680
FXUS63 KMKX 120321
AFDMKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1021 PM CDT SUN OCT 11 2026
KEY MESSAGES
- HIGH TEMPERATURES REMAIN WELL ABOVE NORMAL THROUGH MONDAY.
- ISOLATED TO SCATTERED SHOWERS/THUNDERSTORMS MONDAY AFTERNOON
INTO MONDAY NIGHT FROM CENTRAL TO SOUTHEASTERN WISCONSIN,
MAINLY FROM 5:00 PM TO MIDNIGHT CDT.
- INCREASING POTENTIAL FOR RAINFALL BETWEEN WEDNESDAY NIGHT AND
FRIDAY MORNING, WITH CHANCES FOR THUNDERSTORMS AT TIMES. RAIN
CHANCES PEAK (50-70%) ON THURSDAY.
- VERY GUSTY NORTHWEST WINDS POSSIBLE FRIDAY.
- MUCH COLDER TEMPERATURES ARE EXPECTED NEXT WEEKEND, WITH FROST
BECOMING LIKELY.
SHORT TERM
ISSUED 1015 PM CDT SUN OCT 11 2026
MONDAY AND MONDAY NIGHT:
A MODEST SOUTHWEST BREEZE AND CONTINUED WAA THROUGH MONDAY
SHOULD ALLOW THE WARMTH TO SPREAD TO THE SHORELINE, WITH DAYTIME
HIGHS CHALLENGING RECORDS FOR THE HOLIDAY. HIGHS IN THE LOW TO
MID 80S EXPECTED REGION-WIDE, WARMEST FURTHER SOUTH AND WEST.
OBLONG LOW PRESSURE SPANNING FROM THE GREAT PLAINS TO MN WILL
DRIFT NORTHEAST THROUGH MONDAY, EVENTUALLY REACHING CENTRAL WI
MONDAY EVENING. SOME SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS (15-35% CHANCES) ARE FORECAST ACROSS CENTRAL,
EAST-CENTRAL, AND SOUTHEASTERN WI MONDAY AFTERNOON INTO MONDAY
NIGHT.
NOT ANTICIPATING ANY ORGANIZED OR SEVERE STORMS WITH THIS
ACTIVITY; THE PAST SEVERAL MODEL CYCLES HAVE BEEN STEADY ON
ROUGHLY 1,000 TO 1,500 JOULES MUCAPE, WITH SURFACE INSTABILITY
STRONGLY CAPPED AND THE AVAILABLE ELEVATED INSTABILITY FACING
ROUGHLY 100 JOULES OR LESS CIN. THE SYNOPTIC CONVERGENCE AND
ASCENT INTO THE APPROACHING LOW PRESSURE SYSTEM SHOULD BE ENOUGH
TO CRANK UP SOME ELEVATED CONVECTION, MAINLY BETWEEN 5:00 PM AND
MIDNIGHT. THE HIGHEST POTENTIAL (15-35%) EXISTS NORTH OF A
WISCONSIN DELLS TO KENOSHA LINE, CLOSER TO THE PASSING LOW
PRESSURE (TO THE NORTH) AND IN PROXIMITY TO A NW-SE ORIENTED
AXIS OF SURFACE-850MB CONFLUENCE ALONG THE PRIMARY (OR A
SECONDARY) WARM FRONT.
SHEPPARD
LONG TERM
ISSUED 1015 PM CDT SUN OCT 11 2026
TUESDAY THROUGH SUNDAY:
A COLD FRONT FROM THE AFOREMENTIONED LOW PRESSURE SYSTEM VEERS
SURFACE WINDS TO THE NORTHWEST TUESDAY MORNING, LEAVING THE
ENTIRE DAY WITH PREDOMINANTLY DRY WEATHER AND NOTICEABLY COOLER
(BUT STILL UNSEASONABLY WARM) TEMPERATURES. THIS FRONT WILL THEN
STALL ACROSS NORTHERN IL / CENTRAL IA, SERVING AS A FOCAL POINT
FOR REDEVELOPING SHOWERS AND THUNDERSTORMS TO OUR SOUTH TUESDAY
NIGHT AS THE LLJ CRANKS UP SOUTH OF IT. THE PROXIMITY OF THIS
BOUNDARY YIELDS SOME 30-60% SHOWER AND STORM CHANCES IN
SOUTHERN WI TUESDAY NIGHT, MAINLY ALONG AND SOUTH OF THE I-94
CORRIDOR, AS WELL AS THE HWY 18 CORRIDOR WEST OF MADISON.
HIGHEST CHANCES ARE BY THE IL BORDER. PREDOMINANTLY DRY WEATHER
IS THEN EXPECTED THROUGH THE DAY WEDNESDAY AS HIGH PRESSURE
BUILDS INTO THE GREAT LAKES REGION AND FORCES THE FRONTAL ZONE
FURTHER SOUTH.
A MODEST 500MB TROUGH THEN DIGS SOUTH FROM SOUTH-CENTRAL CANADA
INTO THE GREAT PLAINS WEDNESDAY NIGHT INTO THURSDAY, WITH A
DIRECTLY-ASSOCIATED SURFACE LOW PRESSURE SYSTEM (A CLIPPER SYSTEM)
TRACKING EAST ACROSS SOUTHERN CANADA WITH IT. THE SOUTHERN
COMPONENT OF THIS SAME TROUGH AXIS PHASES WITH LINGERING OBLONG
LOW PRESSURE / BAROCLINICITY LEFT BEHIND BY THE AFOREMENTIONED
COLD FRONT, SEEDING THE DEVELOPMENT OF ANOTHER LOW PRESSURE SYSTEM
NEAR MISSOURI. THE TWO LOW-PRESSURE SYSTEMS (AND THEIR
CORRESPONDING UPPER WAVES) WOULD THEN TRACK EAST AND MERGE
TOGETHER EAST OF THE GREAT LAKES REGION LATER THIS WEEK,
AMPLIFYING AND INTENSIFYING RAPIDLY. MANY THINGS NEED TO PHASE
TOGETHER WELL IN ORDER FOR THIS PICTURE TO COME TOGETHER THE WAY
I'VE DESCRIBED IT, BUT THE GIST OF IT IS WE COULD (POTENTIALLY)
SEE SOME REGION-WIDE RAINFALL LATE WEDNESDAY NIGHT THROUGH
FRIDAY MORNING AS THE SOUTHERN LOW PRESSURE SYSTEM PASSES JUST
SOUTH OF THE REGION. NO ORGANIZED THUNDERSTORM POTENTIAL IS
EVIDENT, BUT THE RAINFALL IS REACHING A GOOD GENERAL CONSENSUS
AMONGST MODEL GUIDANCE (50-70% RAIN CHANCES, WHICH PEAK ON
THURSDAY).
STRONG HIGH PRESSURE IS EXPECTED TO DESCEND FROM CANADA INTO THE
DAKOTAS ON FRIDAY, WORKING WITH THE EQUALLY INTENSE DEPARTING LOW
PRESSURE TO FORM A STRONG PRESSURE GRADIENT AND VERY GUSTY NW
WINDS ACROSS WI ON FRIDAY. STRONG CAA WOULD THEN LEAD TO HIGH
FROST POTENTIAL (OR PERHAPS EVEN A FREEZE) THIS WEEKEND. WITH
SOME OF THE MORE EXTREME GUIDANCE, OVERNIGHT LOW TEMPS INTO THE
20S COULD EVEN BE POSSIBLE. ON THE OTHER END OF THE MODEL
SPECTRUM, THERE ARE FAR LESS AMPLIFIED MODEL SOLUTIONS THAT DEPICT
MORE OF A DOUBLE-BARRELED LOW PRESSURE SYSTEM AS OPPOSED TO A
STRONGER / UNIFIED LOW, AS WELL AS SIGNIFICANTLY WEAKER SURFACE
HIGH PRESSURE COMING IN FROM THE WEST, AND LEAVE TEMPERATURES
BELOW NORMAL BUT PAR FOR THE COURSE IN MID AUTUMN. UNTIL THINGS
BECOME CLEARER, OUR FORECAST FOR THIS WEEKEND WILL STICK WITH THE
MIDDLE-GROUND SOLUTION OF HIGHS IN THE 50S AND LOWS IN THE 30S. WE
WILL KEEP YOU POSTED ON TRENDS.
SHEPPARD
AVIATION
ISSUED 1015 PM CDT SUN OCT 11 2026
LIGHT SOUTH TO SOUTHWEST WINDS CONTINUE OVERNIGHT. A
SOUTHWESTERLY LOW-LEVEL JET WILL RESULT IN LLWS OVERNIGHT, WITH
2,000 FT AGL WINDS AROUND 30 TO 40 KT, FASTEST FURTHER NORTH AND
WEST IN OUR REGION. THIS IS INCLUDED IN THE TAFS WHERE
APPLICABLE; FAR SOUTHEASTERN WI (INCLUDING MKE AND ENW) IS
EXPECTED TO EXPERIENCE WEAKER SHEAR (BELOW TAF INCLUSION
THRESHOLDS).
LLWS WILL WRAP UP AROUND DAWN MONDAY, FOLLOWED BY AN INCREASE IN
SURFACE WINDS (SOUTHWEST WITH GUSTS TO AROUND 20 KT) INTO MONDAY
AFTERNOON. ISOLATED SHOWERS AND THUNDERSTORMS (15-30% COVERAGE)
EXPECTED FROM CENTRAL WI THROUGH SOUTHEASTERN WI MONDAY
AFTERNOON INTO MONDAY NIGHT. OVERALL STORM CHANCES AND COVERAGE
ARE JUST SHY OF TAF INCLUSION THRESHOLDS, THUS THE TAFS REMAIN
DRY FOR NOW. PROB30 GROUPS MAY BE ADDED IN SUBSEQUENT FORECAST
ITERATIONS. ADDITIONAL LLWS POSSIBLE MONDAY NIGHT, PERHAPS MORE
WIDESPREAD AND WITH HIGHER INTENSITY.
SHEPPARD
MARINE
ISSUED 1015 PM CDT SUN OCT 11 2026
OPEN WATERS / SYNOPSIS:
BROAD LOW PRESSURE AROUND 29.5 INCHES OVER THE CENTRAL PLAINS TO
MINNESOTA WILL DRIVE SOUTH-SOUTHWESTERLY WINDS THROUGH THE
OVERNIGHT HOURS AND INTO MONDAY. THIS LOW IS EXPECTED TO LIFT INTO
MINNESOTA AND EVENTUALLY CENTRAL WISCONSIN BY MONDAY EVENING.
EXPECTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS TO DEVELOP
MONDAY NIGHT AS THE LOW APPROACHES AND CROSSES THE OPEN WATERS.
WINDS SHIFT TO NORTHWESTERLY ON TUESDAY AS AN ASSOCIATED COLD
FRONT CROSSES THE LAKE AND THE LOW PRESSURE EXITS EAST. THE FRONT
MAY STALL JUST SOUTH OF THE LAKE TUESDAY NIGHT, WITH A LIGHT
NORTHERLY BREEZE ACROSS THE LAKE AND SHOWER / THUNDERSTORM
POTENTIAL TOWARDS THE SOUTHERN END OF THE LAKE.
HIGH PRESSURE AROUND 30.2 INCHES BUILDING INTO THE NORTHERN PLAINS
WILL KEEP WINDS NORTHERLY INTO WEDNESDAY, TURNING NORTHEASTERLY
WEDNESDAY NIGHT AND EASTERLY INTO THURSDAY AS THE HIGH PRESSURE
PASSES NORTH OF THE LAKE AND LOW PRESSURE OF 29.9 INCHES DEVELOPS
NEAR MISSOURI / ILLINOIS.
LOW PRESSURE LOOKS TO CROSS LAKE MICHIGAN THURSDAY NIGHT, WITH
STRONG HIGH PRESSURE DESCENDING FROM WESTERN CANADA INTO THE
DAKOTAS / NEBRASKA INTO FRIDAY. THE PRESSURE GRADIENT BETWEEN
THESE TWO SYSTEMS WILL DRIVE STRONG NORTHWEST WINDS ACROSS THE
LAKE FRIDAY THROUGH FRIDAY NIGHT, WITH POTENTIAL FOR GALE FORCE
WINDS.
NEARSHORE ZONES:
BREEZY SOUTHWEST WINDS LATE MONDAY MORNING THROUGH LATE MONDAY
AFTERNOON ARE FORECAST TO FALL JUST SHY OF ADVISORY LEVELS,
WITH GUSTS TO ROUGHLY 20 KT.
ADVISORY CONDITIONS ARE POSSIBLE WEDNESDAY, WITH HIGHER
CONFIDENCE INTO THURSDAY DUE TO STEADY ONSHORE WINDS AND
BUILDING WAVES. GUSTY NORTHWEST WINDS (WELL OVER ADVISORY
LEVELS) ARE THEN EXPECTED FRIDAY THROUGH FRIDAY NIGHT, WITH
GALES POSSIBLE.
SHEPPARD
MKX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
LM...NONE.
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