032
FXUS63 KMPX 160831
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
331 AM CDT WED SEP 16 2026
KEY MESSAGES
- WIDESPREAD SOAKING RAIN IS LIKELY FRIDAY INTO EARLY SATURDAY.
BROAD RAINFALL TOTALS OF 1 TO 2 INCHES ARE LIKELY, WITH A
NARROWER STRIP OF 3 TO 5+ INCHES POSSIBLE.
- QUIET WEATHER RETURNS FOR MUCH OF THE WEEKEND, WITH ANOTHER
CHANCE FOR SHOWERS SUNDAY INTO EARLY NEXT WEEK.
DISCUSSION
ISSUED AT 331 AM CDT WED SEP 16 2026
MAINLY CLEAR SKIES ARE IN PLACE THIS MORNING ACROSS THE REGION.
A FEW AREAS OF FOG HAVE DEVELOPED, BUT SURFACE OBS INDICATE THEY
ARE FEW AND FAR BETWEEN AND AREN'T PERSISTENT. TEMPERATURES WILL
REBOUND BACK TO NEAR NORMAL TODAY WITH HIGHS IN THE LOW TO MID
70S.
A LOW AMPLITUDE TROUGH WILL SWING THROUGH TONIGHT. SCATTERED
SHOWERS ARE EXPECTED TO DEVELOP EARLY THIS EVENING ACROSS
WESTERN MN AND INCREASE IN COVERAGE AS THEY TRACK EAST TONIGHT.
AMOUNTS WON'T BE TOO IMPRESSIVE WITH SOME AREAS RECEIVING A
TENTH TO QUARTER OF AN INCH. ANOTHER WARM DAY THURSDAY WITH
CLEARING SKIES AND HIGHS IN THE MID TO UPPER 70S.
THE DISTURBANCE RESPONSIBLE FOR THE HEAVY RAIN THREAT FRIDAY IS
CURRENTLY LOCATED IN THE GULF OF CALIFORNIA. NHC IS MONITORING
POTENTIAL DEVELOPMENT OF IT BEFORE IT MOVES INLAND TODAY. GIVEN
ITS ORIGIN, IT WILL BRING A LOT OF MOISTURE WITH IT AS IT
TRACKS NORTH ACROSS THE FOUR CORNERS TONIGHT, THE WESTERN HIGH
PLAINS THURSDAY NIGHT, AND MN FRIDAY. SHOWERS AND THUNDERSTORMS
WILL DEVELOP OVER THE BLACK HILLS THURSDAY EVENING AS THE
DISTURBANCE REACHES THE HIGH PLAINS. AS IT CONTINUES TOWARD MN,
A 45 KT LLJ WILL DEVELOP AHEAD OF IT AND TRANSPORT +15C TO +17C
DEWPOINTS AT 850 MB NORTHWARD. PWATS WILL INCREASE TO AROUND 2
INCHES. THE 700 MB LOW APPEARS WILL TRACK ACROSS CENTRAL MN,
WITH THE 850 MB LOW A BIT FARTHER SOUTH FROM NORTHEASTERN SD TO
WEST CENTRAL WI, POSSIBLY OVER THE METRO. THE TRACK OF THE 850
MB LOW WILL DETERMINE WHERE THE 850 MB WARM FRONT SETS UP, AND
THIS WILL INFLUENCE WHERE THE HEAVIEST RAIN WILL FALL. WHILE
CONFIDENCE REMAINS MODERATE FOR NOW, IT APPEARS MODELS ARE
STARTING TO HONE IN ON THE AREA MOST AT RISK. THE LONE OUTLIERS
ARE THE 00Z ECMWF AIFS AND RRFS, WHICH PAINT THE AXIS OF
HEAVIEST RAIN ALONG THE MN/IA BORDER. THE AIFS HAS BEEN SHIFTING
NORTH SLIGHTLY IN RECENT RUNS, HOWEVER. THE EPS-AIFS IS FARTHER
NORTH WITH ITS AXIS ROUGHLY FROM REDWOOD FALLS TO RED WING. THE
AIGFS HAS BEEN MAKING REMARKABLE SHIFTS NORTH EACH RUN OF THE
LAST FIVE. THE METRO AND NORTH WAS DRY 24 HOURS AGO; NOW IT IS
WITHIN THE AXIS OF HEAVIEST AMOUNTS. THE REST OF THE GUIDANCE
SUITE IS IN THAT SAME BALLPARK GENERALLY, WITH SOME SMALLER
DISPLACEMENTS NORTH OR SOUTH.
THE 12Z ECMWF EXTREME FORECAST INDEX (EFI) FROM YESTERDAY
HIGHLIGHTS CENTRAL/EASTERN SD THROUGH THE SOUTHERN THIRD OF
MN FOR HIGHLY ANOMALOUS QPF FOR THIS TIME OF YEAR. THE EFI IS
0.8-0.9, MEANING A HUGE PORTION OF ENSEMBLE MEMBERS ARE SHIFTED
TOWARD THE EXTREME END OF THE 5-WEEK ECMWF REFORECAST
CLIMATOLOGY OVER THE PAST 20 YEARS. EVEN MORE IMPRESSIVE, THE
SHIFT OF TAILS (SOT) IS UP TO 2 ACROSS PORTIONS OF SD, WHICH
SIGNIFIES AT LEAST 10% OF ENSEMBLE MEMBERS ARE 2 STANDARD
DEVIATIONS ABOVE THE 99TH PERCENTILE OF CLIMATOLOGY. SIMPLY PUT,
THIS MAY BE AN EXTREME EVENT. THE EFI AND SOT CHARTS ARE
AVAILABLE IN 24-HOUR PERIODS (00Z-00Z). SINCE OUR REGION WILL
EXPERIENCE HEAVY RAIN SPLIT BETWEEN TWO FORECAST PERIODS, THE
PROBABILITIES NATURALLY DROP OFF AS IT PASSES THROUGH MN AND
WESTERN WI, BUT THE THREAT IS JUST AS GREAT HERE.
CONFIDENCE IS HIGH MOST OF THE AREA WILL RECEIVE AN INCH OF
RAIN. CONFIDENCE BEGINS TO DROP OFF WITH THE PLACEMENT OF THE
HEAVIEST AXIS AND THE MAGNITUDE OF TOTALS. FOR NOW IT APPEARS
THE HEAVIEST AXIS WILL LIKELY FALL FROM BETWEEN WILLMAR AND
REDWOOD FALLS, EAST TO THE SOUTHERN TC METRO, TO THE EAU CLAIRE
AND LA CROSSE AREAS BUT THIS IS SUBJECT TO FURTHER SHIFTS. AS
FOR QPF, THERE IS WIDESPREAD AGREEMENT AMONG MANY MODELS THAT A
STRIPE OF AT LEAST 3 INCHES WILL FALL SOMEWHERE AND POSSIBLY
GREATER THAN 5 OR 6. DESPITE THE ONGOING DROUGHT, THIS MAY
RESULT IN FLOODING CONCERNS, PARTICULARLY IF IT FALLS IN AN
URBAN AREA. FLOOD WATCHES MAY EVENTUALLY BE NEEDED.
THE FRONT WILL TEMPORARILY SETTLE SOUTH BEHIND THE FRIDAY
SYSTEM, BRINGING DRIER WEATHER SATURDAY. ANOTHER SYSTEM, A
LARGER UPPER LOW OVER THE ROCKIES, WILL PUSH EAST SUNDAY INTO
EARLY NEXT WEEK. THIS SHOULD LIFT THE FRONT BACK NORTH AND BRING
AN UNSETTLED PERIOD NEXT WEEK.
AVIATION /06Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 1220 AM CDT WED SEP 16 2026
VERY LIGHT WINDS AND MOSTLY CLEAR SKIES WILL ALLOW FOR POCKETS
OF GROUND FOG TO DEVELOP THROUGH DAYBREAK. CONFIDENCE WAS TOO
LOW TO INCLUDE ANY MENTION IN THE 6Z TAF PACKAGE, BUT WILL
MONITOR SATELLITE/OBS AND AMD AS NECESSARY OVERNIGHT. AXN, STC.
RNH, & EAU WOULD BE THE MOST LIKELY TERMINALS TO OBSERVE FOG
DUE TO EFFICIENT COOLING. LIGHT SOUTHEASTERLY WINDS INCREASE
MID-MORNING. MID TO HIGH CLOUDS WILL BUILD AHEAD OF A CHANCE
FOR LOW IMPACT SHOWERS THIS EVENING. FORECAST SOUNDINGS HIGHLIGHT
A FEW HOUR PERIOD WHEN SUFFICIENT SATURATION FOR VFR SHOWERS
WILL OCCUR, SO HAVE INCLUDED PROB30S AT MOST SITES NEAR OR AFTER
00Z. CEILINGS LOWER TO MVFR (OR POSSIBLY LOWER) ACROSS SOUTHERN
MN TOWARDS THE END OF THE PERIOD.
KMSP...VERY QUIET THROUGH MUCH OF THE 06Z PERIOD. WE'VE
MAINTAINED THE PROB30 FOR VFR -SHRA CHANCES AFTER 00Z. MVFR CIGS
POSSIBLE FOLLOWING THE SHOWER CHANCES, WHICH HAS BEEN INCLUDED
IN THE NEW TAF.
/OUTLOOK FOR KMSP/
THU...VFR. CHC MVFR/-SHRA LATE. WIND NE 5KTS.
FRI...MVFR. CHC IFR W/-TSRA. WIND SE 10-15G30KTS.
SAT...VFR. WIND NE 5-10G20KTS.
MPX WATCHES/WARNINGS/ADVISORIES
MN...NONE.
WI...NONE.
DISCUSSION...BORGHOFF
AVIATION...STRUS
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