003
FXUS63 KARX 141127
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
627 AM CDT THU AUG 14 2025
KEY MESSAGES
- POTENTIAL FOR MULTIPLE ROUNDS OF STORMS FROM FRIDAY NIGHT AND
INTO SUNDAY NIGHT. THESE STORMS WILL BE CAPABLE OF HEAVY
RAINFALL WHICH MAY LEAD TO LOCALIZED FLOODING DEPENDING ON
WHERE STORMS FREQUENT. A FEW STRONG TO SEVERE STORMS CANNOT BE
RULED OUT FOR FRIDAY AND SATURDAY.
- HEAT INDICES SATURDAY FROM THE MIDDLE 90S TO AROUND 100F SOUTH
OF INTERSTATE 94.
DISCUSSION
ISSUED AT 344 AM CDT THU AUG 14 2025
TODAY - TONIGHT: SEASONABLE WITH SOME OVERNIGHT SHOWER/STORM CHANCES
GOES-19 WATER VAPOR IMAGERY AND 14.06Z RAP 500MB HEIGHTS SHOW THE
LOCAL REGION SUBJECTED TO QUASI-ZONAL FLOW WITH A SHORTWAVE IMPULSE
SITUATED OVER THE NORTHERN PLAINS EARLY THIS MORNING. AS WE
HEAD THROUGH THE MORNING THIS SHORTWAVE IMPULSE SLOWLY MEANDERS
ITS WAY INTO MINNESOTA, INCREASING OUR CLOUD COVER FOR THE DAY.
THE BULK OF ACCOMPANYING PRECIPITATION CHANCES ARE EXPECTED
REMAIN TO OUR WEST INITIALLY. HOWEVER, AS THIS WAVE PUSHES EAST
BY EVENING AND INTO THE OVERNIGHT, EXPECTING SHOWERS AND MAYBE A
STORM TO MOVE INTO THE AREA AS SOME WARM ADVECTION WITH SOME
ISENTROPIC LIFT ADVANCES NORTH. OVERALL, INSTABILITY INITIALLY
IS VERY WEAK, ON THE ORDER OF AROUND 250 J/KG OR LESS, SO WOULD
EXPECT WEAK CELLS TO DEVELOP AND QUICKLY PULSE DOWN AS REFLECTED
IN MANY OF THE CAMS.
FRIDAY - SUNDAY: INCREASING RISK FOR STORMS, HEAVY RAIN POSSIBLE
AS WE HEAD INTO FRIDAY MORNING, THE WEAKLY FORCED CONVECTION IN THE
AFOREMENTIONED WAVE WANES AS SOME WEAK SUBSIDENCE WORKS IN FROM A
SYNOPTIC UPPER-LEVEL RIDGE PUSHING IN FROM THE SOUTH. CONSEQUENTLY,
EXPECTING TEMPERATURES TO INCREASE FOR FRIDAY WITH HEAT INDICES IN
THE LOWER TO MIDDLE 90S. AS DAYTIME INSTABILITY INCREASES, AN AXIS
OF 850MB MOISTURE TRANSPORT ASSOCIATED WITH AN INCREASING LLJ CAUSES
CONCERN FOR POTENTIAL CONVECTION; INITIALLY DISCRETE AT FIRST BEFORE
TRENDING MORE INTO AN MCS LATER INTO THE EVENING/OVERNIGHT ON FRIDAY
ALONG AND NORTH OF I-90.
HEAVY RAIN WILL BE A CONCERN WITHIN THIS ENVIRONMENT WITH WARM CLOUD
DEPTHS EXCEEDING 4000 METERS AND PRECIPITABLE WATER OVER 2" IN THE
14.00Z NAM. THIS CAUSES AT LEAST SOME LOCALIZED FLOODING RISK IF
STORMS CAN TRAIN OVER THE SAME LOCATIONS. ADDITIONALLY THERE IS SOME
RISK FOR STRONG TO SEVERE STORMS DURING THIS PERIOD GIVEN THE STEEP
MID-LEVEL LAPSE RATES TO AROUND 8 C/KM IN THE 14.03Z RAP COMBINED
WITH MUCAPE VALUES TO AROUND 3000-4000 J/KG, SUPPORTING BOTH A
MARGINALLY SEVERE HAIL AND WIND RISK.
A STATIONARY BOUNDARY WILL THEN SET UP ACROSS THE LOCAL AREA ON
SATURDAY AS THE UPPER-LEVEL RIDGE ATTEMPTS TO TREK NORTHWARD.
THEREFORE, EXPECTING TEMPERATURES TO TREND FAIRLY WARM FOR LOCATIONS
SOUTH OF THIS BOUNDARY WITH FORECAST HEAT INDICES IN THE MIDDLE 90S
TO PERHAPS NEARING 100 IN SOME LOCATIONS IN NORTHEAST IA AND
SOUTHWEST WI. CONTINUING THROUGH THE AFTERNOON, WILL HAVE TO WATCH
AS CONTINUED RIPPLES IN THE MID-LEVEL FLOW WILL TRAVERSE THE
AFOREMENTIONED STATIONARY FRONT. CONTINUAL CONVECTIVE DEVELOPMENT
ALONG THE BOUNDARY WILL LIKELY POSE SOME HEAVY RAIN THREAT WITH THE
AFOREMENTIONED HEAVY RAIN PARAMETERS FROM FRIDAY REMAINING
RELATIVELY UNCHANGED. ALSO CANNOT RULE OUT SOME STRONG TO SEVERE
STORMS WITH THE SHARP CAPE GRADIENT AND POTENTIALLY SOME 0-6KM SHEAR
TO AROUND 30-40 KTS WITH ANY SHORTWAVES IN THE FLOW AS SHOWN IN THE
14.00Z NAM WHICH COULD SEE SOME STRONGER WIND GUSTS, PARTICULARLY IF
CONVECTION CAN SEE SOME ORGANIZATION ALONG ANY COLD POOLS.
RESULTANT WOBBLES IN THE STATIONARY BOUNDARY ON SUNDAY WILL IMPACT
HOW ANY ADDITIONAL CONVECTION WILL DEVELOP. AS A RESULT, CONFIDENCE
STILL REMAINS ON THE LOWER END FOR HOW STORMS WILL MANIFEST AS WE
GET LATER INTO THE WEEKEND. REGARDLESS THE ENVIRONMENT WOULD STILL
FAVOR BOTH A HEAVY RAIN AND A CONDITIONAL STRONG WIND THREAT ON
SUNDAY MUCH LIKE THE DAYS PREVIOUS. ALL SAID, A FAIRLY LOW-
CONFIDENCE FORECAST IN EXACT PLACEMENT OF STORMS FOR FRIDAY AND INTO
THE WEEKEND BUT HIGHER CONFIDENCE THAT THE ENVIRONMENT WILL BE
CONDUCIVE FOR HEAVY RAINFALL THAT MAY LEAD TO LOCALIZED FLOODING
WHERE STORMS CAN FREQUENT.
NEXT WEEK:
LOOKING INTO NEXT WEEK, THE UPPER-LEVEL RIDGE THAT WAS TRYING TO
BUILD INTO OUR AREA WILL FLATTEN TO START THE NEW WEEK WITH A
SECONDARY RIDGE AMPLIFYING ACROSS THE EASTERN ROCKIES. AS A RESULT,
OUR AREA IS SUBJECTED TO NORTHWESTERLY FLOW WITH A COLD FRONT LIKELY
PROGRESSING THROUGH THE AREA ON MONDAY, PUSHING THE MOISTURE-RICH
AIRMASS FUELING OUR WEEKEND CONVECTION FURTHER SOUTH. CONSEQUENTLY,
EXPECTING TEMPERATURES TO TREND NEAR OR EVEN SLIGHTLY BELOW NORMAL
INTO NEXT WEEK AS A COOLER AND DRIER CANADIAN AIRMASS GETS ADVECTED
INTO THE AREA.
AVIATION /12Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 600 AM CDT THU AUG 14 2025
VALLEY FOG IMPACTS AT 14.12Z TAF ISSUANCE MOSTLY LIMITED TO
WISCONSIN RIVER VALLEY WILL LIFT THROUGH THE MORNING HOURS.
PRECIPITATION CHANCES WITH ISOLATED STORMS GRAZE WESTERN PART OF
THE FORECAST AREA IN SOUTHEAST MINNESOTA THIS AFTERNOON INTO
TONIGHT. WIDESPREAD FLIGHT RESTRICTIONS NOT EXPECTED OUTSIDE OF
STRONGER STORMS.
SUBSEQUENT STORMS AND POTENTIAL AVIATION IMPACTS LINGER ALONG
THE INTERSTATE 94 CORRIDOR FRIDAY, BECOMING WIDESPREAD THROUGH
THE WEEKEND. STRONGEST, WIDESPREAD STORMS POSSIBLE SATURDAY.
NIGHTLY VALLEY FOG IMPACTS EXPECTED IN THE WISCONSIN RIVER
VALLEY.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...NAYLOR
AVIATION...JAR
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