Severe Storms

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 PM CDT Mon Aug 18 2025 Valid 190100Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING ACROSS PARTS OF NORTHERN KANSAS AND SOUTHERN NEBRASKA...AND PARTS OF SOUTH CENTRAL SOUTH DAKOTA... ...SUMMARY... A clustering of storms may continue to generate strong to severe wind gusts across parts of the central Great Plains through much of the evening. ...01Z Update... ...Central Great Plains... A low-level convergence zone has become a focus for thunderstorm development near/north of the I-70 corridor of western Kansas, with additional thunderstorm activity approaching the eastern Colorado state border vicinity, aided by a weak short wave impulse progressing around the northeastern periphery of a prominent mid-level high centered east of the Four Corners. This activity, and associated convective outflow, may continue to gradually consolidate into a further enlarging convective cluster, which could eventually generate a notable mesoscale convective vortex while propagating slowly eastward within otherwise light westerly deep-layer mean flow across the central Great Plains. A deeply mixed boundary-layer across the high plains has contributed to an environment conducive to downbursts and surface cold pool development. As the cold pools consolidate and spread into a much more moist boundary layer with large potential instability across south central Nebraska/central Kansas, it is possible that forcing for ascent may overcome increasing inhibition associated with boundary layer cooling, and maintain vigorous convective development into and through the overnight hours. ...Dakotas... Widely scattered strong boundary-layer based thunderstorm development is generally expected to wane over the next few hours, as mid-level inhibition increases with the loss of daytime heating. ..Kerr.. 08/19/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 PM CDT Mon Aug 18 2025 Valid 190100Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING ACROSS PARTS OF NORTHERN KANSAS AND SOUTHERN NEBRASKA...AND PARTS OF SOUTH CENTRAL SOUTH DAKOTA... ...SUMMARY... A clustering of storms may continue to generate strong to severe wind gusts across parts of the central Great Plains through much of the evening. ...01Z Update... ...Central Great Plains... A low-level convergence zone has become a focus for thunderstorm development near/north of the I-70 corridor of western Kansas, with additional thunderstorm activity approaching the eastern Colorado state border vicinity, aided by a weak short wave impulse progressing around the northeastern periphery of a prominent mid-level high centered east of the Four Corners. This activity, and associated convective outflow, may continue to gradually consolidate into a further enlarging convective cluster, which could eventually generate a notable mesoscale convective vortex while propagating slowly eastward within otherwise light westerly deep-layer mean flow across the central Great Plains. A deeply mixed boundary-layer across the high plains has contributed to an environment conducive to downbursts and surface cold pool development. As the cold pools consolidate and spread into a much more moist boundary layer with large potential instability across south central Nebraska/central Kansas, it is possible that forcing for ascent may overcome increasing inhibition associated with boundary layer cooling, and maintain vigorous convective development into and through the overnight hours. ...Dakotas... Widely scattered strong boundary-layer based thunderstorm development is generally expected to wane over the next few hours, as mid-level inhibition increases with the loss of daytime heating. ..Kerr.. 08/19/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 PM CDT Mon Aug 18 2025 Valid 190100Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING ACROSS PARTS OF NORTHERN KANSAS AND SOUTHERN NEBRASKA...AND PARTS OF SOUTH CENTRAL SOUTH DAKOTA... ...SUMMARY... A clustering of storms may continue to generate strong to severe wind gusts across parts of the central Great Plains through much of the evening. ...01Z Update... ...Central Great Plains... A low-level convergence zone has become a focus for thunderstorm development near/north of the I-70 corridor of western Kansas, with additional thunderstorm activity approaching the eastern Colorado state border vicinity, aided by a weak short wave impulse progressing around the northeastern periphery of a prominent mid-level high centered east of the Four Corners. This activity, and associated convective outflow, may continue to gradually consolidate into a further enlarging convective cluster, which could eventually generate a notable mesoscale convective vortex while propagating slowly eastward within otherwise light westerly deep-layer mean flow across the central Great Plains. A deeply mixed boundary-layer across the high plains has contributed to an environment conducive to downbursts and surface cold pool development. As the cold pools consolidate and spread into a much more moist boundary layer with large potential instability across south central Nebraska/central Kansas, it is possible that forcing for ascent may overcome increasing inhibition associated with boundary layer cooling, and maintain vigorous convective development into and through the overnight hours. ...Dakotas... Widely scattered strong boundary-layer based thunderstorm development is generally expected to wane over the next few hours, as mid-level inhibition increases with the loss of daytime heating. ..Kerr.. 08/19/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 PM CDT Mon Aug 18 2025 Valid 190100Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING ACROSS PARTS OF NORTHERN KANSAS AND SOUTHERN NEBRASKA...AND PARTS OF SOUTH CENTRAL SOUTH DAKOTA... ...SUMMARY... A clustering of storms may continue to generate strong to severe wind gusts across parts of the central Great Plains through much of the evening. ...01Z Update... ...Central Great Plains... A low-level convergence zone has become a focus for thunderstorm development near/north of the I-70 corridor of western Kansas, with additional thunderstorm activity approaching the eastern Colorado state border vicinity, aided by a weak short wave impulse progressing around the northeastern periphery of a prominent mid-level high centered east of the Four Corners. This activity, and associated convective outflow, may continue to gradually consolidate into a further enlarging convective cluster, which could eventually generate a notable mesoscale convective vortex while propagating slowly eastward within otherwise light westerly deep-layer mean flow across the central Great Plains. A deeply mixed boundary-layer across the high plains has contributed to an environment conducive to downbursts and surface cold pool development. As the cold pools consolidate and spread into a much more moist boundary layer with large potential instability across south central Nebraska/central Kansas, it is possible that forcing for ascent may overcome increasing inhibition associated with boundary layer cooling, and maintain vigorous convective development into and through the overnight hours. ...Dakotas... Widely scattered strong boundary-layer based thunderstorm development is generally expected to wane over the next few hours, as mid-level inhibition increases with the loss of daytime heating. ..Kerr.. 08/19/2025 Read more

WW 0600 Status Updates
STATUS REPORT ON WW 600 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. ..SPC..08/18/25 ATTN...WFO...UNR...ABR... STATUS REPORT FOR WS 600 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS SDC007-031-033-041-055-065-071-075-085-093-095-102-103-105-107- 117-119-137-182340- SD . SOUTH DAKOTA COUNTIES INCLUDED ARE BENNETT CORSON CUSTER DEWEY HAAKON HUGHES JACKSON JONES LYMAN MEADE MELLETTE OGLALA LAKOTA PENNINGTON PERKINS POTTER STANLEY SULLY ZIEBACH 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 0600 Status Updates
STATUS REPORT ON WW 600 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. ..SPC..08/18/25 ATTN...WFO...UNR...ABR... STATUS REPORT FOR WS 600 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS SDC007-031-033-041-055-065-071-075-085-093-095-102-103-105-107- 117-119-137-182340- SD . SOUTH DAKOTA COUNTIES INCLUDED ARE BENNETT CORSON CUSTER DEWEY HAAKON HUGHES JACKSON JONES LYMAN MEADE MELLETTE OGLALA LAKOTA PENNINGTON PERKINS POTTER STANLEY SULLY ZIEBACH 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 0600 Status Updates
STATUS REPORT ON WW 600 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. ..SPC..08/18/25 ATTN...WFO...UNR...ABR... STATUS REPORT FOR WS 600 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS SDC007-031-033-041-055-065-071-075-085-093-095-102-103-105-107- 117-119-137-182340- SD . SOUTH DAKOTA COUNTIES INCLUDED ARE BENNETT CORSON CUSTER DEWEY HAAKON HUGHES JACKSON JONES LYMAN MEADE MELLETTE OGLALA LAKOTA PENNINGTON PERKINS POTTER STANLEY SULLY ZIEBACH 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 600 SEVERE TSTM SD 182145Z - 190300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 600 NWS Storm Prediction Center Norman OK 345 PM MDT Mon Aug 18 2025 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Western into Central South Dakota * Effective this Monday afternoon and evening from 345 PM until 900 PM MDT. * Primary threats include... Scattered large hail and isolated very large hail events to 3 inches in diameter possible Isolated damaging wind gusts to 70 mph possible SUMMARY...Isolated supercells will likely continue to pose a risk for large to very large hail (1 to 3 inches in diameter) through the late afternoon and early evening. A cluster of thunderstorms may eventually evolve and gradually move east-southeast into central South Dakota this evening. The primary threats with the potential thunderstorm cluster will be large hail and severe gusts (60-70 mph). The severe thunderstorm watch area is approximately along and 85 statute miles north and south of a line from 35 miles north northwest of Rapid City SD to 30 miles east northeast of Pierre SD. 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. && OTHER WATCH INFORMATION...CONTINUE...WW 599... AVIATION...A few severe thunderstorms with hail surface and aloft to 3 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 450. Mean storm motion vector 29015. ...Smith Read more

WW 0601 Status Updates
STATUS REPORT ON WW 601 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. ..SPC..08/18/25 ATTN...WFO...GLD...BOU...LBF...CYS... STATUS REPORT FOR WS 601 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS COC017-063-075-095-115-121-125-182340- CO . COLORADO COUNTIES INCLUDED ARE CHEYENNE KIT CARSON LOGAN PHILLIPS SEDGWICK WASHINGTON YUMA KSC023-039-063-065-071-109-137-153-179-181-193-199-203-182340- KS . KANSAS COUNTIES INCLUDED ARE CHEYENNE DECATUR GOVE GRAHAM GREELEY LOGAN NORTON RAWLINS SHERIDAN SHERMAN THOMAS WALLACE WICHITA NEC029-033-049-057-087-145-182340- NE . NEBRASKA COUNTIES INCLUDED ARE Read more

MD 1989 CONCERNING SEVERE THUNDERSTORM WATCH 599... FOR PORTIONS OF NORTHERN ILLINOIS AND NORTHWEST INDIANA
Mesoscale Discussion 1989 NWS Storm Prediction Center Norman OK 0534 PM CDT Mon Aug 18 2025 Areas affected...portions of northern Illinois and northwest Indiana Concerning...Severe Thunderstorm Watch 599... Valid 182234Z - 190000Z The severe weather threat for Severe Thunderstorm Watch 599 continues. SUMMARY...Several clusters of thunderstorms will remain capable of strong to occasionally severe gusts this evening. Watch extension or replacement is being considered, but the longevity of the threat is uncertain. DISCUSSION...As of 2230 UTC, several clusters of thunderstorms were ongoing over northern IL in proximity to WW599. An additional linear cluster has recently intensified across far eastern IA. A very unstable but modestly sheared environment remains in place ahead of these storms over IL and northwest IN. This could support a continued threat for damaging gusts for a couple hours this evening. Vertical shear is weaker with southward extent (less than 25 kt) suggesting a more transient damaging wind risk as storms continue this evening. Still, some severe risk is possible. With expiration currently set for 2300 UTC, WW599 may need to be locally extended or replaced. ..Lyons/Smith.. 08/18/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...IWX...LOT...ILX...DVN... LAT...LON 40859089 41519035 41878886 41888755 41678688 41328679 40958706 40668762 40608845 40749056 40859089 MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH Read more

WW 0601 Status Updates
STATUS REPORT ON WW 601 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. ..SPC..08/18/25 ATTN...WFO...GLD...BOU...LBF...CYS... STATUS REPORT FOR WS 601 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS COC017-063-075-095-115-121-125-182340- CO . COLORADO COUNTIES INCLUDED ARE CHEYENNE KIT CARSON LOGAN PHILLIPS SEDGWICK WASHINGTON YUMA KSC023-039-063-065-071-109-137-153-179-181-193-199-203-182340- KS . KANSAS COUNTIES INCLUDED ARE CHEYENNE DECATUR GOVE GRAHAM GREELEY LOGAN NORTON RAWLINS SHERIDAN SHERMAN THOMAS WALLACE WICHITA NEC029-033-049-057-087-145-182340- NE . NEBRASKA COUNTIES INCLUDED ARE Read more

WW 601 SEVERE TSTM CO KS NE 182225Z - 190400Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 601 NWS Storm Prediction Center Norman OK 525 PM CDT Mon Aug 18 2025 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Eastern Colorado Northwest Kansas Southwest Nebraska * Effective this Monday afternoon and evening from 525 PM until 1100 PM CDT. * Primary threats include... Scattered damaging winds and isolated significant gusts to 75 mph possible Isolated large hail events to 1.5 inches in diameter possible SUMMARY...Clusters of thunderstorms will continue to develop and gradually move east across the Watch area through the evening. A couple of transient supercells may yield an isolated risk for large hail. Otherwise, scattered severe gusts associated with stronger thunderstorm cores and gusts on the leading edge of outflow will pose a risk for 60-75 mph winds. The severe thunderstorm watch area is approximately along and 80 statute miles east and west of a line from 55 miles northwest of Imperial NE to 60 miles south southeast of Goodland KS. 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. && OTHER WATCH INFORMATION...CONTINUE...WW 599...WW 600... AVIATION...A few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 65 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 27015. ...Smith Read more

WW 0600 Status Updates
STATUS REPORT ON WW 600 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. ..SPC..08/18/25 ATTN...WFO...UNR...ABR... STATUS REPORT FOR WS 600 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS SDC007-031-033-041-055-065-071-075-085-093-095-102-103-105-107- 117-119-137-182340- SD . SOUTH DAKOTA COUNTIES INCLUDED ARE BENNETT CORSON CUSTER DEWEY HAAKON HUGHES JACKSON JONES LYMAN MEADE MELLETTE OGLALA LAKOTA PENNINGTON PERKINS POTTER STANLEY SULLY ZIEBACH 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 600 SEVERE TSTM SD 182145Z - 190300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 600 NWS Storm Prediction Center Norman OK 345 PM MDT Mon Aug 18 2025 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Western into Central South Dakota * Effective this Monday afternoon and evening from 345 PM until 900 PM MDT. * Primary threats include... Scattered large hail and isolated very large hail events to 3 inches in diameter possible Isolated damaging wind gusts to 70 mph possible SUMMARY...Isolated supercells will likely continue to pose a risk for large to very large hail (1 to 3 inches in diameter) through the late afternoon and early evening. A cluster of thunderstorms may eventually evolve and gradually move east-southeast into central South Dakota this evening. The primary threats with the potential thunderstorm cluster will be large hail and severe gusts (60-70 mph). The severe thunderstorm watch area is approximately along and 85 statute miles north and south of a line from 35 miles north northwest of Rapid City SD to 30 miles east northeast of Pierre SD. 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. && OTHER WATCH INFORMATION...CONTINUE...WW 599... AVIATION...A few severe thunderstorms with hail surface and aloft to 3 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 450. Mean storm motion vector 29015. ...Smith Read more

WW 0599 Status Updates
STATUS REPORT ON WW 599 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 WSW RFD TO 10 SE JVL TO 25 E JVL TO 25 SSW RAC TO 25 SE MMO. ..LYONS..08/18/25 ATTN...WFO...LOT...DVN...MKX... STATUS REPORT FOR WS 599 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS ILC007-011-015-037-043-063-073-085-089-093-099-103-111-141-155- 177-195-201-182340- IL . ILLINOIS COUNTIES INCLUDED ARE BOONE BUREAU CARROLL DE KALB DUPAGE GRUNDY HENRY JO DAVIESS KANE KENDALL LA SALLE LEE MCHENRY OGLE PUTNAM STEPHENSON WHITESIDE WINNEBAGO 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 0599 Status Updates
STATUS REPORT ON WW 599 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 WSW RFD TO 10 SE JVL TO 25 E JVL TO 25 SSW RAC TO 25 SE MMO. ..LYONS..08/18/25 ATTN...WFO...LOT...DVN...MKX... STATUS REPORT FOR WS 599 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS ILC007-011-015-037-043-063-073-085-089-093-099-103-111-141-155- 177-195-201-182340- IL . ILLINOIS COUNTIES INCLUDED ARE BOONE BUREAU CARROLL DE KALB DUPAGE GRUNDY HENRY JO DAVIESS KANE KENDALL LA SALLE LEE MCHENRY OGLE PUTNAM STEPHENSON WHITESIDE WINNEBAGO 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 0599 Status Updates
STATUS REPORT ON WW 599 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 WSW RFD TO 10 SE JVL TO 25 E JVL TO 25 SSW RAC TO 25 SE MMO. ..LYONS..08/18/25 ATTN...WFO...LOT...DVN...MKX... STATUS REPORT FOR WS 599 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS ILC007-011-015-037-043-063-073-085-089-093-099-103-111-141-155- 177-195-201-182340- IL . ILLINOIS COUNTIES INCLUDED ARE BOONE BUREAU CARROLL DE KALB DUPAGE GRUNDY HENRY JO DAVIESS KANE KENDALL LA SALLE LEE MCHENRY OGLE PUTNAM STEPHENSON WHITESIDE WINNEBAGO 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 0599 Status Updates
STATUS REPORT ON WW 599 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 WSW RFD TO 10 SE JVL TO 25 E JVL TO 25 SSW RAC TO 25 SE MMO. ..LYONS..08/18/25 ATTN...WFO...LOT...DVN...MKX... STATUS REPORT FOR WS 599 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS ILC007-011-015-037-043-063-073-085-089-093-099-103-111-141-155- 177-195-201-182340- IL . ILLINOIS COUNTIES INCLUDED ARE BOONE BUREAU CARROLL DE KALB DUPAGE GRUNDY HENRY JO DAVIESS KANE KENDALL LA SALLE LEE MCHENRY OGLE PUTNAM STEPHENSON WHITESIDE WINNEBAGO 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 599 SEVERE TSTM IL WI LM 181710Z - 182300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 599 NWS Storm Prediction Center Norman OK 1210 PM CDT Mon Aug 18 2025 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Northern Illinois Southeast Wisconsin Lake Michigan * Effective this Monday afternoon and evening from 1210 PM until 600 PM CDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible A tornado or two possible SUMMARY...A line of thunderstorms is beginning to develop along an outflow boundary that extends from far south-central WI into west-central IL. The airmass ahead of this boundary is very moist and strongly unstable, supporting the potential for robust updrafts. Shear is modest, but outflow-dominant storm structures and water-loaded downdrafts suggest some strong to severe gusts will be possible throughout the afternoon. Backed low-level flow also supports a low-probability tornado risk. The severe thunderstorm watch area is approximately along and 50 statute miles east and west of a line from 30 miles north northwest of Milwaukee WI to 15 miles southwest of Marseilles IL. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU9). 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 24035. ...Mosier Read more

WW 599 SEVERE TSTM IL WI LM 181710Z - 182300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 599 NWS Storm Prediction Center Norman OK 1210 PM CDT Mon Aug 18 2025 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Northern Illinois Southeast Wisconsin Lake Michigan * Effective this Monday afternoon and evening from 1210 PM until 600 PM CDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible A tornado or two possible SUMMARY...A line of thunderstorms is beginning to develop along an outflow boundary that extends from far south-central WI into west-central IL. The airmass ahead of this boundary is very moist and strongly unstable, supporting the potential for robust updrafts. Shear is modest, but outflow-dominant storm structures and water-loaded downdrafts suggest some strong to severe gusts will be possible throughout the afternoon. Backed low-level flow also supports a low-probability tornado risk. The severe thunderstorm watch area is approximately along and 50 statute miles east and west of a line from 30 miles north northwest of Milwaukee WI to 15 miles southwest of Marseilles IL. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU9). 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 24035. ...Mosier Read more