531
FXUS63 KARX 171715
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1215 PM CDT FRI APR 17 2026
KEY MESSAGES
- A COMPLEX SEVERE WEATHER FORECAST FOR THIS AFTERNOON AS
POSSIBLY TWO WAVES OF STORMS ARE IN THE OFFING, WITH THE
STRENGTH AND TIMING OF THE FIRST WAVE OF STORMS PLAYING INTO
HOW THE SECOND WAVE OF STORMS EVOLVES.
- LARGE HAIL UP TO 2-3" IN DIAMETER, DAMAGING WINDS OF 60 TO 70
MPH, A FEW TORNADOES (SOME STRONG), AND LOCALLY HEAVY
RAINFALL ARE ALL ON THE TABLE WITH THESE STORMS.
- MUCH COLDER FOR THE WEEKEND WITH LOW TEMPERATURES FALLING
BELOW FREEZING STARTING TONIGHT THROUGH SUNDAY NIGHT. DAYTIME
HIGHS OVER THE WEEKEND WILL BE STUCK IN THE 40S. CAN'T RULE
OUT SOME FLURRIES ON SATURDAY.
- DRY CONDITIONS AND WARMING TEMPERATURES EXPECTED FOR THE START
OF NEXT WEEK.
UPDATE
ISSUED AT 1215 PM CDT FRI APR 17 2026
CONTINUING TO SEE RAPID EVOLUTION OF THE ENVIRONMENT OVER THE
LOCAL AREA. RIGHT NOW, THE COLD FRONT IS LOCATED NEAR I35 IN MN
TAILING SOUTHWESTWARD INTO IA. SURFACE LOW PRESSURE IS SOUTHWEST
OF MASON CITY AT 17Z. TO THE EAST, WIDESPREAD BILLOW CLOUDS
INDICATE A STABLE BOUNDARY LAYER OVER THE MUCH OF SOUTHEAST MN
AND NORTHEAST IA. CLOSER TO THE FRONT ON I-35, THE CUMULUS FIELD
LOOKS PRIMED TO INITIATE.
WARM FRONT: A CONFLUENCE REGION EXISTS APPROACHING THE MISS
RIVER WHERE SOME ELEVATED ECHO IS SEEN NEAR WINONA. SPC MESOA
DEEP MOISTURE CONVERGENCE IS ALONG THIS AXIS N-S AND THE LATEST
CAMS AGREE ON MORE INITIATION OVER THE NEXT HOUR. THAT EASTERN
ENVIRONMENT IS ELEVATED STILL WITH 2000-2500 J/KG MUCAPE.
DEVELOPMENT ON THIS N-S AXIS IS ROUND 1 AND AS IT HEADS EAST
WITH THE DEWPOINT SURGING NORTHWARD, THESE STORMS HAVE
INCREASING CHANCES AT BECOMING SURFACE-BASED IN WESTERN WI.
HOWEVER, THIS IS MOVING EAST AT A PRETTY GOOD CLIP AND DEPENDING
ON THE INITIATION OF SAID STORMS, THESE MIGHT BE SURFACE-BASED
AND MATURE INTO CENTRAL AND SOUTHWEST WI OR EAST OF THE LOCAL
AREA. THE ENVIRONMENT IS RICH, WITH EFFECTIVE HELICITY OVER 200
M2/S2 AND 25-35 KTS OF 0-1KM BULK SHEAR NOW. IF THE LOW-LEVEL
WINDS REMAINED BACKED, THE CAMS SUGGEST 300 ESRH AND 200 0-500M
SRH IN SWRN WI BY 2 PM. SUPERCELLS AND STRONG TORNADOES POSSIBLE
WITH PROBABILITIES HIGHER TO I90 AND SOUTH IN WI FOR THIS AREA.
COLD FRONT: THE COLD FRONT WILL ALSO INITIATE ON THE WESTERN
EDGE OF THE WARM SECTOR AND WINDS ARE ALL BACKED INTO THE FRONT
RIGHT NOW WITH THE SURFACE LOW TRAVELING NORTH, OVER SERN MN
AND NERN IA, WITH LOOPY LONG HODOGRAPHS THERE AS WELL. THE MAIN
QUESTION REMAINS OF HOW FAST THE STORMS BECOMES A LINE THERE.
INITIAL DISCRETE STORMS WILL WORK TOWARD LINEAR MODES WITH 0-6
SHEAR VECTORS AND THE 850-300 MB MEAN WIND AT 45 DEGREES TO THE
FRONT. STRONG LINEAR FORCING /COLD FRONT/ SEEMS LIKE IT MAY GO
LINEAR THAN REMAIN DISCRETE. BUT, WHILE DISCRETE, THE LOOPING
HODOGRAPHS MEAN TORNADO POTENTIAL IS CERTAIN THERE IN SERN MN
AND WESTERN NERN IA. FIRST LIGHTNING STRIKES JUST SEEN ALONG THE
COLD FRONT NEAR I-35 PER GOES GLM.
TORNADO WATCH IS FORTHCOMING.
DISCUSSION
ISSUED AT 430 AM CDT FRI APR 17 2026
SEVERE WEATHER THREAT FOR THIS AFTERNOON
EVEN AT THE 11TH HOUR, SOME CRITICAL DETAILS ON THE EVOLUTION
OF OUR AFTERNOON SEVERE WEATHER THREAT REMAIN TO BE NAILED DOWN.
THIS IS A SITUATION WHERE ATTENTION NEEDS TO BE PAID TO THE
WEATHER THROUGHOUT THE AFTERNOON AS THE THREATS UNFOLD.
THE EARLY MORNING SURFACE ANALYSIS ACROSS THE UPPER MIDWEST
SHOWS OUR CULPRIT COLD FRONT STRETCHING FROM SIOUX FALLS, SD TO
INTERNATIONAL FALLS, MN AND MARCHING STEADILY TO THE ESE, AIDED
BY AN APPROACHING SEASONABLY STRONG UPPER TROPOSPHERIC NORTHERN
STREAM TROUGH AND STRONG CAA PURSUING OVER THE DAKOTAS. A
994-MB SURFACE LOW PRESSURE CELL OVER EASTERN NEBRASKA WILL
PROPAGATE QUICKLY NORTHEAST ALONG THE FRONT, LIFTING A WARM
FRONT WITH IT THROUGH THE REGION THIS MORNING. STRONG SURFACE
THETA-E ADVECTION IS BEING OBSERVED ACROSS WESTERN IOWA AHEAD OF
THIS LOW WITH DEWPOINTS REACHING THE LOW TO MID 60S JUST AHEAD
OF THE FRONT. THIS IS A CLASSIC "NICK OF TIME" SEVERE WEATHER
SCENARIO WHERE THE FAVORABLE THERMODYNAMIC SEVERE WEATHER
ENVIRONMENT WILL ARRIVE JUST AHEAD OF STORM INITIATION.
THERE ARE TWO WINDOWS OF OPPORTUNITY FOR STORMS TO FORM LATER
THIS MORNING INTO THE AFTERNOON, ONE WAVE ALONG THE LEADING
WARM FRONTAL BOUNDARY AND THE SECOND WITH THE COLD FRONT COMING
THROUGH A FEW HOURS LATER. RAPID DESTABILIZATION IS PROGGED TO
OCCUR IN THE WARM SECTOR AS THE WARM FRONT LIFTS THROUGH THE
REGION BETWEEN 16-19Z WITH WARM SECTOR MLCAPE VALUES OF
2000-2500 J/KG AND DEEP SHEAR PROFILES OF 30-50+ KTS. LOW LEVEL
HODOGRAPHS ALONG THE WARM FRONT WILL FEATURE VERY FAVORABLE
PROFILES IN THE 0-1 TO 0-6-KM LAYER SUPPORTIVE OF STRONGLY
ROTATING UPDRAFTS AND TORNADOES. THIS PARAMETER SPACE EXISTS FOR
SEVERAL HOURS IN THE WARM SECTOR IN THE WAKE OF THE WARM FRONT
UNTIL THE COLD FRONT BLASTS THROUGH BETWEEN 18-00Z TODAY FROM
WEST TO EAST.
THE TIMING OF THE STORMS WILL BE ABSOLUTELY CRITICAL TODAY TO
DETERMINE HOW THE EXACT SEVERE HAZARDS WILL UNFOLD WITH SEVERAL
DIFFERENT SCENARIOS IN PLAY. THE LATEST RUNS OF THE HRRR ARE
FAVORING ELEVATED CONVECTION DEVELOPING NORTH OF THE TRIPLE
POINT AND KICKSTARTING CONVECTION DOWN THE WARM FRONT AS IT
LIFTS INTO THE FORECAST AREA. HOWEVER, THE UPDRAFT STRENGTH IN
THESE MODEL RUNS HAS NOT BEEN OVERLY STRONG WITH THIS ROUND OF
CONVECTION AT FIRST, LIKELY OWING TO THE MEAN STORM MOTIONS (FOR
STORMS DEVELOPING ALONG THE FRONT) OUTPACING THE BOUNDARY AND
RESULTING IN THE STORMS TRACKING INTO A MUCH HIGHER INHIBITION
AIRMASS AHEAD OF THE FRONT BEFORE DEVIANT RIGHT MOVING STORM
MOTIONS CAN BE ACHIEVED. A FEW CAM SOLUTIONS SHOW MORE ROBUST
UPDRAFTS ABLE TO SLOW DOWN AND STAY WITHIN THE MORE FAVORABLE
THERMODYNAMIC ENVIRONMENT, SO HOW THE THREAT ALONG THIS BOUNDARY
EVOLVES MAY HAVE TO BE ASSESSED ON A STORM BY STORM BASIS IN
REAL TIME.
CAN'T FULLY RULE OUT MORE OPEN WARM SECTOR CONVECTION LAGGING
THE WARM FRONT GIVEN THE DYNAMIC ENVIRONMENT IN PLACE, WHICH
WOULD RESULT IN STORMS POSING AN ALL HAZARDS RISK RATHER
QUICKLY. THIS LOOKS TO BE MORE OF A LOWER CONFIDENCE, BUT
POTENTIALLY HIGHER IMPACT SCENARIO.
ATTENTION THEN TURNS TO THE COLD FRONT AS IT CRUISES TO THE ESE
THROUGH THE FORECAST AREA THIS AFTERNOON. RECENT CAM RUNS ARE
HINTING AT A BETTER RISK FOR LARGER AND MORE ROBUST STORMS
FURTHER SOUTH ALONG WHAT WOULD NOW BE MORE OF A PREFRONTAL
TROUGH VERSUS A TRUE WARM FRONT IN IOWA. SHOULD ROBUST
CONVECTION DEVELOP WITHIN THIS CORRIDOR--THE INFLOW FOR OUR COLD
FRONTAL STORMS--THIS MAY CHOKE OFF DEVELOPMENT FURTHER NORTH
ALONG THE COLD FRONT. HOW FAR NORTH REMAINS TO BE SEEN. A
LINEAR UPSCALE GROWTH PROGRESSION IS EXPECTED ALONG THE FRONT AS
THE AFTERNOON GOES ON, WITH THE LINE ADVANCING OUT OF THE
REGION BY 00Z. BOTH SUPERCELLULAR AND QLCS TORNADOES WOULD BE
POSSIBLE ALONG THE LINE GIVEN THE FAVORABLE RESPECTIVE SHEAR
PROFILES FOR BOTH SETUPS.
ALOT TO HAPPEN IN A SHORT 6-7 HOUR WINDOW THIS AFTERNOON AND
ONLY SMALL CHANGES TO THE TIMING OF ANY ONE OF THESE VARIABLES
COULD HAVE A DOMINO EFFECT ON THE REST OF THE EVENT.
THIS WEEKEND & EARLY NEXT WEEK: DRIER & COOLER
AS WE HEAD PAST TODAY, COOLER AIR WORKS ITS WAY IN WITHIN THE
BROADER TROUGHING REGIME ON SATURDAY WITH HIGHS LIKELY
PLUMMETING INTO THE 40S TO LOWER 50S FOR THE WEEKEND. CANNOT
RULE OUT SOME FLURRIES OR LIGHT SNOW SHOWERS NORTH OF I-94
DURING THE MORNING HOURS ON SATURDAY. OVERNIGHT LOWS ON
SATURDAY NIGHT WILL LIKELY FALL BELOW FREEZING FOR MANY SPOTS SO
BE SURE TO COVER ANY PLANTS YOU HAVE SET OUT! HOWEVER, NO
ACCUMULATIONS WOULD BE EXPECTED. OTHERWISE, SURFACE HIGH
PRESSURE MOVES INTO THE REGION FOR SUNDAY KEEPING US RELATIVELY
PRECIPITATION FREE INTO EARLY NEXT WEEK.
AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 545 AM CDT FRI APR 17 2026
A TRANSIENT BAND OF LIFR STRATUS WORKING INTO CENTRAL WISCONSIN
SHOULD LIFT THROUGH THE MID MORNING TODAY. AN MVFR CU FIELD
DEVELOPS TOWARDS LATE MORNING AND PERSISTS INTO THE AFTERNOON.
THUNDERSTORMS ARE EXPECTED TO DEVELOP TODAY ALONG AND AHEAD OF
A COLD FRONT THAT MOVES THROUGH DURING THE AFTERNOON, SOME OF
WHICH COULD BE SEVERE AND PRODUCE LARGE HAIL AND DAMAGING WINDS.
SOUTH TO SOUTHEAST WINDS INCREASE THROUGH THE MORNING TO
10-20G25-30KTS EARLY THIS AFTERNOON WITH WINDS BACKING TO THE
NORTHWEST AT 10-20G20-25KTS BEHIND THE FRONT FOR THE EVENING AND
OVERNIGHT. A BAND OF IFR TO MVFR STRATUS MAY FOLLOW IN THE WAKE
OF THE COLD FRONT, BECOMING MORE SCATTERED AS THE NIGHT GOES ON.
HYDROLOGY
ISSUED AT 430 AM CDT FRI APR 17 2026
A FLOOD WATCH HAS BEEN ISSUED FOR SOUTHWEST WISCONSIN AND
PORTIONS OF WEST CENTRAL WISCONSIN GIVEN THE CHANCE FOR
ADDITIONAL SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING.
THESE AREAS HAVE ALREADY SEEN COPIOUS AMOUNTS OF RAINFALL OVER
THE LAST WEEK WITH MANY RIVERS EXPERIENCING SIGNFICIANT FLOODING
(ENOUGH TO CLOSE SOME ROADS IN MULTIPLE COUNTIES). A
WIDESPREAD 1/2 INCH OF RAIN IS LIKELY WITH LOCALIZED POCKETS OF
1-2 INCHES--ANY ADDITIONAL RAIN WILL BE PROBLEMATIC AND ONLY
EXACERBATE EXISTING PROBLEMS. MUDSLIDES ALSO LOOK TO BE A
PROBLEM AS WE HAVEN'T SEEN A FULL GREEN UP YET SO ROOTS HAVE NOT
TAKEN A STRONG HOLD YET. RIVERS ACROSS WISCONSIN ARE LIKELY TO
SEE ADDITIONAL RISES, ESPECIALLY THE KICKAPOO, YELLOW, BLACK,
AND WISCONSIN.
ARX WATCHES/WARNINGS/ADVISORIES
WI...FLOOD WATCH THROUGH SATURDAY MORNING FOR WIZ042>044-053>055-
061.
MN...NONE.
IA...NONE.
UPDATE...BAUMGARDT
DISCUSSION...NAYLOR/SKOW
AVIATION...SKOW
HYDROLOGY...BARENDSE
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page