043
FXUS63 KARX 220445
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1045 PM CST SAT DEC 21 2024
KEY MESSAGES
- POTENTIAL FOR LIGHT SNOW AND/OR FREEZING DRIZZLE LATE SUNDAY NIGHT
INTO MONDAY MORNING. AMOUNTS LOOK TO BE MINIMAL, BUT THE MORNING
COMMUTE MAY BE AFFECTED IF FREEZING DRIZZLE DOES OCCUR.
- WARMING TREND FOR TUESDAY ONWARD, BUT DETAILS BECOME UNCLEAR
LATE NEXT WEEK.
DISCUSSION
ISSUED AT 327 PM CST SAT DEC 21 2024
POTENTIAL FOR LIGHT SNOW AND/OR FREEZING DRIZZLE LATE SUNDAY NIGHT
INTO MONDAY MORNING
SUNDAY NIGHT INTO MONDAY MORNING, UPPER WAVE, CURRENTLY OFF THE
PACIFIC NORTHWEST COAST, WILL ADVANCE OVER THE CWA. WARM, MOIST
ADVECTION AHEAD OF THIS FEATURE SHOULD SATURATE THE LOW LEVELS
AND WARM TEMPERATURES TO NEAR - BUT LIKELY BELOW - FREEZING. AS
THE UPPER WAVE APPROACHES, DRY AIR INTRUSION AROUND 700MB MAY
DRY OUT THE DGZ WHILE, NEARER TO THE SURFACE, SOME ISENTROPIC
LIFT ON THE 280/285K SURFACES LOOKS TO CONTINUE, AS SUGGESTED BY
THE 21.12Z GFS. THE END RESULT FOR MANY LOCATIONS MAY BE
FREEZING DRIZZLE IF THE MID-LEVEL DRY AIR LEAVES ENOUGH OF THAT
NEAR SURFACE LAYER SATURATED FOR DROPLETS TO FORM. THE FREEZING
DRIZZLE POTENTIAL WILL PRIMARILY RESIDE IN SOUTHWEST OF I-94
WHILE AREAS TO THE NORTHEAST LOOK TO FEATURE DEEPER SATURATION
AND SNOW FOR MUCH OF THE EVENT. FINALLY, LOCATIONS IN SW WI MAY
END UP A BIT TOO WARM FOR FREEZING TEMPERATURES TO HANG ON AT
THE SURFACE DUE TO THE EFFECTS OF AFOREMENTIONED ADVECTION.
THERE ARE A LOT OF REMAINING UNCERTAINTIES WITH THIS SYSTEM,
MAINLY CENTERING AROUND WHERE THE DRY AIR INTRUDES AND HOW DEEP
SAID INTRUSION WILL BE, SO HAVE ENDEAVORED TO KEEP POPS LESS
THAN 50 PERCENT OUTSIDE OF NORTH CENTRAL WI, WHERE CONFIDENCE IN
AT LEAST SOME SNOW IS BETTER (60-70%) AND SPREAD MENTIONS OF
BOTH SNOW AND FREEZING DRIZZLE ACROSS MUCH OF THE AREA. DUE TO
TIMING, THE MORNING COMMUTE MAY BE IMPACTED, SO HOPEFULLY
DETAILS WILL BECOME CLEARER OVER THE NEXT DAY.
WARMING TREND AHEAD
PREDICTABILITY ACROSS GUIDANCE BECOMES RELATIVELY LOW THROUGH THE
REST OF THE FORECAST, WITH POOR AGREEMENT ON TIMING AND PLACEMENT OF
SEVERAL UPPER WAVES, PARTICULARLY BY LATE NEXT WEEK. HOWEVER,
GENERAL TREND IS FOR HIGHER HEIGHTS ALOFT WHICH FAVORS A SLOW RETURN
TO HIGHS IN THE 30S. MAY EVEN SEE SOME TEMPERATURES IN THE 40S
FRIDAY AND NEXT SATURDAY, BUT NBM INTERQUARTILE RANGES AT THAT TIME
BEGIN TO APPROACH 10 DEGREES, REFLECTING THE LOW CONFIDENCE IN THE
EXACT DETAILS OF THE PATTERN BY THAT PORTION OF THE WEEK.
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 FOREMENTIONED WAVE.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...FERGUSON
AVIATION...SHEA
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