572
FXUS63 KARX 130255
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
955 PM CDT WED MAR 12 2025
KEY MESSAGES
- POTENT SPRING STORM SYSTEM REMAINS ON TRACK TO BRING SHOWERS
AND THUNDERSTORMS FOR FRIDAY DURING THE LATE AFTERNOON INTO
THE EVENING HOURS. DAMAGING WIND APPEARS TO BE THE MAIN
THREAT, BUT SOME RISK FOR A TORNADO MAY BE PRESENT AS WELL.
- SOUTHERLY WINDS ARE FAVORED TO GUST TO 30 TO 40 MPH DURING THE
DAY ON FRIDAY AHEAD OF THE STORMS, FOLLOWED BY THE POTENTIAL
FOR GUSTY NORTHWEST WINDS - AND PERHAPS SNOW - ON THE BACKSIDE
OF THE DEPARTING SYSTEM OVER THE WEEKEND.
- WARMING TEMPERATURES FOR THE REMAINDER OF THIS WEEK WITH
RECORD HIGHS POSSIBLE FRIDAY.
DISCUSSION
ISSUED AT 325 AM CDT WED MAR 12 2025
FRIDAY: BREEZY AND POTENTIAL RECORD WARMTH
FRIDAY, UPPER LOW EJECTS EAST-NORTHEASTWARD FROM THE FOUR CORNERS TO
AROUND KANSAS CITY. WITH A STRONG JET STREAK LOCATED ON THE
EQUATORWARD SIDE OF THIS FEATURE, EXPECT ASSOCIATED SURFACE CYCLONE
TO DEEPEN AS IT MOVES NORTHEAST. RESULTING INCREASE IN SURFACE
PRESSURE GRADIENT ACROSS THE CWA WILL CAUSE STRONG WINDS TO DEVELOP
DURING THE DAY, PARTICULARLY DURING THE AFTERNOON AS 850/925MB WINDS
OF 40/30 KNOTS OVERSPREAD THE AREA. GIVEN THE PROPENSITY OF NBM 4.2
TO UNDER-FORECAST DAYTIME WIND SPEEDS, PARTICULARLY DURING HIGHER
WIND SCENARIOS, HAVE BOOSTED WINDS TOWARD THE HIGHER END OF THE
DISTRIBUTION, SUSTAINED SPEEDS OF 20-30 MPH WITH GUSTS TO 40 MPH.
ADDITIONALLY, THESE WINDS WILL ADVECT ANOMALOUSLY WARM AIR TO THE
REGION. DETERMINISTIC NBM OUTPUT, STILL BELOW THE 50TH PERCENTILE OF
ALL THE COMPONENTS GOING INTO THE BLEND, CONTINUES TO TREND WARMER,
NOW IN THE MID 70S, WITH THE PROBABILITY OF REACHING 80 AT 20-30% IN
PARTS OF NORTHEASTERN IOWA AND RIGHT ALONG THE MISSISSIPPI RIVER.
GIVEN THE FACT THAT DETERMINISTIC OUTPUT IS UNDER THE 50TH
PERCENTILE, HAVE LEANED TEMPERATURES UPWARD JUST A BIT. IN ANY CASE,
RECORD HIGHS, MAINLY IN THE MID 70S, ARE IN JEOPARDY FRIDAY
AFTERNOON.
FRIDAY LATE AFTERNOON AND EVENING: SEVERE THUNDERSTORMS POSSIBLE
ROBUST SOUTHERLY WARM, MOIST ADVECTION, IN ADDITION TO POTENTIALLY
BRINGING RECORD TEMPERATURES, SHOULD ALSO SET THE STAGE FOR
WIDESPREAD CONVECTION SWEEPING ACROSS THE CWA DURING THE LATE
AFTERNOON AND EVENING HOURS. AS THE MODIFIED PACIFIC COLD FRONT
ASSOCIATED WITH THE SURFACE LOW RACES NORTHEASTWARD, ENOUGH COOLING
ALOFT WITH THE UPPER LOW SHOULD OCCUR FOR THE LARGE NUMBER OF
PARCELS BEING DISPLACED UPWARD BY THE FRONT TO BECOME FREELY
BUOYANT, LEADING TO NUMEROUS UPDRAFTS DEVELOPING ALONG THIS FEATURE
AS IT SWEEPS ACROSS IA/MO. ADDITIONALLY, PROGGED DEEP SHEAR VECTORS
HAVE A LARGE COMPONENT PARALLEL TO THE SURFACE FRONT. BOTH OF THESE
FACTORS STRONGLY SUGGEST RAPID UPSCALE GROWTH INTO A QLCS WILL OCCUR
BEFORE CONVECTION APPROACHES NE IA. GIVEN THE RAPID MOTION OF THE
CONVECTION AND THE PRESENCE OF 40-55 KNOT WINDS AT 850/925MB,
DAMAGING WINDS WILL BE THE PRIMARY THREAT WITH THESE THUNDERSTORMS.
AS FOR QLCS TORNADO POTENTIAL, KEY UNCERTAINTIES REMAIN REGARDING
THE LEVEL OF SURFACE DESTABILIZATION AND ORIENTATION OF SHEAR WITH
RESPECT TO THE ADVANCING FRONT. 12.00Z LREF PROBABILISTIC OUTPUT
SUGGESTS ABOUT A 30-50 PERCENT TO REALIZE MORE THAN 500 J/KG SBCAPE
WITH UNDER 100 J/KG OF SBCIN SO SURFACE DESTABILIZATION IS CERTAINLY
A POSSIBILITY. FINALLY, WHILE ORIENTATION OF SHEAR IS LARGELY
PARALLEL TO THE BOUNDARY, ENOUGH OF A LINE-NORMAL LOOKS TO BE
PRESENT, PARTICULARLY IN SE MN AND NE IA WHERE THE QLCS MAY BE
ORIENTED MORE NW-SE RATHER THAN N-S, FOR TORNADOGENESIS TO BE
POSSIBLE. THEREFORE, WHILE DAMAGING WIND IS THE MORE PROBABLE (AND
WIDESPREAD) CONCERN, WILL NEED TO CLOSELY MONITOR THE POTENTIAL FOR
A QLCS TORNADOES IN THE COMING DAYS.
SATURDAY AND SUNDAY: BRISK WITH SNOW POTENTIAL
COLD AIR WILL ADVECT INTO THE REGION AS THE UPPER LOW DEPARTS TO THE
NORTHEAST. AS IT DOES SO, GOOD AMOUNT OF MID-LEVEL MOISTURE LOOKS TO
REMAIN. THUS, THERE SHOULD BE AT LEAST A SMALL WINDOW WHERE LIGHT
SNOW MAY OCCUR IF ENOUGH FORCING FOR ASCENT IS PRESENT. GFS/NAM
SUGGEST A SMALL WINDOW SATURDAY NIGHT INTO EARLY SATURDAY WHERE A
FEW SNOW SHOWERS COULD OCCUR AS AN UPPER DISTURBANCE TRANSLATES
DOWNSTREAM. THAT SAID, 12.12Z GFS THERMODYNAMIC PROFILES CLEARLY
ILLUSTRATE THE MAIN LIMITING FACTOR FOR SNOW - QUICK ARRIVAL OF
VERY DRY AIR AROUND 700MB EARLY SUNDAY. THEREFORE, WHILE CONTINUED
MONITORING OF THIS PERIOD IS PRUDENT CONSIDERING THE LIKELIHOOD OF
LINGERING BREEZY CONDITIONS, AT THIS TIME AM DOUBTFUL OF ANYTHING
MORE THAN SPOTTY IMPACTS DUE TO LOCALIZED REDUCED VISIBILITY AS SNOW
FALLS.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 953 PM CDT WED MAR 12 2025
VFR CONDITIONS THROUGH THE TAF PERIOD WITH SOME MID AND HIGH LEVEL
CLOUDS FL100-250. LIGHT AND VARIABLE WINDS BECOME LIGHT SOUTHEAST
OVERNIGHT. THE SOUTHEAST WINDS INCREASE AT KRST 10 TO 15KTS WITH
GUSTS 20 TO 25KTS AFTER 16Z THURSDAY.
CLIMATE
ISSUED AT 234 PM CDT WED MAR 12 2025
POSSIBLE RECORD WARMTH (RECORD / FORECAST):
MAXIMUM MINIMUM
THURSDAY (03/13)
ROCHESTER, MN 68 (2024) / 65 N/A
LA CROSSE, WI 71 (2015) / 68 N/A
FRIDAY (03/14)
ROCHESTER, MN 74 (2012) / 71 49 (2012) / 47
LA CROSSE, WI 75 (2012) / 76 49 (1990) / 49
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...FERGUSON
AVIATION...ZAPOTOCNY
CLIMATE...FERGUSON
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