555
FXUS63 KMPX 170537
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1237 AM CDT THU SEP 17 2026
KEY MESSAGES
- SCATTERED SHOWERS & A FEW THUNDERSTORMS TONIGHT. PATCHY FOG
OVERNIGHT.
- WIDESPREAD HEAVY RAIN IS EXPECTED FRIDAY INTO EARLY SATURDAY,
WITH AMOUNTS IN EXCESS OF 3-4" LIKELY FROM THE SOUTHERN TWIN
CITIES METRO SOUTH TOWARDS THE MINNESOTA/IOWA BORDER.
- FLOODING IS POSSIBLE WHERE REPEATED ROUNDS OF HEAVY RAIN
OCCUR, WITH THE GREATEST CONCERN FRIDAY NIGHT INTO EARLY
SATURDAY MORNING.
DISCUSSION
ISSUED AT 349 PM CDT WED SEP 16 2026
SCATTERED SHOWERS & THUNDERSTORMS DEVELOP ACROSS WESTERN
MINNESOTA THIS EVENING & SPREAD EASTWARDS THROUGH THE OVERNIGHT
HOURS AS A WEAK SHORTWAVE MOVES ACROSS THE REGION COUPLED WITH
AN INCREASING NOCTURNAL LOW-LEVEL JET. RAINFALL AMOUNTS SHOULD
GENERALLY STAY LIGHT, WITH MOST LOCATIONS RECEIVING AROUND
0.1-0.25 BEFORE SHOWERS MOVE EAST THURSDAY MORNING. SOME LOW
CLOUDS & PATCHY FOG COULD LINGER INTO THURSDAY MORNING, BUT
OTHERWISE A QUIET & SEASONABLY WARM DAY IS EXPECTED WITH HIGHS
IN THE LOW TO MID 70S. OUR ATTENTION THEN QUICKLY TURNS TO A
MUCH STRONGER SYSTEM MOVING OUT OF THE CENTRAL PLAINS THURSDAY
NIGHT INTO FRIDAY.
FRIDAY THROUGH EARLY SATURDAY CONTINUES TO BE THE MAIN WEATHER
CONCERN OVER THE NEXT SEVEN DAYS. A STRENGTHENING LOW- LEVEL JET
WILL TRANSPORT AN IMPRESSIVE AMOUNT OF MOISTURE NORTHWARDS WITH
PWAT VALUES APPROACHING 2". THESE VALUES ARE NEAR THE TOP OF
CLIMATOLOGY FOR MID-SEPTEMBER, PRIMING THE ATMOSPHERE FOR
SHOWERS & THUNDERSTORMS CAPABLE OF VERY EFFICIENT RAINFALL
RATES. ATYPICAL OF THESE SUMMER-LIKE PRECIPITABLE WATER VALUES
IS THE STRONG UPPER LEVEL FORCING, AS A SHORTWAVE PASSING
DIRECTLY OVER THE REGION GENERATES STRONG LOW & MID- LEVEL
FRONTOGENESIS NORTH OF A QUASI-STATIONARY SURFACE BOUNDARY
ACROSS SOUTHERN MINNESOTA & WISCONSIN. NUMEROUS SHOWERS &
THUNDERSTORMS ARE EXPECTED TO FIRE ALONG & NORTH OF THIS
BOUNDARY THROUGH THE DAY FRIDAY INTO EARLY SATURDAY MORNING,
WITH HEAVY RAIN & POTENTIAL FLOODING WHERE MULTIPLE ROUNDS OF
THUNDERSTORMS SET UP OVER THE SAME AREAS.
THIS FORCING WILL BEGIN TO PEAK FRIDAY MORNING, WHEN THE FIRST
ROUND OF HEAVY RAIN LOOKS TO SPREAD INTO SOUTHERN & CENTRAL
MINNESOTA. THE HEAVIEST RAIN LOOKS TO FALL ACROSS SOUTHERN
MINNESOTA, BUT AVAILABLE HIGH-RESOLUTION GUIDANCES HIGHLIGHTS
THE POTENTIAL FOR A SECONDARY BAND OF FRONTOGENICALLY-FORCED
RAINFALL FALLING FARTHER NORTH ACROSS CENTRAL MINNESOTA
& WISCONSIN. WE WILL ALSO HAVE TO MONITOR THE STORMS ACROSS
SOUTHERN MINNESOTA FOR POTENTIAL SEVERE WEATHER FRIDAY MORNING
AS HIGH- RESOLUTION GUIDANCE IS DEPICTING A GRAVITY-WAVE INDUCED
DAMAGING WIND SIGNATURE WITH THE THUNDERSTORMS. THERE MAY BE
SOMEWHAT OF A BREAK OR DECREASE IN COVERAGE DURING THE AFTERNOON
BEFORE ANOTHER, LIKELY HEAVIER ROUND DEVELOPS FRIDAY EVENING &
PERSISTS OVERNIGHT INTO EARLY SATURDAY MORNING. THIS SECOND
ROUND IS WHEN THE BEST OVERLAP OF MOISTURE TRANSPORT, ELEVATED
INSTABILITY, & FRONTOGENETIC FORCING SHOULD OCCUR, MAKING IT THE
PERIOD OF GREATEST CONCERN FOR TRAINING THUNDERSTORMS & HIGH
RAINFALL RATES. SEVERE WEATHER CURRENTLY LOOKS LIKE A SECONDARY
CONCERN GIVEN LIMITED SURFACE-BASED INSTABILITY, ALTHOUGH
EMBEDDED THUNDERSTORMS WILL ENHANCE RAINFALL RATES.
WHERE EXACTLY THE HEAVIEST RAIN SETS UP REMAINS THE BIGGEST
FORECAST QUESTION. GUIDANCE CONTINUES TO SPAN SOLUTIONS FROM
CENTRAL MINNESOTA SOUTHWARDS TO THE IOWA BORDER, WITH THE
BROADER SUITE OF LEGACY DETERMINISTIC MODELS GENERALLY A LITTLE
FARTHER NORTH, WHILE DETERMINISTIC & AI ENSEMBLE GUIDANCE
CONTINUES TO FAVOR A MORE SOUTHERN AXIS. FOR NOW, WE FAVOR THIS
FARTHER-SOUTH CAMP, PLACING THE GREATEST RISK FOR AMOUNTS IN
EXCESS OF 3-4" FROM ROUGHLY THE FAR-SOUTHERN TWIN CITIES METRO
SOUTHWARDS TOWARDS THE MINNESOTA/IOWA BORDER, THEN EAST THROUGH
SOUTHEAST MINNESOTA INTO WESTERN WISCONSIN. LOCALIZED AMOUNTS OF
6-8" ARE CERTAINLY POSSIBLE WITHIN THIS HEAVIEST BAND OF
RAINFALL, WITH MUCH OF THIS RAINFALL POTENTIALLY FALLING IN A
SHORT AMOUNT OF TIME OVERNIGHT FRIDAY INTO SATURDAY. AMOUNTS ARE
EXPECTED TO FALL-OFF RATHER SHARPLY NORTH OF THIS SWATH OF THE
HEAVIEST RAIN, ALTHOUGH AMOUNTS AROUND 1-2" ARE STILL LIKELY
INTO CENTRAL MINNESOTA & WEST-CENTRAL WISCONSIN. UNFORTUNATELY
FOR OUR MOST- DROUGHT STRICKEN AREAS, LITTLE IN THE RAINFALL IS
EXPECTED ACROSS NORTH-CENTRAL MINNESOTA & NORTHWEST WISCONSIN.
FLOODING WILL BECOME A CONCERN WHEREVER THE SWATH OF HEAVIEST
RAIN OCCURS. REPEATED ROUNDS OF THUNDERSTORMS COULD PRODUCE
FLASH FLOODING IN URBAN & POOR- DRAINAGE AREAS ALONG WITH RISES
ON SMALLER RIVERS & STREAMS, ESPECIALLY FRIDAY NIGHT INTO EARLY
SATURDAY MORNING WHEN THE HEAVIEST RAIN CURRENTLY APPEARS MOST
LIKELY. SOME FACTORS THAT MAY HELP MITIGATE THE FLOODING THREAT
(DESPITE THE HEAVY RAIN AMOUNTS) ARE THAT ANTECEDENT CONDITIONS
ARE STILL QUITE DRY, & THE LULL BETWEEN THE EXPECTED TWO ROUND
OF HEAVY RAIN MAY HELP PREVENT MAXIMUM RUNOFF OF THE RAINFALL.
STILL - NOW IS THE TIME TIME TO HAVE A FLOOD PLAN IN PLACE IF
YOU LIVE IN A LOW-LYING OR WATER-SENSTIVE AREA WHERE THE
HEAVIEST RAIN IS EXPECTED TO OCCUR.
RAIN SHOULD END FROM WEST TO EAST SATURDAY MORNING AS THE
SYSTEM PULLS AWAY, WITH MUCH OF SATURDAY AFTERNOON LOOKING DRIER
& COOLER. ANOTHER UPPER LOW APPROACHES SUNDAY INTO EARLY NEXT
WEEK, BRINGING ADDITIONAL CHANCES FOR SHOWERS SUNDAY THROUGH
MONDAY. THESE LATER ROUNDS DONT LOOK NEARLY AS HEAVY AT THIS
POINT, BUT ANY ADDITIONAL RAIN COULD PROLONG RIVER RISES IN
AREAS AFFECTED BY THE FRIDAY- SATURDAY EVENT. TEMPERATURES
SETTLE BACK INTO THE 60S TO AROUND 70 EARLY NEXT WEEK.
AVIATION /06Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 1236 AM CDT THU SEP 17 2026
SHIELD OF RAIN & THUNDERSTORMS IS DEPARTING EAST INTO CENTRAL WI
FOR THE START OF THE 6Z PERIOD. WE'LL HAVE A FEW HOURS OF
LINGERING SHOWERS AT THE EASTERN MN/WESTERN WI TERMINALS BEFORE
DRY WEATHER RETURNS. MVFR/IFR CONDITIONS ACROSS SOUTHERN MN WILL
EXPAND NORTHWARD IN THE COMING HOURS AND HAVE INCLUDED TEMPOS
FOR IFR (OR LOWER) CIGS AND VISIBILITY THAT WILL PREVAIL THROUGH
DAYBREAK BEFORE IMPROVEMENTS ARE OBSERVED MID-MORNING. RWF/MKT
WILL BE STUCK IN THE VERY LOWER CIGS/FOG THE LONGEST, BUT
EVENTUALLY ALL TERMINALS OBSERVE IMPROVEMENTS TO VFR BY EARLY
AFTERNOON. LIGHT WINDS BETWEEN 5-7KTS OUT OF THE ENE TODAY.
KMSP...HEAVIEST RAIN HAS MOVED EAST OF THE TERMINAL, THOUGH
WE'LL KEEP THE CHANCE FOR ADDITIONAL SHOWERS IN THE TAF UNTIL
8Z. BANK OF MVFR (AND LOWER) CEILINGS AND VISIBILITY IS CREEPING
NORTH INTO SOUTHERN MN. ANTICIPATE MVFR CEILINGS WILL REACH THE
TERMINAL AROUND 8Z AND WE'VE ALSO INCLUDED A TEMPO FOR IFR CIGS
WITH VISIBILITY REDUCTIONS THROUGH 12Z. MVFR CIGS WILL BE SLOW
TO CLEAR AFTER DAYBREAK, BUT VFR CONDITIONS WITH LIGHT EASTERLY
FLOW SHOULD RETURN BY LATE MORNING.
/OUTLOOK FOR KMSP/
FRI...MVFR/RA. CHC IFR W/-TSRA. WIND SE 10-15G30KTS.
SAT...VFR. WIND NE 5-10G20KTS.
SUN...VFR. WIND NE 5-10G20KTS.
MPX WATCHES/WARNINGS/ADVISORIES
MN...NONE.
WI...NONE.
DISCUSSION...ETA
AVIATION...STRUS
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