766
FXUS63 KARX 181149
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
649 AM CDT FRI APR 18 2025
KEY MESSAGES
- SCATTERED SHOWERS/STORMS EARLY THIS MORNING. STRONGER STORMS WILL
PRODUCE SMALL HAIL, POTENTIALLY STRONG WIND GUSTS. SHOWERS COULD
LINGER INTO THE AFTERNOON.
- ANOTHER ROUND OF WIDESPREAD RAIN SUNDAY AFTERNOON INTO MONDAY. A
STORM OR TWO POSSIBLE. LOW END SNOW CHANCES (10-30%) NORTH OF I-94.
- COOL WEEKEND BUT WARMING FOR NEXT WEEK (HIGHS BACK INTO THE 60S,
NEAR 70 FOR SOME).
DISCUSSION
ISSUED AT 125 AM CDT FRI APR 18 2025
THIS MORNING: RAP SHOWING A REASSERTION OF THE LOW LEVEL JET INTO
NORTHEAST IA BY 08Z WITH SOME ELEVATED FGEN AND A RIPPLE IN THE
UPPER LEVEL FLOW (EVIDENCED IN LATEST WATERVAPOR SATELLITE IMAGERY).
THIS SHOULD SPARK MORE SHOWERS AND STORMS WITH ABOUT 1500 J/KG OF
MUCAPE TO WORK WITH. ENOUGH INSTABILITY FOR HAIL POTENTIAL. LOW
LEVEL CAPPING/STABLE LAYER WILL KEEP THE STORMS ELEVATED. HOWEVER,
SOME HINTS IN THE HRRR THAT STRONGER WINDS COULD STILL BE BROUGHT
TOWARD THE SFC. NOT ANTICIPATING SEVERE, BUT MARGINALLY LARGE HAIL
(1/2-3/4") AND ENHANCED GUSTS (BEHIND ANY STORM) IS POSSIBLE.
AFTERNOON: CONVECTIVE ELEMENTS COULD DEVELOP IN THE BLANKET OF LOW
STRATUS THAT IS CURRENTLY ADVECTING SOUTHWARD FROM NORTHERN MN/WI.
WHETHER SHOWERS DEVELOP IS DEBATABLE AS THE COLD AIR ADVECTIVE
SIGNAL ISN'T STRONG, NOR IS THERE MUCH IN NEAR SFC LAPSE RATES. WITH
LOW CLOUD BASES THOUGH, LIGHT PCPN WON'T HAVE FAR TO GO.
SUNDAY/MONDAY: STORM SYSTEM SET TO BRING RAIN, SOME STORMS, AND
CAN'T SAY NO TO MINOR SNOW ACCUMS IN THE NORTH.
GEFS/EPS CONTINUE TO TAKE A SHORTWAVE TROUGH OUT OF THE DESERT
SOUTHWEST SAT, DEVELOPING A NEGATIVE TILT AS IT LIFTS NORTHEAST
ACROSS THE UPPER MISSISSIPPI RIVER VALLEY SUNDAY NIGHT. WPC CLUSTERS
ALSO ALL SHOW THIS, ALTHOUGH SOME DIFFERENCES IN STRENGTH/TIMING.
THE STORM WILL BE UNDERGOING STRENGTHENING AS IT APPROACHES, THANKS
IN PART TO THE LEFT EXIT REGION OF A CURVED 300 MB JET. SFC LOW
PLACEMENT IN THE EPS AND GEFS MEMBERS DO SHOW A FAIR AMOUNT OF
VARIABILITY - SO THE STORM IS NOT "LOCKED IN" BY ANY MEANS. OF NOTE
IN THE RECENT EPS RUN IS THE BULK OF ITS MEMBERS HAVE THE LOW CENTER
FARTHER NORTHWEST OF OPERATIONAL - SUGGESTING THE LOCAL AREA COULD
BE UNDER A WARMER REGIME AND THE DEFORMATION PCPN WOULD BE DISPLACED
NORTHWEST. NOT NECESSARILY A TREND, BUT SOMETHING TO MONITOR.
LOW LEVEL MOISTURE TRANSPORT IS GOOD AS A 50 KT 850MB JET NOSES INTO
THE STORM'S DEFORMATION REGION. AMPLE, SLOPING FGEN ON THE NORTH
SIDE, EVIDENCED IN TIME/HEIGHT X-SECTIONS WITH A STRONG SWATH OF LOW
LEVEL WARM AIR ADVECTION. QG CONVERGENCE IS ALSO HEFTY AND DEEP IN
THE COLUMN, MAXING OUT SUN AFTERNOON/EVENING.
ALL IN ALL, A LOT OF FORCING ACCOMPANYING THIS STORM WITH A NICE
FETCH OF MOISTURE TO FUEL BROAD AREAS OF PCPN. MEAGER ELEVATED
INSTABILITY INDICATED IN THE GFS/NAM BUFKIT SOUNDINGS, ALL ABOVE A
SIZABLE LOW LEVEL CAPPING INVERSION. SOME ISOLATED THUNDER POSSIBLE,
MOSTLY SOUTH.
FOR AMOUNTS, 25-75% FOR QPF ROUGHLY SITS FROM 1/2 TO 1" FOR SUN
NIGHT THROUGH MONDAY, WITH THE UPPER 10% PUSHING MORE THAN 1 1/4".
THERE ARE EVEN HIGHER OUTLIERS, ESPECIALLY IN THE EPS WHICH HAS A
NON-ZERO SOT AND A COUPLE MEMBERS SUGGESTING 3-4" ARE POSSIBLE.
LOOKS LIKE A GOOD SOAKING FOR MOST OF THE LOCAL AREA.
SNOW STILL CAN'T BE RULED OUT. THE GRANDENSEMBLE CONTINUES TO
SUGGEST A 10-30% FOR MEASURABLE SNOW NORTH OF I-94, WITH ABOUT A 10-
20% CHANCE THAT TO REACH AN INCH. ANY SNOW WOULD BE CONFINED TO
COLD, GRASSY SURFACES AND WOULDN'T STICK AROUND IF REALIZED.
AFTER MONDAY: MOVING INTO THE MIDDLE PART OF NEXT WEEK, BROAD LONG
WAVE RIDGING/HEIGHT RISES PROGGED IN THE LONG RANGE GUIDANCE.
WARMER, AT/ABOVE NORMAL TEMPS RETURN IN THIS SCENARIO WITH HIGHS
PUSHING BACK INTO THE 60S. LREF HAS 10 TO 20% CHANCES FOR 70+ DEGREE
HIGHS. IT'S NOT A STOUT RIDGE, SO RIPPLES IN THE FLOW WOULD HAVE A
CHANCE TO SPIN ACROSS THE REGION - PROVIDING OCCASIONAL RAIN
CHANCES. DECENT CONSENSUS BETWEEN MOST OF THE GEFS AND EPS MEMBERS
FOR JUST THAT LATER TUE/TUE NIGHT.
AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 649 AM CDT FRI APR 18 2025
SHOWERS AND STORMS EXIT THROUGH WESTERN WI LEAVING MVFR TO IFR
CIGS ACROSS THE REGION FOR THE MORNING AND AFTERNOON. LOW-LEVEL
SATURATION WILL MAINTAIN MVFR TO IFR, CANNOT RULE OUT SOME LIFR
AT KRST, THROUGH THE AFTERNOON BEFORE CIGS SLOWLY BEGIN TO
IMPROVE THROUGH THE EVENING TO VFR LEVELS. SOME ISOLATED TO
SCATTERED SHOWERS CANNOT BE RULED OUT THROUGHOUT THE DAY BUT
MINIMAL VSBY REDUCTIONS ARE ANTICIPATED WITH THESE. WINDS WILL
SLIGHTLY INCREASE TO 10-15 KTS FROM THE NORTHWEST FOR THE
AFTERNOON WITH OCCASIONAL GUSTS TO 20 KTS AT KRST POSSIBLE.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...JAR/ZAPOTOCNY
AVIATION...NAYLOR
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