944
FXUS63 KARX 191048
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
548 AM CDT TUE AUG 19 2025
KEY MESSAGES
- LOW CHANCES FOR SHOWERS THIS AFTERNOON, TAPERING OFF THIS
EVENING.
- FOG AND LOW STRATUS CLOUDS CONTINUING THROUGH THE EARLY
MORNING HOURS TODAY AND COULD RETURN AGAIN TONIGHT. FOG MAY BE
DENSE IN SOME LOCATIONS.
- SEASONABLE TEMPERATURES AND MOSTLY DRY CONDITIONS THROUGH THE
WEEK WITH RAIN CHANCES INCREASING (CURRENTLY 20 TO 30%) FOR
FRIDAY AFTERNOON AS A COLD FRONT MOVES THROUGH THE AREA.
TRENDING COOLER FOR THE WEEKEND.
DISCUSSION
ISSUED AT 356 AM CDT TUE AUG 19 2025
TODAY: RAIN SHOWERS POSSIBLE, MORE FOG FOR TONIGHT?
CURRENT NIGHTTIME SATELLITE IMAGERY SHOWS FOG AND LOW STRATUS ACROSS
MUCH OF THE UPPER MIDWEST AS A RESULT OF THE RAIN THAT HAS FALLEN
OVER THE PAST FEW DAYS KEEPING THE LOW LEVELS SATURATED. THERE IS
ALSO A DEEP ENOUGH LIGHT WIND LAYER BASED ON THE LATEST HRRR/RAP
SOUNDINGS. THIS FOG IS EXPECTED TO CONTINUE TO BUILD IN AND THE
DENSE FOG ADVISORY THAT IS CURRENTLY IN PLACE FOR PORTIONS OF
NORTHEAST IOWA AND SOUTHEAST MINNESOTA MAY NEED TO BE EXPANDED OVER
THE NEXT FEW HOURS. ALL FOG AND LOW STRATUS SHOULD DISSIPATE/LEAVE
THE AREA BY LATER THIS MORNING. NBH PROBABILITIES ARE ALSO ALREADY
SHOWING INCREASING VALUES FOR FOG TO FORM AGAIN TONIGHT ACROSS THE
CWA. UNCERTAINTY REMAINS ON WHETHER OR NOT WE WILL SEE WIDESPREAD
DENSE FOG.
RIDGING BUILDS IN TODAY AND LINGERS THROUGH THE WEEK. IN THE LOW
LEVELS, A SURFACE HIGH DEVELOPS OVER THE GREAT LAKES/UPPER MIDWEST
REGIONS. WHILE NORMALLY THIS MEANS DRY CONDITIONS FOR OUR AREA, THE
LOW LEVELS MAINTAIN NORTHWEST FLOW THROUGH TODAY, PWATS BETWEEN 1.1
AND 1.4, AND A LITTLE MOISTURE TRANSPORT FROM THE NORTHWEST, THERE
IS A LOW CHANCE OF SHOWERS TO OCCUR DURING THE AFTERNOON AND
EVENING.
WEDNESDAY-THE WEEKEND: COOLER AND MOSTLY DRY
ENSEMBLE AND DETERMINISTIC GUIDANCE CONTINUES TO SHOW THE RIDGE
BUILDING IN AND LINGERING THROUGH THE WEEK BEFORE A LONGWAVE TROUGH
MOVES INTO THE AREA FOR THE WEEKEND AND EARLY NEXT WEEK. AS THE
SURFACE HIGH BUILDS IN, NORTHEAST WINDS AT THE SURFACE WILL HELP TO
KEEP US MOSTLY DRY FROM WEDNESDAY THROUGH THURSDAY. BY FRIDAY, A
COLD FRONT ASSOCIATED WITH A LONGWAVE TROUGH MOVES THROUGH. PRIOR TO
THIS, A BRIEF PERIOD OF WARM AIR ADVECTION ARRIVES AS SURFACE WINDS
SWITCH TO THE SOUTHWEST. TEMPERATURES FOR FRIDAY ARE SLIGHTLY WARMER
COMPARED TO THURSDAY. LOOKING AT CURRENT AVAILABLE SOUNDINGS FOR
FRIDAY SHOW DECENT SHEAR ALOFT (25 TO 35KTS) AND A LONG SKINNY CAPE
PROFILE WITH UP TO 1500 J/KG OF MLCAPE. WITH THESE INGREDIENTS,
SHOWERS AND STORMS COULD FIRE ALONG THE COLD FRONT AS IT MOVES
THROUGH OUR FORECAST AREA.
AFTER THE COLD FRONT MOVES THROUGH, DEWPOINTS AND TEMPERATURES DROP
FOR THE WEEKEND. THE 850MB TEMPERATURES DROP TO RANGE FROM 5 TO 10C
WHICH WILL TRANSLATE TO HIGH TEMPERATURES IN THE MID 60S TO LOW 70S.
LOW TEMPERATURES FOR SUNDAY MORNING IN THE UPPER 40S TO LOW 50S AND
FOR MONDAY AND TUESDAY MONDAY MORNINGS ARE CURRENTLY FORECASTED TO
MORNING LOWS, TEMPERATURES ARE IN THE MID 40S TO NEAR 50F. IF SKIES
ARE CLEAR ENOUGH, THESE LOWS COULD DIP A FEW MORE DEGREES. TO ADD TO
THE CONFIDENCE OF THESE LOWER TEMPERATURES, CPC HAS A 70 TO 80%
CHANCE FOR BELOW NORMAL TEMPERATURES FOR THEIR 6-10 DAY OUTLOOK
ACROSS THE GREAT LAKES AND PORTIONS OF THE UPPER MIDWEST, INCLUDING
OUR ENTIRE CWA. WITH ALL THIS BEING SAID, THIS WEEKEND IS LOOKING
QUITE PLEASANT!
AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 548 AM CDT TUE AUG 19 2025
FOG AND LOW-STRATUS CONTINUES TO BE THE MAIN AVIATION CONCERN THIS
MORNING WITH LIFR TO VLIFR VSBYS AND CIGS PERSISTING ACROSS MUCH OF
THE LOCAL AREA. THIS IS EXPECTED TO PERSIST THROUGH AROUND 14Z
UNTIL DIURNAL MIXING SUGGESTED IN THE RECENT RAP/HRRR SOUNDINGS
BEGINS TO MANIFEST AND CLEAR OUT THE NEAR-SFC LAYER. THIS
PROCESS TO MIX OUT THE INVERSION AND CLEAR OUT THE LOW-LEVEL
MOISTURE WILL BE RELATIVELY GRADUAL WITH IFR TO MVFR CIGS
REMAINING IN PLACE THROUGH MUCH OF THE MORNING. HOWEVER, CIGS
WILL EVENTUALLY SCATTER OUT AND IMPROVE TO VFR BY AFTERNOON.
SOME LOW-END CHANCES FOR SHOWERS MOVE INTO THE AREA DURING THE
AFTERNOON AND EARLY EVENING AS SOME WEAK INSTABILITY IS SHOWN
ACROSS MUCH OF THE CAMS. HOWWEVER, CONFIDENCE IN A SHOWER
REACHING EITHER TAF SITE IS VERY LOW AND THUS WAS NOT INCLUDED
AT EITHER KRST OR KLSE. FOG AND LOW-STRATUS THEN RE-ENTERS THE
EQUATION TONIGHT AND EARLY TOMORROW MORNING WITH A SIMILAR SETUP
WITH WEAK SFC WINDS, LOW-LEVEL MOISTURE AND A NOCTURNAL
INVERSION IN PLACE. AS A RESULT, HAVE ALREADY INCLUDED SOME
CATEGORY VSBY REDUCTIONS AT BOTH TAF SITES AND THESE MAY NEED TO
BE FURTHER LOWERED TO IFR/LIFR THRESHOLDS IN SUBSEQUENT
ISSUANCES.
HYDROLOGY
ISSUED AT 356 AM CDT TUE AUG 19 2025
WHILE RAINFALL HAS ENDED, THERE CONTINUES TO BE WATER ON ROADWAYS,
PARTICULARLY IN CHICKASAW AND HOWARD COUNTIES IN IOWA, AND SOME
ROADWAYS ALONG AND NEAR THE RIVER BASINS WHERE WE CURRENTLY HAVE
RIVER FLOOD WARNINGS DUE TO THE 2 TO 6 INCHES OF RAIN THAT FELL OVER
THE PAST 24 HOURS. THERE ALSO REMAINS A BIT OF RUNOFF THAT NEEDS TO
GET INTO THE RIVERS, AS WELL AS WATER THAT IS UPSTREAM OF CERTAIN
GAUGES THAT NEEDS TO GET DOWNSTREAM. THE RIVERS THAT HAVE RESPONDED
THE MOST ARE THE CEDAR AND ITS TRIBUTARIES, KICKAPOO, UPPER IOWA,
AND THE TURKEY RIVERS ALL HAVE AT LEAST A COUPLE GAUGES IN MINOR
FLOOD STAGE OR FORECASTED TO REACH MINOR FLOOD STAGE OVER THE NEXT
DAY OR SO.
ARX WATCHES/WARNINGS/ADVISORIES
WI...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR WIZ032-033.
MN...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR MNZ079-
086>088-094>096.
IA...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR IAZ008>011-
018-019-029-030.
DISCUSSION...CECAVA
AVIATION...NAYLOR
HYDROLOGY...CECAVA
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