Severe Storms

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

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

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

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

No Mesoscale Discussions are in effect as of Sun Aug 11 15:51:02 UTC 2019.

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Sun Aug 11 2019 Valid 111300Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FOR PARTS OF NORTHEAST CO...NORTHWEST KS...AND SOUTHWEST NE... ...SUMMARY... Areas of strong to severe storms are expected over portions of the northern through central High Plains this afternoon into tonight. Large hail and severe gusts are the primary threats. ...Central High Plains to the middle MS Valley through tonight... A belt of somewhat enhanced midlevel flow extends from the southern Rockies to the central Plains, around the northwest periphery of the midlevel ridge over the southern Plains. Within this belt, an MCS and associated MCV are moving eastward over northeast KS. The convection has been maintained overnight by warm advection on the nose of a 30-40 kt low-level jet, within a corridor of PW near 2 inches and moderate buoyancy. The low-level jet will veer to more westerly through late morning and weaken, and the MCS will likewise weaken. Some additional storm development is expected during the day along the leading edge of the residual cold pool and zone of ascent preceding the MCV, but the storm environment will be less favorable for organized severe storms with damaging winds/hail with eastward extent across MO/IL. In the wake of the morning convection, an upslope regime will establish from northwest KS into northeast CO/southwest NE, north of a lee cyclone in southeast CO. Recovery of low-level moisture and surface heating will again boost MLCAPE to 2000-3000 J/kg by mid-late afternoon. Thunderstorm development is expected first near and immediately east of the Front Range in CO, while the boundary layer should remain capped through much of the afternoon in far northeast CO and vicinity. Buoyancy and deep-layer vertical shear will be sufficient for both supercells and multicell clusters with large hail/damaging winds 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 and farther east. Any semi-discrete supercells will pose a threat for a couple of tornadoes and large hail, while the damaging wind threat will increase with storm clustering into the evening. Storms will likely evolve into an MCS tonight while spreading eastward on the immediate cool/moist side of a quasi-stationary front expected to reside a little south of I-70. ...MT/northern High Plains this afternoon/evening... A midlevel trough near the OR/ID border will eject east-northeastward over MT this afternoon and reach the northern High Plains overnight. Easterly low-level flow will be maintained through the day across southern MT, to the north of a surface cyclone in central WY. This will help draw 58-62 F dewpoints westward across southern MT, beneath steep midlevel lapse rates, which will contribute to MLCAPE of 1500-2000 J/kg. Convective initiation is expected by early afternoon over the high terrain of southwest MT, with storms subsequently moving northeastward and developing eastward across southern MT to northeast WY by mid-late afternoon. Effective bulk shear of 35-50 kt will favor supercells initially with large hail and possibly a couple of tornadoes, and convection is expected to grow upscale into a couple of clusters/line segments across MT/western SD by this evening, with an accompanying threat for damaging winds. ..Thompson/Kerr.. 08/11/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Sun Aug 11 2019 Valid 111300Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FOR PARTS OF NORTHEAST CO...NORTHWEST KS...AND SOUTHWEST NE... ...SUMMARY... Areas of strong to severe storms are expected over portions of the northern through central High Plains this afternoon into tonight. Large hail and severe gusts are the primary threats. ...Central High Plains to the middle MS Valley through tonight... A belt of somewhat enhanced midlevel flow extends from the southern Rockies to the central Plains, around the northwest periphery of the midlevel ridge over the southern Plains. Within this belt, an MCS and associated MCV are moving eastward over northeast KS. The convection has been maintained overnight by warm advection on the nose of a 30-40 kt low-level jet, within a corridor of PW near 2 inches and moderate buoyancy. The low-level jet will veer to more westerly through late morning and weaken, and the MCS will likewise weaken. Some additional storm development is expected during the day along the leading edge of the residual cold pool and zone of ascent preceding the MCV, but the storm environment will be less favorable for organized severe storms with damaging winds/hail with eastward extent across MO/IL. In the wake of the morning convection, an upslope regime will establish from northwest KS into northeast CO/southwest NE, north of a lee cyclone in southeast CO. Recovery of low-level moisture and surface heating will again boost MLCAPE to 2000-3000 J/kg by mid-late afternoon. Thunderstorm development is expected first near and immediately east of the Front Range in CO, while the boundary layer should remain capped through much of the afternoon in far northeast CO and vicinity. Buoyancy and deep-layer vertical shear will be sufficient for both supercells and multicell clusters with large hail/damaging winds 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 and farther east. Any semi-discrete supercells will pose a threat for a couple of tornadoes and large hail, while the damaging wind threat will increase with storm clustering into the evening. Storms will likely evolve into an MCS tonight while spreading eastward on the immediate cool/moist side of a quasi-stationary front expected to reside a little south of I-70. ...MT/northern High Plains this afternoon/evening... A midlevel trough near the OR/ID border will eject east-northeastward over MT this afternoon and reach the northern High Plains overnight. Easterly low-level flow will be maintained through the day across southern MT, to the north of a surface cyclone in central WY. This will help draw 58-62 F dewpoints westward across southern MT, beneath steep midlevel lapse rates, which will contribute to MLCAPE of 1500-2000 J/kg. Convective initiation is expected by early afternoon over the high terrain of southwest MT, with storms subsequently moving northeastward and developing eastward across southern MT to northeast WY by mid-late afternoon. Effective bulk shear of 35-50 kt will favor supercells initially with large hail and possibly a couple of tornadoes, and convection is expected to grow upscale into a couple of clusters/line segments across MT/western SD by this evening, with an accompanying threat for damaging winds. ..Thompson/Kerr.. 08/11/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Sun Aug 11 2019 Valid 111300Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FOR PARTS OF NORTHEAST CO...NORTHWEST KS...AND SOUTHWEST NE... ...SUMMARY... Areas of strong to severe storms are expected over portions of the northern through central High Plains this afternoon into tonight. Large hail and severe gusts are the primary threats. ...Central High Plains to the middle MS Valley through tonight... A belt of somewhat enhanced midlevel flow extends from the southern Rockies to the central Plains, around the northwest periphery of the midlevel ridge over the southern Plains. Within this belt, an MCS and associated MCV are moving eastward over northeast KS. The convection has been maintained overnight by warm advection on the nose of a 30-40 kt low-level jet, within a corridor of PW near 2 inches and moderate buoyancy. The low-level jet will veer to more westerly through late morning and weaken, and the MCS will likewise weaken. Some additional storm development is expected during the day along the leading edge of the residual cold pool and zone of ascent preceding the MCV, but the storm environment will be less favorable for organized severe storms with damaging winds/hail with eastward extent across MO/IL. In the wake of the morning convection, an upslope regime will establish from northwest KS into northeast CO/southwest NE, north of a lee cyclone in southeast CO. Recovery of low-level moisture and surface heating will again boost MLCAPE to 2000-3000 J/kg by mid-late afternoon. Thunderstorm development is expected first near and immediately east of the Front Range in CO, while the boundary layer should remain capped through much of the afternoon in far northeast CO and vicinity. Buoyancy and deep-layer vertical shear will be sufficient for both supercells and multicell clusters with large hail/damaging winds 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 and farther east. Any semi-discrete supercells will pose a threat for a couple of tornadoes and large hail, while the damaging wind threat will increase with storm clustering into the evening. Storms will likely evolve into an MCS tonight while spreading eastward on the immediate cool/moist side of a quasi-stationary front expected to reside a little south of I-70. ...MT/northern High Plains this afternoon/evening... A midlevel trough near the OR/ID border will eject east-northeastward over MT this afternoon and reach the northern High Plains overnight. Easterly low-level flow will be maintained through the day across southern MT, to the north of a surface cyclone in central WY. This will help draw 58-62 F dewpoints westward across southern MT, beneath steep midlevel lapse rates, which will contribute to MLCAPE of 1500-2000 J/kg. Convective initiation is expected by early afternoon over the high terrain of southwest MT, with storms subsequently moving northeastward and developing eastward across southern MT to northeast WY by mid-late afternoon. Effective bulk shear of 35-50 kt will favor supercells initially with large hail and possibly a couple of tornadoes, and convection is expected to grow upscale into a couple of clusters/line segments across MT/western SD by this evening, with an accompanying threat for damaging winds. ..Thompson/Kerr.. 08/11/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Sun Aug 11 2019 Valid 111300Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FOR PARTS OF NORTHEAST CO...NORTHWEST KS...AND SOUTHWEST NE... ...SUMMARY... Areas of strong to severe storms are expected over portions of the northern through central High Plains this afternoon into tonight. Large hail and severe gusts are the primary threats. ...Central High Plains to the middle MS Valley through tonight... A belt of somewhat enhanced midlevel flow extends from the southern Rockies to the central Plains, around the northwest periphery of the midlevel ridge over the southern Plains. Within this belt, an MCS and associated MCV are moving eastward over northeast KS. The convection has been maintained overnight by warm advection on the nose of a 30-40 kt low-level jet, within a corridor of PW near 2 inches and moderate buoyancy. The low-level jet will veer to more westerly through late morning and weaken, and the MCS will likewise weaken. Some additional storm development is expected during the day along the leading edge of the residual cold pool and zone of ascent preceding the MCV, but the storm environment will be less favorable for organized severe storms with damaging winds/hail with eastward extent across MO/IL. In the wake of the morning convection, an upslope regime will establish from northwest KS into northeast CO/southwest NE, north of a lee cyclone in southeast CO. Recovery of low-level moisture and surface heating will again boost MLCAPE to 2000-3000 J/kg by mid-late afternoon. Thunderstorm development is expected first near and immediately east of the Front Range in CO, while the boundary layer should remain capped through much of the afternoon in far northeast CO and vicinity. Buoyancy and deep-layer vertical shear will be sufficient for both supercells and multicell clusters with large hail/damaging winds 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 and farther east. Any semi-discrete supercells will pose a threat for a couple of tornadoes and large hail, while the damaging wind threat will increase with storm clustering into the evening. Storms will likely evolve into an MCS tonight while spreading eastward on the immediate cool/moist side of a quasi-stationary front expected to reside a little south of I-70. ...MT/northern High Plains this afternoon/evening... A midlevel trough near the OR/ID border will eject east-northeastward over MT this afternoon and reach the northern High Plains overnight. Easterly low-level flow will be maintained through the day across southern MT, to the north of a surface cyclone in central WY. This will help draw 58-62 F dewpoints westward across southern MT, beneath steep midlevel lapse rates, which will contribute to MLCAPE of 1500-2000 J/kg. Convective initiation is expected by early afternoon over the high terrain of southwest MT, with storms subsequently moving northeastward and developing eastward across southern MT to northeast WY by mid-late afternoon. Effective bulk shear of 35-50 kt will favor supercells initially with large hail and possibly a couple of tornadoes, and convection is expected to grow upscale into a couple of clusters/line segments across MT/western SD by this evening, with an accompanying threat for damaging winds. ..Thompson/Kerr.. 08/11/2019 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0352 AM CDT Sun Aug 11 2019 Valid 141200Z - 191200Z ...DISCUSSION... Model consensus is that a low-amplitude pattern will reside across the nation day 4, with some amplification expected days 5-6 as an upper trough becomes established over the western states. Day 4 - A low amplitude upper trough will reside over the eastern states. Richer low-level moisture will persist south of a cold front from southern portions of the Middle Atlantic into the southern Plains. While a few strong storms cannot be ruled out over VA into NC depending on the position of the front, the moist warm sector will have been shunted south of the stronger flow aloft. Elsewhere a few strong to severe storms will be possible as a corridor of modest low-level moisture returns through the central High Plains and storms develop over the higher terrain within a northwesterly flow regime. Days 5-6 Though predictability is low at this range, best chance for a few severe storms will be over the central through northern High Plains within a northwesterly flow regime. Here a corridor of modest low-level moisture will reside beneath steep lapse rates. Timing of any embedded shortwave troughs will be difficult, but potential exists for storms to develop over the higher terrain and spread into the High Plains where vertical shear and instability will be sufficient for storm organization. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0352 AM CDT Sun Aug 11 2019 Valid 141200Z - 191200Z ...DISCUSSION... Model consensus is that a low-amplitude pattern will reside across the nation day 4, with some amplification expected days 5-6 as an upper trough becomes established over the western states. Day 4 - A low amplitude upper trough will reside over the eastern states. Richer low-level moisture will persist south of a cold front from southern portions of the Middle Atlantic into the southern Plains. While a few strong storms cannot be ruled out over VA into NC depending on the position of the front, the moist warm sector will have been shunted south of the stronger flow aloft. Elsewhere a few strong to severe storms will be possible as a corridor of modest low-level moisture returns through the central High Plains and storms develop over the higher terrain within a northwesterly flow regime. Days 5-6 Though predictability is low at this range, best chance for a few severe storms will be over the central through northern High Plains within a northwesterly flow regime. Here a corridor of modest low-level moisture will reside beneath steep lapse rates. Timing of any embedded shortwave troughs will be difficult, but potential exists for storms to develop over the higher terrain and spread into the High Plains where vertical shear and instability will be sufficient for storm organization. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0352 AM CDT Sun Aug 11 2019 Valid 141200Z - 191200Z ...DISCUSSION... Model consensus is that a low-amplitude pattern will reside across the nation day 4, with some amplification expected days 5-6 as an upper trough becomes established over the western states. Day 4 - A low amplitude upper trough will reside over the eastern states. Richer low-level moisture will persist south of a cold front from southern portions of the Middle Atlantic into the southern Plains. While a few strong storms cannot be ruled out over VA into NC depending on the position of the front, the moist warm sector will have been shunted south of the stronger flow aloft. Elsewhere a few strong to severe storms will be possible as a corridor of modest low-level moisture returns through the central High Plains and storms develop over the higher terrain within a northwesterly flow regime. Days 5-6 Though predictability is low at this range, best chance for a few severe storms will be over the central through northern High Plains within a northwesterly flow regime. Here a corridor of modest low-level moisture will reside beneath steep lapse rates. Timing of any embedded shortwave troughs will be difficult, but potential exists for storms to develop over the higher terrain and spread into the High Plains where vertical shear and instability will be sufficient for storm organization. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0236 AM CDT Sun Aug 11 2019 Valid 131200Z - 141200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MIDDLE ATLANTIC INTO THE SOUTHERN OHIO VALLEY REGIONS... ...SUMMARY... A few strong to severe storms with damaging wind and possibly some hail are expected from the Middle Atlantic region westward into the southern portion of the Ohio Valley Tuesday afternoon. ...Middle Atlantic and southern Ohio Valley regions... Convectively enhanced vorticity maxima will be embedded within belt of moderate westerlies from the OH Valley into the Middle Atlantic regions. Within this regime, storms will likely be ongoing from OH into PA on nose of a southwesterly low-level jet and in association with a progressive MCV, and these storms should leave an effective pre-frontal boundary. South of this boundary, diabatic warming of the moistening surface layer will result in moderate instability with 1500-2000 J/kg MLCAPE expected. Additional storms should develop by late morning or afternoon along and south of this boundary, over the higher terrain and farther southwest along the southeast-advancing cold front across southern portion of the OH Valley. Vertical shear should range from 30-40 kt supportive of primarily multicells, though a few supercell structures will be possible, especially with northeast extent in warm sector. Activity will spread east and southeast during the day with strong to damaging wind gusts the main threat before weakening by mid evening. ...Central High Plains... A few storms are expected to develop along a lee trough and higher terrain within an evolving easterly post-frontal regime across the central High Plains. Modest low-level moisture beneath steep lapse rates will support up to 2000 j/kg MLCAPE, and this region will reside within belt of modest northwesterly winds aloft with 30-35 effective bulk shear. This environment may support a few instances of hail and gusty winds before activity weakens by mid evening. ...Upper Mississippi Valley region... Isolated storms may develop over the upper Midwest in association with a southeast-advancing shortwave trough and within a marginally unstable environment. A belt of stronger unidirectional winds aloft will support up to 40 kt effective bulk shear. A few storms could produce locally strong wind gusts and hail, but overall threat should remain marginal. ..Dial.. 08/11/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0236 AM CDT Sun Aug 11 2019 Valid 131200Z - 141200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MIDDLE ATLANTIC INTO THE SOUTHERN OHIO VALLEY REGIONS... ...SUMMARY... A few strong to severe storms with damaging wind and possibly some hail are expected from the Middle Atlantic region westward into the southern portion of the Ohio Valley Tuesday afternoon. ...Middle Atlantic and southern Ohio Valley regions... Convectively enhanced vorticity maxima will be embedded within belt of moderate westerlies from the OH Valley into the Middle Atlantic regions. Within this regime, storms will likely be ongoing from OH into PA on nose of a southwesterly low-level jet and in association with a progressive MCV, and these storms should leave an effective pre-frontal boundary. South of this boundary, diabatic warming of the moistening surface layer will result in moderate instability with 1500-2000 J/kg MLCAPE expected. Additional storms should develop by late morning or afternoon along and south of this boundary, over the higher terrain and farther southwest along the southeast-advancing cold front across southern portion of the OH Valley. Vertical shear should range from 30-40 kt supportive of primarily multicells, though a few supercell structures will be possible, especially with northeast extent in warm sector. Activity will spread east and southeast during the day with strong to damaging wind gusts the main threat before weakening by mid evening. ...Central High Plains... A few storms are expected to develop along a lee trough and higher terrain within an evolving easterly post-frontal regime across the central High Plains. Modest low-level moisture beneath steep lapse rates will support up to 2000 j/kg MLCAPE, and this region will reside within belt of modest northwesterly winds aloft with 30-35 effective bulk shear. This environment may support a few instances of hail and gusty winds before activity weakens by mid evening. ...Upper Mississippi Valley region... Isolated storms may develop over the upper Midwest in association with a southeast-advancing shortwave trough and within a marginally unstable environment. A belt of stronger unidirectional winds aloft will support up to 40 kt effective bulk shear. A few storms could produce locally strong wind gusts and hail, but overall threat should remain marginal. ..Dial.. 08/11/2019 Read more