993
FXUS63 KMPX 181051
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
551 AM CDT FRI SEP 18 2026
KEY MESSAGES
- WIDESPREAD STEADY SOAKING RAIN THROUGH TODAY.
- HEAVY RAIN AND LOCALIZED FLOODING THREAT GREATEST NEAR THE
IOWA BORDER THIS EVENING.
- SEASONABLE TEMPERATURES WITH MAINLY DRY CONDITIONS EXPECTED
FOR THE SUNDAY THROUGH NEXT WORK WEEK.
DISCUSSION
ISSUED AT 231 AM CDT FRI SEP 18 2026
LOOKING AT THE H5 ANALYSIS EARLY THIS MORNING, A RIDGE OF MID-SUMMER
STRENGTH (600 DM!) IS CENTERED OVER THE TX/OK/AR/LA REGION. AROUND
THE PERIPHERY OF THIS RIDGE IS A SHORTWAVE OF SOUTHWEST MONSOON
ORIGIN MOVING OUT OF NORTHERN NEB AND ACROSS SODAK. WIDESPREAD
RAINFALL HAS DEVELOPED WITH THIS WAVE, THOUGH IT'S YOUR CLASSIC
SYNOPTIC SETUP, WITH STRONG WAA AT H85 AND FGEN AROUND H7 COMBINING
TO CREATE THIS PRECIP SHIELD. THIS WILL ALL MOVE EAST ACROSS
SOUTHERN MN AND INTO WESTERN WI, RESULTING IN SEVERAL HOURS OF LIGHT
TO MODERATE RAIN ACROSS THE AREA TODAY. THIS WILL RESULT IN A FAIRLY
WIDESPREAD 1-2 INCHES OF RAIN ALONG AND SOUTH OF A ROUGHLY MORRIS
TO ST. CLOUD AND CHIPPEWA FALLS LINE. MUCAPE WILL BE LIMITED WITH
THIS ROUND OF PRECIPITATION, SO THE EXCESSIVE RAIN RISK WITH THIS
FIRST WAVE IS LOW. IT WILL JUST BE A MUCH NEEDED SOAKING RAIN AND
WASHOUT OF A FRIDAY.
THIS EVENING IS WHEN THE EXCESSIVE RAIN THREAT BEGINS TO SHOW UP AS
THE WARM FRONT BEGINS TO SHARPEN TO THE NORTH OF I-80 IN IOWA, WITH
A PERSISTENT LLJ RIDING UP OVER THE FRONT. PWATS WILL BE NEAR 2"
WITH MUCAPE INCREASING TO OVER 2000 J/KG OVER NORTHERN IOWA. ALL THE
INGREDIENTS ARE IN PLACE FOR A HEAVY RAIN EVENT TONIGHT TO THE NORTH
OF THE WARM FRONT, BUT THE THE HREF/REFS SHOW THE LLJ SETTING UP
FROM ABOUT OMAHA TO THE I-90/94 SPLIT NEAR TOMAH IN WI. IT'S ALONG
THE MN/IA BORDER FROM I-35 EAST THAT THE ATMOSPHERE LOOKS TO HAVE IN
ITS CROSSHAIRS FOR PRODUCING HEAVY RAIN, WHICH MEANS IT'S THE
PORTIONS OF FAR SOUTHEAST MN AND NORTHEAST IA IN THE LA CROSSE WFO
COVERAGE AREA THAT ARE REALLY UNDER THE GREATEST RISK FOR SEEING
EXCESSIVE RAINFALL. HREF AND REFS PMM QPF BOTH SHOW NEAR 8" OF RAIN
FALLING NEAR THE MN/IA BORDER EAST OF I-35, WHICH LOOKS REASONABLE
GIVEN THE SYNOPTIC SETUP WITH THIS EVENT. WE ALREADY HAVE FREEBORN
COUNTY IN A FLOOD WATCH FOR THE EXCESSIVE RAINFALL POTENTIAL AND
THIS LOOKS TO BE OUR ONE COUNTY THAT HAS THE GREATEST RISK OF SEEING
HEAVY RAINFALL, SO WE MAINTAINED THE WATCH FOR ONLY THAT COUNTY.
BESIDES HEAVY RAIN, WITH THAT 2000+ J/KG OF MUCAPE, HREF/REFS BOTH
SHOW SOME STRONGER UPDRAFTS WITH SOME ROTATION DEVELOPING WITH THIS
SECOND ROUND, SO THE INCLUSION OF A MARGINAL RISK UP TOWARD
ROCHESTER FROM THE SPC IN THEIR DAY 1 CONVECTIVE OUTLOOK MAKES
SENSE. WITH THAT SAID, LAPSE RATES LOOK TO BE NEAR MOIST ADIABATIC
IN THE MID-LEVELS, SO THIS LIKELY PUTS THE HAIL CEILING FOR THIS
EVENT AT A WATER COATED 1". THE TIMEFRAME THAT WILL HAVE THE
GREATEST RISK FOR BOTH EXCESSIVE RAINFALL AND SEVERE WEATHER IN THE
MPX AREA WILL BE 00Z TO 06Z THIS EVENING (7PM TO 1AM).
FOR SUNDAY THROUGH WEDNESDAY, THE MAIN FEATURE THAT SHOWS UP ON THE
FORECAST CHARTS IS PERSISTENT HIGH PRESSURE TO THE NORTH OF THE
GREAT LAKES. THIS WILL KEEP LOW LEVEL FLOW OUT OF THE EAST FOR
SUNDAY THROUGH WEDNESDAY. THESE EAST WINDS WILL BE VERY DRY BELOW
H7, WHICH WILL HELP PUSH ANY RAINFALL SOUTH AND WEST OF THE MPX AREA
THROUGH THE MIDDLE OF NEXT WEEK. WE'LL CONTINUE TO SEE WEAK
DISTURBANCES RIDE AROUND THE SOUTHERN RIDGE SUNDAY AND MONDAY, BUT
THOSE LOOK TO RESULT IN CONTINUED MID/UPPER LEVEL CLOUD COVER, BUT
WILL STRUGGLE TO PRODUCE MORE THAN THE OCCASIONAL SPRINKLES GIVEN
THE DRY LOW LEVEL AIR. THESE EAST WINDS WILL ALSO KEEP TEMPERATURES
SEASONABLE, WITH LOWS IN THE 30S/40S AND HIGHS IN THE 60S. DEPENDING
ON WHAT CLOUD COVER LOOKS LIKE, IT IS POSSIBLE WE'LL NEED SOME FROST
HEADLINES MONDAY AND TUESDAY MORNINGS IN WESTERN WI.
BEYOND WEDNESDAY, THE NORTHERN STREAM WILL HAVE RETREATED WELL TO
THE NORTH IN CANADA, WHICH WILL KEEP US DRY. THE ONLY REALLY CHANGE
WE'LL SEE TO THE WEATHER FOR THE END OF NEXT WEEK IS OUR EASTERLY
WINDS WILL BECOME SOUTHEAST, WHICH WILL ALLOW TEMPERATURES TO WARM
UP SOME, WITH THE FROST THREAT GOING AWAY AND HIGHS STARTING TO
CREEP BACK UP INTO THE 70S.
AVIATION /12Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 547 AM CDT FRI SEP 18 2026
RAIN CONTINUES TO SPREAD ACROSS CENTRAL AND SOUTHERN MINNESOTA
THIS MORNING. NOT MUCH CHANGE FROM THE PREVIOUS FORECAST, MAINLY
JUST TIGHTENING UP PRECIP TIMING WINDOWS FOR IFR/LIFR
CONDITIONS. PREVAILING LOW END MVFR/IFR SEEMS PRETTY LIKELY
THROUGH MUCH OF THE TAF PERIOD WITH OCCASIONAL DIPS TO LIFR.
EAST WINDS MAY GUST TO AROUND 20-25KTS DURING THE AFTERNOON
BEFORE DIMINISHING AFTER 00Z. ONCE THE BULK OF THE RAIN COMES TO
AN END EARLY SATURDAY, IFR CIGS/VIS WILL PERSIST WITH
FOG/DRIZZLE THROUGH THE END OF THE FORECAST PERIOD. WINDS WILL
EVENTUALLY TURN MORE NORTHEASTERLY.
KMSP...SLIGHT ADJUSTMENTS TO TIMING AS MENTIONED ABOVE, BUT
OTHERWISE, THE FORECAST REMAINS ON TRACK.
/OUTLOOK FOR KMSP/
SAT...MVFR. CHC IFR. WIND NE 10-20 KTS.
SUN...VFR. WIND NE 10-20 KTS.
MON...VFR. WIND E 5-10G15 KTS.
MPX WATCHES/WARNINGS/ADVISORIES
MN...FLOOD WATCH FROM THIS EVENING THROUGH SATURDAY MORNING FOR
FREEBORN.
WI...NONE.
DISCUSSION...MPG
AVIATION...DYE
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