Severe Storms

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1132 AM CDT Fri Aug 23 2019 Valid 231700Z - 241200Z The previous forecast generally remains on track. The ongoing elevated area has been expanded slightly across portions of south-central Nevada and into northeast Arizona, based on the potential for wind/RH conditions (coinciding with receptive fuels) as depicted in the latest high resolution guidance. Otherwise, see the previous discussion for additional details. ..Karstens.. 08/23/2019 .PREV DISCUSSION... /ISSUED 1259 AM CDT Fri Aug 23 2019/ ...Synopsis... A mid-level trough currently positioned over the southwest Montana vicinity will progress eastward into the central High Plains today. On the back side of this trough, enhanced mid-level flow will be present over parts of southwestern Wyoming into Utah and eastern Nevada. Potential for elevated fire weather conditions will exist from the Great Divide Basin, western Colorado, and portions of the southern Great Basin. In these locations, 15-20 mph surface winds and 5-20% afternoon RH are probable. Two factors introduce some uncertainty to how widespread these elevated conditions will be: 1) a weakening surface pressure gradient throughout the day and 2) potential for mid/upper-level clouds over portions of Utah/Nevada during the afternoon. Current position of dry air aloft on water vapor satellite imagery would indicate that it may only overlap portions of western Colorado during the afternoon, which is also supported by model forecast soundings. Nonetheless, several areas will see at least briefly elevated conditions with potential for locally critical conditions in terrain-favored locations. ...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 1132 AM CDT Fri Aug 23 2019 Valid 231700Z - 241200Z The previous forecast generally remains on track. The ongoing elevated area has been expanded slightly across portions of south-central Nevada and into northeast Arizona, based on the potential for wind/RH conditions (coinciding with receptive fuels) as depicted in the latest high resolution guidance. Otherwise, see the previous discussion for additional details. ..Karstens.. 08/23/2019 .PREV DISCUSSION... /ISSUED 1259 AM CDT Fri Aug 23 2019/ ...Synopsis... A mid-level trough currently positioned over the southwest Montana vicinity will progress eastward into the central High Plains today. On the back side of this trough, enhanced mid-level flow will be present over parts of southwestern Wyoming into Utah and eastern Nevada. Potential for elevated fire weather conditions will exist from the Great Divide Basin, western Colorado, and portions of the southern Great Basin. In these locations, 15-20 mph surface winds and 5-20% afternoon RH are probable. Two factors introduce some uncertainty to how widespread these elevated conditions will be: 1) a weakening surface pressure gradient throughout the day and 2) potential for mid/upper-level clouds over portions of Utah/Nevada during the afternoon. Current position of dry air aloft on water vapor satellite imagery would indicate that it may only overlap portions of western Colorado during the afternoon, which is also supported by model forecast soundings. Nonetheless, several areas will see at least briefly elevated conditions with potential for locally critical conditions in terrain-favored locations. ...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 1132 AM CDT Fri Aug 23 2019 Valid 231700Z - 241200Z The previous forecast generally remains on track. The ongoing elevated area has been expanded slightly across portions of south-central Nevada and into northeast Arizona, based on the potential for wind/RH conditions (coinciding with receptive fuels) as depicted in the latest high resolution guidance. Otherwise, see the previous discussion for additional details. ..Karstens.. 08/23/2019 .PREV DISCUSSION... /ISSUED 1259 AM CDT Fri Aug 23 2019/ ...Synopsis... A mid-level trough currently positioned over the southwest Montana vicinity will progress eastward into the central High Plains today. On the back side of this trough, enhanced mid-level flow will be present over parts of southwestern Wyoming into Utah and eastern Nevada. Potential for elevated fire weather conditions will exist from the Great Divide Basin, western Colorado, and portions of the southern Great Basin. In these locations, 15-20 mph surface winds and 5-20% afternoon RH are probable. Two factors introduce some uncertainty to how widespread these elevated conditions will be: 1) a weakening surface pressure gradient throughout the day and 2) potential for mid/upper-level clouds over portions of Utah/Nevada during the afternoon. Current position of dry air aloft on water vapor satellite imagery would indicate that it may only overlap portions of western Colorado during the afternoon, which is also supported by model forecast soundings. Nonetheless, several areas will see at least briefly elevated conditions with potential for locally critical conditions in terrain-favored locations. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No Mesoscale Discussions are in effect as of Fri Aug 23 16:35:01 UTC 2019.

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1125 AM CDT Fri Aug 23 2019 Valid 231630Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO EARLY TONIGHT ACROSS PARTS OF VA/NC AND THE HIGH PLAINS... ...SUMMARY... Severe thunderstorms appear most probable this afternoon into early tonight for portions of North Carolina and Virginia, as well as the central High Plains. ...VA/NC this afternoon/evening... A surface cold front will continue to move slowly southward across VA this afternoon into NC overnight, in the wake of a midlevel trough crossing New England. The southern fringe of the westerlies extends south to near the VA/NC border, where a series of subtle speed maxima/embedded MCVs will translate eastward this afternoon. Low-level convergence/ascent along the front and an accompanying differential heating zone should support thunderstorm development by early afternoon across central VA, and storms will spread east-southeastward through the remainder of the afternoon/evening. Though midlevel lapse rates will be rather modest, surface heating will steepen low-level lapse rates and boost afternoon MLCAPE to near 1500 J/kg. Given effective bulk shear in the 25-35 kt range, and mix of organized multicell clusters and some low-end supercells can be expected in a broken band along the front this afternoon. Damaging winds should be the main severe threat. ...Central High Plains this afternoon into tonight... A midlevel shortwave trough is moving slowly eastward over the northern Rockies, as other subtle embedded waves progress eastward over the central Rockies. Steep midlevel lapse rates, daytime heating, and low-level upslope flow will promote an environment favorable for afternoon thunderstorm development east of the Front Range from northeast NM northward into eastern WY. Deep-layer vertical shear will not be particularly strong over most of the High Plains. The corridors of the somewhat stronger vertical shear will be immediately east of the midlevel trough in WY, and in the vicinity of southeast CO where low-level east-southeast flow will reside beneath the more westerly flow aloft, contributing to effective bulk shear of 30-35 kt. Thus, expect a mix of multicell clusters and some low-end supercells capable of producing damaging winds and large hail. A few clusters will likely persist into tonight in association with warm advection and a modest low-level jet. ..Thompson/Cook.. 08/23/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1125 AM CDT Fri Aug 23 2019 Valid 231630Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO EARLY TONIGHT ACROSS PARTS OF VA/NC AND THE HIGH PLAINS... ...SUMMARY... Severe thunderstorms appear most probable this afternoon into early tonight for portions of North Carolina and Virginia, as well as the central High Plains. ...VA/NC this afternoon/evening... A surface cold front will continue to move slowly southward across VA this afternoon into NC overnight, in the wake of a midlevel trough crossing New England. The southern fringe of the westerlies extends south to near the VA/NC border, where a series of subtle speed maxima/embedded MCVs will translate eastward this afternoon. Low-level convergence/ascent along the front and an accompanying differential heating zone should support thunderstorm development by early afternoon across central VA, and storms will spread east-southeastward through the remainder of the afternoon/evening. Though midlevel lapse rates will be rather modest, surface heating will steepen low-level lapse rates and boost afternoon MLCAPE to near 1500 J/kg. Given effective bulk shear in the 25-35 kt range, and mix of organized multicell clusters and some low-end supercells can be expected in a broken band along the front this afternoon. Damaging winds should be the main severe threat. ...Central High Plains this afternoon into tonight... A midlevel shortwave trough is moving slowly eastward over the northern Rockies, as other subtle embedded waves progress eastward over the central Rockies. Steep midlevel lapse rates, daytime heating, and low-level upslope flow will promote an environment favorable for afternoon thunderstorm development east of the Front Range from northeast NM northward into eastern WY. Deep-layer vertical shear will not be particularly strong over most of the High Plains. The corridors of the somewhat stronger vertical shear will be immediately east of the midlevel trough in WY, and in the vicinity of southeast CO where low-level east-southeast flow will reside beneath the more westerly flow aloft, contributing to effective bulk shear of 30-35 kt. Thus, expect a mix of multicell clusters and some low-end supercells capable of producing damaging winds and large hail. A few clusters will likely persist into tonight in association with warm advection and a modest low-level jet. ..Thompson/Cook.. 08/23/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1125 AM CDT Fri Aug 23 2019 Valid 231630Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO EARLY TONIGHT ACROSS PARTS OF VA/NC AND THE HIGH PLAINS... ...SUMMARY... Severe thunderstorms appear most probable this afternoon into early tonight for portions of North Carolina and Virginia, as well as the central High Plains. ...VA/NC this afternoon/evening... A surface cold front will continue to move slowly southward across VA this afternoon into NC overnight, in the wake of a midlevel trough crossing New England. The southern fringe of the westerlies extends south to near the VA/NC border, where a series of subtle speed maxima/embedded MCVs will translate eastward this afternoon. Low-level convergence/ascent along the front and an accompanying differential heating zone should support thunderstorm development by early afternoon across central VA, and storms will spread east-southeastward through the remainder of the afternoon/evening. Though midlevel lapse rates will be rather modest, surface heating will steepen low-level lapse rates and boost afternoon MLCAPE to near 1500 J/kg. Given effective bulk shear in the 25-35 kt range, and mix of organized multicell clusters and some low-end supercells can be expected in a broken band along the front this afternoon. Damaging winds should be the main severe threat. ...Central High Plains this afternoon into tonight... A midlevel shortwave trough is moving slowly eastward over the northern Rockies, as other subtle embedded waves progress eastward over the central Rockies. Steep midlevel lapse rates, daytime heating, and low-level upslope flow will promote an environment favorable for afternoon thunderstorm development east of the Front Range from northeast NM northward into eastern WY. Deep-layer vertical shear will not be particularly strong over most of the High Plains. The corridors of the somewhat stronger vertical shear will be immediately east of the midlevel trough in WY, and in the vicinity of southeast CO where low-level east-southeast flow will reside beneath the more westerly flow aloft, contributing to effective bulk shear of 30-35 kt. Thus, expect a mix of multicell clusters and some low-end supercells capable of producing damaging winds and large hail. A few clusters will likely persist into tonight in association with warm advection and a modest low-level jet. ..Thompson/Cook.. 08/23/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1125 AM CDT Fri Aug 23 2019 Valid 231630Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO EARLY TONIGHT ACROSS PARTS OF VA/NC AND THE HIGH PLAINS... ...SUMMARY... Severe thunderstorms appear most probable this afternoon into early tonight for portions of North Carolina and Virginia, as well as the central High Plains. ...VA/NC this afternoon/evening... A surface cold front will continue to move slowly southward across VA this afternoon into NC overnight, in the wake of a midlevel trough crossing New England. The southern fringe of the westerlies extends south to near the VA/NC border, where a series of subtle speed maxima/embedded MCVs will translate eastward this afternoon. Low-level convergence/ascent along the front and an accompanying differential heating zone should support thunderstorm development by early afternoon across central VA, and storms will spread east-southeastward through the remainder of the afternoon/evening. Though midlevel lapse rates will be rather modest, surface heating will steepen low-level lapse rates and boost afternoon MLCAPE to near 1500 J/kg. Given effective bulk shear in the 25-35 kt range, and mix of organized multicell clusters and some low-end supercells can be expected in a broken band along the front this afternoon. Damaging winds should be the main severe threat. ...Central High Plains this afternoon into tonight... A midlevel shortwave trough is moving slowly eastward over the northern Rockies, as other subtle embedded waves progress eastward over the central Rockies. Steep midlevel lapse rates, daytime heating, and low-level upslope flow will promote an environment favorable for afternoon thunderstorm development east of the Front Range from northeast NM northward into eastern WY. Deep-layer vertical shear will not be particularly strong over most of the High Plains. The corridors of the somewhat stronger vertical shear will be immediately east of the midlevel trough in WY, and in the vicinity of southeast CO where low-level east-southeast flow will reside beneath the more westerly flow aloft, contributing to effective bulk shear of 30-35 kt. Thus, expect a mix of multicell clusters and some low-end supercells capable of producing damaging winds and large hail. A few clusters will likely persist into tonight in association with warm advection and a modest low-level jet. ..Thompson/Cook.. 08/23/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0757 AM CDT Fri Aug 23 2019 Valid 231300Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTH CAROLINA AND VIRGINIA...AS WELL AS THE CENTRAL HIGH PLAINS... ...SUMMARY... Organized severe thunderstorms appear most probable today over portions of North Carolina and Virginia, as well as the central High Plains. ...Synopsis... The upper-air pattern over the CONUS this period will be dominated by a fairly high-amplitude northern stream across roughly the northern half, along with several slow-moving shortwaves and related MCVs from the central/southern Plains to the Tidewater region of the Atlantic Coast. A synoptic cyclone over eastern QC will devolve into an open-wave trough, extending southwestward over the lower Great Lakes and interior Mid-Atlantic region. This will contribute to the eastward ejection of a subtle, convectively enhanced vorticity lobe, now apparent in moisture-channel imagery over the Appalachians between southern WV and northeastern GA. This perturbation should move east-northeastward across VA and northern NC today, then offshore from the Delmarva Peninsula by 00Z. Upstream, high-amplitude ridging will shift eastward from the upper Mississippi Valley across the upper Great Lakes. The trailing region of large-scale height falls will be populated by several slowly eastward- to northeastward-moving MCVs and small shortwave troughs over the central/southern Plains. A substantial shortwave trough is located from a closed 500-mb low over southwestern MT southward across UT to northern AZ. This trough will move eastward to central/eastern portions of WY and CO through the period. At the surface, 11Z analysis depicted a cold front from offshore New England across DE, northern VA, central WV, southern IL and central MO, becoming quasistationary northeastward across east-central/ north-central NE and southwestern ND, to a low over northeastern MT north of GDV. As a surface anticyclone over Lake Superior shifts eastward, the front will move southeastward/southward over VA/NC/KY, reaching SC, TN, and northern AR by 12Z. The western segment of the front will move little over NE while shifting northeastward slowly across the Dakotas as a warm front. ...NC/VA... Scattered thunderstorms are expected to develop along/ahead of the front from midday through afternoon, mainly over western and northern VA. This activity should expand and intensify while encountering a favorably moist and destabilizing air mass across central/southern VA, the southern Delmarva and northeastern NC. A few severe gusts will be possible, along with more-widespread damaging wind approaching severe limits. Isolated large hail also may occur, especially over northern portions of the outlook in association with colder air aloft and less-messy convective modes. This area will reside under the southern rim of the stronger midlevel winds aloft, related to the eastern Canadian synoptic trough and the ejecting southern Appalachians shortwave trough, the latter also providing support through subtle DCVA/ascent in midlevels. The associated mass responses should encourage enhanced convergence in the frontal/prefrontal air mass, amidst weak ambient MLCINH. Favorable buoyancy will occur despite modest mid/upper- level lapse rates, thanks to 1. Rich boundary-layer moisture (70s F surface dew points and PW of 1.75 to 2.25 inches being common), and 2. Areas of intermittent (but cumulatively favorable) diabatic surface heating in the warm sector. Peak preconvective MLCAPE should vary from around 500-1000 J/kg in the northern and western parts of the outlook to around 1500-2000 J/kg over northeastern NC. 25-35-kt flow is forecast in much of the 700-400-mb layer, with marginally supercell-favorable effective shear in northern areas. However, deep shear will diminish markedly with southward extent. Upper-level winds will be weaker over most of the area, however, contributing to potential for messy convective modes after early semi-discrete phases. One or more bowing segments may evolve within a band of mostly multicellular thunderstorms across VA and into northeastern SC late this afternoon into early evening before activity weakens and/or moves offshore. ...Central High Plains... Scattered thunderstorms should develop this afternoon over well-heated higher terrain, near that part of the I-25 corridor between CPR-RTN. This activity is forecast to move eastward to northeastward across the adjoining High Plains into a favorable moist, diabatically destabilized air mass, offering damaging gusts and sporadic hail. A tornado cannot be ruled out as well, this threat depending strongly on mesobeta- to storm-scale processes that remain rather uncertain/unfocused in predictability terms as this time. Mid/upper-level support is forecast to be atypically strong for this time of year, with large-scale ascent from the shortwave perturbations and strongly difluent upper flow. Steep midlevel lapse rates and moist/warm advection in low levels will contribute to destabilization as well, west of a well-defined moist axis that parallels the frontal zone from central/eastern KS to the western Dakotas. Surface dew points 50s to low 60s F should become common across the central High Plains, and at least near and east of the axis of the outlook area. These factors will contribute to peak MLCAPE values ranging from around 1500 J/kg over parts of eastern WY to the 2000-3000 J/kg range over much of the NE Panhandle, and parts of eastern CO and western KS. Given the strong veering with height expected in the low/middle- level wind profiles, low-level bulk shear and hodographs will be favorable for supercells and hail, though mid/upper winds will be modest amidst the aforementioned difluence. Effective-shear magnitudes 25-40 kt should be common. Modal uncertainties include timing of the transition from discrete to clustered with respect to storms moving from higher-elevation genesis areas into greater moisture. Still, at least a few cold-pool-driven arcs or bands of convection should develop to contribute to the wind potential, while moving into well-mixed subcloud/inflow layers. ..Edwards/Gleason.. 08/23/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0757 AM CDT Fri Aug 23 2019 Valid 231300Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTH CAROLINA AND VIRGINIA...AS WELL AS THE CENTRAL HIGH PLAINS... ...SUMMARY... Organized severe thunderstorms appear most probable today over portions of North Carolina and Virginia, as well as the central High Plains. ...Synopsis... The upper-air pattern over the CONUS this period will be dominated by a fairly high-amplitude northern stream across roughly the northern half, along with several slow-moving shortwaves and related MCVs from the central/southern Plains to the Tidewater region of the Atlantic Coast. A synoptic cyclone over eastern QC will devolve into an open-wave trough, extending southwestward over the lower Great Lakes and interior Mid-Atlantic region. This will contribute to the eastward ejection of a subtle, convectively enhanced vorticity lobe, now apparent in moisture-channel imagery over the Appalachians between southern WV and northeastern GA. This perturbation should move east-northeastward across VA and northern NC today, then offshore from the Delmarva Peninsula by 00Z. Upstream, high-amplitude ridging will shift eastward from the upper Mississippi Valley across the upper Great Lakes. The trailing region of large-scale height falls will be populated by several slowly eastward- to northeastward-moving MCVs and small shortwave troughs over the central/southern Plains. A substantial shortwave trough is located from a closed 500-mb low over southwestern MT southward across UT to northern AZ. This trough will move eastward to central/eastern portions of WY and CO through the period. At the surface, 11Z analysis depicted a cold front from offshore New England across DE, northern VA, central WV, southern IL and central MO, becoming quasistationary northeastward across east-central/ north-central NE and southwestern ND, to a low over northeastern MT north of GDV. As a surface anticyclone over Lake Superior shifts eastward, the front will move southeastward/southward over VA/NC/KY, reaching SC, TN, and northern AR by 12Z. The western segment of the front will move little over NE while shifting northeastward slowly across the Dakotas as a warm front. ...NC/VA... Scattered thunderstorms are expected to develop along/ahead of the front from midday through afternoon, mainly over western and northern VA. This activity should expand and intensify while encountering a favorably moist and destabilizing air mass across central/southern VA, the southern Delmarva and northeastern NC. A few severe gusts will be possible, along with more-widespread damaging wind approaching severe limits. Isolated large hail also may occur, especially over northern portions of the outlook in association with colder air aloft and less-messy convective modes. This area will reside under the southern rim of the stronger midlevel winds aloft, related to the eastern Canadian synoptic trough and the ejecting southern Appalachians shortwave trough, the latter also providing support through subtle DCVA/ascent in midlevels. The associated mass responses should encourage enhanced convergence in the frontal/prefrontal air mass, amidst weak ambient MLCINH. Favorable buoyancy will occur despite modest mid/upper- level lapse rates, thanks to 1. Rich boundary-layer moisture (70s F surface dew points and PW of 1.75 to 2.25 inches being common), and 2. Areas of intermittent (but cumulatively favorable) diabatic surface heating in the warm sector. Peak preconvective MLCAPE should vary from around 500-1000 J/kg in the northern and western parts of the outlook to around 1500-2000 J/kg over northeastern NC. 25-35-kt flow is forecast in much of the 700-400-mb layer, with marginally supercell-favorable effective shear in northern areas. However, deep shear will diminish markedly with southward extent. Upper-level winds will be weaker over most of the area, however, contributing to potential for messy convective modes after early semi-discrete phases. One or more bowing segments may evolve within a band of mostly multicellular thunderstorms across VA and into northeastern SC late this afternoon into early evening before activity weakens and/or moves offshore. ...Central High Plains... Scattered thunderstorms should develop this afternoon over well-heated higher terrain, near that part of the I-25 corridor between CPR-RTN. This activity is forecast to move eastward to northeastward across the adjoining High Plains into a favorable moist, diabatically destabilized air mass, offering damaging gusts and sporadic hail. A tornado cannot be ruled out as well, this threat depending strongly on mesobeta- to storm-scale processes that remain rather uncertain/unfocused in predictability terms as this time. Mid/upper-level support is forecast to be atypically strong for this time of year, with large-scale ascent from the shortwave perturbations and strongly difluent upper flow. Steep midlevel lapse rates and moist/warm advection in low levels will contribute to destabilization as well, west of a well-defined moist axis that parallels the frontal zone from central/eastern KS to the western Dakotas. Surface dew points 50s to low 60s F should become common across the central High Plains, and at least near and east of the axis of the outlook area. These factors will contribute to peak MLCAPE values ranging from around 1500 J/kg over parts of eastern WY to the 2000-3000 J/kg range over much of the NE Panhandle, and parts of eastern CO and western KS. Given the strong veering with height expected in the low/middle- level wind profiles, low-level bulk shear and hodographs will be favorable for supercells and hail, though mid/upper winds will be modest amidst the aforementioned difluence. Effective-shear magnitudes 25-40 kt should be common. Modal uncertainties include timing of the transition from discrete to clustered with respect to storms moving from higher-elevation genesis areas into greater moisture. Still, at least a few cold-pool-driven arcs or bands of convection should develop to contribute to the wind potential, while moving into well-mixed subcloud/inflow layers. ..Edwards/Gleason.. 08/23/2019 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0339 AM CDT Fri Aug 23 2019 Valid 261200Z - 311200Z ...DISCUSSION... Current medium-range guidance is in good agreement that a cold front will push through the TX Panhandle, much of OK, and the Ozark Plateau on D4/Monday. Given the strong buoyancy and modest vertical shear expected ahead of the front, some severe potential exists. However, despite consensus within the 00Z model suite, forecast confidence is still low owing to the potential for antecedent precipitation and variance in frontal timing noted in previous model runs. After D4/Monday, model solutions diverge with little run-to-run or model-to-model consistency noted. This leads to low forecast confidence, although the persistent moisture across the central and southeastern CONUS suggests severe thunderstorms remain possible. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0339 AM CDT Fri Aug 23 2019 Valid 261200Z - 311200Z ...DISCUSSION... Current medium-range guidance is in good agreement that a cold front will push through the TX Panhandle, much of OK, and the Ozark Plateau on D4/Monday. Given the strong buoyancy and modest vertical shear expected ahead of the front, some severe potential exists. However, despite consensus within the 00Z model suite, forecast confidence is still low owing to the potential for antecedent precipitation and variance in frontal timing noted in previous model runs. After D4/Monday, model solutions diverge with little run-to-run or model-to-model consistency noted. This leads to low forecast confidence, although the persistent moisture across the central and southeastern CONUS suggests severe thunderstorms remain possible. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0339 AM CDT Fri Aug 23 2019 Valid 261200Z - 311200Z ...DISCUSSION... Current medium-range guidance is in good agreement that a cold front will push through the TX Panhandle, much of OK, and the Ozark Plateau on D4/Monday. Given the strong buoyancy and modest vertical shear expected ahead of the front, some severe potential exists. However, despite consensus within the 00Z model suite, forecast confidence is still low owing to the potential for antecedent precipitation and variance in frontal timing noted in previous model runs. After D4/Monday, model solutions diverge with little run-to-run or model-to-model consistency noted. This leads to low forecast confidence, although the persistent moisture across the central and southeastern CONUS suggests severe thunderstorms remain possible. Read more

MD 1837 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF SOUTH-CENTRAL NE INTO NORTH-CENTRAL KS
Mesoscale Discussion 1837 NWS Storm Prediction Center Norman OK 0338 AM CDT Fri Aug 23 2019 Areas affected...Portions of south-central NE into north-central KS Concerning...Severe potential...Watch unlikely Valid 230838Z - 231045Z Probability of Watch Issuance...5 percent SUMMARY...A long-lived supercell thunderstorm may continue to produce severe wind gusts and large hail through the early morning hours. This threat is expected to remain too isolated to justify watch issuance. DISCUSSION...A measured severe wind gust to 66 kt (76 mph) was recorded at 0759Z at Hastings NE (KSI) with a supercell thunderstorm moving slowly southward across south-central NE. This storm may be related to an MCV from convection yesterday across the central Plains, and it is located along a moisture/instability gradient evident on latest 850 mb and MUCAPE mesoanalysis fields. The VWP from KUEX has shown only a modest increase in a 15-20 kt south-southeasterly low-level jet over the past couple of hours, with mid-level westerly flow increasing to only about 30-35 kt. Regardless, this is apparently sufficient to support a persistent supercell, as observed by KUEX radar imagery. Given the ongoing storm organization and modestly steepened mid-level lapse rates across this region, isolated large hail may occur with this supercell in addition to severe wind gusts. It is uncertain how long this storm will persist, but it is moving slowly southward into a region with a relative minimum in convective inhibition owing to upper 60s to low 70s surface dewpoints. A severe risk may continue for the next couple of hours into part of north-central KS, but watch issuance is not currently expected given the very isolated nature of the threat. ..Gleason/Edwards.. 08/23/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...TOP...GID... LAT...LON 40689863 40679819 40179778 39669763 39529814 39609863 40349878 40689863 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Fri Aug 23 2019 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND SOUTHERN PLAINS... ...SUMMARY... Isolated severe thunderstorms are possible on Sunday across portions of the northern and southern Plains. ...Synopsis... Medium-range guidance is in good agreement that a strong shortwave trough embedded within the enhanced westerlies moves from the northern Rockies through the northern Plains on Sunday. This results in a deepening of the cyclonic flow across the north-central CONUS. This pattern evolution will also push a cold front eastward/ southeastward through much of northern Plains. Elsewhere, warm and moist conditions will persist across much of southern Plains and Southeast while weakening high pressure across much of the eastern CONUS will allow for some moisture return into the OH Valley. ...Southern Plains... Air mass across the region will be warm, very moist, and strongly buoyant. Strengthening northwesterly flow aloft will also contribute to moderate vertical shear. Overall environment would support severe potential as long as forcing exists for storm initiation. Current guidance suggests a MCS will be moving out of KS early in the period, with a resulting severe threat anticipated downstream. Low (i.e. 5%) severe probabilities will be introduced with this forecast. More model consistency is needed before issuing higher probabilities. ...Northern Plains... Ample low-level moisture (i.e. dewpoints in the mid to upper 60s) will be in place over the region ahead of the approaching cold front. Even so, relatively warm low to mid-level temperatures will likely limit destabilization, particularly across southern portions of the region where less large-scale forcing for ascent (from the approaching shortwave trough) is expected. The environment supports a severe threat where deep updrafts persists but uncertainty regarding coverage currently precludes higher than 5% probability. ..Mosier.. 08/23/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Fri Aug 23 2019 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND SOUTHERN PLAINS... ...SUMMARY... Isolated severe thunderstorms are possible on Sunday across portions of the northern and southern Plains. ...Synopsis... Medium-range guidance is in good agreement that a strong shortwave trough embedded within the enhanced westerlies moves from the northern Rockies through the northern Plains on Sunday. This results in a deepening of the cyclonic flow across the north-central CONUS. This pattern evolution will also push a cold front eastward/ southeastward through much of northern Plains. Elsewhere, warm and moist conditions will persist across much of southern Plains and Southeast while weakening high pressure across much of the eastern CONUS will allow for some moisture return into the OH Valley. ...Southern Plains... Air mass across the region will be warm, very moist, and strongly buoyant. Strengthening northwesterly flow aloft will also contribute to moderate vertical shear. Overall environment would support severe potential as long as forcing exists for storm initiation. Current guidance suggests a MCS will be moving out of KS early in the period, with a resulting severe threat anticipated downstream. Low (i.e. 5%) severe probabilities will be introduced with this forecast. More model consistency is needed before issuing higher probabilities. ...Northern Plains... Ample low-level moisture (i.e. dewpoints in the mid to upper 60s) will be in place over the region ahead of the approaching cold front. Even so, relatively warm low to mid-level temperatures will likely limit destabilization, particularly across southern portions of the region where less large-scale forcing for ascent (from the approaching shortwave trough) is expected. The environment supports a severe threat where deep updrafts persists but uncertainty regarding coverage currently precludes higher than 5% probability. ..Mosier.. 08/23/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Fri Aug 23 2019 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND SOUTHERN PLAINS... ...SUMMARY... Isolated severe thunderstorms are possible on Sunday across portions of the northern and southern Plains. ...Synopsis... Medium-range guidance is in good agreement that a strong shortwave trough embedded within the enhanced westerlies moves from the northern Rockies through the northern Plains on Sunday. This results in a deepening of the cyclonic flow across the north-central CONUS. This pattern evolution will also push a cold front eastward/ southeastward through much of northern Plains. Elsewhere, warm and moist conditions will persist across much of southern Plains and Southeast while weakening high pressure across much of the eastern CONUS will allow for some moisture return into the OH Valley. ...Southern Plains... Air mass across the region will be warm, very moist, and strongly buoyant. Strengthening northwesterly flow aloft will also contribute to moderate vertical shear. Overall environment would support severe potential as long as forcing exists for storm initiation. Current guidance suggests a MCS will be moving out of KS early in the period, with a resulting severe threat anticipated downstream. Low (i.e. 5%) severe probabilities will be introduced with this forecast. More model consistency is needed before issuing higher probabilities. ...Northern Plains... Ample low-level moisture (i.e. dewpoints in the mid to upper 60s) will be in place over the region ahead of the approaching cold front. Even so, relatively warm low to mid-level temperatures will likely limit destabilization, particularly across southern portions of the region where less large-scale forcing for ascent (from the approaching shortwave trough) is expected. The environment supports a severe threat where deep updrafts persists but uncertainty regarding coverage currently precludes higher than 5% probability. ..Mosier.. 08/23/2019 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Fri Aug 23 2019 Valid 241200Z - 251200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SNAKE RIVER VALLEY INTO SOUTHERN WYOMING... ...Synopsis... On D2/Saturday, a strong mid-level jet will overspread the Pacific Northwest with the nose of the jet impinging upon the northern Great Basin/central Rockies. Critical fire weather will be most likely for portions of the Snake River Valley and southern Wyoming. In these locations, terrain-enhanced downslope flow will promote 20-25 mph winds with 10-15% afternoon RH. Upper and potentially mid-level clouds will again be a factor in stunting afternoon heating/boundary-layer mixing, which will likely limit the spatial extent of the critical fire weather threat. Surrounding portions of the northern Great Basin and central Rockies will see elevated fire weather conditions, with similar afternoon RH but winds generally in the 15-20 mph range. ..Wendt.. 08/23/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Fri Aug 23 2019 Valid 241200Z - 251200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SNAKE RIVER VALLEY INTO SOUTHERN WYOMING... ...Synopsis... On D2/Saturday, a strong mid-level jet will overspread the Pacific Northwest with the nose of the jet impinging upon the northern Great Basin/central Rockies. Critical fire weather will be most likely for portions of the Snake River Valley and southern Wyoming. In these locations, terrain-enhanced downslope flow will promote 20-25 mph winds with 10-15% afternoon RH. Upper and potentially mid-level clouds will again be a factor in stunting afternoon heating/boundary-layer mixing, which will likely limit the spatial extent of the critical fire weather threat. Surrounding portions of the northern Great Basin and central Rockies will see elevated fire weather conditions, with similar afternoon RH but winds generally in the 15-20 mph range. ..Wendt.. 08/23/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Fri Aug 23 2019 Valid 241200Z - 251200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SNAKE RIVER VALLEY INTO SOUTHERN WYOMING... ...Synopsis... On D2/Saturday, a strong mid-level jet will overspread the Pacific Northwest with the nose of the jet impinging upon the northern Great Basin/central Rockies. Critical fire weather will be most likely for portions of the Snake River Valley and southern Wyoming. In these locations, terrain-enhanced downslope flow will promote 20-25 mph winds with 10-15% afternoon RH. Upper and potentially mid-level clouds will again be a factor in stunting afternoon heating/boundary-layer mixing, which will likely limit the spatial extent of the critical fire weather threat. Surrounding portions of the northern Great Basin and central Rockies will see elevated fire weather conditions, with similar afternoon RH but winds generally in the 15-20 mph range. ..Wendt.. 08/23/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more