502
FXUS63 KARX 211720
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
ISSUED BY NATIONAL WEATHER SERVICE DULUTH MN
1220 PM CDT WED MAY 21 2025
KEY MESSAGES
- CLOUDY AND SHOWERY/DRIZZLY TODAY INTO THIS EVENING WITH MANY
AREAS SEEING ANOTHER 0.25-0.40” BEFORE DRIER AIR MOVES IN FOR
THURSDAY.
- COOLER THAN NORMAL TEMPERATURES WILL CONTINUE THROUGH THE
NEXT WEEK WITH 40S/50 TODAY AND THEN THE 60S FOR HIGH
TEMPERATURES. DEPENDING ON CLOUD COVER, LIGHT WINDS COULD
PROMOTE SOME FROST FRIDAY MORNING IN CENTRAL WISCONSIN.
- THE HOLIDAY WEEKEND LOOKS MAINLY DRY WITH NORTHEAST IA AND
SOUTHERN WI POSSIBLY SEEING SOME SHOWER CHANCES ON THE
NORTHERN SIDE OF CENTRAL/SOUTHERN U.S WEATHER SYSTEMS.
CONFIDENCE IS LEANING TOWARD A DRIER FORECAST, BUT SOME SMALL
CHANCES ARE IN THE FORECAST FOR LIGHT RAIN SHOWERS FOR THAT
AREA.
DISCUSSION
ISSUED AT 310 AM CDT WED MAY 21 2025
MORE RAIN EXPECTED TODAY INTO TONIGHT, THEN SOME DRYING
GOES WATER VAPOR IMAGERY AT 06Z SHOWS THE BROAD LARGE SCALE
TROUGH OVER THE UPPER MISSISSIPPI RIVER VALLEY WITH NUMEROUS
SHORTWAVE TROUGHS PINWHEELING AROUND THE LOW. A STRONG EASTWARD
PUSH IS SEEN TO THE SOUTHERN SIDE OF THE TROUGH IN THE ZONAL JET
FLOW ACROSS THE OHIO VALLEY. A SHARP SURFACE TROUGH IS LOCATED
FROM ABERDEEN SD TO AROUND THE I-80 CORRIDOR OF ILLINOIS WITH
THE LOCAL AREA UNDER CONTINUED EASTERLY FLOW. PRECIPITABLE WATER
VALUES REGIONALLY ARE STILL AROUND AN INCH, WITH GRB AND MPX
SHOWING ABUNDANT SATURATION THROUGH MUCH OF THE TROPOSPHERE.
RADAR IS SHOWING ABUNDANT SHOWER ACTIVITY AND RAINFALL AMOUNTS
OF UP TO 0.30” IN THE LAST FEW HOURS.
EAST/SOUTHEASTERLY FLOW IN THE LOW-LEVELS IS CONTINUING A MOIST
FLOW WITH TROUGHING OVERHEAD TODAY AND CYCLONIC FLOW, ALL
PROMOTING SATURATION, CLOUDS, DRIZZLE AND SHOWERS UNTIL THIS AIR
MASS CAN SHIFT OUT OF THE AREA. THAT AIR MASS CHANGE COMES
LATER TONIGHT AND EARLY THURSDAY AS A WELL AGREED UPON LARGE
SCALE TROUGH SHIFTS IN FROM THE HUDSON BAY REGION TO PROVIDE
SOME DRYING AND AN AIR MASS CHANGE FROM THE NORTH/NORTHEAST,
EJECTING THE TROUGH OVER THE AREA DOWNSTREAM INTO THE EASTERN
U.S. SOME LINGERING TROUGHINESS AT THE SURFACE ACROSS THE
FORECAST AREA AND THE INFLUENCE OF COOLER AIR ALOFT FROM THE
LARGE SCALE TROUGH OVER EASTERN LAKE SUPERIOR COULD STILL SPAWN
A FEW SHOWERS THURSDAY AFTERNOON WITH STRATOCUMULUS DEVELOPMENT
ASSURED. SO MAYBE SOME PEAKS OF SUN IN THE MORNING, THEN
CLOUDING UP.
THE COOLER PATTERN CONTINUES, FROST IS POSSIBLE FRIDAY MORNING
THE AREA REMAINS UNDER THE INFLUENCE OF NORTHWEST FLOW AND AT
TIMES IS BRUSHED BY SHORTWAVES MOVING THROUGH THE GREAT LAKES.
NORMAL HIGHS THIS TIME OF YEAR ARE NOW IN AT LEAST THE UPPER 60S
INTO THE 70S, BUT THE FORECAST CONTINUES TO SHOW TEMPERATURES
WILL BE BELOW THAT BY 6-10 DEGREES INTO NEXT WEEK. WITH WEAK
HIGH PRESSURE BUILDING IN AT THE SURFACE FOR FRIDAY, DEPENDING
ON THE EXTENT OF CLOUD COVER, SOME FROST COULD BE OBSERVED IN
CENTRAL WI IN THE MORNING. THE LATEST NBM WOULD PUT A 20-30%
CHANCE THERE FOR 35F OR LESS. HOWEVER, THE PROBABILITIES ARE
LIKELY HIGHER WITH THE WARM BIAS SHOWN BY ALL THE MODELS ON
THESE RADIATIVE NIGHTS IN THE SAND COUNTRY / BOGS OF CENTRAL WI.
WILL HAVE TO SEE THE CLOUD EXTENT DETAILS AS WE APPROACH FRIDAY
MORNING FOR THE FROST POTENTIAL. AFTER THAT, TEMPERATURES
SHOULD MODERATE SLIGHTLY TO AVOID FROST/FREEZE BUT NORTHERLY
FLOW PERSISTS AT THE LOW-LEVELS.
HOLIDAY WEEKEND FORECAST
BY SATURDAY NIGHT AND SUNDAY, TROUGHING MOVING INTO THE
CENTRAL/SOUTHERN PLAINS WILL BATTLE THE GREAT LAKES RIDGING AND
DRIER EASTERLY FLOW, TRYING TO PUSH MOISTURE AND PRECIPITATION
CHANCES IN ACROSS AREAS SOUTH AND WEST OF LA CROSSE. IT REMAINS
TO BE SEEN IF THE ACTIVITY ACROSS THE CENTRAL/SOUTHERN PLAINS
CAN OVERCOME THE DRY AIR IN PLACE FOR SHOWERS THIS FAR NORTH.
THE LATEST 20.12Z GRAND ENSEMBLE AVAILABLE SUGGESTS THIS
PROBABILITY IS LOW WITH THE GEFS SOLUTIONS PROVIDING A MORE
AGGRESSIVE FORECAST FOR RAIN. SOME LOW CHANCES FOR RAIN ARE OUT
THERE FOR THE WEEKEND FORECAST, BUT THOSE MAY BE REMOVED IN
FUTURE FORECASTS BASED ON TRENDS ON THE NORTHERN EXTENT OF THE
SYSTEMS MOVING THROUGH TO THE SOUTH. ON MONDAY, YET ANOTHER
SHORTWAVE TROUGH INFLUENCES THE AREA FROM THE NORTHWEST AND HAS
MODERATE CONFIDENCE AND AGREEMENT IN THE MODELS FOR SOME SHOWER
CHANCES.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1220 PM CDT WED MAY 21 2025
IFR TO MVFR CONDITIONS WILL CONTINUE FOR THE TAF SITES INTO
TONIGHT AS A TROUGH LINGERS ACROSS THE AREA. NUMEROUS SHOWERS
WILL BE SEEN INTO THIS EVENING. WHILE DRIER AIR WILL MOVING INTO
THE REGION OVERNIGHT, LOW LEVEL MOISTURE WILL LIKELY REMAINED
TRAPPED UNDERNEATH A NOCTURNAL INVERSION. THIS INVERSION SHOULD
BREAK AROUND 22.14Z. THERE WILL BE LIKELY BE A BRIEF PERIOD OF
SCATTERED LOW CLOUDS AND THEN AS DIURNAL HEATING OCCURS 900-800
MB LAPSE RATES WILL STEEPEN AND A BROKEN TO OVERCAST 3-5K DECK
OF CLOUDS WILL QUICKLY DEVELOP. WINDS WILL BE NORTH AROUND 10
KNOTS THROUGH THIS EVENING AND THEN BECOME NORTHWEST AND
INCREASE TO 10 TO 15 KNOTS ON THURSDAY MORNING.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...BAUMGARDT
AVIATION...BOYNE/WOLFE
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