762
FXUS63 KGRB 210433
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1033 PM CST MON JAN 20 2025
UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE
KEY MESSAGES
- DANGEROUSLY COLD WEATHER IS EXPECTED THROUGH TUESDAY AFTERNOON.
WIND CHILLS WILL RANGE FROM 25 TO 45 BELOW ZERO IN CENTRAL AND
NORTH CENTRAL WISCONSIN AND 20 TO 35 BELOW ZERO ELSEWHERE. THE
COLDEST WIND CHILLS WILL BE LATE TONIGHT INTO EARLY TUESDAY
MORNING.
- AN EXTREME COLD WARNING IS IN EFFECT FOR NORTH-CENTRAL WISCONSIN THROUGH
NOON TUESDAY.
- A COLD WEATHER ADVISORY IS IN EFFECT FOR CENTRAL AND NORTHEAST WISCONSIN
THROUGH MIDNIGHT TONIGHT. AN EXTREME COLD WARNING IS THEN IN
EFFECT FROM MIDNIGHT TONIGHT THROUGH NOON TUESDAY.
- A WARMING TREND WILL BEGIN ON WEDNESDAY, LASTING INTO THE
WEEKEND.
DISCUSSION
ISSUED AT 153 PM CST MON JAN 20 2025
SHORT TERM...TONIGHT AND TUESDAY
THE LATEST RAP ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW ARCTIC
HIGH PRESSURE CENTERED FROM THE NORTHWEST GREAT PLAINS TO THE
CENTRAL GULF COAST EARLY THIS AFTERNOON. THE COLDEST AIR DURING
THIS ARCTIC AIR OUTBREAK SO FAR LIES FROM NORTHERN MINNESOTA TO
THE DAKOTAS WHERE 32 BELOW TO 36 BELOW TEMPS AT 850MB ARE ANALYZED
BY 12Z RAOBS AT INTERNATIONAL FALLS AND BISMARCK. ACROSS NORTHERN
WISCONSIN, SURFACE TEMPERATURES HAVE WARMED TO AROUND 0 DEGREES
OVER THE FOX VALLEY AND FROM 5 BELOW TO 9 BELOW ZERO OVER NORTH-
CENTRAL WISCONSIN AT 1 PM. WIND CHILLS GENERALLY RANGE FROM 15
BELOW TO 30 BELOW ZERO.
THE CORE OF THE COLDEST AIR WILL SWING ACROSS THE REGION TONIGHT
INTO TUESDAY MORNING. WHILE THERE ARE SCATTERED CLOUDS UPSTREAM,
DON'T THINK THIS WILL HAVE A SIGNIFICANT IMPACT ON TEMPS IF THEY
MOVE INTO NORTHERN WI TONIGHT.
SNOW COVER IS PLAYING A SIGNIFICANT ROLE WITH TEMP/WIND CHILL
FORECASTING. SNOW DEPTHS ARE ANALYZED TO BE GREATER THAN 2 INCHES
GENERALLY NORTH AND WEST OF A WAUSAU TO IRON MOUNTAIN LINE. WHERE
THIS MINOR SNOWPACK EXISTS, WINDS DECOUPLED LAST NIGHT AT TIMES
WHICH MITIGATED THE IMPACTS OF THE EXTREMELY COLD WIND CHILLS. MOS
FORECAST GUIDANCE INDICATES SIMILAR WIND SPEEDS TONIGHT, AND
THINK WILL SEE WINDS DROP OFF AT TIMES. THIS MEANS THAT WHILE LOW
TEMPS WILL LIKELY BE COLDER THAN THE NATIONALBLEND GUIDANCE, WIND
CHILLS MAY NOT ALWAYS FALL INTO WARNING CRITERIA. BUT OF COURSE
WHEN THERE IS EVEN A SLIGHT WIND, WIND CHILLS FROM 35 BELOW TO 45
BELOW ZERO CAN BE EXPECTED. HAVE THEREFORE LOWERED MIN TEMPS OVER
NORTH- CENTRAL WI CLOSER TO ECMWF STATISTICAL GUIDANCE.
ELSEWHERE, WIND CHILLS REMAIN ON TRACK TO FALL INTO THE 30 BELOW
TO 40 BELOW RANGE LATE TONIGHT THROUGH TUESDAY MORNING. NO CHANGES
TO THE EXTREME COLD HEADLINES APPEAR WARRANTED.
HIGHS ON TUESDAY AFTERNOON WILL LIKELY REMAIN BELOW AT OR BELOW ZERO
AWAY FROM LAKE MICHIGAN WITH WIND CHILLS RANGING FROM 20 BELOW TO
25 BELOW ZERO. A COLD WEATHER ADVISORY AFTER THE EXTREME COLD
WARNING EXPIRES WILL LIKELY BE NEEDED THROUGH LATE IN THE
AFTERNOON OR LATE IN THE EVENING. QUITE A BIT OF UNCERTAINTY HOW
LONG TO RUN THE SUBSEQUENT ADVISORY AS WIND CHILLS HOVER RIGHT
NEAR OR JUST BELOW CRITERIA. SO AFTER COORDINATING WITH
SURROUNDING OFFICES, HAVE REFRAINED FROM AN ADVISORY ISSUANCE.
THIS WILL LIKELY BE THE COLDEST STRETCH OF WEATHER SINCE THE LAST
TWO DAYS OF JANUARY 2019. NWS LA CROSSE HAS A NICE WRITE UP OF
THAT EVENT AT WEATHER.GOV/ARX/JAN2019.
LONG TERM...TUESDAY NIGHT THROUGH MONDAY
FOCUS IN THIS PART OF THE FORECAST REMAINS ON THE TAIL END OF THE
ARCTIC OUTBREAK ON TUESDAY NIGHT FOLLOWED BY LIGHT SNOW CHANCES AT
TIMES.
TEMPERATURES/WIND CHILLS: ARCTIC HIGH PRESSURE WILL SLIDE FROM THE
OHIO VALLEY TO THE MID-ATLANTIC STATES AS A WARM FRONT MOVES INTO
THE NORTHERN MISSISSIPPI VALLEY ON TUESDAY NIGHT. AS THE SURFACE
HIGH DEPARTS, BOTH WARM ADVECTION AND CLOUD COVER WILL INCREASE
THROUGH THE NIGHT. BOTH THESE TRENDS SHOULD LEAD TO A WARMING TREND
AFTER LOW TEMPS OCCUR IN THE EVENING. AS A RESULT, IT LOOKS LIKE A
COLD WEATHER ADVISORY WILL ONLY BE REQUIRED THROUGH THE END OF THE
EVENING.
TEMPERATURES WILL MODERATE FROM WEDNESDAY (MIDDLE TEENS TO LOWER
20S) THROUGH THE WEEKEND (MIDDLE TO UPPER 20S). TEMPS APPEAR TO
HAVE TRENDED COLDER THIS WEEKEND, SO THE PROBABILITY OF REACHING 30
DEGREES HAS DECREASED.
LIGHT SNOW CHANCES: FORECAST SOUNDINGS INDICATE SUFFICIENT
SATURATION WILL OCCUR PRIOR TO 6 AM WED FOR A CHANCE OF LIGHT SNOW,
BUT THINK SOME OF THE UPWARD MOTION WILL GET LOST TO CREATING
SATURATION OF A VERY DRY ARCTIC AIRMASS. IT ALSO APPEARS THAT
MOISTURE PROFILES ARE DISJOINTED. THEREFORE SNOW CHANCES WILL
REMAIN LOW ON LATE TUE NIGHT INTO WEDNESDAY NIGHT. ISOLATED
ACCUMULATIONS UP TO 1 INCH APPEAR POSSIBLE BUT MOST LOCATIONS WILL
SEE A DUSTING TO A HALF INCH.
ADDITIONAL SHORTWAVE ENERGY AND A COLD FRONT WILL ARRIVE THIS
WEEKEND IN A SIMILAR FASHION (UNFOCUSED/DISJOINTED). THE CHANCE OF
LIGHT SNOW WILL BE THE HIGHEST DURING THE LATE FRIDAY NIGHT INTO
SATURDAY TIMEFRAME, BUT ACCUMULATION POTENTIAL LOOKS MINOR.
AVIATION
FOR 06Z TAF ISSUANCE
ISSUED AT 1026 PM CST MON JAN 20 2025
LIGHT TO MODERATE WEST WINDS AND MOSTLY CLEAR SKIES ARE EXPECTED
THROUGH TUESDAY MORNING, ALONG WITH CONTINUED FRIGID TEMPERATURES
AND WIND CHILLS. HIGH AND MID-LEVEL CLOUDS WILL INCREASE DURING
THE LATE AFTERNOON AND EVENING, AND FLURRIES OR VERY LIGHT SNOW
WILL BE POSSIBLE IN NC/C WI TOWARD THE END OF THE TAF PERIOD.
SURFACE WINDS WILL BACK SW TO S LATE TUESDAY AFTERNOON INTO
TUESDAY EVENING, BUT WILL GENERALLY BE 10 KTS OR LESS. HOWEVER,
STRONG SOUTHWEST WINDS ALOFT WILL OVERSPREAD THE REGION FROM WEST
TO EAST TUESDAY EVENING, LEADING TO WIDESPREAD LLWS.
GRB WATCHES/WARNINGS/ADVISORIES
EXTREME COLD WARNING UNTIL NOON CST TUESDAY FOR WIZ005-010>012-
018-019.
COLD WEATHER ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR WIZ013-
020>022-030-031-035>040-045-048>050-073-074.
EXTREME COLD WARNING UNTIL NOON CST TUESDAY FOR WIZ013-020>022-
030-031-035>040-045-048>050-073-074.
DISCUSSION.....MPC/MPC
AVIATION.......KIECKBUSCH
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