807
FXUS63 KARX 050539
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1239 AM CDT SAT SEP 5 2026
KEY MESSAGES
- FOGGY CONDITIONS/LOW STRATUS THIS MORNING FOLLOWED BY DRY CONDITIONS
THROUGH THIS EVENING.
- WARM TEMPERATURES CONTINUE TODAY WITH HIGHS IN THE MID 80S FOLLOWED
BY SLIGHTLY COOLER TEMPERATURES FOR SUNDAY AND MONDAY WITH
HIGHS IN THE MID 70S TO LOW 80S.
- SHOWER AND STORM CHANCES RETURN SUNDAY FOR NORTHEAST IOWA AND SOUTHEAST
MINNESOTA (20 TO 40%) WITH THE NEXT WIDESPREAD RAIN CHANCE
(50 TO 80%) FOR TUESDAY INTO WEDNESDAY.
DISCUSSION
ISSUED AT 1225 AM CDT SAT SEP 5 2026
MORNING FOG:
FOGGY CONDITIONS EXPECTED THIS MORNING AS A RIDGE BUILDS INTO THE
UPPER MIDWEST. LIGHT NORTHEAST WINDS COUPLED WITH A MOIST
AIRMASS OF DEWPOINTS NEAR 70F AND A STABILIZING ATMOSPHERE WILL
ALL AID IN FOG DEVELOPMENT. THE FOG MAY BE DENSE AT TIMES WITH
THE 00Z HREF SUGGESTING A 20 TO 40% CHANCE FOR VISIBILITIES TO
DROP BELOW 1/4 MILE. ANY FOG OR LOW STRATUS THAT DEVELOPS WILL
LIKELY DISSIPATE BY MID-MORNING.
SHOWERS/STORMS RETURN SUNDAY:
DRY CONDITIONS WILL BE WITH US THROUGH THIS EVENING UNTIL A
WAVE MOVES DOWN FROM NORTHERN MINNESOTA LATE TONIGHT INTO
SUNDAY. SEVERAL CAMS SHOW SHOWERS AND STORMS SPARKING OFF THIS
WAVE FROM EASTERN SD TO CENTRAL MINNESOTA EARLY SUNDAY MORNING.
SHOWERS AND STORMS CONTINUE DOWN INTO NORTHERN IOWA THROUGH
SUNDAY AFTERNOON AND EVENING. SOME OF THESE COULD GET INTO
PORTIONS OF NORTHEAST IOWA AND SOUTHEAST MINNESOTA (20 TO 40%).
ANY STRONG TO SEVERE STORM CHANCES SHOULD STAY OFF TO OUR WEST
AS LOCAL AREA SHEAR REMAINS QUITE WEAK. ADDITIONALLY, AS THE
RIDGE CONTINUES TO BUILD NORTHWARD, LOW LEVEL DRY AIR WILL BE
IN PLACE RESULTING IN A CAP ACROSS MUCH OF FORECAST AREA.
SHOWERS/STORM POTENTIAL PERSISTS MONDAY:
ANOTHER WAVE MOVES NORTHEASTWARD INTO NORTHERN MINNESOTA AND
FAR NORTHWESTERN WISCONSIN INTO MONDAY, POTENTIALLY RESULTING
IN SHOWERS AND STORMS FOR SOME OF OUR NORTHWESTERN COUNTIES (15
TO 25%). DESPITE THE RIDGE BUILDING IN, TEMPERATURES WILL ONLY
BE SLIGHTLY ABOVE NORMAL AS SURFACE WINDS WILL BE OUT OF THE
SOUTHEAST.
ADDITIONAL SHOWER/STORM CHANCES INTO MIDWEEK:
THE UPPER LEVEL PATTERN SHIFTS TO ZONAL/SOUTHWEST FLOW DUE TO
AN APPROACHING SHORTWAVE TROUGH HEADING INTO TUESDAY. ALL THREE
OF THE GFS, ECMWF, AND CMC HAVE THIS TROUGH AND ASSOCIATED COLD
FRONT PASSING THROUGH LATE TUESDAY INTO WEDNESDAY. THERE ARE
SOME DIFFERENCES IN THE TIMING OF THE FRONT WITH THESE MODELS
AND CAN EXPECT THESE DETAILS TO GET IRONED OUT AS FORECAST HOUR
NEARS. MOISTURE TRANSPORT INCREASES EARLY TUESDAY AHEAD OF THE
FRONT WHICH GIVES THE REGION ITS FIRST DOSE OF PRECIPITATION
CHANCES AS THE FRONT EVENTUALLY MOVES THROUGH LATE TUESDAY INTO
WEDNESDAY WHERE THE LATEST NBM HAS 50 TO 80% POPS WITH THE
FRONTAL PASSAGE.
CURRENT UNCERTAINTY ON COVERAGE OF CONVECTION IS DUE TO
POTENTIAL LOW LEVEL DRY AIR THAT STORMS WOULD HAVE TO OVERCOME.
THEREFORE, LOWER POPS MAY BE REALIZED DURING THIS TIMEFRAME.
A LOW CHANCE FOR SEVERE WEATHER IS EXPECTED WITH FRONTAL
PASSAGE DUE TO 35 TO 45 KTS OF EFFECTIVE SHEAR AND 500 TO 1250
J/KG OF MLCAPE. MOST AI AND ML GUIDANCE HAVE A LOW CHANCE (5 TO
15%) FOR ANY KIND OF SEVERE WEATHER TO OCCUR. WITH A SHIFT
TOWARDS MORE SOUTHWESTERLY FLOW IN THE LOW LEVELS, TEMPERATURES
INCREASE BACK UP INTO THE MID TO UPPER 80S FOR TUESDAY BEFORE
FALLING BACK DOWN INTO THE MID 70S TO MID 80S FOR WEDNESDAY.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 1225 AM CDT SAT SEP 5 2026
MAIN AVIATION IMPACTS FROM DENSE FOG SEEN BUILDING ON SATELLITE
AT 05.06Z TAF ISSUANCE. GIVEN TRENDS AND OBSERVATIONS, HAVE
INCREASED IMPACTS AT KRST INTO THE MORNING HOURS AND SPED UP
IMPACTS AT KLSE. CURRENT CONFIDENCE FOR VLIFR VISIBILITIES
AFFECTING KLSE REMAINS LOW (<20%) GIVEN THE LOW LEVEL STRATUS
PROVIDING OVERNIGHT INSULATION. WILL REQUIRE FURTHER AMENDMENT
SHOULD ADDITIONAL VISIBILITY IMPACTS OCCUR WITHIN THE RIVER
VALLEY.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...CECAVA
AVIATION...JAR
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