848
FXUS63 KMKX 200321
AFDMKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1021 PM CDT SAT JUL 19 2025
KEY MESSAGES
- LOOKING MOSTLY QUIET SUNDAY THROUGH MONDAY. ONLY A 5-20%
CHANCE FOR SHOWERS AND WEAK THUNDERSTORMS IN ILLINOIS TO DRIFT
1 COUNTY INTO WISCONSIN (LATE OVERNIGHT / EARLY SUNDAY
MORNING, AND AGAIN SUNDAY AFTERNOON). OTHERWISE, DRY WEATHER.
- CHANCES FOR STORMS DEVELOP TUESDAY NIGHT, AND AGAIN WEDNESDAY
NIGHT INTO THURSDAY. EXACT TIMING AND INTENSITY REMAINS IN
QUESTION, WITH THE MOST CONFIDENCE IN THURSDAY SEEING
WIDESPREAD CONVECTION.
- HEAT BUILDS BACK INTO THE REGION, WITH HIGHS IN THE UPPER 80S
TO LOWER 90S TUESDAY INTO THE WEEKEND. HEAT INDEX VALUES ARE
LIKELY TO RISE AS HIGH AS 100 DEGREES AND MAY RISE AS HIGH AS
105 DEGREES ON WEDNESDAY.
UPDATE
ISSUED 1020 PM CDT SAT JUL 19 2025
WHAT'S LEFT OF THE SHOWER ACTIVITY OVER EAST-CENTRAL WI HAS
MOVED OVER LAKE MICHIGAN AT THIS TIME, AND THE CLUSTER OF
REMAINING SHOWERS WEST OF GREEN BAY (FORCED BY A WEAK 700MB
THERMAL TROUGH / RIDGE AND WEAK SURFACE CONFLUENCE) WILL SOON BE
UNDERCUT BY THE MUCAPE GRADIENT, DISSIPATING AS NORTHEAST WINDS
AND STABLE AIR ARRIVE BEHIND THE APPROACHING NW TO SE ORIENTED
COLD FRONT. THIS SHOULD LEAVE THE REMAINDER OF THE OVERNIGHT
PERIOD DRY.
CAMS RESOLVE A FEW ROUNDS OF SHOWERS AND WEAK THUNDERSTORMS TO
OUR SOUTH (IOWA / ILLINOIS) OVER THE NEXT 48 HOURS, BUT WITH THE
AFOREMENTIONED FRONTAL BOUNDARY STALLING JUST SOUTH OF US, WE'RE
SEEING ONLY VERY LOW (5-20%) CHANCES FOR SAID SHOWERS / STORMS
TO BUILD INTO THE FARTHEST-SOUTH COUNTIES IN WISCONSIN OVER SAID
PERIOD. PLEASANT WEATHER EXPECTED, WITH A LIGHT EAST TO
NORTHEAST BREEZE.
SHEPPARD
SHORT TERM
ISSUED 253 PM CDT SAT JUL 19 2025
TONIGHT THROUGH SUNDAY NIGHT:
THUNDERSTORM INTENSITY FORECASTS CONTINUE TO TREND DOWNWARD FOR
THIS AFTERNOON AND EVENING'S COLD FRONT. ALTHOUGH THE
ATMOSPHERE HAS BEEN ABLE TO RECOVER SOMEWHAT IN SOUTHWESTERN TO
CENTRAL WISCONSIN, THE FRONT REMAINS QUITE DIFFUSE AND IS
STRUGGLING TO PRODUCE WIDESPREAD CONVECTION. CAMS REMAIN LESS
THAN ENTHUSIASTIC ABOUT THE PRESENCE OF WIDESPREAD CONVECTION AS
WELL, LENDING CONFIDENCE TO THE FORECAST OF GENERAL
THUNDERSTORMS WITH GUSTS AROUND 30 MPH AND SOME SMALL HAIL.
MLCAPE OUTPUT ON CAMS IS AROUND 2000 J/KG FOR THE AFTERNOON, BUT
A VERY DRY LAYER ALOFT WILL LIKELY KEEP STORMS FROM REALIZING
THE FULL POTENTIAL OF THIS INSTABILITY. EXPECTING ISOLATED TO
WIDELY SCATTERED STORMS TO PROGRESS SOUTHEASTWARD THROUGH THE
REGION LATE THIS AFTERNOON INTO THIS EVENING (25-35 PERCENT
CHANCE). STORMS WILL SLOWLY EXIT TO THE SOUTHEAST WHILE
DECAYING LATE THIS EVENING, WITH DRY CONDITIONS THEN EXPECTED
ACROSS THE MAJORITY OF THE AREA.
LATE TONIGHT, AN MCS WILL TRAVERSE CENTRAL IOWA INTO NORTHERN
ILLINOIS, AGAIN DEVELOPING ALONG THE NOSE OF THE 850 MB LLJ.
THE FAR NORTHERN EDGE OF PRECIPITATION FROM THIS SYSTEM MAY
NUDGE INTO FAR SOUTHERN WISCONSIN, BUT MESO MODELS CONTINUE TO
TREND FARTHER SOUTH. STILL, A FEW STORMS MAY CROSS THE BORDER
(15-25 PERCENT CHANCE) AND BEAR WATCHING FOR LIGHTNING.
ASIDE FROM LINGERING CONVECTION IN FAR SOUTHERN WISCONSIN IN THE
MORNING, DRY WEATHER IS EXPECTED SUNDAY WITH HIGHS IN THE UPPER
70S TO NEAR 80 DEGREES. GUSTY NORTHEASTERLY WINDS MAY CREATE A
MODERATE SWIM RISK FROM MILWAUKEE SOUTHWARD AT LAKE MICHIGAN
BEACHES DURING THE MORNING HOURS. BREAKING WAVES AND CURRENTS
ARE EXPECTED. STAY AWAY FROM DANGEROUS AREAS LIKE PIERS,
BREAKWALLS, AND RIVER OUTLETS.
SUNDAY NIGHT, THE LLJ DEVELOPS ONCE AGAIN ACROSS SOUTHEASTERN
IOWA TO NORTHERN ILLINOIS, WITH YET ANOTHER CHANCE (15-25
PERCENT) FOR A FEW STORMS TO CROSS THE ILLINOIS BORDER INTO FAR
SOUTHERN WISCONSIN, BUT AS THE LLJ CONTINUES TO SLOWLY SAG
SOUTHEASTWARD THESE CHANCES DIMINISH.
MH
LONG TERM
ISSUED 253 PM CDT SAT JUL 19 2025
MONDAY THROUGH SATURDAY:
DRY CONDITIONS ARE EXPECTED THROUGHOUT MONDAY AND MONDAY NIGHT
UNDERNEATH HIGH PRESSURE. WINDS SHIFT SOUTHEASTERLY INTO TUESDAY
AND LOW PRESSURE DEVELOPS IN THE LEE OF THE COLORADO ROCKIES AND
BUILDS RIDGING/WAA ACROSS THE SOUTHEASTERN U.S. AND MISSISSIPPI
VALLEY. RIDGE-RIDING SHORTWAVES BEGIN TO TRAVERSE THE UPPER
MIDWEST TUESDAY NIGHT, WITH SEVERAL 500 MB IMPULSES THROUGH
THURSDAY FROM A SEMI-STATIONARY 500 MB LOW IN THE LEE OF THE
NORTHERN CANADIAN ROCKIES. THE MAJORITY OF THESE IMPULSES WILL
PRIMARILY PROGRESS ACROSS NORTHERN TO CENTRAL WISCONSIN (TUESDAY
NIGHT, WEDNESDAY EVENING/NIGHT), BUT STILL MAY PRODUCE
SCATTERED STORMS ACROSS SOUTHERN WISCONSIN (15-30 PERCENT
CHANCE).
WITH CONTINUED WAA AND A BUILDING UPPER LEVEL RIDGE, EXPECTING
TEMPERATURES TO RISE INTO THE UPPER 80S AND LOWER 90S TUESDAY
THROUGH THE END OF THE WEEK. MODELS CONTINUE TO SUPPORT HIGH
HEAT AND HUMIDITY, WITH WEDNESDAY SEEING THE MOST INTENSE
RIDGING. HEAT INDEX VALUES ARE EXPECTED TO RISE ABOVE 100
DEGREES ON WEDNESDAY, AND MAY RISE ABOVE 105 DEGREES. ALTHOUGH
RIDGING BEGINS TO BREAK DOWN ON THURSDAY, STILL EXPECTING HEAT
AND HUMIDITY TO CONTINUE.
RIDGING BEGINS TO BREAK DOWN ON THURSDAY AS THE 500 MB LOW
PROGRESSES EASTWARD THROUGH NORTHERN CANADA, ALLOWING FOR
ENHANCED MCS ACTIVITY SHIFTING SOUTHWARD INTO SOUTHERN
WISCONSIN. ALTHOUGH IT IS TOO EARLY TO TELL SPECIFIC TIMING OR
INTENSITY, THURSDAY AFTERNOON INTO THURSDAY NIGHT SEES THE MOST
LIKELY CHANCES FOR WIDESPREAD THUNDERSTORMS (~40 PERCENT BASED
ON ENSEMBLES, BUT TRENDING UPWARDS). SOUTHERN WISCONSIN REMAINS
ON THE NORTHERN EDGE OF RIDGING THROUGH THE WEEKEND, WITH
PRECIPITATION CHANCES (20-30 PERCENT) LINGERING DUE TO TIMING
DIFFERENCES IN SHORTWAVES FROM MODEL TO MODEL.
MH
AVIATION
ISSUED 1020 PM CDT SAT JUL 19 2025
AN WEAK COLD FRONT (NW TO SE ORIENTED) IS GRADUALLY SAGGING
SOUTH ACROSS THE REGION AT THE MOMENT. MOSTLY DRY WEATHER
EXPECTED OVERNIGHT AS IT PASSES, WITH ONLY A FEW ISOLATED
SHOWERS CURRENTLY EVIDENT ON RADAR TRACKING SOUTHWARD, PASSING
WEST OF LAKE WINNEBAGO (EXPECTING THESE TO DIE OFF IN AN HOUR OR
TWO). LIGHT NORTHEAST WINDS BEHIND THE FRONT WILL CARRY IN MUCH
LOWER (IFR / LIFR) CLOUD CEILINGS LATE TONIGHT (SHEBOYGAN HAS
ALREADY FALLEN TO 600 FT IFR CEILINGS FOR REFERENCE).
LOW CEILINGS WILL GRADUALLY LIFT AND SCATTER THROUGHOUT THE
DAYTIME HOURS OF SUNDAY, RESTORING VFR TO MOST AREAS BY AROUND
NOON. A LIGHT EAST TO NORTHEAST BREEZE CONTINUES.
SHEPPARD
MARINE
ISSUED 253 PM CDT SAT JUL 19 2025
SCATTERED THUNDERSTORMS WILL IMPACT MAINLY THE SOUTHERN HALF OF
LAKE MICHIGAN INTO THE EVENING. WINDS WILL BECOME NORTHERLY
OVERNIGHT AS A COLD FRONT MOVES ACROSS THE LAKE. HIGH PRESSURE
WILL MOVE ACROSS LAKE SUPERIOR ON SUNDAY. WINDS WILL SHIFT TO
THE EAST ON MONDAY AS THE HIGH MOVES INTO ONTARIO.
WINDS WILL INCREASE TO AROUND 20 KNOTS AND BECOME SOUTHEAST ON
TUESDAY AS LOW PRESSURE APPROACHES FROM THE CENTRAL PLAINS.
THERE ARE CHANCES FOR STORMS WEDNESDAY THROUGH FRIDAY ALONG A
FRONTAL BOUNDARY THAT SETS UP ACROSS THE LAKE. SOUTH TO
SOUTHWEST WINDS WILL REMAIN ELEVATED WEDNESDAY AND THURSDAY
AHEAD OF THE FRONT.
MARQUARDT
MKX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
LM...NONE.
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