306
FXUS63 KARX 071033
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
533 AM CDT TUE JUL 7 2026
KEY MESSAGES
- STORMS LIKELY (70-80% CHANCE) ON WEDNESDAY AFTERNOON AND INTO
THE OVERNIGHT. LOCALLY HEAVY RAINFALL MAY OCCURS WITH THESE
STORMS WHICH COULD CONTRIBUTE TO FLOODING IN LOW-LYING AREAS.
- SOME STORMS ON WEDNESDAY AFTERNOON AND EVENING MAY BE STRONG
TO SEVERE WITH DAMAGING WIND GUSTS BEING THE PRIMARY THREAT.
- SEASONABLE TEMPERATURES ARE EXPECTED THROUGHOUT MUCH OF THE
WEEK WITH HIGHS IN THE UPPER 70S TO 80S.
DISCUSSION
ISSUED AT 209 AM CDT TUE JUL 7 2026
TODAY - THURSDAY: SEASONABLE, STORMS LIKELY ON WEDNESDAY WITH
SOME HEAVY RAIN AND SEVERE WEATHER POTENTIAL
ZONAL FLOW ALOFT WITH VARIOUS SHORTWAVE IMPULSES MOVING THROUGH
THE REGION WILL BE THE MAIN UPPER-LEVEL FEATURES FOR HOW MUCH
OF THE STORM POTENTIAL WILL MANIFEST DURING THE MIDDLE OF THIS
WEEK. LATE THIS EVENING AND INTO THE OVERNIGHT HOURS, A
SHORTWAVE IMPULSE WILL MOVE ACROSS PORTIONS OF CENTRAL MN AND
INTO NORTHERN WI BRINGING SOME SHOWER AND STORM POTENTIAL TO
AREAS NORTH OF I-94 AS REFLECTED IN THE CAMS. WHILE THE BULK OF
THE HEAVIEST RAINFALL WILL LIKELY REMAIN NORTH OF THE LOCAL AREA
WITH THIS FEATURE, IT WILL LIKELY ESTABLISH THE THERMAL
GRADIENT AND INITIATING BOUNDARY NEEDED FOR STORMS ON WEDNESDAY.
AS WE HEAD INTO WEDNESDAY, THIS AFOREMENTIONED BOUNDARY WILL BE THE
MAIN INSTIGATING MECHANISM FOR CONVECTIVE INITIATION DURING THE
AFTERNOON AND INTO THE EVENING HOURS ACROSS THE LOCAL AREA.
WHAT WILL NEED TO BE MONITORED IS A FAVORABLE AXIS OF 850MB
MOISTURE TRANSPORT THAT WILL RUN ALONG THIS BOUNDARY.
CONSEQUENTLY, THIS WOULD PROVIDE A FAIRLY RESPECTABLE SYNOPTIC
SETUP FOR HEAVY RAINFALL IN THE VICINITY OF THE AFOREMENTIONED
BOUNDARY ON WEDNESDAY AFTERNOON AND INTO THE OVERNIGHT. THIS IS
SOMEWHAT DEPENDENT ON EXACTLY HOW PROGRESSIVE THIS BOUNDARY IS.
OVERALL THE PARAMETER SPACE FOR HEAVY RAINFALL IS FAIRLY RESPECTABLE
ON WEDNESDAY WITH PRECIPITABLE WATERS APPROACHING AROUND 2" AND WARM
CLOUD DEPTHS OF AROUND 3.5-4KM. THIS ACCOMPANIED WITH AMPLE
INSTABILITY IN THE WARM CLOUD LAYER WOULD SUGGEST THAT STORMS WILL
BE FAIRLY EFFICIENT RAIN PRODUCERS. CONSEQUENTLY, THE NBM HAS
INCREASED PROBABILITIES (30-60%) ACROSS MUCH OF THE LOCAL AREA FOR
RAINFALL AMOUNTS OVER 1" DURING THIS PERIOD, WITH THE HIGHEST
PROBABILITIES NEAR AND NORTH OF I-90. THIS IS A NOTABLE SHIFT SOUTH
IN ENSEMBLE GUIDANCE FROM PREVIOUS FORECAST CYCLES AND WILL BE A
TREND TO WATCH CLOSELY. ADDITIONALLY, WITH 95TH PERCENTILE QPF
VALUES IN THE NBM REACHING 2-4" ACROSS THE REGION, CERTAINLY COULD
SEE SOME IMPRESSIVE RAINFALL TOTALS WHERE STORMS REPEAT OVER THE
SAME LOCATIONS THAT COULD RESULT IN FLOODING CONCERNS.
AS FAR AS SEVERE WEATHER IS CONCERNED ON WEDNESDAY, THE MAIN SIGNAL
THAT IS PRESENT IS SOME HODOGRAPH ELONGATION IN THE 3-6KM LAYER
WHICH WOULD FAVOR SOME POTENTIAL STORM ORGANIZATION DURING THE LATE
AFTERNOON AS THE 500MB SHORTWAVE MOVES THROUGH. THIS WOULD FAVOR
SOME SUPERCELLULAR STRUCTURES WITH A MARGINAL HAIL RISK AND DAMAGING
WIND THREAT BEFORE A BROADER COLD POOL WOULD DEVELOP RESULTING IN A
MULTI-CELLULAR TO LINEAR MODE. OVERALL THE MAIN POINT OF UNCERTAINTY
WITH LOCATION FOR BOTH THE SEVERE RISK AND HEAVY RAIN RISK HINGES ON
HOW THE INITIATING BOUNDARY BEHAVES IN RESPONSE TO VARIOUS ROUNDS OF
CONVECTION. CURRENTLY, THE TREND IN THE CAMS AND ENSEMBLE GUIDANCE
HAS BEEN TO SHIFT THE MAIN AXIS FOR STORM DEVELOPMENT INTO MUCH OF
THE LOCAL AREA FOR THE AFTERNOON AND EVENING HOURS ON WEDNESDAY.
STORMS MAY LINGER INTO THURSDAY DEPENDING ON HOW PROGRESSIVE THE
BOUNDARY PASSAGE IS, HOWEVER THE PROBABILITY FOR SEVERE WEATHER
IS VERY LOW ON THURSDAY.
FRIDAY - THIS WEEKEND: GRADUALLY WARMER THROUGH THE WEEKEND
AS WE HEAD INTO FRIDAY, TEMPERATURES WILL BE NEAR TO SLIGHTLY COOLER
THAN NORMAL WITH HIGHS IN THE UPPER 70S TO MIDDLE 80S. NBM HAS OPTED
TO INTRODUCE SOME LOW-END PRECIPITATION PROBABILITIES (10-30%) SOUTH
OF I-90 IN LIGHT OF THE NAM HAVING A PRONOUNCED SHORTWAVE PUSHING
INTO SOUTHERN PORTIONS OF THE LOCAL AREA. WHILE THE GRAND ENSEMBLE
(GEFS/EC/CANADIAN) HAS RESPECTABLE PROBABILITIES (40-60%) FOR
MEASURABLE PRECIPITATION SOUTH OF I-90, PREDICTABILITY OF ANY
SYSTEMS AT THIS POINT REMAINS LOW. OTHERWISE, UPPER-LEVEL RIDGING
WITH CORRESPONDING GEOPOTENTIAL HEIGHT RISES WILL ENABLE SOME
WARMING THROUGH THE WEEKEND WITH HIGHS RETURNING BACK INTO THE
MIDDLE TO UPPER 80S, PERHAPS EVEN NEARING 90 ON SUNDAY.
AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 533 AM CDT TUE JUL 7 2026
VFR CONDITIONS ARE EXPECTED THROUGHOUT THE TAF PERIOD FOR AREAS NEAR
AND SOUTH OF I-90 WITH VFR CUMULUS AND MID-LEVEL CLOUDS. WINDS WILL
BE FROM THE SOUTH TO SOUTHWEST AND REMAIN UNDER 10 KTS. SHOWERS
AND STORMS MOVE INTO THE REGION FOR AREAS NORTH OF I-94 AFTER
06Z WEDNESDAY WITH THE HIGHEST PROBABILITY (30-50%) FOR SHOWERS
AND STORMS IN TAYLOR COUNTY PRIOR TO 12Z WEDNESDAY.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...NAYLOR
AVIATION...NAYLOR
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