible with any supercells, though relatively weak low-level flow may temper the tornado threat to some extent. Given the expected increase in the severe threat with time, one or more watches are likely across some portion of this region by 19-20Z. ..Dean/Grams.. 08/11/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BIS...UNR...BYZ...GGW...RIW... LAT...LON 46890656 46850435 46320328 45840290 44750289 44070323 43710360 43600416 43660480 43790536 43990621 44600786 44810922 45001013 46120828 46740690 46890656 Read more

No watches are valid as of Sun Aug 11 17:35:01 UTC 2019.

MD 1698 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR SOUTHWEST INTO CENTRAL MT
Mesoscale Discussion 1698 NWS Storm Prediction Center Norman OK 1233 PM CDT Sun Aug 11 2019 Areas affected...Southwest into central MT Concerning...Severe potential...Watch likely Valid 111733Z - 111900Z Probability of Watch Issuance...95 percent SUMMARY...The severe thunderstorm threat will increase into this afternoon. A severe wind swath may eventually develop across central MT, though all severe hazards will be possible. One or two watches will likely be issued by 19-20Z. DISCUSSION...One ongoing thunderstorm cluster is moving into north-central MT as of 1730Z, while another is moving into southwest MT. While the northern cluster may pose some threat of strong wind gusts in the short term, of greater concern is the southern cluster, which will likely increase in coverage and intensity as it moves into an increasingly unstable environment and large-scale ascent is maintained ahead of a seasonably strong mid/upper low across ID. With low-level moisture likely to be maintained or increased somewhat this afternoon due to persistent easterly flow, MLCAPE will likely rise into the 1000-2000 J/kg range this afternoon. Increasing mid/upper southwesterlies will support effective shear in the 35-50 kt range, which will support organized storm structures. The ongoing cluster across southwest MT may evolve into a forward-propagating MCS with time, with more isolated supercell development also possible on the periphery of this system. A severe wind swath will be possible ahead of any upscale-growing cluster, while steep lapse rates will support a hail threat, with very large hail possible with any supercells later this afternoon. Some tornado threat will also be present with any sustained supercells, though the greater tornado threat may eventually develop further east across south-central/southeast MT. ..Dean/Grams.. 08/11/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BYZ...GGW...TFX...MSO... LAT...LON 45871380 46701261 47641107 48380782 47800703 46960691 45850898 45141084 44871179 44501278 44991335 45441375 45871380 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1219 PM CDT Sun Aug 11 2019 Valid 121200Z - 131200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR CENTRAL ILLINOIS... ...SUMMARY... Severe thunderstorms are likely on Monday over the middle Mississippi Valley to the Ohio Valley. Damaging gusts are the primary risk but a few tornadoes are possible. ...Synopsis... Northern-stream upper trough will deamplify as it moves across the Dakotas into MN. In the low levels, a cold front will extend from central ND southward through western NE by Monday evening. A low-amplitude, convectively enhanced shortwave trough will move from the NE/IA area into the southern Great Lakes and OH Valley during the evening into the overnight. A weak surface low will develop eastward from the central Great Plains into IL by late afternoon. A quasi-stationary front will extend eastward from the low through southern IA then southeast as a warm front toward the TN Valley. ...Middle Mississippi Valley into the Ohio Valley... Considerable uncertainty for this forecast is largely related to thunderstorm development expected late tonight into Monday morning across the central Great Plains into the lower MO Valley. This forecast thinking is similar to the previous outlook. Storms will likely be ongoing Monday morning from eastern NE into IA in association with the progressive, low-amplitude shortwave trough and will continue east within zone of isentropic ascent north of the front and on nose of an eastward-migrating low-level jet. A cluster of storms is possible farther southeast along the warm front over northeast MO into IL. By the afternoon, the warm front activity will have weakened and moved farther east. Despite modest 700-500mb lapse rates, strong heating amidst high-quality moisture (16-19 g/kg lowest 100mb mean mixing ratio) will lead to a moderately to very unstable airmass developing across IL south of an effective boundary. A strong belt of westerly 700mb flow (30-40kt) is forecast to move across IA and into the northern half of IL by the mid-late afternoon. It is a possibility that convection is maintained from IA into IL during the day ahead of the mid-level wave moving from eastern NE to Lake MI by early evening. Models are in good agreement in the depiction and evolution of a south-southwesterly LLJ over lower MO Valley being maintained and perhaps intensifying to 40kt as it shifts east into north-central IL by early evening. However, the variability shown by different model solutions in the magnitude of destabilization is very large and is due mostly to convective possibilities modulating the position of the buoyancy gradient across the mid MS Valley. With those uncertainty concerns, it seems prudent at this time to introduce a corridor of higher probabilities given the overlap of shear (40+ kt effective shear) and a moisture-rich/buoyant boundary layer. Supercells are possible, especially early during the convective lifecycle before upscale growth into bows favors potential for severe gusts and a corridor of wind damage. ...Northern Plains region... The atmosphere may become at least marginally unstable east of a cold front across the eastern Dakotas and into eastern NE where a belt of stronger winds within base of the northern-stream shortwave trough will reside. A few storms may redevelop in this region during the afternoon, posing some risk for hail or locally strong wind gusts. ...Maine... A few storms may develop along pre-frontal trough during the afternoon where modest low-level moisture and mid-level lapse rates will support marginal instability. This region will reside within belt of stronger winds aloft within base of an amplifying upper trough supporting 35-40 kt effective shear. A few storms may produce locally strong wind gusts and small to marginally severe hail, but overall threat should remain limited by the expected weak thermodynamic environment. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 30% - Enhanced Hail: 15% - Slight ..Smith.. 08/11/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1219 PM CDT Sun Aug 11 2019 Valid 121200Z - 131200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR CENTRAL ILLINOIS... ...SUMMARY... Severe thunderstorms are likely on Monday over the middle Mississippi Valley to the Ohio Valley. Damaging gusts are the primary risk but a few tornadoes are possible. ...Synopsis... Northern-stream upper trough will deamplify as it moves across the Dakotas into MN. In the low levels, a cold front will extend from central ND southward through western NE by Monday evening. A low-amplitude, convectively enhanced shortwave trough will move from the NE/IA area into the southern Great Lakes and OH Valley during the evening into the overnight. A weak surface low will develop eastward from the central Great Plains into IL by late afternoon. A quasi-stationary front will extend eastward from the low through southern IA then southeast as a warm front toward the TN Valley. ...Middle Mississippi Valley into the Ohio Valley... Considerable uncertainty for this forecast is largely related to thunderstorm development expected late tonight into Monday morning across the central Great Plains into the lower MO Valley. This forecast thinking is similar to the previous outlook. Storms will likely be ongoing Monday morning from eastern NE into IA in association with the progressive, low-amplitude shortwave trough and will continue east within zone of isentropic ascent north of the front and on nose of an eastward-migrating low-level jet. A cluster of storms is possible farther southeast along the warm front over northeast MO into IL. By the afternoon, the warm front activity will have weakened and moved farther east. Despite modest 700-500mb lapse rates, strong heating amidst high-quality moisture (16-19 g/kg lowest 100mb mean mixing ratio) will lead to a moderately to very unstable airmass developing across IL south of an effective boundary. A strong belt of westerly 700mb flow (30-40kt) is forecast to move across IA and into the northern half of IL by the mid-late afternoon. It is a possibility that convection is maintained from IA into IL during the day ahead of the mid-level wave moving from eastern NE to Lake MI by early evening. Models are in good agreement in the depiction and evolution of a south-southwesterly LLJ over lower MO Valley being maintained and perhaps intensifying to 40kt as it shifts east into north-central IL by early evening. However, the variability shown by different model solutions in the magnitude of destabilization is very large and is due mostly to convective possibilities modulating the position of the buoyancy gradient across the mid MS Valley. With those uncertainty concerns, it seems prudent at this time to introduce a corridor of higher probabilities given the overlap of shear (40+ kt effective shear) and a moisture-rich/buoyant boundary layer. Supercells are possible, especially early during the convective lifecycle before upscale growth into bows favors potential for severe gusts and a corridor of wind damage. ...Northern Plains region... The atmosphere may become at least marginally unstable east of a cold front across the eastern Dakotas and into eastern NE where a belt of stronger winds within base of the northern-stream shortwave trough will reside. A few storms may redevelop in this region during the afternoon, posing some risk for hail or locally strong wind gusts. ...Maine... A few storms may develop along pre-frontal trough during the afternoon where modest low-level moisture and mid-level lapse rates will support marginal instability. This region will reside within belt of stronger winds aloft within base of an amplifying upper trough supporting 35-40 kt effective shear. A few storms may produce locally strong wind gusts and small to marginally severe hail, but overall threat should remain limited by the expected weak thermodynamic environment. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 30% - Enhanced Hail: 15% - Slight ..Smith.. 08/11/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1219 PM CDT Sun Aug 11 2019 Valid 121200Z - 131200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR CENTRAL ILLINOIS... ...SUMMARY... Severe thunderstorms are likely on Monday over the middle Mississippi Valley to the Ohio Valley. Damaging gusts are the primary risk but a few tornadoes are possible. ...Synopsis... Northern-stream upper trough will deamplify as it moves across the Dakotas into MN. In the low levels, a cold front will extend from central ND southward through western NE by Monday evening. A low-amplitude, convectively enhanced shortwave trough will move from the NE/IA area into the southern Great Lakes and OH Valley during the evening into the overnight. A weak surface low will develop eastward from the central Great Plains into IL by late afternoon. A quasi-stationary front will extend eastward from the low through southern IA then southeast as a warm front toward the TN Valley. ...Middle Mississippi Valley into the Ohio Valley... Considerable uncertainty for this forecast is largely related to thunderstorm development expected late tonight into Monday morning across the central Great Plains into the lower MO Valley. This forecast thinking is similar to the previous outlook. Storms will likely be ongoing Monday morning from eastern NE into IA in association with the progressive, low-amplitude shortwave trough and will continue east within zone of isentropic ascent north of the front and on nose of an eastward-migrating low-level jet. A cluster of storms is possible farther southeast along the warm front over northeast MO into IL. By the afternoon, the warm front activity will have weakened and moved farther east. Despite modest 700-500mb lapse rates, strong heating amidst high-quality moisture (16-19 g/kg lowest 100mb mean mixing ratio) will lead to a moderately to very unstable airmass developing across IL south of an effective boundary. A strong belt of westerly 700mb flow (30-40kt) is forecast to move across IA and into the northern half of IL by the mid-late afternoon. It is a possibility that convection is maintained from IA into IL during the day ahead of the mid-level wave moving from eastern NE to Lake MI by early evening. Models are in good agreement in the depiction and evolution of a south-southwesterly LLJ over lower MO Valley being maintained and perhaps intensifying to 40kt as it shifts east into north-central IL by early evening. However, the variability shown by different model solutions in the magnitude of destabilization is very large and is due mostly to convective possibilities modulating the position of the buoyancy gradient across the mid MS Valley. With those uncertainty concerns, it seems prudent at this time to introduce a corridor of higher probabilities given the overlap of shear (40+ kt effective shear) and a moisture-rich/buoyant boundary layer. Supercells are possible, especially early during the convective lifecycle before upscale growth into bows favors potential for severe gusts and a corridor of wind damage. ...Northern Plains region... The atmosphere may become at least marginally unstable east of a cold front across the eastern Dakotas and into eastern NE where a belt of stronger winds within base of the northern-stream shortwave trough will reside. A few storms may redevelop in this region during the afternoon, posing some risk for hail or locally strong wind gusts. ...Maine... A few storms may develop along pre-frontal trough during the afternoon where modest low-level moisture and mid-level lapse rates will support marginal instability. This region will reside within belt of stronger winds aloft within base of an amplifying upper trough supporting 35-40 kt effective shear. A few storms may produce locally strong wind gusts and small to marginally severe hail, but overall threat should remain limited by the expected weak thermodynamic environment. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 30% - Enhanced Hail: 15% - Slight ..Smith.. 08/11/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1219 PM CDT Sun Aug 11 2019 Valid 121200Z - 131200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR CENTRAL ILLINOIS... ...SUMMARY... Severe thunderstorms are likely on Monday over the middle Mississippi Valley to the Ohio Valley. Damaging gusts are the primary risk but a few tornadoes are possible. ...Synopsis... Northern-stream upper trough will deamplify as it moves across the Dakotas into MN. In the low levels, a cold front will extend from central ND southward through western NE by Monday evening. A low-amplitude, convectively enhanced shortwave trough will move from the NE/IA area into the southern Great Lakes and OH Valley during the evening into the overnight. A weak surface low will develop eastward from the central Great Plains into IL by late afternoon. A quasi-stationary front will extend eastward from the low through southern IA then southeast as a warm front toward the TN Valley. ...Middle Mississippi Valley into the Ohio Valley... Considerable uncertainty for this forecast is largely related to thunderstorm development expected late tonight into Monday morning across the central Great Plains into the lower MO Valley. This forecast thinking is similar to the previous outlook. Storms will likely be ongoing Monday morning from eastern NE into IA in association with the progressive, low-amplitude shortwave trough and will continue east within zone of isentropic ascent north of the front and on nose of an eastward-migrating low-level jet. A cluster of storms is possible farther southeast along the warm front over northeast MO into IL. By the afternoon, the warm front activity will have weakened and moved farther east. Despite modest 700-500mb lapse rates, strong heating amidst high-quality moisture (16-19 g/kg lowest 100mb mean mixing ratio) will lead to a moderately to very unstable airmass developing across IL south of an effective boundary. A strong belt of westerly 700mb flow (30-40kt) is forecast to move across IA and into the northern half of IL by the mid-late afternoon. It is a possibility that convection is maintained from IA into IL during the day ahead of the mid-level wave moving from eastern NE to Lake MI by early evening. Models are in good agreement in the depiction and evolution of a south-southwesterly LLJ over lower MO Valley being maintained and perhaps intensifying to 40kt as it shifts east into north-central IL by early evening. However, the variability shown by different model solutions in the magnitude of destabilization is very large and is due mostly to convective possibilities modulating the position of the buoyancy gradient across the mid MS Valley. With those uncertainty concerns, it seems prudent at this time to introduce a corridor of higher probabilities given the overlap of shear (40+ kt effective shear) and a moisture-rich/buoyant boundary layer. Supercells are possible, especially early during the convective lifecycle before upscale growth into bows favors potential for severe gusts and a corridor of wind damage. ...Northern Plains region... The atmosphere may become at least marginally unstable east of a cold front across the eastern Dakotas and into eastern NE where a belt of stronger winds within base of the northern-stream shortwave trough will reside. A few storms may redevelop in this region during the afternoon, posing some risk for hail or locally strong wind gusts. ...Maine... A few storms may develop along pre-frontal trough during the afternoon where modest low-level moisture and mid-level lapse rates will support marginal instability. This region will reside within belt of stronger winds aloft within base of an amplifying upper trough supporting 35-40 kt effective shear. A few storms may produce locally strong wind gusts and small to marginally severe hail, but overall threat should remain limited by the expected weak thermodynamic environment. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 30% - Enhanced Hail: 15% - Slight ..Smith.. 08/11/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1219 PM CDT Sun Aug 11 2019 Valid 121200Z - 131200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR CENTRAL ILLINOIS... ...SUMMARY... Severe thunderstorms are likely on Monday over the middle Mississippi Valley to the Ohio Valley. Damaging gusts are the primary risk but a few tornadoes are possible. ...Synopsis... Northern-stream upper trough will deamplify as it moves across the Dakotas into MN. In the low levels, a cold front will extend from central ND southward through western NE by Monday evening. A low-amplitude, convectively enhanced shortwave trough will move from the NE/IA area into the southern Great Lakes and OH Valley during the evening into the overnight. A weak surface low will develop eastward from the central Great Plains into IL by late afternoon. A quasi-stationary front will extend eastward from the low through southern IA then southeast as a warm front toward the TN Valley. ...Middle Mississippi Valley into the Ohio Valley... Considerable uncertainty for this forecast is largely related to thunderstorm development expected late tonight into Monday morning across the central Great Plains into the lower MO Valley. This forecast thinking is similar to the previous outlook. Storms will likely be ongoing Monday morning from eastern NE into IA in association with the progressive, low-amplitude shortwave trough and will continue east within zone of isentropic ascent north of the front and on nose of an eastward-migrating low-level jet. A cluster of storms is possible farther southeast along the warm front over northeast MO into IL. By the afternoon, the warm front activity will have weakened and moved farther east. Despite modest 700-500mb lapse rates, strong heating amidst high-quality moisture (16-19 g/kg lowest 100mb mean mixing ratio) will lead to a moderately to very unstable airmass developing across IL south of an effective boundary. A strong belt of westerly 700mb flow (30-40kt) is forecast to move across IA and into the northern half of IL by the mid-late afternoon. It is a possibility that convection is maintained from IA into IL during the day ahead of the mid-level wave moving from eastern NE to Lake MI by early evening. Models are in good agreement in the depiction and evolution of a south-southwesterly LLJ over lower MO Valley being maintained and perhaps intensifying to 40kt as it shifts east into north-central IL by early evening. However, the variability shown by different model solutions in the magnitude of destabilization is very large and is due mostly to convective possibilities modulating the position of the buoyancy gradient across the mid MS Valley. With those uncertainty concerns, it seems prudent at this time to introduce a corridor of higher probabilities given the overlap of shear (40+ kt effective shear) and a moisture-rich/buoyant boundary layer. Supercells are possible, especially early during the convective lifecycle before upscale growth into bows favors potential for severe gusts and a corridor of wind damage. ...Northern Plains region... The atmosphere may become at least marginally unstable east of a cold front across the eastern Dakotas and into eastern NE where a belt of stronger winds within base of the northern-stream shortwave trough will reside. A few storms may redevelop in this region during the afternoon, posing some risk for hail or locally strong wind gusts. ...Maine... A few storms may develop along pre-frontal trough during the afternoon where modest low-level moisture and mid-level lapse rates will support marginal instability. This region will reside within belt of stronger winds aloft within base of an amplifying upper trough supporting 35-40 kt effective shear. A few storms may produce locally strong wind gusts and small to marginally severe hail, but overall threat should remain limited by the expected weak thermodynamic environment. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 30% - Enhanced Hail: 15% - Slight ..Smith.. 08/11/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Aug 11 2019 Valid 111630Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHERN NE...NORTHERN KS...NORTHEAST CO...AND EAST-CENTRAL MT... ...SUMMARY... Scattered to numerous severe thunderstorms are likely across portions of the northern and central Great Plains. A few tornadoes, damaging wind gusts, and large hail are possible, mainly through this evening. ...Central High Plains to Mid-MS Valley... A belt of somewhat enhanced mid-level flow extends from the southern Rockies to the Lower MO Valley around the anticyclone centered near the Red River. Within this belt, an MCV from a remnant overnight MCS is sliding eastward near the IA/MO border. Some surface-based storm development is possible near this MCV along the leading edge of the residual cold pool and perhaps in the wake of the ongoing stratiform if modest boundary-layer heating can occur. Weak mid-level lapse rates and generally modest effective shear suggests the threat for damaging winds should be localized. Farther west, a low-level upslope regime has become established north of the remnant outflow/effective front that is draped near the I-70 corridor. Recovery of low-level moisture and surface heating will yield large buoyancy north of the front with MLCAPE likely reaching 2500-3500 J/kg by late afternoon. Thunderstorm development is expected first immediately east of the Front Range in CO, while the boundary layer should remain capped through much of the afternoon in far northeast CO vicinity. Buoyancy and deep-layer vertical shear will be sufficient for a mix of supercells and multicell clusters with large hail/severe gusts possible with the initial deep convection east of the Front Range. Wind profiles will be more favorable for supercells farther east on the High Plains where low-level easterly flow and hodograph curvature will be greater, though there will be a tendency for cell interactions and upscale growth later into the evening. Any semi-discrete supercells will pose a threat for a couple of tornadoes and large hail, while the severe wind threat will increase with storm clustering into the evening. These clusters should form into a forward-propagating MCS that may develop into a longer-lived bow along the KS/NE border region tonight. Weak low-level lapse rates should be a limiting factor, but the reservoir of large buoyancy along the nose of the low-level jet lends credence to the possibility of a swath of severe wind gusts into the early overnight. ...Northern High Plains... A shortwave trough will eject from western ID to eastern MT. Easterly low-level flow will be maintained ahead of this trough and its associated cold front that will push east across MT. This flow regime will maintain a broad plume of mid 50s to mid 60s surface dew points from west to east. Rather steep mid-level lapse rates of 8-9 C/km across WY/eastern MT will contribute to a corridor of MLCAPE reaching 2000-3000 J/kg where greater surface heating is underway across southeast MT/northeast WY/western SD. Episodic thunderstorm initiation is expected during the next few hours over the high terrain of southwest MT and downstream of a leading lobe of ascent approaching the WY/MT/Dakota border region, as well as by late afternoon in an arc off the higher terrain of WY. Effective bulk shear of 35-50 kt will favor several supercells initially with large hail and a couple of tornadoes. Convection is expected to grow upscale into multiple clusters/line segments across MT into the western Dakotas with an increasing threat of severe winds. The most likely corridor for a swath of severe gusts is across parts of east-central MT along the northern periphery of the buoyancy plume where large-scale ascent should be greatest ahead of the shortwave trough. ..Grams/Dean.. 08/11/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Aug 11 2019 Valid 111630Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHERN NE...NORTHERN KS...NORTHEAST CO...AND EAST-CENTRAL MT... ...SUMMARY... Scattered to numerous severe thunderstorms are likely across portions of the northern and central Great Plains. A few tornadoes, damaging wind gusts, and large hail are possible, mainly through this evening. ...Central High Plains to Mid-MS Valley... A belt of somewhat enhanced mid-level flow extends from the southern Rockies to the Lower MO Valley around the anticyclone centered near the Red River. Within this belt, an MCV from a remnant overnight MCS is sliding eastward near the IA/MO border. Some surface-based storm development is possible near this MCV along the leading edge of the residual cold pool and perhaps in the wake of the ongoing stratiform if modest boundary-layer heating can occur. Weak mid-level lapse rates and generally modest effective shear suggests the threat for damaging winds should be localized. Farther west, a low-level upslope regime has become established north of the remnant outflow/effective front that is draped near the I-70 corridor. Recovery of low-level moisture and surface heating will yield large buoyancy north of the front with MLCAPE likely reaching 2500-3500 J/kg by late afternoon. Thunderstorm development is expected first immediately east of the Front Range in CO, while the boundary layer should remain capped through much of the afternoon in far northeast CO vicinity. Buoyancy and deep-layer vertical shear will be sufficient for a mix of supercells and multicell clusters with large hail/severe gusts possible with the initial deep convection east of the Front Range. Wind profiles will be more favorable for supercells farther east on the High Plains where low-level easterly flow and hodograph curvature will be greater, though there will be a tendency for cell interactions and upscale growth later into the evening. Any semi-discrete supercells will pose a threat for a couple of tornadoes and large hail, while the severe wind threat will increase with storm clustering into the evening. These clusters should form into a forward-propagating MCS that may develop into a longer-lived bow along the KS/NE border region tonight. Weak low-level lapse rates should be a limiting factor, but the reservoir of large buoyancy along the nose of the low-level jet lends credence to the possibility of a swath of severe wind gusts into the early overnight. ...Northern High Plains... A shortwave trough will eject from western ID to eastern MT. Easterly low-level flow will be maintained ahead of this trough and its associated cold front that will push east across MT. This flow regime will maintain a broad plume of mid 50s to mid 60s surface dew points from west to east. Rather steep mid-level lapse rates of 8-9 C/km across WY/eastern MT will contribute to a corridor of MLCAPE reaching 2000-3000 J/kg where greater surface heating is underway across southeast MT/northeast WY/western SD. Episodic thunderstorm initiation is expected during the next few hours over the high terrain of southwest MT and downstream of a leading lobe of ascent approaching the WY/MT/Dakota border region, as well as by late afternoon in an arc off the higher terrain of WY. Effective bulk shear of 35-50 kt will favor several supercells initially with large hail and a couple of tornadoes. Convection is expected to grow upscale into multiple clusters/line segments across MT into the western Dakotas with an increasing threat of severe winds. The most likely corridor for a swath of severe gusts is across parts of east-central MT along the northern periphery of the buoyancy plume where large-scale ascent should be greatest ahead of the shortwave trough. ..Grams/Dean.. 08/11/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Aug 11 2019 Valid 111630Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHERN NE...NORTHERN KS...NORTHEAST CO...AND EAST-CENTRAL MT... ...SUMMARY... Scattered to numerous severe thunderstorms are likely across portions of the northern and central Great Plains. A few tornadoes, damaging wind gusts, and large hail are possible, mainly through this evening. ...Central High Plains to Mid-MS Valley... A belt of somewhat enhanced mid-level flow extends from the southern Rockies to the Lower MO Valley around the anticyclone centered near the Red River. Within this belt, an MCV from a remnant overnight MCS is sliding eastward near the IA/MO border. Some surface-based storm development is possible near this MCV along the leading edge of the residual cold pool and perhaps in the wake of the ongoing stratiform if modest boundary-layer heating can occur. Weak mid-level lapse rates and generally modest effective shear suggests the threat for damaging winds should be localized. Farther west, a low-level upslope regime has become established north of the remnant outflow/effective front that is draped near the I-70 corridor. Recovery of low-level moisture and surface heating will yield large buoyancy north of the front with MLCAPE likely reaching 2500-3500 J/kg by late afternoon. Thunderstorm development is expected first immediately east of the Front Range in CO, while the boundary layer should remain capped through much of the afternoon in far northeast CO vicinity. Buoyancy and deep-layer vertical shear will be sufficient for a mix of supercells and multicell clusters with large hail/severe gusts possible with the initial deep convection east of the Front Range. Wind profiles will be more favorable for supercells farther east on the High Plains where low-level easterly flow and hodograph curvature will be greater, though there will be a tendency for cell interactions and upscale growth later into the evening. Any semi-discrete supercells will pose a threat for a couple of tornadoes and large hail, while the severe wind threat will increase with storm clustering into the evening. These clusters should form into a forward-propagating MCS that may develop into a longer-lived bow along the KS/NE border region tonight. Weak low-level lapse rates should be a limiting factor, but the reservoir of large buoyancy along the nose of the low-level jet lends credence to the possibility of a swath of severe wind gusts into the early overnight. ...Northern High Plains... A shortwave trough will eject from western ID to eastern MT. Easterly low-level flow will be maintained ahead of this trough and its associated cold front that will push east across MT. This flow regime will maintain a broad plume of mid 50s to mid 60s surface dew points from west to east. Rather steep mid-level lapse rates of 8-9 C/km across WY/eastern MT will contribute to a corridor of MLCAPE reaching 2000-3000 J/kg where greater surface heating is underway across southeast MT/northeast WY/western SD. Episodic thunderstorm initiation is expected during the next few hours over the high terrain of southwest MT and downstream of a leading lobe of ascent approaching the WY/MT/Dakota border region, as well as by late afternoon in an arc off the higher terrain of WY. Effective bulk shear of 35-50 kt will favor several supercells initially with large hail and a couple of tornadoes. Convection is expected to grow upscale into multiple clusters/line segments across MT into the western Dakotas with an increasing threat of severe winds. The most likely corridor for a swath of severe gusts is across parts of east-central MT along the northern periphery of the buoyancy plume where large-scale ascent should be greatest ahead of the shortwave trough. ..Grams/Dean.. 08/11/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Aug 11 2019 Valid 111630Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHERN NE...NORTHERN KS...NORTHEAST CO...AND EAST-CENTRAL MT... ...SUMMARY... Scattered to numerous severe thunderstorms are likely across portions of the northern and central Great Plains. A few tornadoes, damaging wind gusts, and large hail are possible, mainly through this evening. ...Central High Plains to Mid-MS Valley... A belt of somewhat enhanced mid-level flow extends from the southern Rockies to the Lower MO Valley around the anticyclone centered near the Red River. Within this belt, an MCV from a remnant overnight MCS is sliding eastward near the IA/MO border. Some surface-based storm development is possible near this MCV along the leading edge of the residual cold pool and perhaps in the wake of the ongoing stratiform if modest boundary-layer heating can occur. Weak mid-level lapse rates and generally modest effective shear suggests the threat for damaging winds should be localized. Farther west, a low-level upslope regime has become established north of the remnant outflow/effective front that is draped near the I-70 corridor. Recovery of low-level moisture and surface heating will yield large buoyancy north of the front with MLCAPE likely reaching 2500-3500 J/kg by late afternoon. Thunderstorm development is expected first immediately east of the Front Range in CO, while the boundary layer should remain capped through much of the afternoon in far northeast CO vicinity. Buoyancy and deep-layer vertical shear will be sufficient for a mix of supercells and multicell clusters with large hail/severe gusts possible with the initial deep convection east of the Front Range. Wind profiles will be more favorable for supercells farther east on the High Plains where low-level easterly flow and hodograph curvature will be greater, though there will be a tendency for cell interactions and upscale growth later into the evening. Any semi-discrete supercells will pose a threat for a couple of tornadoes and large hail, while the severe wind threat will increase with storm clustering into the evening. These clusters should form into a forward-propagating MCS that may develop into a longer-lived bow along the KS/NE border region tonight. Weak low-level lapse rates should be a limiting factor, but the reservoir of large buoyancy along the nose of the low-level jet lends credence to the possibility of a swath of severe wind gusts into the early overnight. ...Northern High Plains... A shortwave trough will eject from western ID to eastern MT. Easterly low-level flow will be maintained ahead of this trough and its associated cold front that will push east across MT. This flow regime will maintain a broad plume of mid 50s to mid 60s surface dew points from west to east. Rather steep mid-level lapse rates of 8-9 C/km across WY/eastern MT will contribute to a corridor of MLCAPE reaching 2000-3000 J/kg where greater surface heating is underway across southeast MT/northeast WY/western SD. Episodic thunderstorm initiation is expected during the next few hours over the high terrain of southwest MT and downstream of a leading lobe of ascent approaching the WY/MT/Dakota border region, as well as by late afternoon in an arc off the higher terrain of WY. Effective bulk shear of 35-50 kt will favor several supercells initially with large hail and a couple of tornadoes. Convection is expected to grow upscale into multiple clusters/line segments across MT into the western Dakotas with an increasing threat of severe winds. The most likely corridor for a swath of severe gusts is across parts of east-central MT along the northern periphery of the buoyancy plume where large-scale ascent should be greatest ahead of the shortwave trough. ..Grams/Dean.. 08/11/2019 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1048 AM CDT Sun Aug 11 2019 Valid 111700Z - 121200Z The previous forecast remains on track, with no changes made (please see below for more details). Locally elevated fire weather conditions may occur across portions of southern Nevada into far west Utah, but the localized nature of the threat, along with marginally receptive fuels, precludes the addition of an elevated area in this region. A few dry lightning strikes may also accompany thunderstorms across north-central Wyoming into south-central Montana this afternoon and evening, but the expected low density of dry strikes atop marginally receptive fuels precludes an isolated dry thunderstorm delineation in this area. ..Squitieri.. 08/11/2019 .PREV DISCUSSION... /ISSUED 1230 AM CDT Sun Aug 11 2019/ ...Synopsis... Fire weather conditions will gradually improve compared to prior days. A longwave trough initially over Oregon will continue to weaken and lift northeastward toward the northern Rockies. As this occurs, a mid-level jet streak on the periphery of the trough will migrate toward Idaho/Wyoming through peak heating hours. Meanwhile, the widespread thunderstorms observed over Washington/Oregon/northern California and vicinity will diminish significantly as the region comes under the influence of mid/upper subsidence behind the trough. ...Eastern Idaho and western/central Wyoming... Vertical mixing processes beneath the approaching mid-level jet streak will result in areas of 15-25 mph surface winds during peak heating hours - strongest over the Snake River Valley of Idaho and also into southwestern/central Wyoming. RH values will only fall to critical thresholds on a localized basis and will be lowest in central Wyoming (15-30% elsewhere). The atmospheric conditions are most consistent with elevated fire weather thresholds, and the ongoing delineation remains in place for this outlook given the existence of dry fuels across the region. ...Please see www.spc.noaa.gov/fire for graphic product... Read more