691
FXUS63 KGRB 301803
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
103 PM CDT SUN MAR 30 2025
UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE
KEY MESSAGES
- A SIGNIFICANT ICE STORM CONTINUES INTO TODAY, ESPECIALLY FROM
CENTRAL THROUGH NORTH-CENTRAL AND NORTHEAST WISCONSIN WITH
DANGEROUS TRAVEL WHERE ROAD TEMPS ARE COOLER, ALONG WITH TREE
DAMAGE AND POWER OUTAGES AS ICE ACCUMULATES.
- THE RAIN/FREEZING RAIN WILL TRANSITION TO SNOW FROM NORTHWEST
TO SOUTHEAST LATER TODAY INTO TONIGHT WITH 40-70% CHANCES FOR
AT LEAST 2 INCHES ACROSS PARTS OF CENTRAL INTO NORTHERN
WISCONSIN.
- THE WIDESPREAD RAINFALL/PRECIPITATION ALREADY FALLEN AND
OCCURRING THROUGH THE WEEKEND WILL LEAD TO RISING RIVER AND
STREAM LEVELS AND MINOR FLOODING FOR SOME LOCATIONS.
- ANOTHER IMPACTFUL PERIOD OF PRECIPITATION IS LIKELY TUESDAY
INTO WEDNESDAY WITH POTENTIAL FOR ACCUMULATING SNOWFALL,
RAINFALL AND EVEN THUNDERSTORMS.
DISCUSSION
ISSUED AT 345 AM CDT SUN MAR 30 2025
SIGNIFICANT ICE STORM CONTINUES TODAY:
OVERALL, FORECAST REASONING HAS NOT CHANGED SUBSTANTIALLY FROM PRIOR
UPDATES WITH THE ONGOING MAJOR ICE EVENT. STRONG MID-LEVEL WARM
ADVECTION/FRONTOGENESIS HAS BEEN OCCURRING IN ADVANCE OF A
TROUGH APPROACHING FROM THE CENTRAL PLAINS WITH AN ANOMALOUSLY
MOIST AIRMASS ADVECTING NORTHWARD. THE STRONG WARMING ALOFT
OCCURRING ATOP COOL NORTHEASTERLY FLOW CONTINUES TO STRONGLY
FAVOR WIDESPREAD LONGER DURATION FREEZING RAIN ACROSS MUCH OF
CENTRAL INTO NORTHEAST WISCONSIN EARLY THIS MORNING. SOME SNOW
WAS OCCURRING ACROSS VILAS COUNTY WHERE THE ELEVATED WARM NOSE
IS WEAKER. THERE HAVE BEEN NUMEROUS REPORTS OF ICING ON TREES,
SURFACES AND POWER LINES. MRMS SHOWS THE HIGHEST PROBABILITY FOR
SUBFREEZING ROADS FOCUSED ACROSS NORTHEAST WISCONSIN EARLY
TODAY. GENERALLY, THE LOW-LEVEL TEMPERATURE PROFILES COOL
SLIGHTLY WITH NORTHWARD EXTENT ACROSS CENTRAL AND NORTHERN
WISCONSIN, COINCIDING WITH THE HIGHEST PROBABILITIES OF
SIGNIFICANT ICING. SLIGHTLY WARMER SURFACE TEMPS ACROSS THE FOX
VALLEY SHOULD HELP LIMIT IMPACTS IN THIS AREA, BUT SOME ICING
WILL OCCUR, ESPECIALLY ON ELEVATED SURFACES.
STRONG FORCING AHEAD OF THE SURFACE LOW WILL KEEP WIDESPREAD PRECIP
GOING TODAY. SOME MODEST WARMING MAY OCCUR ACROSS PARTS OF
CENTRAL/EAST-CENTRAL WISCONSIN WHILE MUCH OF NORTHEAST AND
NORTH-CENTRAL WISCONSIN STAYS VERY CLOSE TO FREEZING. DAYTIME ROAD
IMPACTS WILL DEPEND HEAVILY ON HOW GROUND TEMPS RESPOND TO LATE
MARCH INSOLATION, BUT IMPACTS WILL LIKELY BE GREATEST FOR
ELEVATED SURFACES. AS THE LOW PASSES EAST, THE MID-LEVEL WARM
NOSE WILL WEAKEN, LEADING TO A TRANSITION TO SNOW, WITH SOME
SLEET POSSIBLY MIXED IN, FROM THE NORTHWEST THIS AFTERNOON INTO
TONIGHT, ESPECIALLY ACROSS PARTS OF CENTRAL INTO NORTHERN
WISCONSIN. CHANCES FOR AT LEAST 2 INCHES OF WET ACCUMULATIONS
ARE 40-70% IN THESE AREA, BUT ONLY 20-40% FOR 4 INCHES. FOR NOW,
HAVE NOT ADJUSTED HEADLINES, BUT SOME ADJUSTMENTS COULD BE
NEEDED, BASED ON HOW ROAD/AIR TEMPS RESPOND DURING THE DAYLIGHT
HOURS AND IMPACTS FROM SLUSHY SNOW ON THE BACKSIDE OF THE
SYSTEM.
THE BOTTOM LINE REMAINS THE SAME. SIGNIFICANT ICING WILL CONTINUE
INTO TODAY ACROSS CENTRAL INTO NORTHEAST WISCONSIN WITH POWER
OUTAGES AND TREE DAMAGE LIKELY AS ICE ACCUMULATES ON ELEVATED
SURFACES. TRAVEL IMPACTS WILL BE HEAVILY DEPENDENT ON ROAD
TEMPERATURES, WITH IMPACTS INCREASING NORTHWARD WHERE TEMPS WILL
GENERALLY BE A TOUCH COOLER. WINDS WILL GUST 20 TO 30 MPH
TODAY, EXACERBATING IMPACTS WHERE ICE COATED SURFACES EXIST.
ANOTHER IMPACTFUL SPRING STORM FOR MID-WEEK.
A BRIEF RESPITE FROM THE ACTIVE WEATHER PATTERN ARRIVES TO START THE
WORK WEEK AS HIGH PRESSURE DRIFTS EAST ACROSS THE GREAT LAKES.
HOWEVER, A VIGOROUS PACIFIC TROUGH AND ASSOCIATED SURFACE LOW WILL
EJECT EASTWARD FROM THE PLAINS LATER TUESDAY INTO WEDNESDAY.
ALTHOUGH MOISTURE DOES NOT LOOK QUITE AS ANOMALOUS AS THE CURRENT
SYSTEM, PRECIPITABLE WATER VALUES ARE FORECAST ABOVE THE 90TH
PERCENTILE VIA THE NAEFS. THE DETAILS OF THIS SYSTEM WILL BE
RESOLVED IN COMING DAYS, BUT THE THE ECMWF EFI SHOWS A FAIRLY ROBUST
SIGNAL FOR IMPACTFUL SNOWFALL ACROSS CENTRAL OR NORTHERN WI WITH
VALUES EXCEEDING 0.7. ONCE AGAIN, THERE IS CONSIDERABLE SPREAD IN
TEMPS AT THIS RANGE, BASED ON UNCERTAINTY IN LOW TRACK, SO SOME
MIXED PRECIP TYPES ARE POSSIBLE, INCLUDING SOME THUNDER POTENTIAL.
HOWEVER, EPS PTYPE PROBABILITIES SUPPORT MORE SNOW/RAIN VS FREEZING
RAIN AT THIS TIME. HOWEVER, BEYOND THIS SYSTEM, TRENDS SUPPORT A
DRIER PERIOD LATER THIS WEEK.
AVIATION
FOR 18Z TAF ISSUANCE
ISSUED AT 103 PM CDT SUN MAR 30 2025
VERY POOR FLYING CONDITIONS WILL CONTINUE FOR THE REMAINDER OF THE
DAY AND INTO TONIGHT WITH MAINLY IFR CIGS. WHILE PERIODS OF RAIN
WILL REMAIN OVER THE EAST-CENTRAL WI TAF SITES THROUGH LATE THIS
AFTERNOON, A WINTRY MIX OF RAIN, FREEZING RAIN, SLEET, AND SNOW IS
EXPECTED OVER THE CENTRAL AND NORTH-CENTRAL WI TAF SITES. THESE
WINTRY MIX CONDITIONS WILL GRADUALLY MOVE EASTWARD AND ARRIVE AT
THE EAST-CENTRAL WI TAF SITES AROUND 00Z MON. AS THIS IS
HAPPENING, A CHANGE OVER TO ALL SNOW WILL OCCUR AT THE CENTRAL AND
NORTH-CENTRAL WI TAF SITES. ALL PRECIPITATION WILL EXIT THE REGION
FROM WEST TO EAST BY EARLY MONDAY MORNING. GUSTY NE WINDS WILL
SHIFT NORTHERLY TONIGHT, WITH GUSTS TO 20 TO 25 KTS.
VFR CONDITIONS WILL RETURN FROM WEST TO EAST MONDAY MORNING AS
HIGH PRESSURE BUILDS OVER THE AREA.
HYDROLOGY
ISSUED AT 345 AM CDT SUN MAR 30 2025
RECENT RAINFALL HAS LED TO SATURATED GROUND ACROSS MUCH OF THE
AREA WITH RISES ON AREA RIVERS/STREAMS, INCLUDING NEAR BANKFULL
OR MINOR FLOODING AT A FEW LOCATIONS. WITH ADDITIONAL
PRECIPITATION CONTINUING TODAY AND ANOTHER BOUT OF IMPACTFUL
RAIN/SNOW LIKELY FOR MID-WEEK, ADDITIONAL RIVER RISES AND
ELEVATED RIVER LEVELS ARE LIKELY INTO THE COMING WEEK.
GRB WATCHES/WARNINGS/ADVISORIES
WINTER STORM WARNING UNTIL 10 PM CDT THIS EVENING FOR WIZ005.
ICE STORM WARNING UNTIL 7 PM CDT THIS EVENING FOR WIZ010>013-
018>022-030-031-035>037-073-074.
WINTER STORM WARNING FROM 7 PM THIS EVENING TO 1 AM CDT MONDAY
FOR WIZ010>012-018-019-030-035.
WINTER STORM WARNING FROM 7 PM THIS EVENING TO 4 AM CDT MONDAY
FOR WIZ013-020>022-031-036-037-073-074.
DISCUSSION.....JM
AVIATION.......KRUK
HYDROLOGY......JM
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