886
FXUS63 KARX 051724
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1224 PM CDT TUE MAY 5 2026
KEY MESSAGES
- BELOW NORMAL TEMPERATURES FOR THE REMAINDER OF THE WEEK,
WARMING BACK TO AROUND AVERAGE ON SATURDAY.
- BEST CHANCE FOR AREAWIDE FROST/FREEZING TEMPERATURES
COMES WEDNESDAY MORNING, WITH THE THREAT FOR FROST SHIFTING
EAST OF THE MISSISSIPPI RIVER FOR THURSDAY AND FRIDAY
MORNINGS.
- ASIDE FROM A 10-20% CHANCE FOR AFTERNOON SHOWERS ON THURSDAY
AND FRIDAY, LOOK FOR DRY CONDITIONS FOR THE REST OF THE WORK
WEEK. NEXT CHANCE OF WIDESPREAD RAIN COMES LATE SATURDAY AND
EARLY SUNDAY.
DISCUSSION
ISSUED AT 1240 AM CDT TUE MAY 5 2026
TODAY - WEDNESDAY: DRY WITH TEMPS 10-15 DEGREES BELOW NORMAL
A STEADY FETCH OF MODIFIED ARCTIC AIR FLOODS SOUTHWARD IN THE
WAKE OF THE COLD FRONT THAT PASSED THROUGH MONDAY AFTERNOON,
WITH 850-MB TEMPERATURES TODAY RUNNING 10-13C COLDER THAN AT
THIS TIME ON MONDAY. WE WILL SEE DEEP MIXING OF THE BOUNDARY
LAYER BOTH THIS AFTERNOON AND WEDNESDAY AFTERNOON, RESULTING IN
THE DEVELOPMENT OF DAYTIME CUMULUS CLOUDS BUT OTHERWISE RESULT
IN LITTLE SENSIBLE WEATHER IMPACTS GIVEN THE LESSENING PRESSURE
GRADIENT/850-700-MB WINDS AHEAD OF AN APPROACHING HIGH PRESSURE
CELL.
AS WITH OUR LAST ROUND OF FROST/FREEZE POTENTIAL, WINDS AND PASSING
MID TO HIGH CLOUDS MAKE THE EXACT TEMPERATURE FORECAST LESS THAN
STRAIGHTFORWARD. GIVEN THE DEWPOINTS IN THE MID-20S, IT WOULD NOT
TAKE MUCH DECOUPLING AND CLEARING TO RESULT IN RAPIDLY FALLING
TEMPERATURES THAT COULD FALL BELOW FREEZING IN FAVORED LOW-LYING/BOG
LOCALES AND COME VERY CLOSE TO FREEZING ELSEWHERE. WEDNESDAY MORNING
IS SHAPING UP TO BE THE COLDEST OF THE WEEK WITH THE FROST/FREEZE
THREAT SHIFTING EASTWARD LATER IN THE WEEK.
THURSDAY - FRIDAY: WARMING, SLIGHT CHANCE OF PM SHOWERS
THE AXIS OF THE MEAN LONGWAVE TROUGH RESPONSIBLE FOR OUR COOL
WEATHER PASSES THROUGH WEDNESDAY NIGHT. WHILE THE MAIN RESERVOIR OF
POLAR AIR SHUNTS OFF TO THE EAST, THE UPSTREAM PACIFIC AIRMASS
STRUGGLES TO WORK EAST OF THE HIGH PLAINS AS A SERIES OF TRAILING
SHORTWAVES ROTATE AROUND THE WESTERN FLANK OF THE LONGWAVE TROUGH.
THEREFORE, WHILE SURFACE TEMPERATURES RECOVER SOMEWHAT FOR THURSDAY
AND FRIDAY, IT WON'T BE UNTIL SATURDAY THAT THIS AIRMASS FINALLY
PENETRATES FARTHER INTO THE UPPER MIDWEST.
WITH INCREASING LOWER TROPOSPHERIC THETA-E VALUES, THE RISK FOR
DIURNAL SHOWERS INCREASES FOR THURSDAY AND FRIDAY. AT THIS POINT,
THERE IS AMPLE UNCERTAINTY ON THE DEPTH OF AFTERNOON MIXING, WHICH
PLAYS DIRECTLY INTO THE SHOWER COVERAGE. A QUICK LOOK AT THE LREF
SHOWS A 40-50% CHANCE OF MEASURABLE PRECIP ON THURSDAY AFTERNOON,
MAINLY ALONG AND EAST OF THE MISSISSIPPI RIVER, WHICH SHIFTS TO
MAINLY NE IOWA AND SW WISCONSIN ALONG A DECAYING FRONT RANGE LOW.
HOWEVER, WILL HAVE TO SEE HOW THE CONVECTIVE ALLOWING MODELS RESOLVE
THIS BOUNDARY LAYER BEFORE PUSHING THE OFFICIAL POP VALUES UP THAT
HIGH.
THE WEEKEND: WARMER TO START, RAIN SAT PM/SUN AM
SATURDAY LOOKS TO FEATURE THE WARMEST TEMPERATURES OF THE WEEK AS A
+10C 850-MB THERMAL RIDGE TRANSLATES SOUTHEASTWARD THROUGH THE
REGION AHEAD OF AN APPROACHING COLD FRONT. THE WARMEST AIR STAYS OFF
TO THE SOUTHWEST, BUT HIGHS COULD TOUCH 70 DEGREES AT MANY LOCALES
WITH THERE BEING A 10-20% CHANCE OF HIGHS PUSHING INTO THE MID TO
UPPER 70S IF THE WARM AIR ADVECTION IS STRONGER THAN FORECAST. THE
COLD FRONT SWEEPS DOWN FOR SATURDAY PM/SUNDAY AM AND BRINGS WITH IT
THE NEXT BEST SHOT OF WIDESPREAD RAINFALL, BUT AT THIS RANGE THERE
IS AMPLE SPREAD IN SOME KEY SYNOPTIC VARIABLES THAT WILL DRIVE THE
RAIN RISK ALONG THE FRONT.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1223 PM CDT TUE MAY 5 2026
COOL, NORTHWEST FLOW WILL BRING DIURNAL CUMULUS AROUND 5KFT
TODAY AND TOMORROW WITH VFR CONDITIONS EXPECTED. DAYTIME HEATING
WILL ALLOW WINDS TO GUST BETWEEN 20 TO 25KTS ACROSS THE REGION. NO
FLIGHT RULES REDUCTIONS APPEAR ON THE HORIZON FOR SEVERAL DAYS.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...SKOW
AVIATION...JAW/FERGUSON
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