208
FXUS63 KGRB 190420
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1020 PM CST SAT JAN 18 2025
UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE
KEY MESSAGES
- A BITTERLY COLD ARCTIC AIRMASS WILL BRING A PROLONGED PERIOD OF
WIND CHILLS REACHING FROM 20 TO 40 DEGREES BELOW ZERO LATE
TONIGHT THROUGH WEDNESDAY MORNING. THE COLDEST WIND CHILLS WILL
OCCUR ON MONDAY NIGHT INTO TUESDAY MORNING WHEN WIND CHILLS AS
COLD AS 40 BELOW WILL BE POSSIBLE.
- A COLD WEATHER ADVISORY GOES INTO EFFECT AT 9 PM TONIGHT FOR
NORTH-CENTRAL WISCONSIN AND 3 AM FOR NORTHEAST WISCONSIN,
LASTING THROUGH 9 PM MONDAY. CONFIDENCE CONTINUES TO INCREASE
THAT AN EXTREME COLD WARNING WILL BE REQUIRED ON LATE MONDAY
NIGHT INTO TUESDAY MORNING.
- A WARMING TREND WILL START ON WEDNESDAY WHICH WILL CONTINUE INTO
THE WEEKEND. HIGH TEMPERATURES RANGING FROM 10 TO 20 DEGREES ON
WEDNESDAY WILL WARM INTO THE MIDDLE 20S TO LOWER 30S BY
SATURDAY.
DISCUSSION
ISSUED AT 132 PM CST SAT JAN 18 2025
SHORT TERM...TONIGHT AND SUNDAY
THE LATEST RAP ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW AN
AMPLIFYING UPPER AIR PATTERN CONSISTING OF A BEEFY RIDGE
POSITIONED FROM THE FAR EASTERN PACIFIC TO EASTERN ALASKA AND A
DOWNSTREAM TROUGH FROM HUDSON BAY TO THE WESTERN GREAT LAKES.
MID-LEVEL HEIGHT FALLS CONTINUE OVER THE GREAT LAKES EARLY THIS
AFTERNOON AS COLD ADVECTION DROPS 850MB TEMPS INTO THE UPPER
TEENS AND LOW 20S BELOW ZERO. THE LEADING EDGE OF THE VERY COLD
AIR IS LOCATED OVER NORTHERN MINNESOTA AND POISED TO MOVE INTO THE
STATE TONIGHT. MEANWHILE, THE COLD AIR IS GENERATING LIGHT LAKE
EFFECT SNOW SHOWERS AND FLURRIES NEAR THE UPPER PENINSULA BORDER
EARLY THIS AFTERNOON. FORECAST CONCERNS MAINLY CENTER AROUND THE
DANGEROUS WIND CHILLS, THEN FOLLOWED BY LAKE EFFECT SNOW SHOWERS
OVER FAR NORTHERN WI.
DANGEROUS WIND CHILLS: COLD ADVECTION WILL CONTINUE OVER THE NEXT
24 HOURS AS 850MB TEMPS FALL TO 28 BELOW BY LATE TONIGHT AND AS
COLD AS 30 BELOW ON SUNDAY. WHILE WINDS WON'T BE STRONG AND GUSTY,
THEY WILL BE SUSTAINED AT 5 TO 10 MPH TONIGHT AND 10 TO 15 MPH ON
SUNDAY.
THIS VERY COLD AIRMASS APPEARS TO BE SLIGHTLY DELAYED MOVING INTO
THE REGION BASED ON THE PREVIOUS FORECAST FOR TONIGHT. WHILE LOWS
WILL FALL FROM ZERO TO 15 BELOW BY EARLY SUNDAY MORNING, WIND
CHILLS ARE NOT FORECAST TO FALL TO NEAR ADVISORY CRITERIA UNTIL
SHORTLY AFTER MIDNIGHT OVER NORTH-CENTRAL WI AND TO AROUND 4-6 AM
OVER NORTHEAST WI. THE COLD WEATHER ADVISORY STARTS AT 9 PM, WHICH
IS ON THE EARLY SIDE, PARTICULARLY OVER NORTHEAST WI. WILL REFINE
THE START TIME OVER NORTHEAST WI TO START AT 09Z (3 AM).
DO NOT EXPECT MUCH IMPROVEMENT IN WIND CHILLS ON SUNDAY AS THEY
REMAIN IN THE 15 BELOW TO 25 BELOW RANGE THROUGH THE DAY. DON'T
SEE A REASON TO END THE ADVISORY EARLY AS IT IS STILL VERY COLD
AND IT KEEPS HEADLINE MANAGEMENT SIMPLER.
LIGHT LAKE EFFECT SNOW: WIND TRAJECTORIES WILL REMAIN FROM THE
WEST-NORTHWEST THOUGH SUNDAY AFTERNOON. LOW INVERSION HEIGHTS AND
LOWERING SNOW TO LIQUID RATIOS AS THE EXTREME COLD ARRIVES MEANS
POTENTIAL IS VERY LOW FOR ANY SORT OF SIGNIFICANT SNOWFALL OVER
FAR NORTHERN WI. BUT LIGHT SNOW AND FLURRIES CAN BE EXPECTED AT
TIMES OVER THE NEXT 24 HOURS NEAR THE UPPER PENINSULA BORDER.
LONG TERM...SUNDAY NIGHT THROUGH SATURDAY
FOCUS OF THE DISCUSSION CONTINUES TO REVOLVE AROUND DANGEROUSLY COLD
TEMPERATURES THROUGH TUESDAY FOLLOWED BY LIGHT SNOW CHANCES
THEREAFTER.
TEMPERATURES/WIND CHILLS: THE COLDEST AIR REMAINS PROJECTED TO MOVE
ACROSS THE REGION ON MONDAY NIGHT INTO TUESDAY WHEN 850MB TEMPS
RANGE FROM 29 BELOW TO 33 BELOW ZERO. COMBINED WITH A BRISK BUT
PERSISTENT 5 TO 8 MPH WIND, WIND CHILLS FROM MONDAY EVENING THROUGH
TUESDAY MORNING RANGE FROM 30 TO 40 BELOW ZERO ACROSS THE ENTIRE
AREA.
WIND CHILLS ARE FORECAST TO MODERATE INTO THE 15 BELOW TO 25 BELOW
ZERO RANGE ON TUESDAY AFTERNOON, BUT THE LATEST GUIDANCE SHOWS WIND
CHILLS FALLING BACK INTO THE 20 BELOW TO 30 BELOW ZERO RANGE ON
TUESDAY NIGHT. THIS PERIOD WILL LIKELY BE TRICKY CONSIDERING WIND
CHILLS WILL BE ON THE LOWER END OF ADVISORY CRITERIA AND LOW LEVEL
TEMPS WILL BE WARMING AS THE CORE OF THE ARCTIC AIRMASS DEPARTS.
HEADLINES: A COLD WEATHER ADVISORY REMAINS IN EFFECT THROUGH 9 PM
MONDAY. AS BEEN ADVERTISED FOR DAYS, CONFIDENCE IS RELATIVELY HIGH
THAT AN EXTREME COLD WARNING WILL BE NEEDED FOR THE REST OF MONDAY
NIGHT INTO PART OF TUESDAY MORNING BEFORE GOING BACK TO AN ADVISORY.
HOW LONG THE LATTER ADVISORY RUNS WILL BE DIFFICULT, BUT THERE IS
POTENTIAL FOR IT TO RUN THROUGH TUESDAY NIGHT.
SNOW CHANCES: CLIPPER ENERGY WILL BE TRAVERSING THE REGION ON
WEDNESDAY NIGHT THROUGH THURSDAY WHICH WILL PROVIDE LIGHT SNOW
CHANCES AT TIMES. THIS ENERGY LOOKS RATHER DISJOINTED AND MOISTURE
WILL BE IN SHORT SUPPLY, SO SNOWFALL AMOUNTS WILL BE VERY LIGHT.
AVIATION
FOR 06Z TAF ISSUANCE
ISSUED AT 1004 PM CST SAT JAN 18 2025
ASIDE FROM SOME LAKE-EFFECT LOW CLOUDS IN NORTHWEST VILAS COUNTY,
SKIES WERE CLEAR ACROSS THE FORECAST AREA LATE THIS EVENING.
LIGHT TO MODERATE NORTHWEST WINDS WERE ONGOING, WITH GUSTS TO
15 TO 20 KTS STILL BEING REPORTED IN PARTS OF CENTRAL AND EASTERN
WI.
MOST OF THE LOW CLOUDS THAT WERE EVIDENT OVER MN IN THE LATE
AFTERNOON DISSIPATED AFTER SUNSET, SO HAVE BACKED OFF ON SKY COVER
FOR THE OVERNIGHT AND DAYTIME PERIODS ON SUNDAY. THERE ARE STILL
SOME MODEL INDICATIONS THAT CLOUDS WILL INCREASE SUNDAY EVENING,
BUT THINK THAT MODELS ARE OVERPLAYING THIS GIVEN THE EXTREMELY DRY
ARCTIC AIRMASS THAT WILL BE IN PLACE. WILL LIKELY CONTINUE WITH
NOTHING MORE THAN SCT COVERAGE THROUGH THE TAF PERIOD. MODERATE
NORTHWEST WINDS WILL CONTINUE TO GUST AT 15 TO 20 KTS AT TIMES,
AND A FEW LIGHT SNOW SHOWERS MAY PERSIST NEAR THE U.P. BORDER.
GRB WATCHES/WARNINGS/ADVISORIES
COLD WEATHER ADVISORY UNTIL 9 PM CST MONDAY FOR WIZ005-010>012-
018-019-030-035-036.
COLD WEATHER ADVISORY FROM 3 AM SUNDAY TO 9 PM CST MONDAY FOR
WIZ013-020>022-031-037>040-045-048>050-073-074.
DISCUSSION.....MPC/MPC
AVIATION.......KIECKBUSCH
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