186
FXUS63 KGRB 291728
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1228 PM CDT SAT MAR 29 2025
UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE
KEY MESSAGES
- A SIGNIFICANT ICE ACCUMULATION IS LIKELY ACROSS NORTH-CENTRAL
AND FAR NORTHEAST WISCONSIN TONIGHT THROUGH SUNDAY AFTERNOON. THERE
IS A 60-90% CHANCE THAT THE AREA BETWEEN MERRILL AND IRON
MOUNTAIN WILL SEE AT LEAST 0.25" OF ICE ACCUMULATION.
- THE FREEZING RAIN COULD CREATE SIGNIFICANT DISRUPTIONS IN TRAVEL,
ALONG WITH DAMAGE TO TREES AND POWER OUTAGES. ICE STORM
WARNINGS AND A WINTER STORM WARNING HAVE BEEN ISSUED FOR NORTH-
CENTRAL AND FAR NORTHEAST WISCONSIN.
- THERE IS A 20-30% CHANCE OF THUNDERSTORMS ACROSS THE FORECAST
AREA TONIGHT. SOME OF THE STRONGER STORMS COULD PRODUCE SMALL
HAIL.
- THE WEEKEND PRECIPITATION WILL LEAD TO FAST FLOWS AND RISING
RIVERS AND STREAMS INTO NEXT WEEK. ISOLATED MINOR FLOODING IS POSSIBLE.
DISCUSSION
ISSUED AT 446 AM CDT SAT MAR 29 2025
SHORT TERM...TODAY THROUGH SUNDAY NIGHT
CHANGES: ICE STORM WARNINGS AND WINTER WEATHER ADVISORIES HAVE
BEEN EXTENDED SOUTH AND EAST. ICE ACCUMULATIONS HAVE INCREASED
FROM THE PREVIOUS FORECAST.
DISCUSSION:
SCATTERED THUNDERSTORMS CONTINUED ACROSS PORTIONS OF CENTRAL AND
EAST-CENTRAL WISCONSIN EARLY THIS MORNING. SOME BRIEF HEAVY RAIN
AND SMALL HAIL ARE POSSIBLE WITH THE STRONG STORMS. TEMPERATURES
WERE IN THE 30S, MEANWHILE IT WAS STILL IN THE LOWER TO MIDDLE 60S
ACROSS SOUTHERN WISCONSIN.
DURING FREEZING RAIN/ICE STORM EVENTS IN MARCH AND EARLY APRIL,
THE HUDSON BAY HIGH PLAYS A SIGNIFICANT ROLE BY PROVIDING A COLD
AND DRY AIR MASS FLOWING SOUTHWEST INTO THE AREA ON GUSTY
NORTHEAST WINDS. THIS IS IMPORTANT TONIGHT AS THE COLDER AIR
THAT WILL HELP TRANSITION THE PRECIPITATION OVER TO FREEZING RAIN
AND SLEET IS A LITTLE FURTHER SOUTH THAN EXPECTED. THE REASON WHY
THIS IS MENTIONED, AS THE PRECIPITATION IS ONGOING TONIGHT,
SURFACE DEWPOINTS CONTINUE TO FALL BY SEVERAL DEGREES. I CAN'T
RECALL THE LAST TIME I SAW DEWPOINTS DROPPING SEVERAL DEGREES
AFTER SEVERAL HOURS OF PRECIPITATION.
THERE IS STILL A LOT GOING ON THIS MORNING, SO LETS GET TO IT.
AT THE SURFACE, THE FRONTAL BOUNDARY SOUTH OF THE AREA IS EXPECTED
TO SAG SOUTHWARD TODAY. MEANWHILE, THE PRECIPITATION ACROSS THE
NORTH SHOULD DIMINISH OR END AS THE FIRST WAVE OF LOW PRESSURE
MOVES EAST OF THE AREA. ACROSS CENTRAL AND EAST-CENTRAL WISCONSIN
WHERE THE 850MB WARM FRONT RESIDES, 850MB WINDS WILL OVERRIDE THE
SURFACE WARM FRONT COMBINED WITH STEEP 700/500MB LAPSE RATES
WILL CONTINUE TO PRODUCE SHOWERS AND A FEW STORMS. DURING
THE LATE AFTERNOON, THE 850MB WARM FRONT WILL LIFT NORTHWARD
AS THE LOW LEVEL JET INCREASES LATE THIS AFTERNOON. THE STRONG
OVERRUNNING EVENT WILL LEAD TO PRECIPITATION EXPANDING AND LIFTING
NORTHWARD DURING THE AFTERNOON. SCATTERED THUNDERSTORMS ARE
EXPECTED TO BREAK OUT LATER THIS AFTERNOON AND TONIGHT ACROSS
THE ENTIRE AREA. SMALL HAIL ARE LIKELY WITH THE STRONGER STORMS,
AND COULD NOT ENTIRELY RULE AN ISOLATED ONE INCH HAIL REPORT.
MEANWHILE, THE SURFACE FRONT WILL REMAIN WELL SOUTH OF THE AREA
TODAY AND TONIGHT. THE COLD NORTHEAST FLOW WILL LOCK THE FRONT
IN PLACE UNTIL THE SURFACE LOW MOVES UP ON SUNDAY. THE SURFACE LOW
SHOULD PASS SOUTH OF THE AREA. AS MENTIONED BEFORE, AIR
TEMPERATURES A FEW DEGREES COOLER FOR TONIGHT INTO SUNDAY. THIS
RESULTED IN ICE ACCUMULATIONS INCREASING WHICH RESULTED IN
ICE STORM WARNINGS OR WINTER WEATHER ADVISORIES WERE EXPANDED
SOUTH AND EAST. SURFACE DEWPOINTS FALLING SEVERAL DEGREES DURING
A STEADY PRECIPITATION EVENT OCCURRING OVER SEVERAL HOURS
ON SUNDAY, ONGOING FREEZING RAIN AND RAIN WILL CONTINUE. SOME
CONCERN ON WHAT THE IMPACTS WILL BE AFTER TEMPERATURES RISE TO
OR A FEW DEGREES ABOVE FREEZING DURING THE AFTERNOON. FOR
LOCATIONS NOT IN THE ADVISORY OR WARNING, POTENTIALLY SLIPPERY
TRAVEL IS POSSIBLE ACROSS THE FOX VALLEY AND LAKESHORE SUNDAY
NIGHT AS THE PRECIPITATION WILL LIKELY CHANGE OVER TO FREEZING
RAIN OR SLEET BEFORE CHANGING TO ALL SNOW BEFORE ENDING. HIGHEST.
LONG TERM...MONDAY THROUGH FRIDAY
WEATHER CONDITIONS ACROSS CENTRAL AND NORTHEAST WISCONSIN QUIET
DOWN FOR THE SECOND HALF OF MONDAY AS THE WEEKEND SYSTEM DEPARTS.
ROAD CONDITIONS MAY REMAIN SLIPPERY, ESPECIALLY MONDAY MORNING.
HIGH PRESSURE RIDGE ALLOWS FOR QUIET WEATHER FOR MOST OF TUESDAY,
FOLLOWED BY ANOTHER SYSTEM APPROACHING TUESDAY NIGHT.
STILL LOOKING AT DIFFERENCES IN THE TRACK AND TIMING OF THIS LOW
PROGGED TO MOVE ACROSS THE PLAINS ON TUESDAY INTO WEDNESDAY, AND
THEN THROUGH WI LATER WEDNESDAY. THESE DETAILS AFFECT THE
TEMPERATURE PROFILES, AND ULTIMATELY PRECIPITATION TYPE. HOWEVER,
REGARDLESS OF THE SPECIFIC TRACK THIS EVENT IS CURRENTLY LOOKING
MORE LIKE RAIN/SNOW, AS SUPPOSED TO A VARIETY OF MIXED/ICY PTYPES.
THERE COULD BE A BRIEF PERIOD OF FREEZING RAIN TUESDAY
NIGHT/EARLY WED AS SURFACE TEMPS FALL BELOW FREEZING, BUT
SOUNDINGS OTHERWISE SUGGEST RAIN OR SNOW. WITH ONSET TIMING
LOOKING LATER TUESDAY EVENING, TEMPERATURES WOULD SUGGEST MAINLY
SNOW (WITH PERHAPS A LITTLE FREEZING RAIN) TUESDAY NIGHT INTO
WEDNESDAY MORNING, AND THEN BECOMING ALL RAIN WEDNESDAY AFTERNOON
IN CENTRAL AND EAST- CENTRAL WI, WITH A MIX OF RAIN AND SNOW
ACROSS NORTHERN WI. ANY REMAINING RAIN WEDNESDAY NIGHT MAY
TRANSITION BACK TO ALL SNOW. DETERMINING SNOW TOTALS AND ULTIMATE
IMPACTS IS CHALLENGING GIVEN THE MULTIPLE TRANSITIONS AND WARMING
DAYTIME TEMPS AND ROADS. NBM PROBABILITIES SHOW A 30-50% CHANCE
FOR AT LEAST 3" NORTH AND WEST OF THE FOX VALLEY, AND CLOSER TO
20% CHANCE FROM THE FOX VALLEY TO EAST- CENTRAL WI. THERE IS A 25%
CHANCE FOR A TENTH OF A INCH OF ICE IN NORTH- CENTRAL WI. ALSO OF
NOTE, A 30-50% CHANCE OF PRECIP GREATER THAN 1.0" FOR CENTRAL AND
NORTHEAST WI, WHICH WOULD ADD TO MANY ALREADY SWOLLEN RIVERS AND
STREAMS.
TEMPERATURES WILL BE BELOW NORMAL MONDAY AND TUESDAY WITH HIGHS IN
THE 30S AND LOW 40S, AND AT OR ABOVE NORMAL FROM WEDNESDAY
THROUGH SATURDAY WITH HIGHS IN THE 40S AND 50S.
AVIATION
FOR 18Z TAF ISSUANCE
ISSUED AT 1227 PM CDT SAT MAR 29 2025
POOR FLYING CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD. LOW
PRESSURE WILL TRACK INTO THE GREAT LAKES SPREADING A MIX OF RAIN,
FREEZING RAIN, SLEET AND SNOW ACROSS THE REGION. THE SNOW WILL BE
CONFINED TO FAR NORTH CENTRAL WI, LIKELY NORTH OF RHI. MAINLY
FREEZING RAIN IS EXPECTED AT RHI/AUW/CWA WITH SOME SLEET MIXING IN
AT TIMES. SIGNIFICANT ICING IS EXPECTED. MAINLY RAIN IS EXPECTED
AT ATW/GRB, BUT SOME LIGHT ICING WILL BE POSSIBLE IF THE SURFACE
TEMP CAN DROP TO OR SLIGHTLY BELOW FREEZING. RAIN IS EXPECTED AT
MTW. LOOK FOR MAINLY IFR/LIFR CONDITIONS AREA-WIDE. THERE WILL BE
SMALL CHANCES FOR THUNDER (UNDER 30%) AS ELEVATED INSTABILITY
ARRIVES TONIGHT, BUT HAVE LEFT THUNDER OUT AS CHANCES ARE TOO
LOW.
WINDS WILL REMAIN NORTHEAST INTO SUNDAY, GUSTING TO 25 KTS,
LOCALLY HIGHER NEAR THE BAY AND LAKE.
GRB WATCHES/WARNINGS/ADVISORIES
WINTER STORM WARNING FROM 7 PM THIS EVENING TO 7 PM CDT SUNDAY
FOR WIZ005.
ICE STORM WARNING FROM 7 PM THIS EVENING TO 7 PM CDT SUNDAY FOR
WIZ010>013-018>021-030-031-073.
WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 PM CDT
SUNDAY FOR WIZ035>037-074.
DISCUSSION.....ECKBERG/KLJ
AVIATION.......BERSCH
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