877
FXUS63 KARX 221144
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
544 AM CST SUN DEC 22 2024
KEY MESSAGES
- MIXED PRECIPITATION POSSIBLE OVERNIGHT INTO MONDAY. SNOW,
RAIN, FREEZING DRIZZLE POSSIBLE.
- WARMER TODAY; NEAR SEASONABLE THROUGH CHRISTMAS; WARMER INTO
NEXT WEEKEND
DISCUSSION
ISSUED AT 335 AM CST SUN DEC 22 2024
WARMER TODAY; SEASONABLE THROUGH CHRISTMAS:
THE WARMER TREND CONTINUES TODAY AS EARLY MORNING TEMPERATURES ARE
10 TO 20 DEGREES WARMER THAN YESTERDAY MORNING. THE BETTER LOW LEVEL
WAA WAS SEEN AS FAR NORTH AS THE NORTHERN PLAINS LATE LAST
NIGHT ON POES DERIVED IMAGERY WITH A 5C/100MI WEST-SOUTHWEST TO
EAST-NORTHEAST GRADIENT NEAR THE MISSOURI RIVER VALLEY.
THEREFORE, WAA RAMPS UP LATER TODAY AFTER A WEAK PERTURBATION,
OVER THE CANADIAN BORDER EARLY THIS MORNING ON GOES WV IMAGERY,
PASSES TO THE SOUTHEAST.
NEAR SEASONABLE TEMPERATURES EXPECTED THROUGH THE WEEK WITH DAYTIME
HIGHS IN THE 30S THROUGH CHRISTMAS DAY (WEDNESDAY) AND OVERNIGHT
LOWS IN THE 20S. AS THE LONGER WAVE TROUGH DEPARTS MIDWEEK, A WARM
UP INTO THE WEEKEND BRINGS THE 40 DEGREE ISOTHERM ACROSS THE
FORECAST AREA.
PRECIPITATION TONIGHT & MONDAY:
STILL MUCH DISAGREEMENT IN PRECIPITATION TYPE AND LOCATION BETWEEN
FORECAST MODELS. AS THE LOW CENTER REACHES SOUTHEAST MINNESOTA EARLY
MONDAY MORNING, 5+ UBAR/S ISENTROPIC UPGLIDE BRINGS INITIAL POPS
INTO CENTRAL WISCONSIN INITIAL PRECIPITATION TYPE WOULD BE SNOW
IF LOW TO MID LEVEL DRY AIR INTRUSION STAVES AWAY. THE LOW
RAPIDLY PHASES AS IT CROSSES OVER THE UPPER MISSISSIPPI RIVER
VALLEY, ADVECTING LOW LEVEL MOISTURE NORTH OF IT'S CENTER AS
LOW-MID LEVEL DRY AIR INTRUDES FROM THE WEST.
LOCATION OF THIS NARROWER PLUME OF LOW-MID DRY AIR BECOMES THE FIRST
DIFFICULTY AS POPS SAG SOUTHWEST THROUGH THE EARLY MORNING. WHILE
COEXISTENCE OF LOW LEVEL SATURATION AND LOW-MID LEVEL DESATURATION
INCREASES AS POPS MOVE THROUGH SOUTHEAST MINNESOTA, THE SURFACE
FREEZING ISOTHERM NOSES AS FAR NORTH AS FILLMORE COUNTY WITH
THE LOW CENTER DURING THIS TIME. THEREFORE, EXACT LOW TRACK
REMAINS CRUCIAL.
AS THE LOW PASSES EAST THROUGH CENTRAL WISCONSIN THROUGH
MONDAY, AFOREMENTIONED MOISTURE NORTH OF THE LOW CENTER THEN
BECOMES THE SUBSEQUENT CONCERN. COLDER NORTHWEST FLOW UPSTREAM
TRAILS THE WEST TO EAST EXIT POP EXIT. PERPETUATING LOW
CONFIDENCE FREEZING DRIZZLE POTENTIAL.
IN SUMMARY, SATURATION AT ANY LOCATION AND HEIGHT WILL GREATLY VARY
SO NAILING DOWN EXACT PRECIPITATION POTENTIAL AND SUBSEQUENT TYPE AT
A CERTAIN LOCATION AND TIME AT THE CURRENT FORECAST HOUR IS A LOSING
BATTLE. SNOWFALL WOULD LIMIT FZDZ IMPACTS THOUGH WHICH IS NICE.
LATTER HALF OF THE WEEK PRECIPITATION CHANCES:
A SOUTHEAST SHIFT IN A PROGRESSIVE MID LEVEL TROUGH HAS ABATED
LOCAL RAIN CHANCES ON CHRISTMAS DAY. IF ANY IMPACTS WERE TO BE
FELT, CONFIDENCE IS ALONG OUR SOUTHEASTERN PERIPHERY.
A CLOSED LOW THEN LIFTS FROM THE SOUTHERN PLAINS WEDNESDAY
NIGHT. WHILE LONG TERM GLOBAL ENSEMBLES (EPS/GEFS) REMAIN CONFIDENT
FOR OVERALL WEAKENING AS IT THE UPPER MISSISSIPPI RIVER VALLEY,
ADDITIONAL FORCING IS EXPECTED TO BUILD UPSTREAM, PERPETUATING
RAIN CHANCES THROUGH THE WEEKEND. THROUGH THE SECOND HALF OF THE
WEEK AT THE CURRENT FORECAST HOUR.
AVIATION /12Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 543 AM CST SUN DEC 22 2024
A SHORTWAVE TROUGH WILL MOVE INTO THE REGION FROM THE NORTHERN
PLAINS TONIGHT. THIS SYSTEM WILL BRING MID AND HIGH CLOUDS TO
THE TAFS THROUGH THIS EVENING, AND THEN THE CEILINGS WILL
GRADUALLY BECOME IFR/MVFR TONIGHT. THE WINDS WILL BE SOUTH AT
10 TO 20 KNOTS WITH GUSTS OF 20 TO 30 KNOTS THROUGH THIS
EVENING. THE WINDS WILL THEN SHIFT TO THE SOUTHWEST AND WEST AS
A COLD FRONT MOVES THROUGH THE REGION OVERNIGHT. THERE MAY BE
SOME LIGHT SNOW AT THE TAF SITES OVERNIGHT, BUT CONFIDENCE WAS
LOW THAT IT WOULD CAUSE VISIBILITY RESTRICTIONS. ANOTHER LOW
CONFIDENCE THING FOR OVERNIGHT IS THAT THERE MAYBE SOME
FREEZING DRIZZLE. CONFIDENCE WAS SO LOW THAT IT WAS INCLUDED IN
THE TAFS.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...JAR
AVIATION...BOYNE
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