594
FXUS63 KARX 151842
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
140 PM CDT MON SEP 15 2025
KEY MESSAGES
- ONGOING SHOWERS/STORMS LIKELY TO PERSIST INTO THIS EVENING, WITH
CHANCES CONTINUING OVERNIGHT INTO TUE. DRIVEN BY MICRO SCALE
FEATURES - REFINING TIMING/LOCATION OF HIGHER CHANCES CHALLENGING.
EXPECT SOME UPDATES TO THE RAIN CHANCES THROUGH TUE AS A RESULT.
- INCREASING RAIN CHANCES FOR FRI/WEEKEND AS UPPER LEVEL LOW MOVES
IN.
- WARMING LINGERS INTO FRIDAY NOW WITH COOLER, CLOSER TO SEASONABLE
TEMPS (BACK INTO THE 70S) LIKELY FOR THE WEEKEND.
DISCUSSION
ISSUED AT 140 PM CDT MON SEP 15 2025
> FIRST - REST OF TODAY INTO TUE: SOMETIMES IT'S NOT THE LARGE
SCALE. SOMETIMES IT'S NOT EVEN THE MESOSCALE. SOMETIMES ITS ALL
ABOUT THE MICRO SCALE. THOSE SMALL ELEMENTS THAT YOU CAN'T ALWAYS
DISCERN UNTIL A FEW HOURS OUT. THAT'S WHAT'S OCCURRING RIGHT NOW,
AND WILL LIKELY BE A FACTOR IN THE RAIN CHANCES THROUGH TUE.
CONVECTIVELY PRODUCED ENERGY A LOFT, IMPINGEMENT OF THE LOW LEVEL
JET, SFC CONVERGENCE, OUTFLOW BOUNDARIES, DEFERENTIAL HEATING
INDUCED BOUNDARIES - ALL WEAK - BUT WHEN MIXED TOGETHER YOU CAN GET
WHAT YOU SEE OUTSIDE (RIGHT NOW). ADD IN 1-2K J/KG OF MUCAPE AND THE
CONVECTION CAN BECOME MORE PERKY.
SOME MOVEMENT EAST ON RECENT RADAR/SATELLITE TRENDS, BUT SATELLITE
SHOWS SOME DRYING/DECREASING CLOUDS MOVING INTO CENTRAL WI - A SIGN
OF SINKING AND/OR DRYING.
EXPECTATION IS FOR CURRENT CONVECTION TO CONTINUE FOR THE REST OF
THE AFTERNOON. HOW IT PLAYS OUT TONIGHT INTO TUE ISN'T CLEAR AND THE
CAMS AREN'T REALLY HELPFUL. BUT WITH ALL THOSE MICROSCALE ELEMENTS
LINGERING IN SOME FASHION, 20-30% RAIN CHANCES ARE REASONABLE. WILL
UPDATE AS NEEDED - WITH A CLOSE EYE ON THE NEAR TERM ENVIRONMENT
WHICH, AS MENTIONED, IS THE MAIN DRIVER OF THE RAIN. OF NOTE, THE
SHORT TERM MODELS SUGGEST SOME REGRESSION WEST WITH THE INSTABILITY
AXIS, WHICH COULD ALSO SHIFT THE RAIN CHANCES WEST.
> WHAT'S CHANGED: WHAT LOOKED LIKE A MORE PROGRESSIVE PATTERN JUST A
FEW DAYS AGO IS TRENDING SLOWER, WITH MORE BLOCKING FROM A MORE
STOUT OF A RIDGE THAN ENSEMBLE GUIDANCE PREVIOUS DEPICTED. THIS
IMPACTS THE LOCAL AREA WITH A MORE PROLONGED PERIOD OF SUMMER-LIKE
TEMPS WHILE ALSO HOLDING OFF THE BRUNT OF THE RAIN CHANCES WITH THE
UPPER LEVEL LOW UNTIL THE WEEKEND.
> OVERVIEW: UPPER LEVEL RIDGE AXIS CONTINUES TO EAST EAST TODAY, BUT
"BENDS OVER" MORE SO THAN EXITS, EXTENDING SOUTHEAST FROM THE
EASTERN GREAT LAKES. A SIGNAL THAT SOME OF THE LONGER RANGE GUIDANCE
SUGGESTED YESTERDAY. SOME WEAK RIPPLES IN THE UPPER LEVEL COULD
CREEP EASTWARD FROM THE TROUGH OVER THE PLAINS, BUT THE BULK OF THE
SHORTWAVE ENERGY WOULD HOLD WEST/NORTH IN THIS SCENARIO.
A MORE SIGNFICIANT CHANGE IS THE EPS AND GEFS START TO RETROGRADE
THAT RIDGE AXIS WEST THU/FRI, NOT PUSHING EAST UNTIL THE END OF THE
WEEKEND. WPC CLUSTERS LOOK SIMILAR - ALTHOUGH A COUPLE SOLUTIONS
WOULD HOLD ONTO THE RIDGE A DAY OR TWO LONGER. THE TROUGH AXIS WOULD
FINALLY SWING ACROSS THE REGION SAT NIGHT/SUN.
> TEMPERATURES: THE UNSEASONABLY WARM, SUMMER-ISH AIRMASS WILL STICK
AROUND A BIT LONGER IF THE CURRENT RIDGE RETROGRATION WESTWARD COMES
TO PASS. EPS/GEFS FAVOR IT, AS DOES THE WPC CLUSTERS, SO THE NBM
MODEL BLEND HAS SHIFTED FROM COOLING INTO THE 60S AND 70S FOR THE
WEEKEND TO HOLDING IN THE 80S THROUGH THU, THEN MOSTLY 70S THROUGH
THE WEEKEND (AT OR ABOVE THE NORMALS). CLOUDS/RAIN CHANCES COULD
PUSH THOSE DOWN A FEW DEGREES AT TIMES.
> RAIN CHANCES: WITH THE SLOWER MOVEMENT OF THE UPPER LEVEL TROUGH
EASTWARD, THE BRUNT OF THE RAIN CHANCES WILL HOLD ACROSS MN, IA AND
NORTHWEST WI FOR THE BETTER PART OF THE WORK WEEK. BITS OF SHORTWAVE
ENERGY, WEAK CONVERGENCE SFC/NEAR SFC BOUNDARIES, ALONG WITH POCKETS
OF INSTABILITY AND IMPINGEMENT FROM RELATIVELY WEAK LOW LEVEL JETS,
COULD BRING SHRA/TS TO PORTIONS OF THE LOCAL AREA, MOSTLY WEST OF
THE MISSISSIPPI RIVER AND NORTH OF I-94. THE SMALLER SCALE NATURE,
AND POTENTIAL INTERACTIONS FROM OTHER WEAK FEATURES AND POTENTIAL
DEFERENTIAL HEATING BOUNDARIES, MAKE TIMING/LOCATION OF THE CHANCES
PROBLEMATIC. SUFFICE TO SAY THOUGH, THE WIDESPREAD RAINS OF MID WEEK
NOW ARE SHIFTING MORE INTO FRIDAY/THE WEEKEND - PER THE RECENT MODEL
TRENDS.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 1210 PM CDT MON SEP 15 2025
SHOWERS AND STORMS WILL BE THE PRIMARY AVIATION CONCERN THIS
AFTERNOON AND INTO THE OVERNIGHT HOURS AS ONGOING SHOWERS AND STORMS
CONTINUE TO PROGRESS THROUGH THE REGION. ADDITIONAL SHOWERS AND
STORMS MAY DEVELOP LATER THIS EVENING AND INTO THE OVERNIGHT AS THE
NOCTURNAL LOW-LEVEL JET STRENGTHENS SLIGHTLY WITH EXACT COVERAGE OF
THESE SHOWERS AND STORMS REMAINING UNCERTAIN. MVFR TO IFR VISIBILITY
REDUCTIONS WILL BE POSSIBLE WITH ANY SHOWERS/STORMS THROUGH THE
OVERNIGHT. OTHERWISE, VFR CONDITIONS ARE GENERALLY EXPECTED WITH
WINDS PERSISTING FROM THE SOUTHEAST AT AROUND 8-12 KTS BEFORE
FALLING TO AROUND 5 KTS AFTER SUNSET THIS EVENING.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...RIECK
AVIATION...NAYLOR
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