Aggregator

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1137 AM CDT Sat Aug 10 2019 Valid 101700Z - 111200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF EASTERN NEVADA INTO FAR WEST-CENTRAL UTAH... The isolated dry thunderstorm delineation has been extended farther eastward into Idaho, where greater confidence exists for lightning atop fuels that are at least modestly receptive to fire spread. A scattered dry thunderstorm delineation was considered for parts of Oregon into Idaho, given the expected overall density of lightning. Nonetheless, wetting rains from the previous day's thunderstorm activity, combined with the expected relatively widespread coverage of heavier precipitation today, have precluded the need for a scattered dry thunderstorm area. Still, new fire ignitions are possible with strikes on the periphery of storm cores. In addition, strong to severe wind gusts may promote erratic surface conditions amidst complex terrain to potentially locally enhance fire starts or agitate ongoing fires in the absence of heavier rain, and assuming receptive fuels are present. Please see the Day 1 Convective Outlook for more details pertaining to the severe threat. Otherwise, the previous forecast remains on track. Please see below for more details. ..Squitieri.. 08/10/2019 .PREV DISCUSSION... /ISSUED 1247 AM CDT Sat Aug 10 2019/ ...Synopsis... A mid-level trough just off the northern California coast will begin to transition into an open wave and take on a negative tilt while ejecting toward Idaho today. As this occurs, a belt of enhanced mid-level flow will shift eastward toward the western Great Basin, overspreading dry areas of NV/UT/ID during peak heating hours. Meanwhile, areas of thunderstorms will once again affect portions of the Northwest, with isolated dry thunderstorm potential expected during the afternoon, evening, and overnight. ...Eastern Nevada, western Utah, and eastern Idaho... Beneath the belt of enhanced mid/upper flow, vertical mixing processes and a favorable surface gradient will favor increased surface winds within this corridor during peak heating hours. Areas of 15-25 mph south-southwesterly winds will become common amidst critically low RH values and broad areas of dry fuels in areas unaffected by recent rainfall. At this time, it appears that the greatest confidence of critical fire weather thresholds being exceeded will occur across east-central NV, far west-central UT, although locally critical fire weather can be expected as far north as eastern Idaho. ...Northern California through Washington and eastward into western Idaho for thunderstorms... The presence of cool temperatures aloft associated with the mid-level trough resulted in broad areas of wetting thunderstorms especially from central into north-central Oregon this afternoon and evening. These wetting downpours have undoubtedly altered fuel states in several areas, and widespread wetting thunderstorms are also expected to develop and migrate from south to north this afternoon and evening also. The isolated dry thunder area covers the potential for dry lightning strikes on the periphery of wetting thunderstorm cores in areas that continue to have cured fuels that can sustain fires. ...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 1137 AM CDT Sat Aug 10 2019 Valid 101700Z - 111200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF EASTERN NEVADA INTO FAR WEST-CENTRAL UTAH... The isolated dry thunderstorm delineation has been extended farther eastward into Idaho, where greater confidence exists for lightning atop fuels that are at least modestly receptive to fire spread. A scattered dry thunderstorm delineation was considered for parts of Oregon into Idaho, given the expected overall density of lightning. Nonetheless, wetting rains from the previous day's thunderstorm activity, combined with the expected relatively widespread coverage of heavier precipitation today, have precluded the need for a scattered dry thunderstorm area. Still, new fire ignitions are possible with strikes on the periphery of storm cores. In addition, strong to severe wind gusts may promote erratic surface conditions amidst complex terrain to potentially locally enhance fire starts or agitate ongoing fires in the absence of heavier rain, and assuming receptive fuels are present. Please see the Day 1 Convective Outlook for more details pertaining to the severe threat. Otherwise, the previous forecast remains on track. Please see below for more details. ..Squitieri.. 08/10/2019 .PREV DISCUSSION... /ISSUED 1247 AM CDT Sat Aug 10 2019/ ...Synopsis... A mid-level trough just off the northern California coast will begin to transition into an open wave and take on a negative tilt while ejecting toward Idaho today. As this occurs, a belt of enhanced mid-level flow will shift eastward toward the western Great Basin, overspreading dry areas of NV/UT/ID during peak heating hours. Meanwhile, areas of thunderstorms will once again affect portions of the Northwest, with isolated dry thunderstorm potential expected during the afternoon, evening, and overnight. ...Eastern Nevada, western Utah, and eastern Idaho... Beneath the belt of enhanced mid/upper flow, vertical mixing processes and a favorable surface gradient will favor increased surface winds within this corridor during peak heating hours. Areas of 15-25 mph south-southwesterly winds will become common amidst critically low RH values and broad areas of dry fuels in areas unaffected by recent rainfall. At this time, it appears that the greatest confidence of critical fire weather thresholds being exceeded will occur across east-central NV, far west-central UT, although locally critical fire weather can be expected as far north as eastern Idaho. ...Northern California through Washington and eastward into western Idaho for thunderstorms... The presence of cool temperatures aloft associated with the mid-level trough resulted in broad areas of wetting thunderstorms especially from central into north-central Oregon this afternoon and evening. These wetting downpours have undoubtedly altered fuel states in several areas, and widespread wetting thunderstorms are also expected to develop and migrate from south to north this afternoon and evening also. The isolated dry thunder area covers the potential for dry lightning strikes on the periphery of wetting thunderstorm cores in areas that continue to have cured fuels that can sustain fires. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 10 2019 Valid 101630Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF ID/MT/WY AND EASTERN NC... ...SUMMARY... Scattered severe thunderstorms with large hail and damaging wind gusts are most likely across parts of Idaho, Montana, Wyoming, and eastern North Carolina. The severe threat should be greatest during the late afternoon to early evening. ...Northwest... A closed mid-level low near the CA/OR coastal border will gradually evolve into an open wave while ejecting towards the OR/ID border through tonight, as other subtle speed maxima rotate around the eastern periphery of the low. A plume of weak to moderate buoyancy will develop at peak heating, arcing from OR/ID east across the northern Rockies and High Plains where scattered thunderstorms will likely form by late afternoon. Greatest effective shear should be centered across southern MT where weak low-level easterlies will be present beneath southwesterlies aloft that strengthen with height. This should yield an elongated, straight-line hodograph favorable for several splitting supercell structures. Large hail and severe wind gusts will be the primary hazards. Relatively high LCLs may limit the overall tornado threat, but brief ones are possible where 50s surface dew points can be sustained. ...Eastern NC... Sea breeze circulations along with a weakly convergent quasi-stationary front should be the focus for isolated to perhaps scattered thunderstorm development during the next few hours. Rich boundary-layer moisture characterized by low to mid 70s surface dew points exists over coastal southern NC into SC which will result in a confined corridor of MLCAPE in excess of 2000 J/kg. A few cells should briefly organize amid 30-40 kt 500-mb west-northwesterlies. Isolated large hail and damaging winds are anticipated. A marginal severe threat may persist into tonight amid weak low-level warm advection. ...Central High Plains to IA vicinity... A messy/low confidence scenario is anticipated through tonight with multiple MCVs and lingering cloud debris across the region. Forcing for ascent will likely persist across the Mid-MO Valley in a zone of low-level warm advection. Pockets of greater surface heating are apparent within cloud breaks into IA which combined with low-level moistening should support weak to moderate MLCAPE. Moderate enlargement/curvature to the low-level hodograph may foster a conditional brief tornado/locally damaging wind risk. Relatively warm profiles aloft and weak mid-level lapse rates will be unfavorable for large hail. Otherwise, scattered late afternoon storms should develop off the southern Rockies across eastern CO. Modest effective shear may be adequate to support multicell clustering as convection impinges on substantially greater buoyancy across KS/NE. Low-level warm advection will also increase across KS tonight in response to a nocturnal low-level jet, when more widespread convection is expected in the form of multiple clusters. Given the shear profiles, convection may be only weakly organized and slow-moving. But a threat for locally severe wind gusts should exist given heavy precipitation loading amid PW in excess of 2 inches. ..Grams/Dean.. 08/10/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 10 2019 Valid 101630Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF ID/MT/WY AND EASTERN NC... ...SUMMARY... Scattered severe thunderstorms with large hail and damaging wind gusts are most likely across parts of Idaho, Montana, Wyoming, and eastern North Carolina. The severe threat should be greatest during the late afternoon to early evening. ...Northwest... A closed mid-level low near the CA/OR coastal border will gradually evolve into an open wave while ejecting towards the OR/ID border through tonight, as other subtle speed maxima rotate around the eastern periphery of the low. A plume of weak to moderate buoyancy will develop at peak heating, arcing from OR/ID east across the northern Rockies and High Plains where scattered thunderstorms will likely form by late afternoon. Greatest effective shear should be centered across southern MT where weak low-level easterlies will be present beneath southwesterlies aloft that strengthen with height. This should yield an elongated, straight-line hodograph favorable for several splitting supercell structures. Large hail and severe wind gusts will be the primary hazards. Relatively high LCLs may limit the overall tornado threat, but brief ones are possible where 50s surface dew points can be sustained. ...Eastern NC... Sea breeze circulations along with a weakly convergent quasi-stationary front should be the focus for isolated to perhaps scattered thunderstorm development during the next few hours. Rich boundary-layer moisture characterized by low to mid 70s surface dew points exists over coastal southern NC into SC which will result in a confined corridor of MLCAPE in excess of 2000 J/kg. A few cells should briefly organize amid 30-40 kt 500-mb west-northwesterlies. Isolated large hail and damaging winds are anticipated. A marginal severe threat may persist into tonight amid weak low-level warm advection. ...Central High Plains to IA vicinity... A messy/low confidence scenario is anticipated through tonight with multiple MCVs and lingering cloud debris across the region. Forcing for ascent will likely persist across the Mid-MO Valley in a zone of low-level warm advection. Pockets of greater surface heating are apparent within cloud breaks into IA which combined with low-level moistening should support weak to moderate MLCAPE. Moderate enlargement/curvature to the low-level hodograph may foster a conditional brief tornado/locally damaging wind risk. Relatively warm profiles aloft and weak mid-level lapse rates will be unfavorable for large hail. Otherwise, scattered late afternoon storms should develop off the southern Rockies across eastern CO. Modest effective shear may be adequate to support multicell clustering as convection impinges on substantially greater buoyancy across KS/NE. Low-level warm advection will also increase across KS tonight in response to a nocturnal low-level jet, when more widespread convection is expected in the form of multiple clusters. Given the shear profiles, convection may be only weakly organized and slow-moving. But a threat for locally severe wind gusts should exist given heavy precipitation loading amid PW in excess of 2 inches. ..Grams/Dean.. 08/10/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 10 2019 Valid 101630Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF ID/MT/WY AND EASTERN NC... ...SUMMARY... Scattered severe thunderstorms with large hail and damaging wind gusts are most likely across parts of Idaho, Montana, Wyoming, and eastern North Carolina. The severe threat should be greatest during the late afternoon to early evening. ...Northwest... A closed mid-level low near the CA/OR coastal border will gradually evolve into an open wave while ejecting towards the OR/ID border through tonight, as other subtle speed maxima rotate around the eastern periphery of the low. A plume of weak to moderate buoyancy will develop at peak heating, arcing from OR/ID east across the northern Rockies and High Plains where scattered thunderstorms will likely form by late afternoon. Greatest effective shear should be centered across southern MT where weak low-level easterlies will be present beneath southwesterlies aloft that strengthen with height. This should yield an elongated, straight-line hodograph favorable for several splitting supercell structures. Large hail and severe wind gusts will be the primary hazards. Relatively high LCLs may limit the overall tornado threat, but brief ones are possible where 50s surface dew points can be sustained. ...Eastern NC... Sea breeze circulations along with a weakly convergent quasi-stationary front should be the focus for isolated to perhaps scattered thunderstorm development during the next few hours. Rich boundary-layer moisture characterized by low to mid 70s surface dew points exists over coastal southern NC into SC which will result in a confined corridor of MLCAPE in excess of 2000 J/kg. A few cells should briefly organize amid 30-40 kt 500-mb west-northwesterlies. Isolated large hail and damaging winds are anticipated. A marginal severe threat may persist into tonight amid weak low-level warm advection. ...Central High Plains to IA vicinity... A messy/low confidence scenario is anticipated through tonight with multiple MCVs and lingering cloud debris across the region. Forcing for ascent will likely persist across the Mid-MO Valley in a zone of low-level warm advection. Pockets of greater surface heating are apparent within cloud breaks into IA which combined with low-level moistening should support weak to moderate MLCAPE. Moderate enlargement/curvature to the low-level hodograph may foster a conditional brief tornado/locally damaging wind risk. Relatively warm profiles aloft and weak mid-level lapse rates will be unfavorable for large hail. Otherwise, scattered late afternoon storms should develop off the southern Rockies across eastern CO. Modest effective shear may be adequate to support multicell clustering as convection impinges on substantially greater buoyancy across KS/NE. Low-level warm advection will also increase across KS tonight in response to a nocturnal low-level jet, when more widespread convection is expected in the form of multiple clusters. Given the shear profiles, convection may be only weakly organized and slow-moving. But a threat for locally severe wind gusts should exist given heavy precipitation loading amid PW in excess of 2 inches. ..Grams/Dean.. 08/10/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 10 2019 Valid 101630Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF ID/MT/WY AND EASTERN NC... ...SUMMARY... Scattered severe thunderstorms with large hail and damaging wind gusts are most likely across parts of Idaho, Montana, Wyoming, and eastern North Carolina. The severe threat should be greatest during the late afternoon to early evening. ...Northwest... A closed mid-level low near the CA/OR coastal border will gradually evolve into an open wave while ejecting towards the OR/ID border through tonight, as other subtle speed maxima rotate around the eastern periphery of the low. A plume of weak to moderate buoyancy will develop at peak heating, arcing from OR/ID east across the northern Rockies and High Plains where scattered thunderstorms will likely form by late afternoon. Greatest effective shear should be centered across southern MT where weak low-level easterlies will be present beneath southwesterlies aloft that strengthen with height. This should yield an elongated, straight-line hodograph favorable for several splitting supercell structures. Large hail and severe wind gusts will be the primary hazards. Relatively high LCLs may limit the overall tornado threat, but brief ones are possible where 50s surface dew points can be sustained. ...Eastern NC... Sea breeze circulations along with a weakly convergent quasi-stationary front should be the focus for isolated to perhaps scattered thunderstorm development during the next few hours. Rich boundary-layer moisture characterized by low to mid 70s surface dew points exists over coastal southern NC into SC which will result in a confined corridor of MLCAPE in excess of 2000 J/kg. A few cells should briefly organize amid 30-40 kt 500-mb west-northwesterlies. Isolated large hail and damaging winds are anticipated. A marginal severe threat may persist into tonight amid weak low-level warm advection. ...Central High Plains to IA vicinity... A messy/low confidence scenario is anticipated through tonight with multiple MCVs and lingering cloud debris across the region. Forcing for ascent will likely persist across the Mid-MO Valley in a zone of low-level warm advection. Pockets of greater surface heating are apparent within cloud breaks into IA which combined with low-level moistening should support weak to moderate MLCAPE. Moderate enlargement/curvature to the low-level hodograph may foster a conditional brief tornado/locally damaging wind risk. Relatively warm profiles aloft and weak mid-level lapse rates will be unfavorable for large hail. Otherwise, scattered late afternoon storms should develop off the southern Rockies across eastern CO. Modest effective shear may be adequate to support multicell clustering as convection impinges on substantially greater buoyancy across KS/NE. Low-level warm advection will also increase across KS tonight in response to a nocturnal low-level jet, when more widespread convection is expected in the form of multiple clusters. Given the shear profiles, convection may be only weakly organized and slow-moving. But a threat for locally severe wind gusts should exist given heavy precipitation loading amid PW in excess of 2 inches. ..Grams/Dean.. 08/10/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 AM CDT Sat Aug 10 2019 Valid 101300Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO THIS EVENING FOR PARTS OF OR...ID...MT AND NC... ...SUMMARY... Severe storms producing large hail and locally damaging wind gusts are expected from eastern Oregon into western and southern Montana during the afternoon and evening. A cluster of storms, some severe, is also expected over eastern North Carolina during the afternoon. Other isolated activity is likely from the Black Hills into the central High Plains with marginal hail and wind. ...Northern Rockies this afternoon/evening... A closed midlevel low near the northern CA coast this morning will evolve gradually into an open wave while ejecting northeastward toward ID by tonight, as other subtle speed maxima rotate around the eastern periphery of the low. Northeast of the ongoing convection across northern CA, surface heating beneath relatively cool midlevel temperatures will contribute to MLCAPE of 500-1000 J/kg, within a corridor of deep-layer southerly shear of 35-50 kt. Scattered thunderstorm development is likely in the zone of ascent immediately northeast of the ejecting trough, where a few storms could produce damaging outflow winds and isolated large hail. Farther northeast into ID and MT, broken bands of convection are expected this afternoon as surface heating over the high terrain coincides with ascent accompanying a lead speed max aloft. Storm development should extend eastward across southern MT through the afternoon. Surface heating and boundary-layer dewpoints in the 50s beneath steep midlevel lapse rates will drive moderate buoyancy (MLCAPE up to 1500 J/kg). Meanwhile, low-level easterly flow beneath southwesterly flow aloft will result in long hodographs favoring supercells. The stronger storms will be capable of producing large hail and damaging winds, primarily from mid afternoon into this evening. ...Eastern NC this afternoon... A quasi-stationary front just inland from the NC coast, in conjunction with local sea breeze circulations, will help focus thunderstorm development this afternoon. Rich low-level moisture (boundary-layer dewpoints in the mid-upper 70s) along the coast and strong surface heating inland along the boundary will contribute to MLCAPE in excess of 2000 J/kg. West-northwesterly flow aloft and any sea breeze augmentation of near-surface, south-southeasterly flow will result in sufficient vertical shear for organized clusters and/or some supercell structures, with the potential to produce damaging winds and isolated large hail. ...Central Plains vicinity this afternoon into tonight... A messy scenario is unfolding across CO/NE/IA/KS today into tonight with multiple MCVs, ongoing convection, and cloud debris within the northeast extent of the southern Rockies monsoonal moisture plume. Forcing for ascent will likely persist across IA in a zone of low-level warm advection, and some low-level moistening and destabilization is expected. However, relatively warm profiles aloft and modest lapse rates do not appear favorable for large hail, and it is not clear if storms will be rooted clearly at the surface where low-level shear/hodograph curvature will be stronger. Farther west, forcing for ascent will be weak and confined to a diffuse surface boundary into southeast NE, which could focus isolated strong thunderstorm development this evening. A few diurnal storms are expected in the developing upslope flow regime by this evening across eastern CO and western KS. Farther east, clouds will likely slow surface heating and a lingering EML will be warm enough to maintain some convective inhibition through much of the afternoon. Low-level warm advection will increase across KS tonight in response to a weak nocturnal low-level jet, when more widespread convection is expected in one or more clusters. Lingering steep low-midlevel lapse rates and PW in excess of 2 inches will support some threat for isolated strong/damaging winds with heavy precipitation loading, and perhaps isolated marginally severe hail. ..Thompson/Kerr.. 08/10/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 AM CDT Sat Aug 10 2019 Valid 101300Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO THIS EVENING FOR PARTS OF OR...ID...MT AND NC... ...SUMMARY... Severe storms producing large hail and locally damaging wind gusts are expected from eastern Oregon into western and southern Montana during the afternoon and evening. A cluster of storms, some severe, is also expected over eastern North Carolina during the afternoon. Other isolated activity is likely from the Black Hills into the central High Plains with marginal hail and wind. ...Northern Rockies this afternoon/evening... A closed midlevel low near the northern CA coast this morning will evolve gradually into an open wave while ejecting northeastward toward ID by tonight, as other subtle speed maxima rotate around the eastern periphery of the low. Northeast of the ongoing convection across northern CA, surface heating beneath relatively cool midlevel temperatures will contribute to MLCAPE of 500-1000 J/kg, within a corridor of deep-layer southerly shear of 35-50 kt. Scattered thunderstorm development is likely in the zone of ascent immediately northeast of the ejecting trough, where a few storms could produce damaging outflow winds and isolated large hail. Farther northeast into ID and MT, broken bands of convection are expected this afternoon as surface heating over the high terrain coincides with ascent accompanying a lead speed max aloft. Storm development should extend eastward across southern MT through the afternoon. Surface heating and boundary-layer dewpoints in the 50s beneath steep midlevel lapse rates will drive moderate buoyancy (MLCAPE up to 1500 J/kg). Meanwhile, low-level easterly flow beneath southwesterly flow aloft will result in long hodographs favoring supercells. The stronger storms will be capable of producing large hail and damaging winds, primarily from mid afternoon into this evening. ...Eastern NC this afternoon... A quasi-stationary front just inland from the NC coast, in conjunction with local sea breeze circulations, will help focus thunderstorm development this afternoon. Rich low-level moisture (boundary-layer dewpoints in the mid-upper 70s) along the coast and strong surface heating inland along the boundary will contribute to MLCAPE in excess of 2000 J/kg. West-northwesterly flow aloft and any sea breeze augmentation of near-surface, south-southeasterly flow will result in sufficient vertical shear for organized clusters and/or some supercell structures, with the potential to produce damaging winds and isolated large hail. ...Central Plains vicinity this afternoon into tonight... A messy scenario is unfolding across CO/NE/IA/KS today into tonight with multiple MCVs, ongoing convection, and cloud debris within the northeast extent of the southern Rockies monsoonal moisture plume. Forcing for ascent will likely persist across IA in a zone of low-level warm advection, and some low-level moistening and destabilization is expected. However, relatively warm profiles aloft and modest lapse rates do not appear favorable for large hail, and it is not clear if storms will be rooted clearly at the surface where low-level shear/hodograph curvature will be stronger. Farther west, forcing for ascent will be weak and confined to a diffuse surface boundary into southeast NE, which could focus isolated strong thunderstorm development this evening. A few diurnal storms are expected in the developing upslope flow regime by this evening across eastern CO and western KS. Farther east, clouds will likely slow surface heating and a lingering EML will be warm enough to maintain some convective inhibition through much of the afternoon. Low-level warm advection will increase across KS tonight in response to a weak nocturnal low-level jet, when more widespread convection is expected in one or more clusters. Lingering steep low-midlevel lapse rates and PW in excess of 2 inches will support some threat for isolated strong/damaging winds with heavy precipitation loading, and perhaps isolated marginally severe hail. ..Thompson/Kerr.. 08/10/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 AM CDT Sat Aug 10 2019 Valid 101300Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO THIS EVENING FOR PARTS OF OR...ID...MT AND NC... ...SUMMARY... Severe storms producing large hail and locally damaging wind gusts are expected from eastern Oregon into western and southern Montana during the afternoon and evening. A cluster of storms, some severe, is also expected over eastern North Carolina during the afternoon. Other isolated activity is likely from the Black Hills into the central High Plains with marginal hail and wind. ...Northern Rockies this afternoon/evening... A closed midlevel low near the northern CA coast this morning will evolve gradually into an open wave while ejecting northeastward toward ID by tonight, as other subtle speed maxima rotate around the eastern periphery of the low. Northeast of the ongoing convection across northern CA, surface heating beneath relatively cool midlevel temperatures will contribute to MLCAPE of 500-1000 J/kg, within a corridor of deep-layer southerly shear of 35-50 kt. Scattered thunderstorm development is likely in the zone of ascent immediately northeast of the ejecting trough, where a few storms could produce damaging outflow winds and isolated large hail. Farther northeast into ID and MT, broken bands of convection are expected this afternoon as surface heating over the high terrain coincides with ascent accompanying a lead speed max aloft. Storm development should extend eastward across southern MT through the afternoon. Surface heating and boundary-layer dewpoints in the 50s beneath steep midlevel lapse rates will drive moderate buoyancy (MLCAPE up to 1500 J/kg). Meanwhile, low-level easterly flow beneath southwesterly flow aloft will result in long hodographs favoring supercells. The stronger storms will be capable of producing large hail and damaging winds, primarily from mid afternoon into this evening. ...Eastern NC this afternoon... A quasi-stationary front just inland from the NC coast, in conjunction with local sea breeze circulations, will help focus thunderstorm development this afternoon. Rich low-level moisture (boundary-layer dewpoints in the mid-upper 70s) along the coast and strong surface heating inland along the boundary will contribute to MLCAPE in excess of 2000 J/kg. West-northwesterly flow aloft and any sea breeze augmentation of near-surface, south-southeasterly flow will result in sufficient vertical shear for organized clusters and/or some supercell structures, with the potential to produce damaging winds and isolated large hail. ...Central Plains vicinity this afternoon into tonight... A messy scenario is unfolding across CO/NE/IA/KS today into tonight with multiple MCVs, ongoing convection, and cloud debris within the northeast extent of the southern Rockies monsoonal moisture plume. Forcing for ascent will likely persist across IA in a zone of low-level warm advection, and some low-level moistening and destabilization is expected. However, relatively warm profiles aloft and modest lapse rates do not appear favorable for large hail, and it is not clear if storms will be rooted clearly at the surface where low-level shear/hodograph curvature will be stronger. Farther west, forcing for ascent will be weak and confined to a diffuse surface boundary into southeast NE, which could focus isolated strong thunderstorm development this evening. A few diurnal storms are expected in the developing upslope flow regime by this evening across eastern CO and western KS. Farther east, clouds will likely slow surface heating and a lingering EML will be warm enough to maintain some convective inhibition through much of the afternoon. Low-level warm advection will increase across KS tonight in response to a weak nocturnal low-level jet, when more widespread convection is expected in one or more clusters. Lingering steep low-midlevel lapse rates and PW in excess of 2 inches will support some threat for isolated strong/damaging winds with heavy precipitation loading, and perhaps isolated marginally severe hail. ..Thompson/Kerr.. 08/10/2019 Read more

000
ABPZ20 KNHC 101143
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Sat Aug 10 2019

For the eastern North Pacific...east of 140 degrees west longitude:

A trough of low pressure located about 100 miles south of Acapulco,
Mexico is producing a large area of showers and thunderstorms.
Environmental conditions could still favor some gradual development
during the next couple of days while the system moves
west-northwestward just off the southwestern coast of Mexico. After
that time, conditions are forecast to become unfavorable for
tropical cyclone formation. Regardless of development, the
disturbance will likely bring locally heavy rainfall along portions
of the southwestern coast of Mexico during the next couple of days.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...medium...40 percent.

A broad area of low pressure has developed a few hundred miles
south-southwest of Manzanillo, Mexico and is producing disorganized
showers and thunderstorms. Some slow development of this system is
possible over the next few days.
* Formation chance through 48 hours...low...20 percent.
* Formation chance through 5 days...low...30 percent.

A tropical wave located a little less than 1000 miles south-
southwest of the Baja California peninsula is producing an area of
disorganized showers and thunderstorms. Environmental conditions
are expected to become more conducive for tropical cyclone formation
early next week while the system moves westward or west-
northwestward at 10 to 15 mph.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...medium...50 percent.

$$
Forecaster Latto/Brown

000
ABNT20 KNHC 101123
TWOAT

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Sat Aug 10 2019

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

Tropical cyclone formation is not expected during the next 5 days.

$$
Forecaster Brown

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0342 AM CDT Sat Aug 10 2019 Valid 131200Z - 181200Z ...DISCUSSION... Model consensus is that the synoptic upper pattern will trend to a quasi-zonal regime over most of the northern tier states days 4-5 before another upper trough amplifies over the Pacific Northwest and moves into the northern Plains in the 6-7 day time frame. The richer moisture will be shunted south of the stronger winds aloft by a cold front advancing southeast through the OH Valley region days 4-5. However, by days 6-7 moisture will gradually return through the Plains downstream from an approaching northern stream trough. While at least a modest threat for severe weather may exist along front from the Middle Atlantic into the southern portion of the OH Valley day 4, and then the northern Plains days 6-7, overall predictability with this pattern remains low. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0342 AM CDT Sat Aug 10 2019 Valid 131200Z - 181200Z ...DISCUSSION... Model consensus is that the synoptic upper pattern will trend to a quasi-zonal regime over most of the northern tier states days 4-5 before another upper trough amplifies over the Pacific Northwest and moves into the northern Plains in the 6-7 day time frame. The richer moisture will be shunted south of the stronger winds aloft by a cold front advancing southeast through the OH Valley region days 4-5. However, by days 6-7 moisture will gradually return through the Plains downstream from an approaching northern stream trough. While at least a modest threat for severe weather may exist along front from the Middle Atlantic into the southern portion of the OH Valley day 4, and then the northern Plains days 6-7, overall predictability with this pattern remains low. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0342 AM CDT Sat Aug 10 2019 Valid 131200Z - 181200Z ...DISCUSSION... Model consensus is that the synoptic upper pattern will trend to a quasi-zonal regime over most of the northern tier states days 4-5 before another upper trough amplifies over the Pacific Northwest and moves into the northern Plains in the 6-7 day time frame. The richer moisture will be shunted south of the stronger winds aloft by a cold front advancing southeast through the OH Valley region days 4-5. However, by days 6-7 moisture will gradually return through the Plains downstream from an approaching northern stream trough. While at least a modest threat for severe weather may exist along front from the Middle Atlantic into the southern portion of the OH Valley day 4, and then the northern Plains days 6-7, overall predictability with this pattern remains low. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0342 AM CDT Sat Aug 10 2019 Valid 131200Z - 181200Z ...DISCUSSION... Model consensus is that the synoptic upper pattern will trend to a quasi-zonal regime over most of the northern tier states days 4-5 before another upper trough amplifies over the Pacific Northwest and moves into the northern Plains in the 6-7 day time frame. The richer moisture will be shunted south of the stronger winds aloft by a cold front advancing southeast through the OH Valley region days 4-5. However, by days 6-7 moisture will gradually return through the Plains downstream from an approaching northern stream trough. While at least a modest threat for severe weather may exist along front from the Middle Atlantic into the southern portion of the OH Valley day 4, and then the northern Plains days 6-7, overall predictability with this pattern remains low. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CDT Sat Aug 10 2019 Valid 121200Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MIDDLE AND UPPER MISSISSIPPI VALLEY INTO THE OHIO VALLEY REGION... ...SUMMARY... Severe storms with damaging wind will be possible on Monday, mainly from a portion of the Middle Mississippi Valley to the Ohio Valley. ...Middle Mississippi Valley and Ohio Valley regions... Northern-stream upper trough will deamplify further Monday as it continues through the northern Plains and before turning southeast into the upper MS Valley. Farther south, a convectively enhanced shortwave trough will move from eastern NE through IA and into the southern Great Lakes and OH Valley. Storms should be ongoing north of a stalled front from eastern NE into IA in association with the shortwave trough. These storms will continue east within zone of isentropic ascent north of the front and on nose of an eastward- migrating low-level jet. Moderate instability is expected in warm sector as the moist boundary layer warms. Theta-e advection and ascent along the low-level jet may promote additional storm development and intensification in vicinity of the front and along southern periphery of the MCS. Wind profiles with 40 + kt effective bulk shear will support organized storm structures with damaging wind the primary threat. Activity will spread east during the evening into the southern Great Lakes and OH Valley regions. ..Dial.. 08/10/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CDT Sat Aug 10 2019 Valid 121200Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MIDDLE AND UPPER MISSISSIPPI VALLEY INTO THE OHIO VALLEY REGION... ...SUMMARY... Severe storms with damaging wind will be possible on Monday, mainly from a portion of the Middle Mississippi Valley to the Ohio Valley. ...Middle Mississippi Valley and Ohio Valley regions... Northern-stream upper trough will deamplify further Monday as it continues through the northern Plains and before turning southeast into the upper MS Valley. Farther south, a convectively enhanced shortwave trough will move from eastern NE through IA and into the southern Great Lakes and OH Valley. Storms should be ongoing north of a stalled front from eastern NE into IA in association with the shortwave trough. These storms will continue east within zone of isentropic ascent north of the front and on nose of an eastward- migrating low-level jet. Moderate instability is expected in warm sector as the moist boundary layer warms. Theta-e advection and ascent along the low-level jet may promote additional storm development and intensification in vicinity of the front and along southern periphery of the MCS. Wind profiles with 40 + kt effective bulk shear will support organized storm structures with damaging wind the primary threat. Activity will spread east during the evening into the southern Great Lakes and OH Valley regions. ..Dial.. 08/10/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CDT Sat Aug 10 2019 Valid 121200Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MIDDLE AND UPPER MISSISSIPPI VALLEY INTO THE OHIO VALLEY REGION... ...SUMMARY... Severe storms with damaging wind will be possible on Monday, mainly from a portion of the Middle Mississippi Valley to the Ohio Valley. ...Middle Mississippi Valley and Ohio Valley regions... Northern-stream upper trough will deamplify further Monday as it continues through the northern Plains and before turning southeast into the upper MS Valley. Farther south, a convectively enhanced shortwave trough will move from eastern NE through IA and into the southern Great Lakes and OH Valley. Storms should be ongoing north of a stalled front from eastern NE into IA in association with the shortwave trough. These storms will continue east within zone of isentropic ascent north of the front and on nose of an eastward- migrating low-level jet. Moderate instability is expected in warm sector as the moist boundary layer warms. Theta-e advection and ascent along the low-level jet may promote additional storm development and intensification in vicinity of the front and along southern periphery of the MCS. Wind profiles with 40 + kt effective bulk shear will support organized storm structures with damaging wind the primary threat. Activity will spread east during the evening into the southern Great Lakes and OH Valley regions. ..Dial.. 08/10/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CDT Sat Aug 10 2019 Valid 121200Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MIDDLE AND UPPER MISSISSIPPI VALLEY INTO THE OHIO VALLEY REGION... ...SUMMARY... Severe storms with damaging wind will be possible on Monday, mainly from a portion of the Middle Mississippi Valley to the Ohio Valley. ...Middle Mississippi Valley and Ohio Valley regions... Northern-stream upper trough will deamplify further Monday as it continues through the northern Plains and before turning southeast into the upper MS Valley. Farther south, a convectively enhanced shortwave trough will move from eastern NE through IA and into the southern Great Lakes and OH Valley. Storms should be ongoing north of a stalled front from eastern NE into IA in association with the shortwave trough. These storms will continue east within zone of isentropic ascent north of the front and on nose of an eastward- migrating low-level jet. Moderate instability is expected in warm sector as the moist boundary layer warms. Theta-e advection and ascent along the low-level jet may promote additional storm development and intensification in vicinity of the front and along southern periphery of the MCS. Wind profiles with 40 + kt effective bulk shear will support organized storm structures with damaging wind the primary threat. Activity will spread east during the evening into the southern Great Lakes and OH Valley regions. ..Dial.. 08/10/2019 Read more