158
FXUS63 KARX 170831
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
331 AM CDT WED SEP 17 2025
KEY MESSAGES
- A GRADUAL INCREASE IN SHOWER AND THUNDERSTORM POTENTIAL AS WE
MOVE INTO THE WEEKEND.
- WARM TEMPERATURES PERSIST INTO THURSDAY (80S FOR MOST),
DROPPING TO MORE SEASONABLE LEVELS (70S) FOR THE WEEKEND INTO
POTENTIALLY EARLY NEXT WEEK.
- POTENTIAL FOR SOME FORM OF NOTABLE WEATHER NEXT MONDAY,
TUESDAY BUT UNCERTAINTY IS VERY HIGH.
DISCUSSION
ISSUED AT 330 AM CDT WED SEP 17 2025
POTENTIAL FOR SHOWERS, THUNDERSTORMS RAMPS UP INTO THE WEEKEND:
FLOW PATTERN WILL SLOWLY PROGRESS OVER THE NEXT SEVERAL DAYS WITH
THE CWA UNDER SOUTHWESTERLY ALOFT ALOFT BETWEEN A RIDGE TO OUR EAST
AND TROUGHINESS OVER THE NORTHERN PLAINS. WITHIN THIS FLOW,
SHORTWAVES ALOFT WILL HELP TO KICK OFF SPORADIC CONVECTION WHERE
TEMPERATURES ALOFT ARE COOL ENOUGH AND LOW LEVEL MOISTURE IS
SUFFICIENT. OVER THE NEXT 2 DAYS, THE AREA WITH POTENTIAL CONVECTION
WILL EXPAND - TODAY MAINLY ENCOMPASSING ALL BUT SW WI AND THURSDAY
AREAWIDE - AS THE RIDGE BREAKS DOWN. FRIDAY INTO SATURDAY,
ADDITIONAL SHOWERS AND THUNDERSTORMS MAY OCCUR AREAWIDE BUT BEST
FORCING NOW LOOKS TO BE DISPLACED TO OUR SOUTH.
PRIMARY POTENTIAL HAZARD THROUGH THIS WEEKEND CONTINUES TO APPEAR TO
BE LOCALIZED HEAVY RAINFALL WITH PROGGED PWATS MAINLY IN THE 1.25"-
1.5" RANGE AND RELATIVELY SLOW STORM MOTIONS, PARTICULARLY OVER THE
NEXT 2 DAYS (5 TO 15 MPH). ON THE SUBJECT OF SEVERE THUNDERSTORMS,
WHILE THESE CONTINUE TO APPEAR UNLIKELY, CANNOT TOTALLY RULE OUT A
STAY REPORT OR TWO GIVEN AMOUNT OF AVAILABLE INSTABILITY (AROUND
1000 J/KG OF MLCAPE) BUT SHEAR REMAINS VERY LOW (15 KNOTS OR LESS)
AND MID-LEVEL LAPSE RATES, WHICH DID APPROACH 7 C/KM NEAR WHERE HAIL
REPORTS OCCURRED TUESDAY, MODERATE TO CLOSER TO 6 C/KM.
WARM THROUGH TOMORROW, A BIT COOLER FRIDAY ONWARD:
TEMPERATURES IN THE 80S ARE EXPECTED TODAY AND TOMORROW AS THE UPPER
RIDGE REMAINS TO OUR EAST. TEMPERATURES THROUGH THE REMAINDER OF THE
NEXT WEEK LOOK TO LARGELY BE IN THE 70S BUT NBM VALUES SEEM TO BE
CREEPING UPWARD A BIT WITH TOP END OF 17.01Z NBM INTERQUARTILE RANGE
NOW AROUND 80 IN MANY LOCATIONS.
INTRIGUE EARLY NEXT WEEK:
17.00Z OPERATIONAL GFS/EC/CMC RUNS ALL DEPICT A STRONG UPPER JET
ADVANCING OVER CENTRAL TO NORTHERN CASCADIA WITH AN UPPER TROUGH
DOWNSTREAM AMPLIFYING IN RESPONSE. SPREAD BETWEEN THESE OPERATIONAL
RUNS AND ACROSS THE BROADER UNIVERSE OF ENSEMBLE RUNS WITH REGARD TO
THE TIMING AND EVOLUTION OF THIS UPPER TROUGH IS LARGE TO SAY THE
LEAST. FOR EXAMPLE, 17.00Z GFS BRINGS THE UPPER TROUGH OVER MN
MONDAY NIGHT WITH THIS FEATURE DEEPENING INTO AN UPPER LOW OVER THE
GREAT LAKES IN THE FOLLOW DAYS, 17.00Z CMC DEPICTS A SIMILAR
EVOLUTION INTO AN UPPER LOW BUT PLACES THIS FEATURE OVER THE CENTRAL
TO SOUTHERN PLAINS, WHILE THE 17.00Z EC DEPICTS A MUCH MORE
PROGRESSIVE PATTERN WITH THE TROUGH REMAINING TO OUR NORTH OVER
CANADA. WILL NEED TO WATCH THIS PERIOD AS THIS COULD RESULT IN ONE
OR MORE OF MANY OUTCOMES - RAIN, A SEVERE STORM OR TWO, WINDY
CONDITIONS, OR A TURN TOWARD COOLER TEMPERATURES.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1208 AM CDT WED SEP 17 2025
PERSISTENT LOW CONFIDENCE (<30%) IN FLIGHT IMPACTS THROUGH THE
17.06Z TAF PERIOD ACROSS THE FORECAST AREA FROM SOUTHEAST
MINNESOTA, NORTHEAST IOWA, AND SOUTHWEST THROUGH CENTRAL
WISCONSIN. LOW STORM CHANCES (20-30%) INITIALLY AFFECT AIRPORTS
WEST OF THE MISSISSIPPI RIVER VALLEY (KAUM/KCCY) THROUGH THE
MORNING HOURS, SPREADING EAST BY LATE MORNING. IFR VISIBILITIES
LIKELY WHERE STORMS FORM SHOULD THEY PASS OVER ASOS/AWOS.
THURSDAY THROUGH SUNDAY..STORM CHANCES INCREASE AND SPREAD EAST
THURSDAY, BECOMING WIDESPREAD FRIDAY AND LINGERING THROUGH THE
WEEKEND.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...FERGUSON
AVIATION...JAR
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