Severe Storms

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1155 AM CDT Tue Aug 20 2019 Valid 201700Z - 211200Z ...NO CRITICAL AREAS... No changes. Previous discussion follows. ..Bentley.. 08/20/2019 .PREV DISCUSSION... /ISSUED 0136 AM CDT Tue Aug 20 2019/ ...Synopsis... An upper-level ridge will continue to amplify over the western CONUS into western Canada today as an upper-level shortwave trough approaches the Pacific Northwest. Subtropical moisture will begin to move northward into the Southwest and eastward into southwest Montana from the northern Plains. A surface cold front will push southward up against the eastern slopes of the northern/central Rockies with hot/dry/unstable conditions prevailing across much of the Intermountain West. Isolated dry thunderstorms may form across southwest Montana and northwest Wyoming this afternoon/evening. However, given the uncertainty regarding coverage and marginal fuel conditions where storms are currently forecast to develop, an isolated dry thunderstorm area was not included. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

WW 0602 Status Updates
STATUS REPORT ON WW 602 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 ENE CDJ TO 10 SSW UIN TO 15 ENE ALN TO 10 ESE CMI TO 35 ENE MMO. ..SMITH..08/20/19 ATTN...WFO...DVN...LSX...ILX...LOT...EAX... STATUS REPORT FOR WS 602 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS ILC005-013-019-023-025-027-029-033-035-041-045-049-051-061-075- 079-083-091-101-117-119-121-133-135-139-149-159-163-173-183-189- 197-201720- IL . ILLINOIS COUNTIES INCLUDED ARE BOND CALHOUN CHAMPAIGN CLARK CLAY CLINTON COLES CRAWFORD CUMBERLAND DOUGLAS EDGAR EFFINGHAM FAYETTE GREENE IROQUOIS JASPER JERSEY KANKAKEE LAWRENCE MACOUPIN MADISON MARION MONROE MONTGOMERY MOULTRIE PIKE RICHLAND ST. CLAIR SHELBY VERMILION WASHINGTON WILL INC007-073-111-201720- IN . INDIANA COUNTIES INCLUDED ARE Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1123 AM CDT Tue Aug 20 2019 Valid 201630Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON FOR PARTS OF IL/IN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE ENHANCED RISK ACROSS THE MIDDLE MS AND OH VALLEYS THIS AFTERNOON...NORTHERN VA AND VICINITY THIS AFTERNOON...AND PARTS OF THE CENTRAL PLAINS THIS EVENING INTO TONIGHT... ...SUMMARY... An ongoing thunderstorm cluster across Illinois will continue to pose a threat for damaging winds into this afternoon into Indiana. Damaging winds will be possible with a few storms this afternoon in the vicinity of northern Virginia. Large hail and damaging winds will be possible this evening into tonight across parts of the central Plains. ...Mid MS/OH Valley region through this afternoon... A well-developed MCS and associated MCV will continue to move east-southeastward across IL/IN through the afternoon. Convection will likely be maintained into the afternoon along the gust front as the cold pool encounters a warming boundary layer with dewpoints in the mid-upper 70s, resulting in MLCAPE in excess of 3000 J/kg with weakening convective inhibition. Vertical shear will weaken with southeastward extent aside from the MCV itself, which suggests that convective organization will be driven more by lift along the gust front by mid-late afternoon. Still, the established cold pool and potential for strong downdrafts will maintain a threat for damaging winds through the afternoon at least into IN/KY, and perhaps into OH late this afternoon. ...Northern VA and vicinity this afternoon... A small thunderstorm cluster and diffuse MCV will move eastward from the eastern WV Panhandle across northern VA/MD this afternoon. Surface heating in advance of this minor wave will contribute to moderate buoyancy (MLCAPE near 2000 J/kg), and some loose clustering of storms is expected this afternoon. Steep low-level lapse rates and DCAPE near 1000 J/kg will favor occasional downbursts with some potential for wind damage. ...Central Plains/High Plains this evening into tonight... The western extent of the outflow is effectively reinforcing a front across NE. Dry abiabatic midlevel lapse rates atop boundary-layer dewpoints in the 70s, with surface heating, will contribute to MLCAPE of 3000-4000 J/kg. Regional 12z soundings suggest that surface temperatures will need to warm to near 100-105 F to eliminate convective inhibition, thus storm formation this afternoon along the effective front is in question. The more probable scenarios are for storms to form this evening in the upslope regime near the WY/CO/NE border, and overnight across NE in the strengthening warm advection immediately north of the front. The evening upslope storms could be supercells initially as deep-layer vertical shear is augmented within the easterly low-level flow along and north of the front, and large hail would be the main concern. Some upscale growth into a cluster with damaging winds will be possible early tonight as a southerly low-level jet and warm advection strengthen. The warm advection could also support additional elevated storm development farther east across NE overnight, with an attendant threat for isolated large hail/damaging winds. ..Thompson/Coniglio.. 08/20/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1123 AM CDT Tue Aug 20 2019 Valid 201630Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON FOR PARTS OF IL/IN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE ENHANCED RISK ACROSS THE MIDDLE MS AND OH VALLEYS THIS AFTERNOON...NORTHERN VA AND VICINITY THIS AFTERNOON...AND PARTS OF THE CENTRAL PLAINS THIS EVENING INTO TONIGHT... ...SUMMARY... An ongoing thunderstorm cluster across Illinois will continue to pose a threat for damaging winds into this afternoon into Indiana. Damaging winds will be possible with a few storms this afternoon in the vicinity of northern Virginia. Large hail and damaging winds will be possible this evening into tonight across parts of the central Plains. ...Mid MS/OH Valley region through this afternoon... A well-developed MCS and associated MCV will continue to move east-southeastward across IL/IN through the afternoon. Convection will likely be maintained into the afternoon along the gust front as the cold pool encounters a warming boundary layer with dewpoints in the mid-upper 70s, resulting in MLCAPE in excess of 3000 J/kg with weakening convective inhibition. Vertical shear will weaken with southeastward extent aside from the MCV itself, which suggests that convective organization will be driven more by lift along the gust front by mid-late afternoon. Still, the established cold pool and potential for strong downdrafts will maintain a threat for damaging winds through the afternoon at least into IN/KY, and perhaps into OH late this afternoon. ...Northern VA and vicinity this afternoon... A small thunderstorm cluster and diffuse MCV will move eastward from the eastern WV Panhandle across northern VA/MD this afternoon. Surface heating in advance of this minor wave will contribute to moderate buoyancy (MLCAPE near 2000 J/kg), and some loose clustering of storms is expected this afternoon. Steep low-level lapse rates and DCAPE near 1000 J/kg will favor occasional downbursts with some potential for wind damage. ...Central Plains/High Plains this evening into tonight... The western extent of the outflow is effectively reinforcing a front across NE. Dry abiabatic midlevel lapse rates atop boundary-layer dewpoints in the 70s, with surface heating, will contribute to MLCAPE of 3000-4000 J/kg. Regional 12z soundings suggest that surface temperatures will need to warm to near 100-105 F to eliminate convective inhibition, thus storm formation this afternoon along the effective front is in question. The more probable scenarios are for storms to form this evening in the upslope regime near the WY/CO/NE border, and overnight across NE in the strengthening warm advection immediately north of the front. The evening upslope storms could be supercells initially as deep-layer vertical shear is augmented within the easterly low-level flow along and north of the front, and large hail would be the main concern. Some upscale growth into a cluster with damaging winds will be possible early tonight as a southerly low-level jet and warm advection strengthen. The warm advection could also support additional elevated storm development farther east across NE overnight, with an attendant threat for isolated large hail/damaging winds. ..Thompson/Coniglio.. 08/20/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1123 AM CDT Tue Aug 20 2019 Valid 201630Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON FOR PARTS OF IL/IN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE ENHANCED RISK ACROSS THE MIDDLE MS AND OH VALLEYS THIS AFTERNOON...NORTHERN VA AND VICINITY THIS AFTERNOON...AND PARTS OF THE CENTRAL PLAINS THIS EVENING INTO TONIGHT... ...SUMMARY... An ongoing thunderstorm cluster across Illinois will continue to pose a threat for damaging winds into this afternoon into Indiana. Damaging winds will be possible with a few storms this afternoon in the vicinity of northern Virginia. Large hail and damaging winds will be possible this evening into tonight across parts of the central Plains. ...Mid MS/OH Valley region through this afternoon... A well-developed MCS and associated MCV will continue to move east-southeastward across IL/IN through the afternoon. Convection will likely be maintained into the afternoon along the gust front as the cold pool encounters a warming boundary layer with dewpoints in the mid-upper 70s, resulting in MLCAPE in excess of 3000 J/kg with weakening convective inhibition. Vertical shear will weaken with southeastward extent aside from the MCV itself, which suggests that convective organization will be driven more by lift along the gust front by mid-late afternoon. Still, the established cold pool and potential for strong downdrafts will maintain a threat for damaging winds through the afternoon at least into IN/KY, and perhaps into OH late this afternoon. ...Northern VA and vicinity this afternoon... A small thunderstorm cluster and diffuse MCV will move eastward from the eastern WV Panhandle across northern VA/MD this afternoon. Surface heating in advance of this minor wave will contribute to moderate buoyancy (MLCAPE near 2000 J/kg), and some loose clustering of storms is expected this afternoon. Steep low-level lapse rates and DCAPE near 1000 J/kg will favor occasional downbursts with some potential for wind damage. ...Central Plains/High Plains this evening into tonight... The western extent of the outflow is effectively reinforcing a front across NE. Dry abiabatic midlevel lapse rates atop boundary-layer dewpoints in the 70s, with surface heating, will contribute to MLCAPE of 3000-4000 J/kg. Regional 12z soundings suggest that surface temperatures will need to warm to near 100-105 F to eliminate convective inhibition, thus storm formation this afternoon along the effective front is in question. The more probable scenarios are for storms to form this evening in the upslope regime near the WY/CO/NE border, and overnight across NE in the strengthening warm advection immediately north of the front. The evening upslope storms could be supercells initially as deep-layer vertical shear is augmented within the easterly low-level flow along and north of the front, and large hail would be the main concern. Some upscale growth into a cluster with damaging winds will be possible early tonight as a southerly low-level jet and warm advection strengthen. The warm advection could also support additional elevated storm development farther east across NE overnight, with an attendant threat for isolated large hail/damaging winds. ..Thompson/Coniglio.. 08/20/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1123 AM CDT Tue Aug 20 2019 Valid 201630Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON FOR PARTS OF IL/IN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE ENHANCED RISK ACROSS THE MIDDLE MS AND OH VALLEYS THIS AFTERNOON...NORTHERN VA AND VICINITY THIS AFTERNOON...AND PARTS OF THE CENTRAL PLAINS THIS EVENING INTO TONIGHT... ...SUMMARY... An ongoing thunderstorm cluster across Illinois will continue to pose a threat for damaging winds into this afternoon into Indiana. Damaging winds will be possible with a few storms this afternoon in the vicinity of northern Virginia. Large hail and damaging winds will be possible this evening into tonight across parts of the central Plains. ...Mid MS/OH Valley region through this afternoon... A well-developed MCS and associated MCV will continue to move east-southeastward across IL/IN through the afternoon. Convection will likely be maintained into the afternoon along the gust front as the cold pool encounters a warming boundary layer with dewpoints in the mid-upper 70s, resulting in MLCAPE in excess of 3000 J/kg with weakening convective inhibition. Vertical shear will weaken with southeastward extent aside from the MCV itself, which suggests that convective organization will be driven more by lift along the gust front by mid-late afternoon. Still, the established cold pool and potential for strong downdrafts will maintain a threat for damaging winds through the afternoon at least into IN/KY, and perhaps into OH late this afternoon. ...Northern VA and vicinity this afternoon... A small thunderstorm cluster and diffuse MCV will move eastward from the eastern WV Panhandle across northern VA/MD this afternoon. Surface heating in advance of this minor wave will contribute to moderate buoyancy (MLCAPE near 2000 J/kg), and some loose clustering of storms is expected this afternoon. Steep low-level lapse rates and DCAPE near 1000 J/kg will favor occasional downbursts with some potential for wind damage. ...Central Plains/High Plains this evening into tonight... The western extent of the outflow is effectively reinforcing a front across NE. Dry abiabatic midlevel lapse rates atop boundary-layer dewpoints in the 70s, with surface heating, will contribute to MLCAPE of 3000-4000 J/kg. Regional 12z soundings suggest that surface temperatures will need to warm to near 100-105 F to eliminate convective inhibition, thus storm formation this afternoon along the effective front is in question. The more probable scenarios are for storms to form this evening in the upslope regime near the WY/CO/NE border, and overnight across NE in the strengthening warm advection immediately north of the front. The evening upslope storms could be supercells initially as deep-layer vertical shear is augmented within the easterly low-level flow along and north of the front, and large hail would be the main concern. Some upscale growth into a cluster with damaging winds will be possible early tonight as a southerly low-level jet and warm advection strengthen. The warm advection could also support additional elevated storm development farther east across NE overnight, with an attendant threat for isolated large hail/damaging winds. ..Thompson/Coniglio.. 08/20/2019 Read more

WW 0602 Status Updates
STATUS REPORT ON WW 602 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 WNW IRK TO 15 SW SPI TO 15 NE BMI TO 30 NNW MMO. ..SMITH..08/20/19 ATTN...WFO...DVN...LSX...ILX...LOT...EAX... STATUS REPORT FOR WS 602 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS ILC001-005-013-019-021-027-029-035-037-039-041-045-049-051-053- 061-063-075-083-089-091-093-099-105-107-113-115-117-119-121-133- 135-137-139-147-149-163-167-171-173-183-189-197-201630- IL . ILLINOIS COUNTIES INCLUDED ARE ADAMS BOND CALHOUN CHAMPAIGN CHRISTIAN CLINTON COLES CUMBERLAND DE KALB DE WITT DOUGLAS EDGAR EFFINGHAM FAYETTE FORD GREENE GRUNDY IROQUOIS JERSEY KANE KANKAKEE KENDALL LA SALLE LIVINGSTON LOGAN MCLEAN MACON MACOUPIN MADISON MARION MONROE MONTGOMERY MORGAN MOULTRIE PIATT PIKE ST. CLAIR SANGAMON SCOTT SHELBY VERMILION WASHINGTON WILL MOC001-007-019-027-041-071-079-089-099-103-111-113-115-121-127- Read more

MD 1809 CONCERNING SEVERE THUNDERSTORM WATCH 602... FOR MUCH OF ILLINOIS...FAR WESTERN INDIANA...AND NORTHERN MISSOURI
Mesoscale Discussion 1809 NWS Storm Prediction Center Norman OK 0904 AM CDT Tue Aug 20 2019 Areas affected...Much of Illinois...far western Indiana...and northern Missouri Concerning...Severe Thunderstorm Watch 602... Valid 201404Z - 201530Z The severe weather threat for Severe Thunderstorm Watch 602 continues. SUMMARY...A risk of widespread damaging wind gusts continues across WW 602. DISCUSSION...Damaging wind gusts remain possible area-wide this morning along and ahead of a mature bow echo now located from near MLI to IRK. More isolated convection persists ahead of this complex near MTO and west of the WW near LWD. This complex has also accelerated east-southeastward (likely due to strengthening mid-level rotation and an attendant rear-inflow jet). With a continued motion of 300/45, the leading edge of the complex should begin to approach the eastern edge of WW 602 around 1630-1730Z or so. Shear profiles are generally weak ahead of the complex, though weak to moderate instability in the pre-convective airmass and enhanced organization associated with the MCV should maintain some risk of strong to severe wind gusts and isolated hail over at least the next couple of hours or so. The severe risk downstream of WW 602 (into Indiana and northern Kentucky) will be re-evaluated around 1600Z or so as storms approach, and a new WW will be considered around that time. ..Cook.. 08/20/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LMK...IWX...IND...PAH...LOT...ILX...LSX...DVN... DMX...EAX... LAT...LON 40639296 40689221 40859168 41379133 42069080 42249029 42068905 41858787 41538695 40968636 40318620 39138646 38328706 37978791 37758878 37938959 38269021 38759098 39339233 39649328 39989364 40339383 40519374 40599333 40639296 Read more

WW 0602 Status Updates
STATUS REPORT ON WW 602 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 35 SW OTM TO 30 SSW BRL TO 30 NE BRL TO 20 NW MLI TO 35 ESE DBQ. ..SMITH..08/20/19 ATTN...WFO...DVN...LSX...ILX...LOT...EAX... STATUS REPORT FOR WS 602 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS ILC001-005-009-011-013-015-017-019-021-027-029-035-037-039-041- 045-049-051-053-057-061-063-067-073-075-083-089-091-093-095-099- 103-105-107-109-113-115-117-119-121-123-125-129-131-133-135-137- 139-141-143-147-149-155-161-163-167-169-171-173-175-179-183-187- 189-195-197-203-201440- IL . ILLINOIS COUNTIES INCLUDED ARE ADAMS BOND BROWN BUREAU CALHOUN CARROLL CASS CHAMPAIGN CHRISTIAN CLINTON COLES CUMBERLAND DE KALB DE WITT DOUGLAS EDGAR EFFINGHAM FAYETTE FORD FULTON GREENE GRUNDY HANCOCK HENRY IROQUOIS JERSEY KANE KANKAKEE KENDALL KNOX LA SALLE LEE LIVINGSTON LOGAN MCDONOUGH MCLEAN MACON MACOUPIN MADISON MARION MARSHALL MASON MENARD MERCER MONROE MONTGOMERY MORGAN MOULTRIE Read more

WW 0602 Status Updates
STATUS REPORT ON WW 602 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 35 NNW IRK TO 15 W BRL TO 25 ESE CID TO 20 ESE DBQ. ..SMITH..08/20/19 ATTN...WFO...DVN...LSX...ILX...LOT...EAX... STATUS REPORT FOR WS 602 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS ILC001-005-009-011-013-015-017-019-021-027-029-035-037-039-041- 045-049-051-053-057-061-063-067-071-073-075-083-089-091-093-095- 099-103-105-107-109-113-115-117-119-121-123-125-129-131-133-135- 137-139-141-143-147-149-155-161-163-167-169-171-173-175-179-183- 187-189-195-197-203-201350- IL . ILLINOIS COUNTIES INCLUDED ARE ADAMS BOND BROWN BUREAU CALHOUN CARROLL CASS CHAMPAIGN CHRISTIAN CLINTON COLES CUMBERLAND DE KALB DE WITT DOUGLAS EDGAR EFFINGHAM FAYETTE FORD FULTON GREENE GRUNDY HANCOCK HENDERSON HENRY IROQUOIS JERSEY KANE KANKAKEE KENDALL KNOX LA SALLE LEE LIVINGSTON LOGAN MCDONOUGH MCLEAN MACON MACOUPIN MADISON MARION MARSHALL MASON MENARD MERCER MONROE MONTGOMERY MORGAN Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 AM CDT Tue Aug 20 2019 Valid 201300Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM EXTREME SOUTHEASTERN IOWA AND NORTHEASTERN MISSOURI TO WESTERN INDIANA AND SOUTHERN ILLINOIS... ...SUMMARY... The greatest severe-storm threat will be destructive winds from an ongoing complex of thunderstorms, which is forecast to continue southeastward at least across portions of Missouri, Illinois, and Indiana, as well as remaining parts of Iowa. ...Synopsis... In mid/upper levels, a belt of seasonally active northern-stream westerlies will continue across the northern 1/2-2/3 of the CONUS, while a high shifts/erodes westward from the southern Plains toward the southern Rockies. An elongated cyclone across northern portions of QC/ON/MB and adjoining parts of Hudson Bay will split, with the western portion digging southeastward across northern ON. The trailing strong shortwave trough will approach northern MN and Lake Superior late in the period. Meanwhile, a pre-existing shortwave perturbation over the western IA/southern MN region -- with reinforcing/convectively generated vorticity to its southeast -- will move southeastward to Indiana by 00Z then across the Ohio Valley into parts of the central Appalachians by 12Z. At the surface, 11Z analysis depicted a cold front offshore from most of New England, transitioning to a wavy/quasistationary front from northern MD across northern WV, southern OH, southern IN, becoming a warm front over central IL and a small part of southeastern IA prior to being overtaken by an ongoing MCS. The Ohio Valley States part of this front should move little before being overtaken by the MCS. Meanwhile, a separate cold front -- initially analyzed from northwestern MN and southeastern ND across southwestern SD and northeastern WY -- will move southward across much of the central Plains and Upper Midwest this period. By 12Z, the front should be positioned from Lake Michigan across northern MO, northern KS and east-central CO. ...Corn Belt...mid Mississippi Valley... An expansive, severe wind-producing MCS will continue to organize and offer damaging, possibly significant-severe wind across the mid Mississippi Valley and toward the lower Ohio Valley through the early-mid afternoon. Please refer to SPC watch 602 and related mesoscale discussions for the latest near-term guidance. With a favorably moist and diurnally destabilizing air mass projected downshear, within and south of the warm-frontal zone, the distance this MCS will travel before weakening is uncertain. It will depend to a great extent on internal cold-pool characteristics such as rear-inflow jet organization and lifting related to eventually decreasing depth of the density current along and shortly behind the gust front. In the meantime, continued lateral expansion of the cold pool and related forced ascent will encourage additional convective development along the margins of the MCS, especially in any bookend vortices, while the greatest severe-wind potential should continue to be in the bowing portion either side of its apex. Diabatic heating and rich low-level moisture, beneath favorable midlevel lapse rates, will help to boost preconvective MLCAPE to the 3000-4500 J/kg range ahead of the complex. ...Central Plains... Widely scattered thunderstorms are expected to develop late this afternoon onto evening, initially over higher terrain in the post-frontal moist/upslope-flow regime. This activity should proceed southeastward across parts of western/central NE this evening and tonight, offering large hail and severe gusts. Some of the hail may become especially destructive, exceeding two inches in diameter. Additional convection may form tonight ahead of the downshear progression of early storms, as well. Uncertainties exist regarding convective coverage, especially after about 03Z and over eastern parts of the outlook area; however, any sustained convection in this environment will be capable of an organized severe threat. Although some weaknesses will exist in the midlevel wind profiles, strong veering with height will contribute to favorable deep shear, with effective-shear magnitudes in the 35-45-kt range. This will favor supercell characteristics. An axis of strong buoyancy will set up across western through central/southeaster NE, with the width of the favorably unstable air mass increasing eastward. Rich low-level moisture -- with surface dew points commonly in the mid 60s to mid 70s F -- will underlie steep lapse rates in support of MLCAPE in the 3000-4500 J/kg range. ..Edwards/Marsh.. 08/20/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 AM CDT Tue Aug 20 2019 Valid 201300Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM EXTREME SOUTHEASTERN IOWA AND NORTHEASTERN MISSOURI TO WESTERN INDIANA AND SOUTHERN ILLINOIS... ...SUMMARY... The greatest severe-storm threat will be destructive winds from an ongoing complex of thunderstorms, which is forecast to continue southeastward at least across portions of Missouri, Illinois, and Indiana, as well as remaining parts of Iowa. ...Synopsis... In mid/upper levels, a belt of seasonally active northern-stream westerlies will continue across the northern 1/2-2/3 of the CONUS, while a high shifts/erodes westward from the southern Plains toward the southern Rockies. An elongated cyclone across northern portions of QC/ON/MB and adjoining parts of Hudson Bay will split, with the western portion digging southeastward across northern ON. The trailing strong shortwave trough will approach northern MN and Lake Superior late in the period. Meanwhile, a pre-existing shortwave perturbation over the western IA/southern MN region -- with reinforcing/convectively generated vorticity to its southeast -- will move southeastward to Indiana by 00Z then across the Ohio Valley into parts of the central Appalachians by 12Z. At the surface, 11Z analysis depicted a cold front offshore from most of New England, transitioning to a wavy/quasistationary front from northern MD across northern WV, southern OH, southern IN, becoming a warm front over central IL and a small part of southeastern IA prior to being overtaken by an ongoing MCS. The Ohio Valley States part of this front should move little before being overtaken by the MCS. Meanwhile, a separate cold front -- initially analyzed from northwestern MN and southeastern ND across southwestern SD and northeastern WY -- will move southward across much of the central Plains and Upper Midwest this period. By 12Z, the front should be positioned from Lake Michigan across northern MO, northern KS and east-central CO. ...Corn Belt...mid Mississippi Valley... An expansive, severe wind-producing MCS will continue to organize and offer damaging, possibly significant-severe wind across the mid Mississippi Valley and toward the lower Ohio Valley through the early-mid afternoon. Please refer to SPC watch 602 and related mesoscale discussions for the latest near-term guidance. With a favorably moist and diurnally destabilizing air mass projected downshear, within and south of the warm-frontal zone, the distance this MCS will travel before weakening is uncertain. It will depend to a great extent on internal cold-pool characteristics such as rear-inflow jet organization and lifting related to eventually decreasing depth of the density current along and shortly behind the gust front. In the meantime, continued lateral expansion of the cold pool and related forced ascent will encourage additional convective development along the margins of the MCS, especially in any bookend vortices, while the greatest severe-wind potential should continue to be in the bowing portion either side of its apex. Diabatic heating and rich low-level moisture, beneath favorable midlevel lapse rates, will help to boost preconvective MLCAPE to the 3000-4500 J/kg range ahead of the complex. ...Central Plains... Widely scattered thunderstorms are expected to develop late this afternoon onto evening, initially over higher terrain in the post-frontal moist/upslope-flow regime. This activity should proceed southeastward across parts of western/central NE this evening and tonight, offering large hail and severe gusts. Some of the hail may become especially destructive, exceeding two inches in diameter. Additional convection may form tonight ahead of the downshear progression of early storms, as well. Uncertainties exist regarding convective coverage, especially after about 03Z and over eastern parts of the outlook area; however, any sustained convection in this environment will be capable of an organized severe threat. Although some weaknesses will exist in the midlevel wind profiles, strong veering with height will contribute to favorable deep shear, with effective-shear magnitudes in the 35-45-kt range. This will favor supercell characteristics. An axis of strong buoyancy will set up across western through central/southeaster NE, with the width of the favorably unstable air mass increasing eastward. Rich low-level moisture -- with surface dew points commonly in the mid 60s to mid 70s F -- will underlie steep lapse rates in support of MLCAPE in the 3000-4500 J/kg range. ..Edwards/Marsh.. 08/20/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 AM CDT Tue Aug 20 2019 Valid 201300Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM EXTREME SOUTHEASTERN IOWA AND NORTHEASTERN MISSOURI TO WESTERN INDIANA AND SOUTHERN ILLINOIS... ...SUMMARY... The greatest severe-storm threat will be destructive winds from an ongoing complex of thunderstorms, which is forecast to continue southeastward at least across portions of Missouri, Illinois, and Indiana, as well as remaining parts of Iowa. ...Synopsis... In mid/upper levels, a belt of seasonally active northern-stream westerlies will continue across the northern 1/2-2/3 of the CONUS, while a high shifts/erodes westward from the southern Plains toward the southern Rockies. An elongated cyclone across northern portions of QC/ON/MB and adjoining parts of Hudson Bay will split, with the western portion digging southeastward across northern ON. The trailing strong shortwave trough will approach northern MN and Lake Superior late in the period. Meanwhile, a pre-existing shortwave perturbation over the western IA/southern MN region -- with reinforcing/convectively generated vorticity to its southeast -- will move southeastward to Indiana by 00Z then across the Ohio Valley into parts of the central Appalachians by 12Z. At the surface, 11Z analysis depicted a cold front offshore from most of New England, transitioning to a wavy/quasistationary front from northern MD across northern WV, southern OH, southern IN, becoming a warm front over central IL and a small part of southeastern IA prior to being overtaken by an ongoing MCS. The Ohio Valley States part of this front should move little before being overtaken by the MCS. Meanwhile, a separate cold front -- initially analyzed from northwestern MN and southeastern ND across southwestern SD and northeastern WY -- will move southward across much of the central Plains and Upper Midwest this period. By 12Z, the front should be positioned from Lake Michigan across northern MO, northern KS and east-central CO. ...Corn Belt...mid Mississippi Valley... An expansive, severe wind-producing MCS will continue to organize and offer damaging, possibly significant-severe wind across the mid Mississippi Valley and toward the lower Ohio Valley through the early-mid afternoon. Please refer to SPC watch 602 and related mesoscale discussions for the latest near-term guidance. With a favorably moist and diurnally destabilizing air mass projected downshear, within and south of the warm-frontal zone, the distance this MCS will travel before weakening is uncertain. It will depend to a great extent on internal cold-pool characteristics such as rear-inflow jet organization and lifting related to eventually decreasing depth of the density current along and shortly behind the gust front. In the meantime, continued lateral expansion of the cold pool and related forced ascent will encourage additional convective development along the margins of the MCS, especially in any bookend vortices, while the greatest severe-wind potential should continue to be in the bowing portion either side of its apex. Diabatic heating and rich low-level moisture, beneath favorable midlevel lapse rates, will help to boost preconvective MLCAPE to the 3000-4500 J/kg range ahead of the complex. ...Central Plains... Widely scattered thunderstorms are expected to develop late this afternoon onto evening, initially over higher terrain in the post-frontal moist/upslope-flow regime. This activity should proceed southeastward across parts of western/central NE this evening and tonight, offering large hail and severe gusts. Some of the hail may become especially destructive, exceeding two inches in diameter. Additional convection may form tonight ahead of the downshear progression of early storms, as well. Uncertainties exist regarding convective coverage, especially after about 03Z and over eastern parts of the outlook area; however, any sustained convection in this environment will be capable of an organized severe threat. Although some weaknesses will exist in the midlevel wind profiles, strong veering with height will contribute to favorable deep shear, with effective-shear magnitudes in the 35-45-kt range. This will favor supercell characteristics. An axis of strong buoyancy will set up across western through central/southeaster NE, with the width of the favorably unstable air mass increasing eastward. Rich low-level moisture -- with surface dew points commonly in the mid 60s to mid 70s F -- will underlie steep lapse rates in support of MLCAPE in the 3000-4500 J/kg range. ..Edwards/Marsh.. 08/20/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 AM CDT Tue Aug 20 2019 Valid 201300Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM EXTREME SOUTHEASTERN IOWA AND NORTHEASTERN MISSOURI TO WESTERN INDIANA AND SOUTHERN ILLINOIS... ...SUMMARY... The greatest severe-storm threat will be destructive winds from an ongoing complex of thunderstorms, which is forecast to continue southeastward at least across portions of Missouri, Illinois, and Indiana, as well as remaining parts of Iowa. ...Synopsis... In mid/upper levels, a belt of seasonally active northern-stream westerlies will continue across the northern 1/2-2/3 of the CONUS, while a high shifts/erodes westward from the southern Plains toward the southern Rockies. An elongated cyclone across northern portions of QC/ON/MB and adjoining parts of Hudson Bay will split, with the western portion digging southeastward across northern ON. The trailing strong shortwave trough will approach northern MN and Lake Superior late in the period. Meanwhile, a pre-existing shortwave perturbation over the western IA/southern MN region -- with reinforcing/convectively generated vorticity to its southeast -- will move southeastward to Indiana by 00Z then across the Ohio Valley into parts of the central Appalachians by 12Z. At the surface, 11Z analysis depicted a cold front offshore from most of New England, transitioning to a wavy/quasistationary front from northern MD across northern WV, southern OH, southern IN, becoming a warm front over central IL and a small part of southeastern IA prior to being overtaken by an ongoing MCS. The Ohio Valley States part of this front should move little before being overtaken by the MCS. Meanwhile, a separate cold front -- initially analyzed from northwestern MN and southeastern ND across southwestern SD and northeastern WY -- will move southward across much of the central Plains and Upper Midwest this period. By 12Z, the front should be positioned from Lake Michigan across northern MO, northern KS and east-central CO. ...Corn Belt...mid Mississippi Valley... An expansive, severe wind-producing MCS will continue to organize and offer damaging, possibly significant-severe wind across the mid Mississippi Valley and toward the lower Ohio Valley through the early-mid afternoon. Please refer to SPC watch 602 and related mesoscale discussions for the latest near-term guidance. With a favorably moist and diurnally destabilizing air mass projected downshear, within and south of the warm-frontal zone, the distance this MCS will travel before weakening is uncertain. It will depend to a great extent on internal cold-pool characteristics such as rear-inflow jet organization and lifting related to eventually decreasing depth of the density current along and shortly behind the gust front. In the meantime, continued lateral expansion of the cold pool and related forced ascent will encourage additional convective development along the margins of the MCS, especially in any bookend vortices, while the greatest severe-wind potential should continue to be in the bowing portion either side of its apex. Diabatic heating and rich low-level moisture, beneath favorable midlevel lapse rates, will help to boost preconvective MLCAPE to the 3000-4500 J/kg range ahead of the complex. ...Central Plains... Widely scattered thunderstorms are expected to develop late this afternoon onto evening, initially over higher terrain in the post-frontal moist/upslope-flow regime. This activity should proceed southeastward across parts of western/central NE this evening and tonight, offering large hail and severe gusts. Some of the hail may become especially destructive, exceeding two inches in diameter. Additional convection may form tonight ahead of the downshear progression of early storms, as well. Uncertainties exist regarding convective coverage, especially after about 03Z and over eastern parts of the outlook area; however, any sustained convection in this environment will be capable of an organized severe threat. Although some weaknesses will exist in the midlevel wind profiles, strong veering with height will contribute to favorable deep shear, with effective-shear magnitudes in the 35-45-kt range. This will favor supercell characteristics. An axis of strong buoyancy will set up across western through central/southeaster NE, with the width of the favorably unstable air mass increasing eastward. Rich low-level moisture -- with surface dew points commonly in the mid 60s to mid 70s F -- will underlie steep lapse rates in support of MLCAPE in the 3000-4500 J/kg range. ..Edwards/Marsh.. 08/20/2019 Read more

WW 0601 Status Updates
STATUS REPORT ON WW 601 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 35 NNE SDA TO 35 S FOD TO 30 E OTG AND 30 ENE SDA TO 20 W OXV TO 40 SW ALO. ..MARSH..08/20/19 ATTN...WFO...DMX...FSD...OAX... STATUS REPORT FOR WS 601 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS IAC007-039-051-053-099-117-123-125-135-157-159-171-173-175-179- 185-201240- IA . IOWA COUNTIES INCLUDED ARE APPANOOSE CLARKE DAVIS DECATUR JASPER LUCAS MAHASKA MARION MONROE POWESHIEK RINGGOLD TAMA TAYLOR UNION WAPELLO WAYNE 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 0601 Status Updates
STATUS REPORT ON WW 601 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 35 NNE SDA TO 35 S FOD TO 30 E OTG AND 30 ENE SDA TO 20 W OXV TO 40 SW ALO. ..MARSH..08/20/19 ATTN...WFO...DMX...FSD...OAX... STATUS REPORT FOR WS 601 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS IAC007-039-051-053-099-117-123-125-135-157-159-171-173-175-179- 185-201240- IA . IOWA COUNTIES INCLUDED ARE APPANOOSE CLARKE DAVIS DECATUR JASPER LUCAS MAHASKA MARION MONROE POWESHIEK RINGGOLD TAMA TAYLOR UNION WAPELLO WAYNE 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 0601 Status Updates
STATUS REPORT ON WW 601 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 35 NNE SDA TO 35 S FOD TO 30 E OTG AND 30 ENE SDA TO 20 W OXV TO 40 SW ALO. ..MARSH..08/20/19 ATTN...WFO...DMX...FSD...OAX... STATUS REPORT FOR WS 601 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS IAC007-039-051-053-099-117-123-125-135-157-159-171-173-175-179- 185-201240- IA . IOWA COUNTIES INCLUDED ARE APPANOOSE CLARKE DAVIS DECATUR JASPER LUCAS MAHASKA MARION MONROE POWESHIEK RINGGOLD TAMA TAYLOR UNION WAPELLO WAYNE 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 0601 Status Updates
STATUS REPORT ON WW 601 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 35 NNE SDA TO 35 S FOD TO 30 E OTG AND 30 ENE SDA TO 20 W OXV TO 40 SW ALO. ..MARSH..08/20/19 ATTN...WFO...DMX...FSD...OAX... STATUS REPORT FOR WS 601 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS IAC007-039-051-053-099-117-123-125-135-157-159-171-173-175-179- 185-201240- IA . IOWA COUNTIES INCLUDED ARE APPANOOSE CLARKE DAVIS DECATUR JASPER LUCAS MAHASKA MARION MONROE POWESHIEK RINGGOLD TAMA TAYLOR UNION WAPELLO WAYNE 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 601 SEVERE TSTM IA MN SD 200455Z - 201200Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 601 NWS Storm Prediction Center Norman OK 1155 PM CDT Mon Aug 19 2019 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Western and central Iowa Far southwest Minnesota Far southeast South Dakota * Effective this Monday night and Tuesday morning from 1155 PM until 700 AM CDT. * Primary threats include... Scattered damaging winds likely with isolated significant gusts to 75 mph possible Scattered large hail and isolated very large hail events to 2.5 inches in diameter possible SUMMARY...Multiple elevated supercells will likely develop through the early morning hours before growing upscale into a linear cluster that may eventually bow across central to south-central Iowa. The severe thunderstorm watch area is approximately along and 75 statute miles east and west of a line from 45 miles east of Lamoni IA to 15 miles west northwest of Worthington MN. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU1). 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 2.5 inches. Extreme turbulence and surface wind gusts to 65 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 33030. ...Grams Read more

WW 0602 Status Updates
STATUS FOR WATCH 0602 HAS NOT BEEN ISSUED YET Read more