Severe Storms

WW 0601 Status Updates
STATUS FOR WATCH 0601 HAS NOT BEEN ISSUED YET Read more

WW 0601 Status Updates
STATUS FOR WATCH 0601 HAS NOT BEEN ISSUED YET Read more

WW 0601 Status Updates
STATUS FOR WATCH 0601 HAS NOT BEEN ISSUED YET Read more

MD 1805 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF EASTERN ND INTO NORTHWESTERN MN
Mesoscale Discussion 1805 NWS Storm Prediction Center Norman OK 1122 PM CDT Mon Aug 19 2019 Areas affected...Portions of eastern ND into northwestern MN Concerning...Severe potential...Watch possible Valid 200422Z - 200615Z Probability of Watch Issuance...60 percent SUMMARY...An increasing threat for large hail and eventually damaging winds may require watch issuance in the next 1-2 hours. DISCUSSION...A pair of supercells has recently developed across north-central ND just to the east of a weak surface low. These storms are likely elevated at the moment owing to substantial convective inhibition, but they will pose an isolated large hail risk in the short term owing to moderate to strong elevated instability coupled with effective bulk shear around 50 kt. Additional storms are expected to develop along a southward-moving cold front in the vicinity of the international border in the next couple of hours. Upscale growth into a MCS appears probable, and a damaging wind threat may increase through the overnight. Watch issuance is possible in the next 1-2 hours depending on observational trends. ..Gleason/Grams.. 08/20/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...DLH...FGF...BIS... LAT...LON 47919969 48360008 48770002 49059929 49039565 48709425 47659421 47069433 46499491 46449610 46509681 46719798 47559828 47919969 Read more

No watches are valid as of Tue Aug 20 04:07:01 UTC 2019.

MD 1804 CONCERNING SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY FOR PORTIONS OF WESTERN/CENTRAL IA...FAR SOUTHEASTERN SD...FAR SOUTHWESTERN MN...AND FAR EASTERN NE
Mesoscale Discussion 1804 NWS Storm Prediction Center Norman OK 1105 PM CDT Mon Aug 19 2019 Areas affected...Portions of western/central IA...far southeastern SD...far southwestern MN...and far eastern NE Concerning...Severe potential...Severe Thunderstorm Watch likely Valid 200405Z - 200600Z Probability of Watch Issuance...80 percent SUMMARY...A threat for mainly large hail should increase over the next couple of hours as storms increase in coverage and intensity. Severe Thunderstorm Watch issuance is likely. DISCUSSION...A well-defined surface warm front extends eastward from a low over western SD across southern SD, roughly along the NE/IA border, and into southern IA. Warm air advection is occurring atop this front as a southwesterly low-level jet gradually strengthens late this evening. The VWP from KOAX has shown an increase in the 0-2 km layer over the past couple of hours, generally to around 30-35 kt above 1 km. Ascent associated with this low-level jet has encouraged elevated showers to develop across parts of northwestern IA, with a few recent lightning strikes noted with this activity. The 00Z sounding from OAX showed very steep mid-level lapse rates (around 8.6 C/km in the 700-500 mb layer) associated with an EML were present across this region. These lapse rates aloft coupled with ample low-level moisture are supporting moderate to very strong instability along and to the cool side of the front (MUCAPE of 2000-4500+) per latest mesoanalysis. Westerly winds strengthen with height through mid levels, and a subtle vorticity maximum along the NE/SD border maximum noted on water vapor may provide an additional source of lift to encourage at least scattered storm development. Around 40-50 kt of effective bulk shear will likely remain across this region through the overnight hours, which will support supercells initially. Given the large degree of elevated instability and strong shear present, robust updrafts appear likely. Large hail should be the primary hazard with initial storm development, with these storms likely remaining elevated above a near-surface stable layer to the cool side of the surface front. However, there is some potential for upscale growth into a MCS later tonight across parts of central IA, which could result in an eventual damaging wind threat materializing. Watch issuance is likely in the next couple of hours to address the initial large hail risk. ..Gleason/Grams.. 08/20/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MPX...DMX...FSD...OAX... LAT...LON 42999379 42499378 41829411 41399485 41359556 41539614 42029655 42799688 43569680 43709587 43659501 43559445 42999379 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0758 PM CDT Mon Aug 19 2019 Valid 200100Z - 201200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN IA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN MN... ...SUMMARY... Large hail and damaging gusts are expected late tonight across Iowa and northern Minnesota. ...01Z Update... ...Northern Plains into the Upper Midwest... A thunderstorm or two is still possible across ND and northeast SD as the front moves eastward tonight. Later tonight, increased storm coverage is anticipated along the front as it moves through northern MN. Moderate buoyancy and enhanced westerly flow aloft will result in an environment supportive of strong, organized updrafts. Potential for severe hail and strong wind gusts appears high enough to merit an increase in wind/hail probabilities and a Slight Risk. ...IA... Severe thunderstorms are still expected to develop late tonight amidst ample low-level moisture and a strong low-level jet. Large hail (isolated over 2" in diameter) will be the primary hazard with the initial development with the threat then shifting to strong wind gusts as upscale growth occurs. Primary change over this area was to pull the Slight Risk back farther west (to the MO River) to account for a greater potential for storms farther west. ..Mosier.. 08/20/2019 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0758 PM CDT Mon Aug 19 2019 Valid 200100Z - 201200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN IA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN MN... ...SUMMARY... Large hail and damaging gusts are expected late tonight across Iowa and northern Minnesota. ...01Z Update... ...Northern Plains into the Upper Midwest... A thunderstorm or two is still possible across ND and northeast SD as the front moves eastward tonight. Later tonight, increased storm coverage is anticipated along the front as it moves through northern MN. Moderate buoyancy and enhanced westerly flow aloft will result in an environment supportive of strong, organized updrafts. Potential for severe hail and strong wind gusts appears high enough to merit an increase in wind/hail probabilities and a Slight Risk. ...IA... Severe thunderstorms are still expected to develop late tonight amidst ample low-level moisture and a strong low-level jet. Large hail (isolated over 2" in diameter) will be the primary hazard with the initial development with the threat then shifting to strong wind gusts as upscale growth occurs. Primary change over this area was to pull the Slight Risk back farther west (to the MO River) to account for a greater potential for storms farther west. ..Mosier.. 08/20/2019 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0758 PM CDT Mon Aug 19 2019 Valid 200100Z - 201200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN IA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN MN... ...SUMMARY... Large hail and damaging gusts are expected late tonight across Iowa and northern Minnesota. ...01Z Update... ...Northern Plains into the Upper Midwest... A thunderstorm or two is still possible across ND and northeast SD as the front moves eastward tonight. Later tonight, increased storm coverage is anticipated along the front as it moves through northern MN. Moderate buoyancy and enhanced westerly flow aloft will result in an environment supportive of strong, organized updrafts. Potential for severe hail and strong wind gusts appears high enough to merit an increase in wind/hail probabilities and a Slight Risk. ...IA... Severe thunderstorms are still expected to develop late tonight amidst ample low-level moisture and a strong low-level jet. Large hail (isolated over 2" in diameter) will be the primary hazard with the initial development with the threat then shifting to strong wind gusts as upscale growth occurs. Primary change over this area was to pull the Slight Risk back farther west (to the MO River) to account for a greater potential for storms farther west. ..Mosier.. 08/20/2019 Read more

MD 1803 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF SOUTHERN ILLINOIS AND VICINITY
Mesoscale Discussion 1803 NWS Storm Prediction Center Norman OK 0707 PM CDT Mon Aug 19 2019 Areas affected...portions of southern Illinois and vicinity Concerning...Severe potential...Watch unlikely Valid 200007Z - 200130Z Probability of Watch Issuance...5 percent SUMMARY...Thunderstorms continue to develop across portions of southern Illinois and vicinity with large hail and damaging wind gusts possible. A watch is unlikely. DISCUSSION...A hot, moist, and unstable airmass is across the mid Mississippi Valley with surface temperatures in the 90s F and dewpoints 70+ F. MLCAPE of 3000-4500 J/kg has resulted and as convective temperatures have been breached, thunderstorms have developed this evening. While flow/shear are rather weak across the area, the large buoyancy will help compensate with marginally large hail possible. Water-loaded downdrafts coupled with steep low-level lapse rates may result in damaging wind gusts as well. Storms will likely weaken after sunset and given the lack of organization/shear, the severe threat should remain isolated and marginal. ..Nauslar/Grams.. 08/20/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...IND...PAH...ILX...LSX... LAT...LON 38479044 38919030 39408965 39628902 39748826 39638771 39358726 38748743 38228813 37898920 37778986 38219038 38479044 Read more

MD 1802 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF WESTERN/SOUTHERN ND INTO NORTHERN SD
Mesoscale Discussion 1802 NWS Storm Prediction Center Norman OK 0606 PM CDT Mon Aug 19 2019 Areas affected...Portions of western/southern ND into northern SD Concerning...Severe potential...Watch unlikely Valid 192306Z - 200100Z Probability of Watch Issuance...20 percent SUMMARY...An isolated large hail and wind threat should increase this evening. A watch will probably not be needed unless greater than expected storm coverage occurs. DISCUSSION...A surface trough is located across western ND at 23Z per observations. Weak low-level convergence along this boundary has fostered a gradually deepening cumulus field across this region, and convective initiation may occur over the next couple of hours (through 02Z). The lack of more obvious large-scale ascent suggests overall storm coverage will probably remain isolated. Low-level moisture return is occurring across the central into northern Plains early this evening, with upper 60s to lower 70s surface dewpoints extending as far north as the ND/SD border region as of 23Z. Modestly steepened mid-level lapse rates have overspread this region from the higher terrain of the northern Rockies/High Plains, which combined with the returning low-level moisture and strong diurnal heating is supporting weak to moderate instability along and just ahead of the surface trough. RAP forecast soundings across western ND show a veering wind profile through about 3 km, with generally westerly winds strengthening with height through the remainder of the troposphere. Resultant effective bulk shear of 45-50 kt will easily support supercells with an associated large hail threat. Some severe wind gusts may also occur where low-level lapse rates have become steepened. Current expectations are for a relatively greater severe threat to develop across southwestern ND initially, as somewhat greater low-level moisture and stronger instability should be present. There is some potential for a supercell or two to move east-southeastward through the evening along the ND/SD border along an instability gradient. Overall storm coverage is still somewhat uncertain, and a watch will probably not be issued unless at least a few supercells develop. ..Gleason/Grams.. 08/19/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ABR...BIS...UNR... LAT...LON 45890317 46860339 48290315 49060286 49020145 48030148 47100138 46520064 46010031 45590046 45280099 45310174 45520262 45890317 Read more

MD 1802 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF WESTERN/SOUTHERN ND INTO NORTHERN SD
Mesoscale Discussion 1802 NWS Storm Prediction Center Norman OK 0606 PM CDT Mon Aug 19 2019 Areas affected...Portions of western/southern ND into northern SD Concerning...Severe potential...Watch unlikely Valid 192306Z - 200100Z Probability of Watch Issuance...20 percent SUMMARY...An isolated large hail and wind threat should increase this evening. A watch will probably not be needed unless greater than expected storm coverage occurs. DISCUSSION...A surface trough is located across western ND at 23Z per observations. Weak low-level convergence along this boundary has fostered a gradually deepening cumulus field across this region, and convective initiation may occur over the next couple of hours (through 02Z). The lack of more obvious large-scale ascent suggests overall storm coverage will probably remain isolated. Low-level moisture return is occurring across the central into northern Plains early this evening, with upper 60s to lower 70s surface dewpoints extending as far north as the ND/SD border region as of 23Z. Modestly steepened mid-level lapse rates have overspread this region from the higher terrain of the northern Rockies/High Plains, which combined with the returning low-level moisture and strong diurnal heating is supporting weak to moderate instability along and just ahead of the surface trough. RAP forecast soundings across western ND show a veering wind profile through about 3 km, with generally westerly winds strengthening with height through the remainder of the troposphere. Resultant effective bulk shear of 45-50 kt will easily support supercells with an associated large hail threat. Some severe wind gusts may also occur where low-level lapse rates have become steepened. Current expectations are for a relatively greater severe threat to develop across southwestern ND initially, as somewhat greater low-level moisture and stronger instability should be present. There is some potential for a supercell or two to move east-southeastward through the evening along the ND/SD border along an instability gradient. Overall storm coverage is still somewhat uncertain, and a watch will probably not be issued unless at least a few supercells develop. ..Gleason/Grams.. 08/19/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ABR...BIS...UNR... LAT...LON 45890317 46860339 48290315 49060286 49020145 48030148 47100138 46520064 46010031 45590046 45280099 45310174 45520262 45890317 Read more

WW 0600 Status Updates
STATUS REPORT ON WW 600 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 NW GON TO 20 SSW ORH TO 25 NNW HYA. ..GLEASON..08/19/19 ATTN...WFO...BOX...GYX... STATUS REPORT FOR WS 600 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS CTC015-192340- CT . CONNECTICUT COUNTIES INCLUDED ARE WINDHAM MAC005-023-192340- MA . MASSACHUSETTS COUNTIES INCLUDED ARE BRISTOL PLYMOUTH RIC001-003-005-007-009-192340- RI . RHODE ISLAND COUNTIES INCLUDED ARE BRISTOL KENT NEWPORT PROVIDENCE WASHINGTON Read more

WW 600 SEVERE TSTM CT MA ME NH RI CW 191820Z - 200000Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 600 NWS Storm Prediction Center Norman OK 220 PM EDT Mon Aug 19 2019 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Northeastern Connecticut Much of Massachusetts Extreme southern Maine Southeastern New Hampshire Rhode Island Coastal Waters * Effective this Monday afternoon and evening from 220 PM until 800 PM EDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1 inch in diameter possible SUMMARY...Scattered thunderstorms will form and spread eastward through the afternoon in advance of a surface cold front. The storm environment ahead of the front will favor multicell clusters capable of producing damaging winds and marginally severe hail through the afternoon. The severe thunderstorm watch area is approximately along and 45 statute miles east and west of a line from 20 miles west northwest of Portland ME to 25 miles southeast of Windsor Locks CT. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU0). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 27025. ...Thompson Read more

MD 1801 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF THE CENTRAL AND SOUTHERN HIGH PLAINS
Mesoscale Discussion 1801 NWS Storm Prediction Center Norman OK 0437 PM CDT Mon Aug 19 2019 Areas affected...portions of the central and southern High Plains Concerning...Severe potential...Watch unlikely Valid 192137Z - 200000Z Probability of Watch Issuance...5 percent SUMMARY...Storms are developing across portions of the central and southern High Plains with isolated severe wind possible. A watch issuance is unlikely. DISCUSSION...A weak mid-level shortwave trough rotating around the upper high over the central/southern High Plains is evident in water vapor imagery. A slight steepening in mid-level lapse rates along with a surface pressure trough and strong insolation has helped initiate thunderstorms stretching from far western Kansas into the Texas Panhandle. A sharp instability gradient exists across the High Plains with MLCAPE increasing from 500 J/kg in far eastern Colorado to 2000-3000 J/kg in western Kansas and Oklahoma/Texas Panhandles. Additionally, a modest increase of 700-400 mb flow in northwest/western Kansas has increased effective bulk shear to 30-35 knots. A mixed storm mode of discrete, weaker supercells to multicellular clusters is expected into the evening. Given higher LCLs and steep low-level lapse rates, damaging winds gusts are the main severe threat, although marginally severe hail cannot be ruled out even with the warmer temperatures through the profile. Convection could continue past sunset as the low-level jet does increase with some upscale organization possible. However, the overall severe threat should remain marginal and isolated. ..Nauslar/Grams.. 08/19/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...OUN...GID...LBF...DDC...GLD...AMA...PUB... LAT...LON 34900223 35540256 37320244 39700271 40310235 40560146 40410028 39819993 37969985 37459982 36799982 36139990 35749996 35340013 35060041 34830104 34900223 Read more

WW 0600 Status Updates
STATUS REPORT ON WW 600 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 S BDL TO 30 NNE ORH TO 30 SE PSM. ..GLEASON..08/19/19 ATTN...WFO...BOX...GYX... STATUS REPORT FOR WS 600 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS CTC013-015-192240- CT . CONNECTICUT COUNTIES INCLUDED ARE TOLLAND WINDHAM MAC005-009-017-021-023-025-027-192240- MA . MASSACHUSETTS COUNTIES INCLUDED ARE BRISTOL ESSEX MIDDLESEX NORFOLK PLYMOUTH SUFFOLK WORCESTER RIC001-003-005-007-009-192240- RI . RHODE ISLAND COUNTIES INCLUDED ARE BRISTOL KENT NEWPORT PROVIDENCE WASHINGTON Read more

WW 0600 Status Updates
STATUS REPORT ON WW 600 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 20 SSE BDL TO 25 ESE EEN TO 20 WNW PWM. ..SMITH..08/19/19 ATTN...WFO...BOX...GYX... STATUS REPORT FOR WS 600 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS CTC013-015-192140- CT . CONNECTICUT COUNTIES INCLUDED ARE TOLLAND WINDHAM MEC005-023-031-192140- ME . MAINE COUNTIES INCLUDED ARE CUMBERLAND SAGADAHOC YORK MAC005-009-017-021-023-025-027-192140- MA . MASSACHUSETTS COUNTIES INCLUDED ARE BRISTOL ESSEX MIDDLESEX NORFOLK PLYMOUTH SUFFOLK WORCESTER Read more

No Mesoscale Discussions are in effect as of Mon Aug 19 20:54:05 UTC 2019.

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0243 PM CDT Mon Aug 19 2019 Valid 192000Z - 201200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE TONIGHT ACROSS PARTS OF SOUTHERN IOWA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON AND EARLY EVENING ACROSS PARTS OF NEW JERSEY INTO SOUTHERN PORTIONS OF NEW ENGLAND... ...SUMMARY... A few damaging gusts will be possible from the Mid-Atlantic into New England this afternoon, while large hail and damaging gusts are expected late tonight across Iowa. ...20Z Outlook Update... Some adjustments have been made to categorical and probabilistic lines to account for ongoing trends, and the latest observational data and model output. A "marginal" risk for severe weather has been extended southward near the eastern and southern slopes of the southern Appalachians, mainly to include low probabilities for severe wind gusts. Strong heating has contributed to rather steep low-level lapse rates along this corridor, where convective inhibition is also relatively weak beneath weak mid/upper troughing. This has allowed for the development of numerous thunderstorms which may continue to pose a risk for potentially damaging wind gusts, associated with localized downbursts and perhaps some upscale growing, convectively generated cold pools through 22-00Z. Otherwise, the plume of very warm elevated mixed-layer air overspreading much of the Plains and mid Missouri Valley region may substantially inhibit convective development into and perhaps through the 20/03-06Z time frame. Thereafter, it appears that thunderstorm development may become focused in two general areas. One of these may be ahead of another cold frontal surge into the North Dakota/Minnesota international border area by late tonight. A more prominent thunderstorm cluster may initiate in response to lower/mid tropospheric warm advection, near/east of the mid Missouri Valley, near the northeastern periphery of the more strongly capping elevated mixed layer air. ..Kerr.. 08/19/2019 .PREV DISCUSSION... /ISSUED 1130 AM CDT Mon Aug 19 2019/ ...IA late tonight... Low-level warm advection and moistening will focus across IA overnight, on the nose of a 30-35 kt southwesterly low-level jet. The richer moisture observed this morning at TOP and LBF will spread northeastward beneath a warm elevated mixed layer which will act to cap the boundary layer through the day. After 06z, ascent and moistening with the warm advection should be sufficient for elevated thunderstorm development across IA, and storms will subsequently spread southeastward and likely evolve into an MCS. Large hail will be the initial threat with elevated supercells. As storms coalesce into an MCS, there will be increasing potential for damaging surface winds to reach the ground, given large buoyancy (MUCAPE at or above 3000 J/kg), steep midlevel lapse rates, and DCAPE at or above 1000 J/kg. ...New England to the Mid-Atlantic this afternoon/evening... A midlevel shortwave trough will move eastward over PA/NY and New England this afternoon/evening, with an accompanying surface cold front. East of a band of thicker clouds near the front, surface heating and boundary-layer dewpoints ranging from the upper 60s in southern NH to the mid 70s in NJ will contribute to afternoon MLCAPE ranging from 1500 J/kg north to 3000 J/kg south. Midlevel west-southwesterly flow of 25-30 kt and the moderate to strong buoyancy will favor primarily multicell clusters capable of producing occasional wind damage with 45-60 mph outflow gusts. More persistent clouds across Maine will slow surface heating/destabilization, though deep-layer vertical shear will be a little stronger with northward extent compared to southern New England. Farther south, a weak lee trough will persist through the afternoon across the Piedmont, with a warm/moist air mass to its east. Strong surface heating will boost MLCAPE into the 2000-3000 J/kg range east of the surface trough, where DCAPE near 1000 J/kg will favor isolated strong/damaging winds with multicell storms in a weak vertical shear environment. ...Northern Plains through tonight... Low-level moisture is returning northward from the central Plains to the Dakotas, east of a diffuse lee trough. Surface heating/mixing could be sufficient for isolated high-based storms across western ND this evening, but overall storm coverage is expected to remain sparse in response to weak forcing for ascent and a lingering cap. Storm development will be more probable tonight near the international border along a cold front as an embedded speed max moves across southern SK/MB. This convection should be elevated, posing a threat for isolated large hail and a few strong gusts could reach the ground. ...Central High Plains this afternoon/evening... Deep mixing with strong surface heating could support isolated, high-based thunderstorm development this afternoon along the surface lee trough in the vicinity of the KS/CO border. Inverted-v profiles will favor gusty outflow winds with any sustained storms or small clusters for a few hours late this afternoon/evening. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0243 PM CDT Mon Aug 19 2019 Valid 192000Z - 201200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE TONIGHT ACROSS PARTS OF SOUTHERN IOWA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON AND EARLY EVENING ACROSS PARTS OF NEW JERSEY INTO SOUTHERN PORTIONS OF NEW ENGLAND... ...SUMMARY... A few damaging gusts will be possible from the Mid-Atlantic into New England this afternoon, while large hail and damaging gusts are expected late tonight across Iowa. ...20Z Outlook Update... Some adjustments have been made to categorical and probabilistic lines to account for ongoing trends, and the latest observational data and model output. A "marginal" risk for severe weather has been extended southward near the eastern and southern slopes of the southern Appalachians, mainly to include low probabilities for severe wind gusts. Strong heating has contributed to rather steep low-level lapse rates along this corridor, where convective inhibition is also relatively weak beneath weak mid/upper troughing. This has allowed for the development of numerous thunderstorms which may continue to pose a risk for potentially damaging wind gusts, associated with localized downbursts and perhaps some upscale growing, convectively generated cold pools through 22-00Z. Otherwise, the plume of very warm elevated mixed-layer air overspreading much of the Plains and mid Missouri Valley region may substantially inhibit convective development into and perhaps through the 20/03-06Z time frame. Thereafter, it appears that thunderstorm development may become focused in two general areas. One of these may be ahead of another cold frontal surge into the North Dakota/Minnesota international border area by late tonight. A more prominent thunderstorm cluster may initiate in response to lower/mid tropospheric warm advection, near/east of the mid Missouri Valley, near the northeastern periphery of the more strongly capping elevated mixed layer air. ..Kerr.. 08/19/2019 .PREV DISCUSSION... /ISSUED 1130 AM CDT Mon Aug 19 2019/ ...IA late tonight... Low-level warm advection and moistening will focus across IA overnight, on the nose of a 30-35 kt southwesterly low-level jet. The richer moisture observed this morning at TOP and LBF will spread northeastward beneath a warm elevated mixed layer which will act to cap the boundary layer through the day. After 06z, ascent and moistening with the warm advection should be sufficient for elevated thunderstorm development across IA, and storms will subsequently spread southeastward and likely evolve into an MCS. Large hail will be the initial threat with elevated supercells. As storms coalesce into an MCS, there will be increasing potential for damaging surface winds to reach the ground, given large buoyancy (MUCAPE at or above 3000 J/kg), steep midlevel lapse rates, and DCAPE at or above 1000 J/kg. ...New England to the Mid-Atlantic this afternoon/evening... A midlevel shortwave trough will move eastward over PA/NY and New England this afternoon/evening, with an accompanying surface cold front. East of a band of thicker clouds near the front, surface heating and boundary-layer dewpoints ranging from the upper 60s in southern NH to the mid 70s in NJ will contribute to afternoon MLCAPE ranging from 1500 J/kg north to 3000 J/kg south. Midlevel west-southwesterly flow of 25-30 kt and the moderate to strong buoyancy will favor primarily multicell clusters capable of producing occasional wind damage with 45-60 mph outflow gusts. More persistent clouds across Maine will slow surface heating/destabilization, though deep-layer vertical shear will be a little stronger with northward extent compared to southern New England. Farther south, a weak lee trough will persist through the afternoon across the Piedmont, with a warm/moist air mass to its east. Strong surface heating will boost MLCAPE into the 2000-3000 J/kg range east of the surface trough, where DCAPE near 1000 J/kg will favor isolated strong/damaging winds with multicell storms in a weak vertical shear environment. ...Northern Plains through tonight... Low-level moisture is returning northward from the central Plains to the Dakotas, east of a diffuse lee trough. Surface heating/mixing could be sufficient for isolated high-based storms across western ND this evening, but overall storm coverage is expected to remain sparse in response to weak forcing for ascent and a lingering cap. Storm development will be more probable tonight near the international border along a cold front as an embedded speed max moves across southern SK/MB. This convection should be elevated, posing a threat for isolated large hail and a few strong gusts could reach the ground. ...Central High Plains this afternoon/evening... Deep mixing with strong surface heating could support isolated, high-based thunderstorm development this afternoon along the surface lee trough in the vicinity of the KS/CO border. Inverted-v profiles will favor gusty outflow winds with any sustained storms or small clusters for a few hours late this afternoon/evening. Read more