401
FXUS63 KMKX 180501
AFDMKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1201 AM CDT TUE AUG 18 2026
KEY MESSAGES
- CHANCE OF SHOWERS AND STORMS TODAY; COVERAGE REMAINS
UNCERTAIN. A FEW STRONGER STORMS WITH HAIL AND GUSTY WINDS ARE
POSSIBLE IN THE MID TO LATE AFTERNOON.
- DRY AND PLEASANT CONDITIONS WEDNESDAY THROUGH THURSDAY. RAIN
CHANCES RETURN FRIDAY, BUT OVERALL NICE WEATHER IS EXPECTED
FOR THE WEEKEND.
SHORT TERM
ISSUED 1201 AM CDT TUE AUG 18 2026
REST OF TONIGHT THROUGH WEDNESDAY:
THE STORMS IN MN THIS EVENING ARE FOCUSED ALONG THE NOSE OF THE
LOW LEVEL JET (LLJ). THE JET WILL SHIFT INTO WI OVERNIGHT, VEER
TO THE WEST, AND HAVE A WEAKENING TREND; THUS THE STORMS WILL
TOO. HOWEVER, THESE DIMINISHING SHOWERS COULD GET A BOOST
TUESDAY MORNING OVER SOUTH CENTRAL WI AS LOW-LEVEL, MOIST, WARM
ADVECTION FOCUSES OVER US. THE RAP IS SHOWING A SLIGHT INCREASE
IN CAPE (UP TO 500 J/KG) AND MODEST BULK SHEAR UP TO 40 KT
DURING THE MORNING HOURS (BETWEEN 8 AND NOON). THIS WOULD BE
ENOUGH FORCING TO JUSTIFY GENERAL THUNDER. COVERAGE OF THESE
SHOWERS/STORMS IS STILL UNCERTAIN DUE TO THEM MOVING INTO AN
ALREADY-DRY ENVIRONMENT.
A MID LEVEL SHORTWAVE TROUGH AND COINCIDENT RIGHT ENTRANCE
REGION OF AN UPPER JET THAT IS CURRENTLY OVER SOUTHEAST MONTANA
WILL TRACK INTO SOUTHERN WI AROUND MIDDAY TUESDAY. THIS STRONGER
SYNOPTIC FORCING WILL GIVE US A BETTER ENVIRONMENT FOR
THUNDERSTORMS DURING THE MID AFTERNOON TO EARLY EVENING HOURS,
BUT THERE IS A LACK OF FOCUS FOR THESE STORMS. THERE WILL HAVE
TO BE BE VERY SMALL-SCALE FEATURE SUCH AS AN OUTFLOW BOUNDARY
OR MCV THAT PLAYS A ROLE IN WHERE THESE STORMS POP.
DEPENDING ON HOW MUCH/LITTLE CLOUD COVER LINGERS OVER SOUTHERN
WI DURING THE DAY, WE COULD BUILD UP TO 1500 J/KG CAPE WITH
CONTINUED BULK SHEAR AROUND 40 KT. THIS WOULD BE ENOUGH FOR A
FEW NEAR-SEVERE GUSTS OR SMALL HAIL. SINCE PRECIPITABLE WATER
VALUES ARE GOING TO BE INCREASING TO AROUND 1.5 INCH BY LATE
AFTERNOON, HEAVY RAIN WITH ANY STORMS IS LIKELY.
THE UPPER TROUGH AND SLOW-MOVING SURFACE FRONT WILL FINALLY EXIT
SOUTHERN WI BY WEDNESDAY MORNING. EXPECT SUNSHINE WITH DIURNAL
CUMULUS CLOUDS AND HIGHS IN THE UPPER 70S. LIGHT WINDS UNDER
HIGH PRESSURE WILL ALLOW FOR A WEAK LAKE BREEZE AS WELL. WITH
THE DRY AIR MASS IN PLACE, WED NT LOWS WILL DROP INTO THE MID
50S FOR INLAND AREAS.
CRONCE
LONG TERM
ISSUED 1201 AM CDT TUE AUG 18 2026
THURSDAY THROUGH MONDAY:
NORTHWEST FLOW AT 500 MB IS GENERALLY EXPECTED ACROSS THE WESTERN
GREAT LAKES REGION DURING THIS PERIOD, WITH A DIGGING SHORTWAVE
TROUGH/LOW SHIFTING THROUGH LAKE HURON AND SOUTHEAST ONTARIO
SATURDAY NIGHT INTO SUNDAY. ANOTHER DIGGING SHORTWAVE TROUGH MAY
MOVE SOUTHEAST INTO THE REGION EARLY NEXT WEEK.
ENSEMBLES SUGGEST THAT HIGH PRESSURE AT THE SURFACE THURSDAY WILL
PUSH OFF TO THE SOUTHEAST THURSDAY NIGHT INTO FRIDAY, WITH LOW
PRESSURE SHIFTING EAST SOUTHEAST THROUGH A SIMILAR PATH TO THE
DIGGING SHORTWAVE TROUGH LATER FRIDAY/FRIDAY NIGHT, THEN SHIFTING
SOUTHEAST ON SATURDAY. THIS SHOULD BRING A COLD FRONT SOUTHEAST
THROUGH THE AREA, WITH SOME LOW LEVEL WARM AIR ADVECTION AHEAD OF
IT.
FORECAST SOUNDINGS ARE SHOWING SOME TALL SKINNY MEAN LAYER CAPE
DEVELOPING AHEAD OF THE FRONT FRIDAY AFTERNOON, THOUGH DEEP LAYER
BULK SHEAR IS MODEST AT BEST. ENSEMBLE MEMBERS ARE GENERALLY
SHOWING MEASURABLE PRECIPITATION LATER FRIDAY INTO FRIDAY NIGHT,
SO WILL CONTINUE TO MENTION CHANCES FOR SHOWERS AND THUNDERSTORMS
IN THE FORECAST. SOME OF THIS COULD LINGER INTO SATURDAY IF THE
FRONTAL PASSAGE IS A LITTLE SLOWER, OR THE SHORTWAVE TROUGH HELPS
BRING SOME SCATTERED SHOWERS BEHIND IT.
ENSEMBLES SUGGEST TEMPERATURES NEAR SEASONAL NORMAL VALUES WITH
DEW POINTS INTO THE 60S FRIDAY INTO FRIDAY NIGHT AHEAD OF THE
COLD FRONT. HIGH PRESSURE SHOULD THEN BRING QUIET WEATHER FOR
SATURDAY NIGHT INTO SUNDAY NIGHT OR MONDAY, DEPENDING ON WHEN THE
NEXT DIGGING SHORTWAVE TROUGH APPROACHES THE REGION FROM THE
NORTHWEST.
WOOD
AVIATION
ISSUED 1201 AM CDT TUE AUG 18 2026
A LINE OF DIMINISHING THUNDERSTORMS MIGHT HOLD TOGETHER AS THEY
GET INTO SOUTH CENTRAL WI AROUND 12Z TUE. SCATTERED SHOWERS AND
A FEW WEAK THUNDERSTORMS ARE POSSIBLE DURING THE MID-LATE
MORNING, BUT THERE IS LESS CERTAINTY IN THESE OCCURRING NOW.
WITH MINOR STORM CHANCES ALL DAY, I TRIED TO PICK A 4 HOUR
WINDOW TO INCLUDE THUNDER AND DECIDED ON THE LATE AFTERNOON TO
EARLY EVENING TIME. ANY STORMS DURING THIS TIME WILL BE WIDELY
SCATTERED AND BRIEF BUT WOULD HAVE GUSTY WINDS AND HEAVY
DOWNPOURS.
CRONCE
MARINE
ISSUED 1201 AM CDT TUE AUG 18 2026
A SLOW-MOVING LOW PRESSURE TROUGH OF AROUND 29.9 INCHES WILL SLIDE
ACROSS LAKE MICHIGAN DURING THE DAY TUESDAY. WINDS WILL BE
PREDOMINANTLY WESTERLY. A FEW STORMS ARE POSSIBLE WITHIN THE
VICINITY OF THE TROUGH/FRONT THROUGH TUESDAY NIGHT. AN ISOLATED
STRONGER STORM WITH GUSTY WINDS AND HAIL CANNOT BE RULED OUT. HIGH
PRESSURE OF 30.0 INCHES WILL MOVE THROUGH THE WESTERN GREAT LAKES
WEDNESDAY THROUGH THURSDAY, WITH LIGHT AND VARIABLE WINDS
PREVAILING ACROSS THE WATERS. THE NEXT THUNDERSTORM CHANCES ARRIVE
FRIDAY AFTERNOON AND EVENING, WHEN THE NEXT COLD FRONT IS
EXPECTED TO MOVE ACROSS LAKE MICHIGAN.
CRONCE
MKX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
LM...NONE.
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