360
FXUS63 KARX 252029
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
229 PM CST WED DEC 25 2024
KEY MESSAGES
- MERRY CHRISTMAS AND HAPPY HOLIDAYS FROM NWS LA CROSSE!
- FREEZING DRIZZLE IS POSSIBLE TONIGHT INTO THURSDAY MORNING
WITH NORTHEAST IOWA INTO CENTRAL WISCONSIN THE MOST LIKELY
AREAS (40-60%) TO SEE A GLAZE OF ICE. ROADS MAY BE SLIPPERY
FOR THE MORNING COMMUTE, ESPECIALLY IN WEST-CENTRAL TO CENTRAL
WISCONSIN.
- RAIN IS EXPECTED THURSDAY INTO SATURDAY WITH THE HIGHEST
AMOUNTS EXPECTED ON FRIDAY.
- PRECIPITATION CHANCES INCREASE AGAIN EARLY NEXT WEEK.
DISCUSSION
ISSUED AT 229 PM CST WED DEC 25 2024
FREEZING DRIZZLE POTENTIAL
THE MAIN CONCERN IN THE NEAR TERM REMAINS THE POTENTIAL FOR FREEZING
DRIZZLE THIS EVENING INTO THURSDAY MORNING. CONFIDENT THAT DRIZZLE
WILL OCCUR ACROSS THE AREA TONIGHT INTO THURSDAY MORNING ALONG
THE WEAK ISENTROPIC LIFT ON THE 280K THETA SURFACE COINCIDING
WITH A NORTHWARD SURGE OF MOISTURE IN THE 925-850HPA LAYER, BUT
UNFORTUNATELY THE FREEZING ASPECT OF THE FORECAST REMAINS
TRICKY. THE 25.12Z HREF SOUNDINGS INDICATE THE SURFACE TO ~3KFT
LAYER REMAINS BELOW FREEZING THROUGH THURSDAY MORNING,
SUFFICIENT FOR FREEZING DRIZZLE, BEFORE WARM AIR ADVECTION IS
ABLE TO PUSH TEMPERATURES ABOVE FREEZING, ENDING THE FREEZING
DRIZZLE THREAT LATE THURSDAY MORNING. AS SUCH, THE 25.12Z HREF
PROBABILITIES FOR AT LEAST A GLAZE OF ICE HAVE INCREASED AS
COMPARED TO THE PREVIOUS RUN, NOW SHOWING A 40-60% PROBABILITY
MAINLY FROM NORTHEAST IOWA INTO CENTRAL WISCONSIN. HOWEVER, ICE
ACCUMULATIONS REMAIN LOW, GENERALLY JUST A GLAZE IS EXPECTED, AS
THE BIGGEST CHALLENGE CONTINUES TO LIE WITH THE DEPENDENCE ON
ROAD TEMPERATURES THIS EVENING/OVERNIGHT AND WHETHER OR NOT THEY
ARE ABLE TO DROP BELOW FREEZING. ROAD TEMPERATURES HAVE RISEN
TO NEAR 40F THIS AFTERNOON ALONG AND WEST OF THE MISSISSIPPI
RIVER WHILE THEY REMAIN IN THE LOW 30S IN SOUTH TO CENTRAL
WISCONSIN LEADING TO UNCERTAINTY IN HOW COLD THE ROADS GET WITH
WARMING TEMPERATURES OVERNIGHT. THINKING AREAS TOWARDS WEST-
CENTRAL AND CENTRAL WISCONSIN ARE THE MOST LIKELY TO SEE IMPACTS
FROM FREEZING DRIZZLE THURSDAY MORNING WHERE ROAD TEMPERATURES
CURRENTLY REMAIN AROUND FREEZING AND WHERE THE 25.13Z NBM AND 25.12Z
HREF ARE MOST CONFIDENT (90-100%) AIR TEMPERATURES WILL FALL
BELOW FREEZING OVERNIGHT.
IN COORDINATION WITH SURROUNDING OFFICES, HAVE OPTED TO NOT ISSUE AN
ADVISORY FOR THE ICING POTENTIAL AT THIS TIME AND INSTEAD WOULD LIKE
TO MONITOR TRENDS AS WE HEAD INTO THE OVERNIGHT HOURS. IN ADDITION
TO THE FREEZING DRIZZLE POTENTIAL OVERNIGHT, PATCHY FOG MAY DEVELOP
ACROSS THE AREA AS SOUTHERLY WINDS USHER WARMER AIR OUR
SNOWPACK, ADDING A FURTHER CHALLENGE TO TRAVEL. USE CAUTION IF
ON THE ROADS THIS EVENING THROUGH THURSDAY MORNING.
RAIN THURSDAY INTO SATURDAY
THE WELL ADVERTISED RAIN HEADED OUR WAY THURSDAY AFTERNOON INTO THE
WEEKEND REMAINS ON TRACK THIS AFTERNOON. THE 500HPA TROUGH CURRENTLY
OVER THE FOUR CORNERS REGION EJECTS EASTWARD INTO NORTHERN
TEXAS TONIGHT BEFORE LIFTING NORTHWARD INTO THE MIDWEST FRIDAY
MORNING. VARIOUS SHORTWAVES PRECEDING THIS MAIN WAVE PROVIDE
CHANCES FOR PRECIPITATION AHEAD OF THE MAIN RAIN MAKER THURSDAY
AFTERNOON AND FRIDAY MORNING, BUT THE PRIMARY FORCING ASSOCIATED
WITH THE EVENT ARRIVES FRIDAY AFTERNOON, COINCIDING WITH THE
HEAVIEST RAINFALL. ENSEMBLE GUIDANCE REMAINS IN GOOD AGREEMENT
ABOUT TEMPERATURES WARMING ABOVE FREEZING AS WARM AIR ADVECTION
IS USHERED INTO THE REGION UNDER SOUTHERLY FLOW. AS SUCH, RAIN
REMAINS THE PRIMARY PRECIPITATION TYPE. STILL NEED TO MONITOR
AMOUNTS AS THE NBM SUGGESTS A 40-60% PROBABILITY OF MORE THAN
1/4 INCH OF RAIN AND A 10-20% PROBABILITY OF GREATER THAN 1/2 AN
INCH ACROSS MUCH OF THE AREA.
PRECIPITATION CHANCES EARLY NEXT WEEK
MODEL SOLUTIONS CONTINUE TO INDICATE ANOTHER WAVE DEEPENS ACROSS THE
CENTRAL UNITED STATES EARLY NEXT WEEK. THIS WAVE DEVELOPS A SURFACE
LOW PRESSURE SYSTEM ACROSS THE GREAT PLAINS WHICH THEN LIFTS INTO
THE NORTHEAST. THE 25.00Z LREF HAS KEPT THESE FEATURES ON A MORE
SOUTHERLY TRAJECTORY AS COMPARED TO THIS TIME YESTERDAY, ALTHOUGH
THERE IS STILL A FAIR AMOUNT OF DISAGREEMENT IN TIMING AND DEPTH
AMONGST THE GEFS/EPS/GEPS. WILL NEED TO CONTINUE MONITORING THIS
EVENT FOR POTENTIAL IMPACTS OR IF THE SYSTEM CONTINUES TO TREND
SOUTHWARD. AT THIS TIME, IT LOOKS AS THOUGH A MIX OF RAIN AND
SNOW COULD IMPACT AREAS SOUTH OF HIGHWAY 10.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1136 AM CST WED DEC 25 2024
LUCKILY ALL THE FLYING REINDEER HAVE COME AND GONE SINCE THE
AVIATION WEATHER IS NOT LOOKING GOOD MOVING FORWARD.
PERSISTENT STRATUS REMAINS IN PLACE WITH RELATIVELY LIGHT FLOW,
BUT AS SUCH FLOW INCREASES FROM THE SOUTH AHEAD OF WAVE OVER THE
ROCKIES, WE WILL SEE INCREASING THETA-E AND BROAD LIFT LEADING
TO MORE AND MORE LOW LEVEL SATURATION. THE MIX OF CEILINGS THIS
MORNING, RANGING FROM IFR IN THE WEST TO VFR ACROSS SOUTHERN
WISCONSIN, WILL DETERIORATE TONIGHT AND WORSEN GOING INTO THE
DAY THURSDAY. WHILE WE MAY ALSO SEE SOME DRIZZLE DEVELOP, FOR
AVIATION PURPOSES, THE MAIN STORY WILL BE LOW CEILINGS AND
LIKELY THICKENING FOG LEADING TO IFR TO LIFR CONDITIONS.
WHILE GUIDANCE IS NOT SUPER EXCITED ABOUT <1SM VISIBILITIES,
ONLY 40-50% CHANCE, FEELING IS THESE ARE UNDERPLAYING RISK SO
LOWERED IN TAFS. CONFIDENCE IS FAR HIGHER WITH CEILINGS AS MODEL
BLENDS ARE AT 90% OR HIGHER FOR IFR. EVEN RUDOLPH WOULD PASS ON
THOSE CONDITIONS.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...FALKINHAM
AVIATION...SHEA
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