657
FXUS63 KARX 101050
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
550 AM CDT THU SEP 10 2026
KEY MESSAGES
- MILD AND DRY THROUGH FRIDAY AFTERNOON WITH HIGHS IN THE MID
70S TO LOW 80S.
- SHOWER AND STORM CHANCES RETURN FRIDAY NIGHT INTO SATURDAY
MORNING (30 TO 60%). SEVERE POTENTIAL IS LOW (<10%) WITH THESE
STORMS.
- WIDESPREAD RAIN IS LIKELY MONDAY (70 TO 90%). THERE IS A HEAVY
RAIN AND FLOODING POTENTIAL, ESPECIALLY FOR LOCATIONS THAT
PICK UP RAIN ON SUNDAY PRIOR TO THIS EVENT.
DISCUSSION
ISSUED AT 1230 AM CDT THU SEP 10 2026
FRIDAY - SATURDAY: STORM CHANCES RETURN, SLIGHT COOL DOWN
AN UPPER LEVEL LOW IS EXPECTED TO ROTATE ACROSS THE WESTERN HUDSON
BAY FRIDAY WITH A LONGWAVE UPPER TROUGH PIVOTING ACROSS THE NORTHERN
PLAINS AND UPPER MIDWEST THROUGH SATURDAY. AT THE SURFACE, A
TRAILING COLD FRONT IS EXPECTED TO SWING THROUGH THE NORTHERN PLAINS
DURING THE DAY ON FRIDAY. WITH A SURFACE HIGH DEPARTING TO THE EAST,
THE PRESSURE GRADIENT WILL TIGHTEN ACROSS THE UPPER MIDWEST ALLOWING
FOR AMPLE RETURN FLOW AND SUBSEQUENT DESTABILIZATION THROUGH THE
DAY. WESTERLY WINDS ON THE LEE SIDE OF THE SIDE OF THE TROUGH AXIS
ARE EXPECTED TO INCREASE FRIDAY AFTERNOON INTO SATURDAY MORNING,
HELPING TO INTRODUCE PLENTY OF SHEAR ACROSS THE REGION. WITH THIS
INSTABILITY AND SHEAR, STORMS ARE EXPECTED TO FORM IN THE VICINITY
OF THE COLD FRONT. HOWEVER, GUIDANCE HAS BACKED OFF ON THE SPEED OF
THIS FRONTAL BOUNDARY, BRINGING IT THROUGH OUR AREA BY MID SATURDAY
MORNING WHEN THERE WILL BE LITTLE TO NO INSTABILITY TO WORK WITH.
GUIDANCE AS ALSO TRENDED FURTHER NORTH WITH THE SHEAR SO THE
ENVIRONMENT ACROSS OUR AREA DOES NOT LOOK OVERLY CONDUCIVE FOR
SEVERE THUNDERSTORMS. RAIN SHOWERS AND SUB-SEVERE THUNDERSTORMS LOOK
MORE LIKELY WITH THE FRONTAL PASSAGE AT THIS TIME WITH A LOW CHANCE
(LESS THAN 10%) FOR A SEVERE STORM SATURDAY AFTERNOON ACROSS
SOUTHWEST WISCONSIN WHERE THE FRONT MAY NOT HAVE CLEARED THE AREA
JUST YET. EVEN THOUGH THE FRONT THAT MOVED THROUGH WILL BE A "COLD
FRONT", ZONAL FLOW ALOFT WILL PREVENT ANY SIGNIFICANT COOL DOWN FOR
SATURDAY WITH HIGHS STILL IN THE MID TO UPPER 70S.
SUNDAY - MID NEXT WEEK: HEAVY RAIN MONDAY, MUCH COOLER MID WEEK
ON SUNDAY, AN UPPER LOW OVER THE PACIFIC NORTHWEST WILL BEGIN TO
EJECT TO THE NORTHEAST AS A STRONG RIDGE BUILDS OVER THE
SOUTHEASTERN US. THIS WILL LEAD TO A BELT OF STRONG SOUTHWESTERLY
FLOW OVER OUR REGION FOR THE FIRST HALF OF NEXT WEEK. MOISTURE
ADVECTION RAMPS UP AFTER THE PASSAGE OF SATURDAY'S COLD FRONT BUT IT
ISN'T UNTIL LATE IN THE DAY SUNDAY INTO MONDAY THAT THE BULK OF THE
DEEPER MOISTURE WORKS ITS WAY INTO THE UPPER MISSISSIPPI VALLEY. AT
THE SURFACE, A WARM FRONT IS EXPECTED TO LIFT NORTH INTO THE AREA BY
THE MORNING HOURS ON MONDAY WITH STRONG 850 MB MOISTURE TRANSPORT
INTO THE FRONTAL BOUNDARY. ECMWF PWATS ARE IN THE 90TH-99.5TH
PERCENTILES WITH A BROAD SWATH OF 1.75 INCHES AVERAGED ACROSS THE
AREA 00Z MONDAY - 00Z TUESDAY. WPC ALREADY HAS MOST OF OUR AREA IN
THEIR DAY 5 SLIGHT RISK FOR EXCESSIVE RAINFALL, INDICATING A
POTENTIAL FOR HEAVY RAINFALL LEADING TO FLASH FLOODING. WHILE
LOOKING AT THE EFI, THE SHIFT OF TAILS OR SOT HAS THE AREA NORTH OF
I-90 HIGHLIGHTED, A SIMILAR AREA TO WHERE THE NBM HAS THE HIGHEST
PROBABILITIES OF 2 INCHES OR MORE RAINFALL OVER A 48 HOUR PERIOD
ENDING AT 7AM TUESDAY MORNING. IT SHOULD BE NOTED THAT LOOKING AT
THE RAW NBM DATA VS THE BIAS CORRECTED NBM DATA SHOWS A VASTLY
DIFFERING PICTURE. THE RAW NBM DATA IS MUCH LOWER (HALF AN INCH TO
ALMOST AN INCH LOWER IN SOME PLACES) WHICH SEEMS TO BE MORE IN LINE
WITH THE 09.12Z LREF PROBABILITIES. GIVEN THE RECENT WET PERIOD
WE'VE HAD ACROSS THE AREA, ITS EASY TO SEE WHY THE BIAS CORRECTION
OF THE NBM IS TRENDING A LITTLE ON THE HIGH SIDE. SOME OF THESE
TOTALS WILL LIKELY BE LOWERED IN THE COMING DAYS BUT THERE IS STILL
A VERY REAL CHANCE FOR A HEAVY RAINFALL EVENT THAT COULD LEAD TO
FLOODING. THE PWATS AND WARM CLOUD DEPTHS WILL BE THERE BUT THE
QUESTION IS WHETHER STORMS ALONG THE BOUNDARY WILL TRAIN ENOUGH TO
CAUSE A FLOODING PROBLEM. THIS WILL BE SOMETHING TO KEEP AN EYE ON
OVER THE COMING DAYS. THE SOAKING RAINS WILL ALSO HELP TO KNOCK
TEMPERATURES DOWN QUITE A BIT WITH HIGHS BY MID WEEK LIKELY ONLY
REACHING INTO THE UPPER 60S TO LOW 70S, MUCH MORE REPRESENTATIVE OF
THE FALL TIMEFRAME WE'RE IN.
AVIATION /12Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 550 AM CDT THU SEP 10 2026
FOG HAS DEVELOPED OVER THE WISCONSIN RIVER VALLEY AND SOME OF
THE MISSISSIPPI RIVER VALLEY TRIBUTARIES. ALL FOG WILL
DISSIPATE BY MID-MORNING. OTHER THAN THE FOG THIS MORNING,
EXPECT VFR CONDITIONS THROUGH THE TAF PERIOD. LIGHT AND
VARIABLE WINDS CONTINUE THROUGH MID- MORNING BECOMING MORE WEST
TO NORTHWEST BY THE LATE MORNING. WINDS THEN SHIFT TO THE
SOUTHEAST BY THIS EVENING.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...BARENDSE
AVIATION...CECAVA
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