800
FXUS63 KARX 221002
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
402 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 /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 1045 PM CST SAT DEC 21 2024
APPEARS BULK OF AVIATION CONCERNS WILL BE AT THE START OF THE
FORECAST AS ISENTROPIC LIFT AREA CONTINUES TO SPREAD STRATUS
FIELD ACROSS NORTHERN IOWA INTO MINNESOTA. CEILINGS HAVE BEEN
MAINLY MVFR BUT A FEW POCKETS INTO IFR. THIS AREA CONTINUES TO
SPREAD EAST NORTHEAST AS LOW LEVEL WARMING FIELD INTENSIFIES
OVERNIGHT. WHILE CONFIDENCE IS HIGH IN AT LEAST MVFR CEILINGS AT
KRST, NOT SO MUCH FOR AREAS EAST AND SOUTH OF THERE.
SUNDAY MORNING IT APPEARS THE LOWER CEILINGS SHOULD ADVECT
NORTHWARD WITH BETTER LIFT, BUT APPROACHING SHORT WAVE WILL
SPREAD MID AND HIGH LEVEL CLOUDS IN JUST AS FAST. GENERAL VFR
CONDITIONS SHOULD PREVAIL BUT GOING INTO SUNDAY NIGHT, WILL HAVE
TO WATCH THE POTENTIAL FOR LOWER CEILINGS AGAIN AS SATURATION
OCCURS WITH AFOREMENTIONED WAVE.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...JAR
AVIATION...SHEA
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