814
FXUS63 KARX 211211
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
611 AM CST SAT DEC 21 2024
KEY MESSAGES
- ANOTHER COLD DAY WITH DAYTIME HIGHS IN THE TEENS TO LOW 20S.
WARMING ARRIVES LATE TONIGHT INTO EARLY SUNDAY MORNING.
GRADUAL WARMING THROUGH THE WEEK.
- MIXED PRECIPITATION POTENTIAL INITIALLY EARLY MONDAY MORNING
PRIMARILY AFFECTS LOCAL COUNTIES IN WISCONSIN. FREEZING
PRECIPITATION CANNOT BE RULED OUT.
- LOW RAIN CHANCES GRAZE LOCAL COUNTIES FROM SOUTHWEST INTO
CENTRAL WISCONSIN CHRISTMAS DAY.
DISCUSSION
ISSUED AT 317 AM CST SAT DEC 21 2024
STAYING COLD TODAY, GRADUALLY WARMING:
THE HIGH PRESSURE RESPONSIBLE FOR THIS MORNING'S WELL BELOW
NORMAL TEMPERATURES LINGERS TODAY, RESULTING IN COLD DAYTIME
HIGHS FROM THE TEENS TO LOW 20S. UPPER LEVEL FLOW PROGRESSES
EAST LATE TONIGHT PERMITTING LOW LEVEL WARM AIR ADVECTION,
OVERNIGHT LOWS WILL BE NEAR NORMAL, IN THE TEENS AREA WIDE.
TEMPERATURES GRADUALLY INCREASE THROUGH THE WEEK AS LOW LEVEL
THETA E PLUMES PUSH NORTHEAST.
PRECIPITATION CHANCES EARLY MONDAY
PRECIPITATION CHANCES REACH THE FORECAST AREA EARLY MONDAY
MORNING AS AN UPPER LEVEL TROUGH, SEEN ON EARLY MORNING UPPER
LEVEL GOES WATER VAPOR IMAGERY OVER THE PACIFIC COAST, ADVECTS
THROUGH THE UPPER MISSISSIPPI RIVER VALLEY. MODELS EXHIBIT
STRONG AGREEMENT FOR AN ACCOMPANYING NARROW FILAMENT OF LOW
LEVEL MOISTURE RAPIDLY PROGRESSING NORTHEAST THROUGH THE
MISSISSIPPI RIVER VALLEY AS THE LOW DEEPENS THROUGH SUNDAY. AS
THE LOW TIGHTENS, QUICKENS IT'S PACE, AND CAREENS SLIGHTLY SOUTH
OF IT'S INITIAL TRAJECTORY, TWO STOUT AREAS OF VERY (10TH
PERCENTILE) DRY AIR PRESENT SOME CHALLENGES IN PRECIPITATION
CONFIDENCE AND TYPE. SNOW, RAIN, AND FREEZING DRIZZLE REMAIN
POSSIBLE.
LONG TERM GLOBAL MODELS (GEFS/GFS/EPS/ECMWF) EXHIBIT SOME
VARIABILITY IN STORM TRACK AND INTENSITY. MOST NOTICEABLE CHANGE
OVER RECENT RUNS IS SUSTAINING A STRONGER UPPER LEVEL JET
STREAK ACROSS THE PLAINS PROVIDING A MORE PROGRESSIVE,
POTENTIALLY SLIGHTLY DEEPER SURFACE LOW. THESE SAME RUNS ALSO
DEPICT A QUASI-ZONAL AREA OF HEIGHTENED PRECIPITATION NORTH OF
THE LOW CENTER. THE QUICK PROGRESSION AND HIGH TRACK VARIABILITY
KEEPS CONFIDENCE AND IMPACT EXPECTATIONS LOW. CONFIDENCE IN
OVERALL AVAILABLE MOISTURE IS ALSO QUITE LOW. MOST RECENT
FV3/NAMNEST GUIDANCE QUADRUPLED THE QPF WITHIN THIS NARROW BAND
ALONG OUR NORTHWESTERN PERIPHERY.
ALL IN ALL, HAVE COLLABORATED WITH NEIGHBORING OFFICES TO BLEND
STORM TOTAL QPF DOWN TO <0.07" THROUGH MONDAY, ALIGNED WITH
GLOBAL ENSEMBLE CONFIDENCE. WHILE OVERALL SNOWFALL ACCUMULATIONS
ARE EXPECTED TO BE LIGHT, A NARROW BAND OF TRANSIENT HEAVIER
SNOWFALL RATES CANNOT BE RULED OUT.
CHRISTMAS PRECIPITATION CHANCES:
A SUBSEQUENT PLUME OF MOISTURE RAPIDLY ADVECTS NORTHEAST WITHIN AN
AMPLIFIED TROUGH THROUGH CHRISTMAS DAY. ASSOCIATED NBM POPS HAVE
INCREASED 10-20% ALONG OUR SOUTHEAST. ACCOMPANYING SURFACE
TEMPERATURES APPEAR TO BE ABOVE FREEZING (70% CONFIDENCE) AS THE
32 DEGREE ISOTHERM PARKS NEAR OUR NORTHWESTERN PERIPHERY.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 535 AM CST SAT DEC 21 2024
A SHORTWAVE TROUGH WILL BRING MID AND HIGH CLOUDS TO THE AREA
THROUGH TONIGHT. WINDS WILL LIGHT OUT OF THE SOUTHEAST AND SOUTH
TODAY AND THEN INCREASE INTO THE 10 TO 15 KNOT RANGE TONIGHT.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...JAR
AVIATION...BOYNE
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