721
FXUS63 KARX 040543
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1243 AM CDT THU SEP 4 2025
KEY MESSAGES
- ISOLATED TO SCATTERED SHOWERS ARE POSSIBLE THIS AFTERNOON
(10-30%). FROST IS POSSIBLE NORTH OF I-94 TONIGHT (40-60%).
A FROST ADVISORY HAS BEEN ISSUED.
- A QUICK HITTING SYSTEM MOVES THROUGH THE REGION THURSDAY
NIGHT, BRINGING RAIN AND PERHAPS A RUMBLE OF THUNDER (60-90%).
- TEMPERATURES REMAIN COOL THROUGH THE WEEKEND BEFORE A WARMING
TREND NEXT WEEK.
DISCUSSION
ISSUED AT 211 PM CDT WED SEP 3 2025
TODAY AND TONIGHT
ISOLATED TO SCATTERED SHOWERS ARE EXPECTED LATE THIS AFTERNOON
INTO THE EVENING ASSOCIATED WITH STEEPENING LAPSE RATES IN THE
850-700HPA LAYER VIA COLD AIR ADVECTION (10-30%). ANY SHOWERS
THAT DEVELOP WILL BE LIGHT.
THE ABNORMALLY COLD AIRMASS SINKING INTO THE UPPER MIDWEST THIS
AFTERNOON WILL DROP TEMPERATURES TO BELOW NORMAL VALUES THROUGH
THE END OF THE WEEK. TONIGHT APPEARS TO BE THE COLDEST, AS THE
03.13Z NBM DEPICTS LOW TEMPERATURES OF 35 TO 40 DEGREES OVER THE
REGION, LOWEST ALONG AND NORTH OF I-94. CLOUDS CONTINUE TO
THROW A WRENCH INTO THE MIX THOUGH, AS LINGERING 850HPA MOISTURE
IS SHOWN IN RAP/HRRR SOUNDINGS, MAKING THE ULTIMATE LOW
TEMPERATURE TRICKY TO FORECAST. LINGERING STRONGER LOW LEVEL
WINDS VIA THE TIGHTENED PRESSURE GRADIENT ASSOCIATED WITH
DEPARTING LOW PRESSURE OVER THE GREAT LAKES COULD ALSO HINDER
FROST DEVELOPMENT BY DECREASING CONDENSATION/DEPOSITION.
HOWEVER, THE FAVORABLE TEMPERATURES AND EARLY SEASON TIMEFRAME
DOES LEAD TO MORE CONCERN OF IMPACTS FROM FROST. OVERALL, A
MARGINAL SET-UP FOR FROST DEVELOPMENT IS EXPECTED OVERNIGHT,
HINGING ON SEVERAL FACTORS THAT NEED TO COME TOGETHER CORRECTLY.
PROVIDED SKIES CLEAR AND WINDS DIMINISH OVERNIGHT, CONFIDENCE
IS HIGH THAT FROST WILL DEVELOP.
QUICK HITTING SYSTEM THURSDAY NIGHT INTO FRIDAY
MODEL GUIDANCE IS IN MUCH BETTER AGREEMENT REGARDING A 500HPA
SHORTWAVE TROUGH DIVING SOUTH OUT OF CANADA THURSDAY,
PROPAGATING THROUGH OUR NORTHWEST FLOW ALOFT. FORCING ASSOCIATED
WITH THIS FEATURE PROVIDES SUBSTANTIAL SUPPORT FOR DEEPENING
THROUGHOUT THE TROPOSPHERE AND SURFACE CYCLOGENESIS. THE SURFACE
LOW AND ASSOCIATED FRONTAL SYSTEM PROPAGATE EASTWARD THROUGH
THE UPPER MISSISSIPPI RIVER VALLEY THURSDAY NIGHT. AHEAD OF THE
SURFACE FEATURES, SEASONABLE PWATS AROUND 1 INCH WILL COINCIDE
WITH STRONG MOISTURE CONVERGENCE FOCUSED ACROSS THE REGION.
CONDITIONS APPEAR MORE THAN SUITABLE FOR RAIN DURING THIS
PERIOD, BUT LESS CONFIDENT IN STORMS GIVEN MEAGER INSTABILITY
AND THE OVERNIGHT TIME PERIOD AS MUCAPE VALUES ONLY CLIMB TO 250
J/KG, BUT A RUMBLE OF THUNDER CAN'T BE RULED OUT. GIVEN THE
PROGRESSIVE NATURE OF THIS SYSTEM AND THE SEASONABLE MOISTURE,
PRECIPITATION AMOUNTS SHOULD GENERALLY BE ON THE LOWER END WITH
THE 03.13Z NBM SUGGESTING A 30-70% PROBABILITY OF 24 HOUR TOTALS
GREATER THAN 0.25 INCHES. TOWARDS NORTH-CENTRAL WISCONSIN,
ALONG AND NORTH OF I-94, WHERE THE GREATEST CONVERGENT SIGNAL OF
THE MOISTURE TRANSPORT IS CURRENTLY EXPECTED TO RESIDE,
CONDITIONS ARE MORE FAVORABLE FOR HIGHER AMOUNTS THOUGH,
GENERALLY 20-50% FOR GREATER THAN 0.5 INCHES.
INCREASING TEMPERATURES NEXT WEEK
THE COOLER TEMPERATURES WILL CONTINUE THROUGH THE WEEKEND UNDER
THE LONGWAVE TROUGH SITUATED OVER THE UPPER GREAT LAKES. AFTER
ONE LAST SHORTWAVE PIVOTS THROUGH THE LONGWAVE PATTERN SATURDAY
AFTERNOON, POSSIBLY BRINGING ADDITIONAL SHOWERS TO THE AREA
(30-50% IN THE 03.00Z LREF), RIDGING BUILDS INTO THE UPPER
MIDWEST. UNDER THE RISING HEIGHTS AND SOUTHERLY FLOW BEGINNING
TO TAKE BACK OVER, TEMPERATURES ARE EXPECTED TO INCREASE INTO
THE 70S FOR MUCH OF THE AREA.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 1215 AM CDT THU SEP 4 2025
MODERATE (60-80%) CONFIDENCE FOR AREA WIDE VFR THROUGH THE
04.06Z TAF PERIOD. NEAR SURFACE SMOKE CONCENTRATIONS OVER THE
MISSOURI RIVER VALLEY EARLY THIS MORNING CAUSING MVFR
VISIBILITIES ARE EXPECTED TO LESSEN, DECREASING CONFIDENCE FOR
ANY LOCAL IMPACTS TODAY. MAIN CONCERN FOR AFTERNOON SMOKE
IMPACTS WILL LIE WEST OF THE MISSISSIPPI RIVER VALLEY WITH LOW
CONFIDENCE IN OVERALL EASTERN EXTENT, POTENTIALLY TONIGHT
BEFORE PRECIPITATION CHANCES INCREASE.
OTHER THAN RAINFALL ACCOMPANYING VISIBILITY IMPACTS, HIGH WINDS
WILL BE MAIN CONCERN WITH INCOMING PRECIPITATION CHANCES AS
WIDESPREAD 30+KT GUSTS ARE POSSIBLE. RAPID ROTATION TO STRONGER
WINDS FROM INITIALLY SOUTH NEAR 05.00Z, WEST NEAR 05.03Z, TO
WEST-NORTHWEST SHORTLY THEREAFTER. STRONGEST WINDS SUBSIDE
THROUGH FRIDAY MORNING ALBEIT REMAINING STRONG, SUSTAINED 15+KT
FROM THE NORTHWEST UNTIL FRIDAY NIGHT.
WHILE LLWS WASN'T ADDED AT THE CURRENT FORECAST DUE TO SURFACE
GUSTS INSTEAD CAUSING LOW LEVEL TURBULENCE, LLWS WILL NEED TO
BE REFINED IN COMING FORECAST(S) PRIMARILY AT INITIAL ONSET,
BEFORE SURFACE WINDS RESPOND TO STRONG LOW LEVEL JET.
SUBSEQUENT AVIATION IMPACTS POSSIBLE FRIDAY NIGHT THROUGH
SATURDAY WITH CURRENT CONFIDENCE PRIMARILY ALONG AND EAST OF THE
MISSISSIPPI RIVER IN CENTRAL WISCONSIN.
CLIMATE
ISSUED AT 211 PM CDT WED SEP 3 2025
THERE STILL APPEARS TO BE SOME CHANCE AT SETTING A RECORD COOL
MAXIMUM TEMPERATURE ON FRIDAY (SEP 5) BASED ON THE CURRENT
FORECAST.
LA CROSSE, WI
DATE RECORD COLD HIGH FORECAST HIGH
----- ----------- -----------
9/4 60F(2008) 66F
9/5 59F(1896) 62F
9/6 60F(1965) 64F
ROCHESTER, MN
DATE RECORD COLD HIGH FORECAST HIGH
----- ----------- -----------
9/4 60F(1994) 62F
9/5 59F(1956) 59F
9/6 58F(1965) 61F
ARX WATCHES/WARNINGS/ADVISORIES
WI...FROST ADVISORY UNTIL 8 AM CDT THIS MORNING FOR WIZ017-029.
MN...NONE.
IA...NONE.
DISCUSSION...FALKINHAM
AVIATION...JAR
CLIMATE...FALKINHAM
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