Severe Storms

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0726 AM CDT Wed Aug 07 2019 Valid 071300Z - 081200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MISSISSIPPI VALLEY...CENTRAL PLAINS AND EASTERN SEABOARD... ...SUMMARY... Thunderstorms associated with wind damage and isolated large hail will be possible across parts of the Upper Mississippi Valley and central Plains today. Additional storms with isolated damaging wind gusts may occur from parts of the Carolinas northward into the Northeast. ...Upper Mississippi Valley... An upper-level trough will move across western Ontario and the upper Mississippi Valley today as northwest mid-level flow remains over the Upper Midwest. At the surface, a cold front in northern Minnesota and eastern South Dakota will advance southeastward reaching Upper Michigan, northern Wisconsin, southern Minnesota and eastern Nebraska this afternoon. As surface heating takes place ahead of the front, surface dewpoints in the mid to upper 60s F will contribute to an axis of moderate instability. Thunderstorm development will be possible along the instability gradient near the front during the mid to late afternoon. Convection is first expected to initiate in Upper Michigan ahead of the upper-level trough with storms developing west-southwestward into northern Wisconsin. It is uncertain how far west convection can develop but at least a few storms will be possible in southern Minnesota. RAP forecast soundings along the axis of instability late this afternoon show 0-6 km shear near 35 kt, steep lapse rates in the lowest 1 km AGL and veered west-southwesterly winds just ahead of the front. This setup should be sufficient for damaging wind gusts with the multicell line segments that organize and move southeastward during the late afternoon and early evening. Hail will also be possible with convection that develops in the strongest instability. ...Central Plains/Ozarks... Northwest mid-level flow will remain in place today across the central states as a couple of minor shortwave troughs move southeastward across the region. The southern shortwave trough is forecast to move into the lower Missouri Valley today. Thunderstorms are ongoing ahead of this feature in eastern Kansas. Substantial uncertainty exists concerning how long the severe threat with the MCS will be maintained. Some models suggest that the MCS will become marginally severe by the time it reaches southeast Kansas. Some of the same models regenerate storms by afternoon near the instability axis in south-central Nebraska and move this new convection southeastward into central Kansas. Deep-layer shear along this corridor along with steepening low-level lapse rates could result in the development of another cold pool. If that happens, then a wind-damage threat can be expected to redevelop late this afternoon into early this evening from north-central Kansas southeastward into far northeast Oklahoma and far southwest Missouri. ...Eastern Seaboard... An upper-level trough will move across the eastern states today as southwest mid-level flow remains in place ahead of the trough from the Mid-Atlantic into New England. At the surface, a cold front will advance slowly southeastward across the lower Great Lakes. A pre-frontal trough will deepen across the Eastern Seaboard. Surface dewpoints ahead of the pre-frontal trough will be in the upper 60s F to near 70 F. As surface temperatures warm today, a corridor of instability will develop from the eastern Carolinas northward to eastern New York and western New England. As the upper-level trough approaches, scattered to numerous thunderstorms should develop west of the strongest instability with convection moving east-northeastward across the region. Although deep-layer shear is forecast to be in the 20 to 30 kt range in much of the eastern states, steep low-level lapse rates will make conditions favorable for damaging wind gusts with the better-organized multicell line segments. The severe threat should be maximized in the mid to late afternoon. ..Broyles/Edwards.. 08/07/2019 Read more

MD 1661 CONCERNING SEVERE THUNDERSTORM WATCH 558... FOR PORTIONS OF EASTERN KS AND EXTREME WESTERN MO.
Mesoscale Discussion 1661 NWS Storm Prediction Center Norman OK 0657 AM CDT Wed Aug 07 2019 Areas affected...portions of eastern KS and extreme western MO. Concerning...Severe Thunderstorm Watch 558... Valid 071157Z - 071400Z The severe weather threat for Severe Thunderstorm Watch 558 continues. SUMMARY...An MCS continues to move southeastward across the watch area, offering the threat for occasionally severe/damaging gusts. Convective and instability trends have been fluctuating, and will be monitored for the possibility of an additional watch to the southeast into more of eastern KS and parts of western MO. DISCUSSION...The complex continues to more atop a relatively stable near-surface layer yielding 150-250 J/kg of MLCINH, which may be suppressing the potential for more than isolated severe gusts to reach surface. A near-severe gust (48 kt) was measured at MHK at 1054Z, with 42 kt at TOP at 1141Z. Slight weakening/disorganization has been noted in the past 1/2 to 1 hour in radar presentation and IR imagery (with some cloud-top warming), recent observed gusts have not been as intense as farther northwest in southern NE, and the surface isallobaric perturbation's magnitude has lessened in the last couple hours. While these trends additively indicate that the MCS may have peaked, at least for the time being, they are subtle, and additional strengthening may still occur. A very moist air mass and a zone of favorable baroclinicity continue to extend southeast of its location. 500-1500 J/kg MLCAPE and 1500-3000 J/kg MUCAPE are evident along the projected track near the frontal zone, which extends from the complex southeastward over west-central/ southwestern MO. Another watch across the KS/MO border region and more of eastern KS may be needed, especially if any re-intensification trends are noted that indicate strengthening forced ascent via internally driven cold-pool processes. ..Edwards.. 08/07/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...SGF...EAX...TOP...ICT... LAT...LON 39479719 39139603 39339513 38849450 38349416 38059414 37929445 37829519 38029587 38439645 39479719 Read more

WW 0558 Status Updates
STATUS REPORT ON WW 558 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 WNW SLN TO 20 NNE CNK TO 35 ENE CNK TO 10 NNE MHK TO 20 ENE MHK TO 35 N TOP TO 25 SSE FNB. MESOSCALE DISCUSSION FORTHCOMING. ..EDWARDS..08/07/19 ATTN...WFO...ICT...TOP...GID...OAX... STATUS REPORT FOR WS 558 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS KSC017-027-029-031-041-045-059-061-085-087-111-115-127-139-143- 149-157-161-169-177-197-201-071240- KS . KANSAS COUNTIES INCLUDED ARE CHASE CLAY CLOUD COFFEY DICKINSON DOUGLAS FRANKLIN GEARY JACKSON JEFFERSON LYON MARION MORRIS OSAGE OTTAWA POTTAWATOMIE REPUBLIC RILEY SALINE SHAWNEE WABAUNSEE WASHINGTON THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES. Read more

WW 0558 Status Updates
STATUS REPORT ON WW 558 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 WNW SLN TO 20 NNE CNK TO 35 ENE CNK TO 10 NNE MHK TO 20 ENE MHK TO 35 N TOP TO 25 SSE FNB. MESOSCALE DISCUSSION FORTHCOMING. ..EDWARDS..08/07/19 ATTN...WFO...ICT...TOP...GID...OAX... STATUS REPORT FOR WS 558 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS KSC017-027-029-031-041-045-059-061-085-087-111-115-127-139-143- 149-157-161-169-177-197-201-071240- KS . KANSAS COUNTIES INCLUDED ARE CHASE CLAY CLOUD COFFEY DICKINSON DOUGLAS FRANKLIN GEARY JACKSON JEFFERSON LYON MARION MORRIS OSAGE OTTAWA POTTAWATOMIE REPUBLIC RILEY SALINE SHAWNEE WABAUNSEE WASHINGTON THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES. Read more

WW 0558 Status Updates
STATUS REPORT ON WW 558 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 NW CNK TO 35 NNW CNK TO 5 SSE FNB. ..EDWARDS..08/07/19 ATTN...WFO...ICT...TOP...GID...OAX... STATUS REPORT FOR WS 558 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS KSC017-027-029-031-041-045-059-061-085-087-111-115-117-127-131- 139-143-149-157-161-169-177-197-201-071140- KS . KANSAS COUNTIES INCLUDED ARE CHASE CLAY CLOUD COFFEY DICKINSON DOUGLAS FRANKLIN GEARY JACKSON JEFFERSON LYON MARION MARSHALL MORRIS NEMAHA OSAGE OTTAWA POTTAWATOMIE REPUBLIC RILEY SALINE SHAWNEE WABAUNSEE WASHINGTON THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES. Read more

WW 0558 Status Updates
STATUS FOR WATCH 0558 HAS NOT BEEN ISSUED YET Read more

WW 0558 Status Updates
STATUS FOR WATCH 0558 HAS NOT BEEN ISSUED YET Read more

MD 1660 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR PORTIONS OF NORTHEASTERN AND EAST-CENTRAL KS.
Mesoscale Discussion 1660 NWS Storm Prediction Center Norman OK 0344 AM CDT Wed Aug 07 2019 Areas affected...portions of northeastern and east-central KS. Concerning...Severe potential...Watch likely Valid 070844Z - 070945Z Probability of Watch Issuance...80 percent SUMMARY...Given the persistence and organization of a complex of severe thunderstorms in southern NE, and somewhat-favorable conditions downshear over parts of northern KS, an additional watch looks increasingly probable. DISCUSSION...Surface mesoanalysis and objective analyses above the surface indicate little movement to the low-level frontal zone and instability gradient. As of 8Z, this boundary was evident from the leading part of the MCS over the HSI/GRI area southeastward near CNK, FRI, TOP and into east-central KS. In the absence of appreciable mid/upper influences, and with its orientation largely parallel to the flow aloft, little motion of the front is expected over the next several hours prior to being overtaken by the MCS. Uncertainty remains in terms of MCS longevity, given the extensive field of around 200 J/kg MLCINH in its projected path. However, the convection remains well-organized, as evident by the 65-kt gust measured at GRI and 61 kt at HSI since 8Z, on the leading rim of a substantial isallobaric perturbation. Pressure rises of around 8 mb/2 hours were noted in the GRI area with a 5-mb/2-hour wake depression over northeastern NE. Given these conditions, their support for additional, internally reinforced forward-propagational forcing, the favorable low-level moisture available, and supportive storm-relative low-level flow just off the surface observed at UEX prior to passage of the convection, the MCS should persist far enough into KS to justify a new watch. ..Edwards/Broyles.. 08/07/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...OAX...TOP...ICT...GID... LAT...LON 40159752 40149681 39639598 39189559 38559530 38089581 38389704 38809761 39449796 39989815 40159752 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0329 AM CDT Wed Aug 07 2019 Valid 101200Z - 151200Z ...DISCUSSION... Extended range guidance generally maintains the upper ridge across the south-central U.S. during the Day 4-8 period. A mean upper trough will be maintained across the northwest states, and various shortwave impulses migrating through northern stream flow will suppress the ridge over the northern Plains and Upper Midwest. A series of shortwave troughs also will migrate across the northeastern U.S. Severe potential across the central/southern Plains toward the mid-MS Valley will be driven by subtle impulses migrating through the ridge, as well as by mesoscale processes not resolved well at this time-scale. Additionally, run-to-run and model-to-model inconsistency is resulting in low predictability. Severe potential also could exist across the northern Plains into the Great Lakes and Northeast as the series of troughs move across this region early next week. However, the GFS and ECMWF are out of phase with the timing of these features, resulting in low predictability at this time. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0329 AM CDT Wed Aug 07 2019 Valid 101200Z - 151200Z ...DISCUSSION... Extended range guidance generally maintains the upper ridge across the south-central U.S. during the Day 4-8 period. A mean upper trough will be maintained across the northwest states, and various shortwave impulses migrating through northern stream flow will suppress the ridge over the northern Plains and Upper Midwest. A series of shortwave troughs also will migrate across the northeastern U.S. Severe potential across the central/southern Plains toward the mid-MS Valley will be driven by subtle impulses migrating through the ridge, as well as by mesoscale processes not resolved well at this time-scale. Additionally, run-to-run and model-to-model inconsistency is resulting in low predictability. Severe potential also could exist across the northern Plains into the Great Lakes and Northeast as the series of troughs move across this region early next week. However, the GFS and ECMWF are out of phase with the timing of these features, resulting in low predictability at this time. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0329 AM CDT Wed Aug 07 2019 Valid 101200Z - 151200Z ...DISCUSSION... Extended range guidance generally maintains the upper ridge across the south-central U.S. during the Day 4-8 period. A mean upper trough will be maintained across the northwest states, and various shortwave impulses migrating through northern stream flow will suppress the ridge over the northern Plains and Upper Midwest. A series of shortwave troughs also will migrate across the northeastern U.S. Severe potential across the central/southern Plains toward the mid-MS Valley will be driven by subtle impulses migrating through the ridge, as well as by mesoscale processes not resolved well at this time-scale. Additionally, run-to-run and model-to-model inconsistency is resulting in low predictability. Severe potential also could exist across the northern Plains into the Great Lakes and Northeast as the series of troughs move across this region early next week. However, the GFS and ECMWF are out of phase with the timing of these features, resulting in low predictability at this time. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0329 AM CDT Wed Aug 07 2019 Valid 101200Z - 151200Z ...DISCUSSION... Extended range guidance generally maintains the upper ridge across the south-central U.S. during the Day 4-8 period. A mean upper trough will be maintained across the northwest states, and various shortwave impulses migrating through northern stream flow will suppress the ridge over the northern Plains and Upper Midwest. A series of shortwave troughs also will migrate across the northeastern U.S. Severe potential across the central/southern Plains toward the mid-MS Valley will be driven by subtle impulses migrating through the ridge, as well as by mesoscale processes not resolved well at this time-scale. Additionally, run-to-run and model-to-model inconsistency is resulting in low predictability. Severe potential also could exist across the northern Plains into the Great Lakes and Northeast as the series of troughs move across this region early next week. However, the GFS and ECMWF are out of phase with the timing of these features, resulting in low predictability at this time. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0234 AM CDT Wed Aug 07 2019 Valid 091200Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND CENTRAL PLAINS...AND ACROSS PARTS OF OR INTO SOUTHEAST WA AND NORTHWEST ID... ...SUMMARY... Strong to severe thunderstorms are possible across portions of the northern and central Plains Friday afternoon and evening. Additional strong storms are possible across parts of the Pacific Northwest. ...Northern and Central Plains... The upper ridge will meander eastward over the Plains on Friday. A couple of shortwave impulses will float through the ridge in northwesterly deep-layer flow. The first ejects eastward from the northern Rockies as an upstream upper trough begins to move inland over the Pacific Northwest. This impulse will aid in weak surface cyclogenesis over the western Dakotas. Strengthening low-level south/southeasterly flow will transport low to mid 60s surface dewpoints northwestward into far eastern MT/WY/CO and across parts of the Dakotas/NE/KS. Strong heating will lead to moderate/strong destabilization by early afternoon with steep midlevel lapse rates in place beneath the upper ridge. Forecast soundings suggest shear profiles capable of supporting rating updrafts and large hail will be possible with initial storms from eastern MT/WY toward western ND/SD. Some tornado threat cannot be ruled out in the vicinity of the surface low where backed low level flow will maximize SRH coincident with mean mixing ratios approaching 14 g/kg. A 40 kt south/southwesterly low level jet is then forecast to increase during the evening and overnight hours, which could lead to upscale growth and increase in damaging wind potential across parts of SD. Given several periods of convection in days leading up to Friday and model differences in exact location of surface features, will introduce Marginal severe probs at this time, though upgrades in subsequent outlooks are possible. Further south, convection will develop over the higher terrain in CO. As convection moves off of higher terrain, high-based cells could produce hail and possibly strong gusts. However, the threat appears more conditional southward across eastern CO into parts of southeast WY and NE where capping may be stronger. Additionally, forecast soundings show weak midlevel flow, which could hinder storm organization/longevity of intense updrafts. ...Pacific Northwest... Thunderstorms will develop during the afternoon ahead of an upper shortwave trough moving onshore and a surface cold front moving inland during the evening. Modest boundary layer moisture with dewpoints in the upper 40s to low 50s and strong heating will result in MLCAPE values as high as 1500 J/kg with inverted-v thermodynamic profiles beneath the cloud bases. Strong southwesterly deep layer flow and effective shear values greater than 40 kt will lead to fast moving storms capable of strong downburst winds. Additionally, steep midlevel lapse rates could result in marginally severe hail. ..Leitman.. 08/07/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0234 AM CDT Wed Aug 07 2019 Valid 091200Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND CENTRAL PLAINS...AND ACROSS PARTS OF OR INTO SOUTHEAST WA AND NORTHWEST ID... ...SUMMARY... Strong to severe thunderstorms are possible across portions of the northern and central Plains Friday afternoon and evening. Additional strong storms are possible across parts of the Pacific Northwest. ...Northern and Central Plains... The upper ridge will meander eastward over the Plains on Friday. A couple of shortwave impulses will float through the ridge in northwesterly deep-layer flow. The first ejects eastward from the northern Rockies as an upstream upper trough begins to move inland over the Pacific Northwest. This impulse will aid in weak surface cyclogenesis over the western Dakotas. Strengthening low-level south/southeasterly flow will transport low to mid 60s surface dewpoints northwestward into far eastern MT/WY/CO and across parts of the Dakotas/NE/KS. Strong heating will lead to moderate/strong destabilization by early afternoon with steep midlevel lapse rates in place beneath the upper ridge. Forecast soundings suggest shear profiles capable of supporting rating updrafts and large hail will be possible with initial storms from eastern MT/WY toward western ND/SD. Some tornado threat cannot be ruled out in the vicinity of the surface low where backed low level flow will maximize SRH coincident with mean mixing ratios approaching 14 g/kg. A 40 kt south/southwesterly low level jet is then forecast to increase during the evening and overnight hours, which could lead to upscale growth and increase in damaging wind potential across parts of SD. Given several periods of convection in days leading up to Friday and model differences in exact location of surface features, will introduce Marginal severe probs at this time, though upgrades in subsequent outlooks are possible. Further south, convection will develop over the higher terrain in CO. As convection moves off of higher terrain, high-based cells could produce hail and possibly strong gusts. However, the threat appears more conditional southward across eastern CO into parts of southeast WY and NE where capping may be stronger. Additionally, forecast soundings show weak midlevel flow, which could hinder storm organization/longevity of intense updrafts. ...Pacific Northwest... Thunderstorms will develop during the afternoon ahead of an upper shortwave trough moving onshore and a surface cold front moving inland during the evening. Modest boundary layer moisture with dewpoints in the upper 40s to low 50s and strong heating will result in MLCAPE values as high as 1500 J/kg with inverted-v thermodynamic profiles beneath the cloud bases. Strong southwesterly deep layer flow and effective shear values greater than 40 kt will lead to fast moving storms capable of strong downburst winds. Additionally, steep midlevel lapse rates could result in marginally severe hail. ..Leitman.. 08/07/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0234 AM CDT Wed Aug 07 2019 Valid 091200Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND CENTRAL PLAINS...AND ACROSS PARTS OF OR INTO SOUTHEAST WA AND NORTHWEST ID... ...SUMMARY... Strong to severe thunderstorms are possible across portions of the northern and central Plains Friday afternoon and evening. Additional strong storms are possible across parts of the Pacific Northwest. ...Northern and Central Plains... The upper ridge will meander eastward over the Plains on Friday. A couple of shortwave impulses will float through the ridge in northwesterly deep-layer flow. The first ejects eastward from the northern Rockies as an upstream upper trough begins to move inland over the Pacific Northwest. This impulse will aid in weak surface cyclogenesis over the western Dakotas. Strengthening low-level south/southeasterly flow will transport low to mid 60s surface dewpoints northwestward into far eastern MT/WY/CO and across parts of the Dakotas/NE/KS. Strong heating will lead to moderate/strong destabilization by early afternoon with steep midlevel lapse rates in place beneath the upper ridge. Forecast soundings suggest shear profiles capable of supporting rating updrafts and large hail will be possible with initial storms from eastern MT/WY toward western ND/SD. Some tornado threat cannot be ruled out in the vicinity of the surface low where backed low level flow will maximize SRH coincident with mean mixing ratios approaching 14 g/kg. A 40 kt south/southwesterly low level jet is then forecast to increase during the evening and overnight hours, which could lead to upscale growth and increase in damaging wind potential across parts of SD. Given several periods of convection in days leading up to Friday and model differences in exact location of surface features, will introduce Marginal severe probs at this time, though upgrades in subsequent outlooks are possible. Further south, convection will develop over the higher terrain in CO. As convection moves off of higher terrain, high-based cells could produce hail and possibly strong gusts. However, the threat appears more conditional southward across eastern CO into parts of southeast WY and NE where capping may be stronger. Additionally, forecast soundings show weak midlevel flow, which could hinder storm organization/longevity of intense updrafts. ...Pacific Northwest... Thunderstorms will develop during the afternoon ahead of an upper shortwave trough moving onshore and a surface cold front moving inland during the evening. Modest boundary layer moisture with dewpoints in the upper 40s to low 50s and strong heating will result in MLCAPE values as high as 1500 J/kg with inverted-v thermodynamic profiles beneath the cloud bases. Strong southwesterly deep layer flow and effective shear values greater than 40 kt will lead to fast moving storms capable of strong downburst winds. Additionally, steep midlevel lapse rates could result in marginally severe hail. ..Leitman.. 08/07/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0234 AM CDT Wed Aug 07 2019 Valid 091200Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND CENTRAL PLAINS...AND ACROSS PARTS OF OR INTO SOUTHEAST WA AND NORTHWEST ID... ...SUMMARY... Strong to severe thunderstorms are possible across portions of the northern and central Plains Friday afternoon and evening. Additional strong storms are possible across parts of the Pacific Northwest. ...Northern and Central Plains... The upper ridge will meander eastward over the Plains on Friday. A couple of shortwave impulses will float through the ridge in northwesterly deep-layer flow. The first ejects eastward from the northern Rockies as an upstream upper trough begins to move inland over the Pacific Northwest. This impulse will aid in weak surface cyclogenesis over the western Dakotas. Strengthening low-level south/southeasterly flow will transport low to mid 60s surface dewpoints northwestward into far eastern MT/WY/CO and across parts of the Dakotas/NE/KS. Strong heating will lead to moderate/strong destabilization by early afternoon with steep midlevel lapse rates in place beneath the upper ridge. Forecast soundings suggest shear profiles capable of supporting rating updrafts and large hail will be possible with initial storms from eastern MT/WY toward western ND/SD. Some tornado threat cannot be ruled out in the vicinity of the surface low where backed low level flow will maximize SRH coincident with mean mixing ratios approaching 14 g/kg. A 40 kt south/southwesterly low level jet is then forecast to increase during the evening and overnight hours, which could lead to upscale growth and increase in damaging wind potential across parts of SD. Given several periods of convection in days leading up to Friday and model differences in exact location of surface features, will introduce Marginal severe probs at this time, though upgrades in subsequent outlooks are possible. Further south, convection will develop over the higher terrain in CO. As convection moves off of higher terrain, high-based cells could produce hail and possibly strong gusts. However, the threat appears more conditional southward across eastern CO into parts of southeast WY and NE where capping may be stronger. Additionally, forecast soundings show weak midlevel flow, which could hinder storm organization/longevity of intense updrafts. ...Pacific Northwest... Thunderstorms will develop during the afternoon ahead of an upper shortwave trough moving onshore and a surface cold front moving inland during the evening. Modest boundary layer moisture with dewpoints in the upper 40s to low 50s and strong heating will result in MLCAPE values as high as 1500 J/kg with inverted-v thermodynamic profiles beneath the cloud bases. Strong southwesterly deep layer flow and effective shear values greater than 40 kt will lead to fast moving storms capable of strong downburst winds. Additionally, steep midlevel lapse rates could result in marginally severe hail. ..Leitman.. 08/07/2019 Read more

MD 1659 CONCERNING SEVERE THUNDERSTORM WATCH 557... FOR PORTIONS OF CENTRAL AND SOUTHERN NE
Mesoscale Discussion 1659 NWS Storm Prediction Center Norman OK 0222 AM CDT Wed Aug 07 2019 Areas affected...portions of central and southern NE Concerning...Severe Thunderstorm Watch 557... Valid 070722Z - 070845Z The severe weather threat for Severe Thunderstorm Watch 557 continues. SUMMARY...At least isolated severe gust/hail potential may continue in remaining parts of the watch area past its original 8Z expiration, with some potential to spread south of I-80. As such, portions of the watch are being extended in both southward extent and time. Persistence southward into KS at severe levels appears less probable, given the weaker parameters in that region, but trends will be monitored. DISCUSSION...A persistent complex of strong-severe thunderstorms, with a couple of marginally severe measured gusts since 05Z, is undergoing a gradual evolution from forward-dominant propagational motion component to mixed forward/rear. This is occurring in a warm-advection and moisture-transport regime atop the cold pool, with a modest upstream LLJ -- manifest by 30-kt southwesterly 850-mb winds at the LNX and UEX radar sites. Surface mesoanalysis shows a quasistationary frontal zone from the GRI/HSI area southeastward across northeastern KS near FRI and TOP, with only minor movement at most being expected during the next several hours. Convection should continue to be maximized in the associated instability/buoyancy gradient, just over the cool side of the surface boundary, across portions of central/southern NE. Modified RAOBs and model soundings indicate a transition from around 2000- 2500 J/kg MLCAPE and MUCAPE on the warm side of the boundary, over central/south-central NE where surface dew points remain in the mid 60s to low 70s F, to less than 250 J/kg close to the Missouri River. However, continued severe-gust potential at the surface likely will be rendered isolated and episodic given the nocturnally stabilizing boundary layer with MLCINH in the 150-400 J/kg range. Ambient deep shear is strong, with 50-70-kt northwesterly effective-shear vectors common over the region, and some forward propagation with damaging- wind threat may persist with the leading convection toward the GRI/HSI/HJH areas. Hail potential will exist with the most intense trailing cells over the cold pool. ..Edwards.. 08/07/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...OAX...GID...LBF... LAT...LON 42219934 41889877 41419801 40939758 40459734 40149756 40139889 40649939 41429970 42059968 42219934 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0159 AM CDT Wed Aug 07 2019 Valid 081200Z - 091200Z ...Synopsis... The upper ridge across the Southwest into the Intermountain West is expected to shift slowly eastward on Thursday, as a deep upper trough approaches the Pacific Coast. Gradually increasing moisture in advance of the upper trough will continue to support at least isolated thunderstorm activity across portions of the Great Basin and interior Northwest. ...Central/northern NV into the interior Northwest... Thunderstorm coverage will likely increase compared to D1/Wednesday across central/northern NV into the interior Northwest on Thursday, as moisture gradually increases and the deep upper trough impinges on the region. Given the presence of potentially scattered thunderstorms overlapping regions of receptive fuels, lightning-related ignitions will again be possible, though there will also be greater potential for rainfall compared to D1/Wednesday. The greatest thunderstorm coverage is forecast to be over central/northern NV, but due to lingering uncertainty regarding convective evolution and potentially greater rainfall with any thunderstorm activity, the ISODRYT area is maintained in this outlook with no upgrade at this time. ..Dean.. 08/07/2019 ...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 0159 AM CDT Wed Aug 07 2019 Valid 081200Z - 091200Z ...Synopsis... The upper ridge across the Southwest into the Intermountain West is expected to shift slowly eastward on Thursday, as a deep upper trough approaches the Pacific Coast. Gradually increasing moisture in advance of the upper trough will continue to support at least isolated thunderstorm activity across portions of the Great Basin and interior Northwest. ...Central/northern NV into the interior Northwest... Thunderstorm coverage will likely increase compared to D1/Wednesday across central/northern NV into the interior Northwest on Thursday, as moisture gradually increases and the deep upper trough impinges on the region. Given the presence of potentially scattered thunderstorms overlapping regions of receptive fuels, lightning-related ignitions will again be possible, though there will also be greater potential for rainfall compared to D1/Wednesday. The greatest thunderstorm coverage is forecast to be over central/northern NV, but due to lingering uncertainty regarding convective evolution and potentially greater rainfall with any thunderstorm activity, the ISODRYT area is maintained in this outlook with no upgrade at this time. ..Dean.. 08/07/2019 ...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 0159 AM CDT Wed Aug 07 2019 Valid 081200Z - 091200Z ...Synopsis... The upper ridge across the Southwest into the Intermountain West is expected to shift slowly eastward on Thursday, as a deep upper trough approaches the Pacific Coast. Gradually increasing moisture in advance of the upper trough will continue to support at least isolated thunderstorm activity across portions of the Great Basin and interior Northwest. ...Central/northern NV into the interior Northwest... Thunderstorm coverage will likely increase compared to D1/Wednesday across central/northern NV into the interior Northwest on Thursday, as moisture gradually increases and the deep upper trough impinges on the region. Given the presence of potentially scattered thunderstorms overlapping regions of receptive fuels, lightning-related ignitions will again be possible, though there will also be greater potential for rainfall compared to D1/Wednesday. The greatest thunderstorm coverage is forecast to be over central/northern NV, but due to lingering uncertainty regarding convective evolution and potentially greater rainfall with any thunderstorm activity, the ISODRYT area is maintained in this outlook with no upgrade at this time. ..Dean.. 08/07/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more