631
FXUS63 KARX 272344
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
644 PM CDT MON OCT 27 2025
KEY MESSAGES
- RAIN SHOWERS MOVE IN LATE TONIGHT THROUGH TUESDAY, THE BIG
QUESTION BEING HOW FAR EAST THEY PROGRESS. RECENT TRENDS ARE
NOW POINTING TO A WESTWARD SHIFT IN THE RAINFALL AND AREAS
EAST OF THE MISSISSIPPI RIVER MAY STAY MOSTLY DRY.
- COOLING OFF THROUGH THE WEEK WITH HIGHS FALLING TO THE UPPER
40S TO AROUND 50 BY SATURDAY.
- DRIER AFTER TUESDAY WITH A TOKEN CHANCE OF SHOWERS FRIDAY INTO
THE WEEKEND.
DISCUSSION
ISSUED AT 130 PM CDT MON OCT 27 2025
TUESDAY - TUESDAY NIGHT: RAINFALL DETAILS
AN AMPLIFYING UPPER TROPOSPHERIC GREAT LAKES OMEGA BLOCK
GRADUALLY NUDGES EASTWARD THIS AFTERNOON AND TONIGHT, WITH AN
UPSTREAM LONGWAVE TROUGH ELONGATING AND EVENTUALLY SPLITTING ON
TUESDAY AS IT RUNS UP AGAINST THE DOWNSTREAM BLOCK. MUCH OF THE
WAVE ENERGY SLIDES SOUTHEASTWARD UNDER THE BLOCK ACROSS THE OHIO
RIVER VALLEY ON TUESDAY AND GRADUALLY EJECTS INTO THE
NORTHEASTERN CONUS TO END THE WEEK. A SURFACE FRONT SLIDES
EASTWARD WITH THIS ADVANCING UPPER TROPOSPHERIC TROUGH AND
STALLS AS THE WAVE ENERGY BIFURCATES AROUND THE RIDGE. THIS
SURFACE FRONT THEN PIVOTS AND WASHES OUT TUESDAY NIGHT AS THE
SOUTHERN LOW TAKES OVER.
DESPITE BEING ON OUR DOORSTEP, THERE REMAINS AMPLE UNCERTAINTY
IN HOW FAR EAST THE ASSOCIATED RAIN SHOWERS CAN ADVANCE BEFORE
BEING UNDERCUT BY DRIER AIR OFF THE GREAT LAKES RIDGE. THE EXACT
MORPHOLOGY OF THE UPSTREAM WAVE AS IT CUTS OFF HAS BEEN A POINT
OF UNCERTAINTY IN THE FORECAST FOR DAYS AND PLAYS DIRECTLY IN
THE EASTWARD PROGRESSION OF THE FRONT AND RAIN SHIELD. AN
AGGREGATE LOOK AT THE GFS/EC UPPER LEVEL PLOTS OVER THE LAST FEW
DAYS HAS SHOWN A SLIGHT WESTWARD EXPANSION OF THE GREAT LAKES
RIDGE, RESULTING IN THE TROUGH SPLITTING AND THE SURFACE FRONT
STALLING SOONER THAN EARLIER FORECAST.
THE BIG QUESTION IS...HOW MUCH STOCK TO PUT INTO THESE TRENDS?
FORECAST SOUNDINGS FROM THE RAP/HRRR SHOW AMPLE SATURATION AND
ISENTROPIC LIFT ABOVE THIS LOW-LEVEL DRY WEDGE, SO THE RAINFALL
WILL BE GENERATED ALOFT, IT IS JUST A MATTER OF HOW MUCH
PRECIPITATION LOADING IT WILL TAKE TO OVERCOME THIS DRY AIR.
HAVE TRENDED THE FORECAST IN THE DRIER DIRECTION, ESPECIALLY FOR
THE MORNING HOURS EAST OF THE MISSISSIPPI RIVER. WITH THE
BOUNDARY STALLING SOONER AND FARTHER WEST, THE PREVIOUSLY
ADVERTISED HEAVY RAIN AXIS LOOKS TO BE SHIFTING WEST OF THE
FORECAST AREA.
ALONG WITH THE WESTWARD SHIFT IN THE PRECIPITATION FIELD, THE
MEDIUM RANGE SOLUTIONS ARE CLEARING THE RAINFALL SOONER TUESDAY
NIGHT INTO EARLY WEDNESDAY MORNING.
OUTLOOK FOR THE REST OF THE WEEK
A PROGRESSIVE NORTHWESTERLY FLOW PATTERN SETS UP FOR THE END OF
THE WEEK, WITH A COL/RIDGING PASSING THROUGH LATE WEDNESDAY
INTO THURSDAY AND AN ELONGATED TROUGH ROTATING DOWN FOR FRIDAY.
CYCLONIC FLOW LINGERS INTO THE WEEKEND WITH WEAK PERTURBATIONS
ROTATING THROUGH THAT WILL BRING PERIODIC LIGHT ROUNDS OF
RAINFALL. THE OVERALL IMPACTS FROM THIS RAIN LOOK TO BE MINIMAL.
THE NORTHWESTERLY FLOW WILL STEADILY COOL TEMPERATURES TO NEAR
OR SLIGHTLY BELOW SEASONAL NORMS WITH HIGHS IN THE MID TO UPPER
40S TO END THE WEEK.
AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/
ISSUED AT 629 PM CDT MON OCT 27 2025
GUIDANCE CONTINUES TO TREND TOWARD A SLOWER ARRIVAL FOR SHOWERS
AND ASSOCIATED LOW CEILINGS WEST OF THE MISSISSIPPI RIVER SO
HAVE SLOWED THEM ACCORDINGLY IN THE AVIATION FORECAST.
ADDITIONALLY, HAVE KEPT REDUCTIONS ALL WEST OF THE MISSISSIPPI
AS THIS RAIN LOOKS TO ENCOMPASS LESS OF THE AREA OVERALL ONCE IT
DOES ARRIVE. EXPECT ADDITIONAL TIMING REFINEMENTS OVER THE
COMING CYCLES.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...SKOW
AVIATION...FERGUSON
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