252
FXUS63 KGRB 290412
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1112 PM CDT FRI MAR 28 2025
UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE
AND NEW INFORMATION ADDED TO UPDATE SECTION
UPDATE
ISSUED AT 1055 PM CDT FRI MAR 28 2025
BASED ON TEMPERATURE TRENDS, HAVE ADDED LANGLADE AND NORTHERN
OCONTO COUNTIES TO THE WINTER WEATHER ADVISORY OVERNIGHT. ANTIGO
IS ALREADY AT 33 DEGREES, AND WILL LIKELY DROP A FEW DEGREES
OVERNIGHT. THERE IS SOME CONCERN FOR NORTHERN DOOR COUNTY, WITH
CURRENT EMPS OF 32 DEGREES AT WASHINGTON ISLAND AND EPHRAIM, BUT
CALLS TO THE SHERIFF ONLY INDICATED WET CONDITIONS THERE, SO WILL
HOLD OFF ON ADDING THEM TO THE ADVISORY.
UPDATE
ISSUED AT 908 PM CDT FRI MAR 28 2025
A MIX OF WINTER AND SPRING OCCURRING AT THE SAME TIME THIS
EVENING, WITH STRONG TO MARGINALLY SEVERE STORMS OCCURRING
OVER THE SOUTHERN 3/4 OF THE CWA, AND FREEZING RAIN POTENTIAL
OVER THE FAR NORTH. THE CONVECTIVE THREAT SHOULD GRADUALLY
WANE LATER THIS EVENING, THEN DROP OFF SIGNIFICANTLY DURING THE
OVERNIGHT HOURS.
HAVE ALREADY VERIFIED SOME MINOR ICING OCCURRING OVER WESTERN
VILAS COUNTY, AND WITH SURFACE TEMPS/WET BULB TEMPS ALREADY AROUND
FREEZING AND ADDITIONAL FRONTOGENETIC FORCING EXPECTED FOR MOST
OF THE NIGHT, EXPECT ADDITIONAL ICING (AROUND A TENTH OF AN INCH).
HAVE ISSUED A WINTER WEATHER ADVISORY FOR VILAS, ONEIDA, FOREST,
FLORENCE AND NORTHERN MARINETTE COUNTIES THROUGH 7 AM SATURDAY.
UPDATE ISSUED AT 640 PM CDT FRI MAR 28 2025
A COUPLE AREAS OF CONVECTION WERE INCREASING EARLY THIS EVENING;
ONE IN ASSOCIATION WITH STRONG MID-LEVEL GFEN FORCING IN FAR
NORTHERN WI, AND ANOTHER IN SE MN/WC WI NORTH OF THE SURFACE WARM
FRONT. THE SOUTHERNMOST AREA OF CONVECTION WAS THE STRONGEST, AS
IT WAS FORMING WHERE MUCAPE VALUES OF 1000-1500 J/KG AND DEEP
LAYER SHEAR OF 45-50 KTS EXISTED. A COUPLE OF THESE CELLS COULD
PRODUCE MARGINALLY SEVERE HAIL AS THEY MOVE THROUGH CENTRAL WI
THIS EVENING. INSTABILITY DROPS OFF A BIT FARTHER EAST, SO NOT
SURE IF THE STORMS WILL MAINTAIN THEIR INTENSITY AS THEY PUSH
TOWARD THE FOX VALLEY/LAKESHORE AREAS.
KEY MESSAGES
- THERE IS A 30-50% CHANCE OF THUNDERSTORMS ACROSS THE FORECAST
AREA TONIGHT. SOME OF THE STRONGER STORMS COULD PRODUCE SMALL
HAIL. ISOLATED HAIL REPORTS OVER AN INCH ARE POSSIBLE.
- A SIGNIFICANT ICE ACCUMULATION IS POSSIBLE ACROSS NORTH- CENTRAL
AND FAR NORTHEAST WISCONSIN FROM EARLY SATURDAY EVENING 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.
- PRECIPITATION TOTALS ARE LIKELY (40-70%) TO BE GREATER THAN 1
INCH THROUGHOUT THE EVENT, WHICH COULD LEAD TO FAST FLOWS AND
MINOR FLOODING ALONG THE SHORELINES OF AREA RIVERS AND STREAMS
NEXT WEEK.
DISCUSSION
ISSUED AT 233 PM CDT FRI MAR 28 2025
SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT
THE LATEST RAP ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW LOW
PRESSURE TRACKING EAST ACROSS EASTERN SOUTH DAKOTA EARLY THIS
AFTERNOON AND A WARM FRONT EXTENDING EAST FROM THIS LOW TO ABOUT
SHEBOYGAN. AFTER SOME MORNING THUNDER ACROSS PARTS OF CENTRAL TO
EAST-CENTRAL WI, PRECIPITATION HAS BEEN RELATIVELY QUIET THROUGH
EARLY THIS AFTERNOON. FREEZING DRIZZLE REMAINED PATCHY THIS
ACROSS NORTH-CENTRAL WI THIS MORNING WHERE CLOUD BASES DIDN'T GET
NEARLY AS LOW AS MODELS FORECASTED YESTERDAY. AS THE LOW TRACKS
EAST, THE FIRST FOCUS OF THIS FORECAST REMAINS ON THUNDERSTORM
POTENTIAL TONIGHT. THIS FOCUS WILL BE FOLLOWED BY A POTENTIAL ICE
STORM ON SATURDAY NIGHT INTO SUNDAY AS THE NEXT SURFACE WAVE
TRACKS ALONG THE FRONT.
THUNDERSTORM POTENTIAL TONIGHT: AS LOW PRESSURE TRACKS ALONG THE
WARM FRONT, A STRENGTHENING LOW LEVEL JET WILL LEAD TO INCREASING
MOISTURE TRANSPORT AND MID-LEVEL FGEN ACROSS FAR NORTHERN
WISCONSIN AND THE UPPER PENINSULA BY EARLY TO MID EVENING. AT THE
SAME TIME, ELEVATED INSTABILITY UPWARDS OF 1000 J/KG WILL SURGE
INTO NORTHERN WI ABOVE A STOUT INVERSION CENTERED AT AROUND 800MB.
COMBINED WITH PRECIPITABLE WATER VALUES ABOVE 200% OF NORMAL,
INGREDIENTS ARE COMING TOGETHER FOR A BAND OF SHOWERS AND STORMS
DEVELOPING THIS EVENING GENERALLY NORTH OF A TOMAHAWK TO WAUSAUKEE
LINE. EFFECTIVE SHEARS OF 40-50 KTS AND A COLD THERMAL PROFILE
WILL BE FAVORABLE FOR HAIL. LARGE HAIL WILL BE POSSIBLE IN THE
STRONGEST CELLS, PARTICULARLY THOSE THAT CONTAIN MID-LEVEL
ROTATION. THE LATEST MODELS HAVE INCREASED THE AMOUNT OF
PRECIPITATION ACROSS THE FAR NORTH AND AMOUNTS FROM 0.50" TO 1.00"
SEEM POSSIBLE.
AS THE BOUNDARY LAYER COOLS OVERNIGHT, MINOR FREEZING RAIN IS
POSSIBLE THAT COULD LEAVE A LIGHT GLAZE ON SURFACES. BUT
PRECIPITATION WILL BE ENDING AS TEMPERATURES APPROACH THE FREEZING
MARK, SO DON'T THINK SIGNIFICANT ICING WILL BE POSSIBLE. BUT THERE
MAY BE JUST ENOUGH FOR A LOW END ADVISORY. ROAD TEMPERATURES ARE
FORECAST TO REMAIN ABOVE FREEZING AND THAT MAY MITIGATE IMPACTS
FROM FREEZING RAIN. WILL REFRAIN FROM ISSUING A ADVISORY GIVEN THE
SHORT WINDOW AND UNCERTAINTY ABOUT IMPACTS.
ICE STORM POTENTIAL: A LULL IN THE PRECIPITATION REMAINS EXPECTED
ON SATURDAY MORNING AS THE FRONT STALLS ACROSS SOUTHERN WI AND
LIGHT PRECIP CHANCES BECOME HIGHEST OVER THE SOUTHERN FOX VALLEY.
BUT AS UPPER LEVEL FLOW STRENGTHENS AND BACKS AHEAD OF THE NEXT
SURFACE LOW, MID-LEVEL FGEN WILL INCREASE AGAIN ON LATE SATURDAY
AFTERNOON THROUGH SUNDAY MORNING. AS HAS BEEN SEEMINGLY ADVERTISED
FOR DAYS, THE SYNOPTIC SETUP IS VERY FAVORABLE FOR AN ICE STORM
THANKS TO A 1030 MB HIGH OVER NORTHERN ONTARIO FEEDING IN COLD AIR
INTO THE REGION. MODELS ARE BECOMING IN BETTER AGREEMENT WITH THE
TRACK OF THE SURFACE LOW AND POSITION OF THE FREEZING LINE,
THEREBY INCREASING CONFIDENCE WHERE THE GREATEST THREAT FOR
SIGNIFICANT ICING WILL BE LOCATED. THE NARROWING OF SOLUTIONS HAS
LED TO AN INCREASE OF ICE ACCUMULATIONS OVER NORTH-CENTRAL TO FAR
NORTHEAST WI, WHERE THE GREATEST THREAT IS CENTERED. MOST OF THE
FREEZING RAIN WILL FALL BETWEEN 7 PM SAT AND 1 PM SUN. THE LATEST
NBM INDICATES A 40-50% CHANCE OF A HALF INCH OR MORE OF FREEZING
RAIN IN A CORRIDOR FROM RHINELANDER TO IRON MOUNTAIN.
MODERATE TO HEAVY SNOW WILL BE POSSIBLE NORTH OF THE MIXED
PRECIPITATION WHICH COULD RESULT IN SEVERAL INCHES OF SNOW
ACCUMULATIONS IN ADDITION TO THE ICE ACCUMULATIONS.
SOME MIXED PRECIPITATION COULD MAKE IT INTO THE FOX VALLEY AND
LAKESHORE AREAS, BUT THAT SHOULD ONLY FALL FOR A SHORT TIME ON
LATE SUNDAY AFTERNOON AND EVENING.
IN TERMS OF HEADLINES, THE START OF IMPACTFUL ICING DOESN'T APPEAR
TO START UNTIL SATURDAY EVENING AS TEMPS FALL TO FREEZING AND
SOLAR INSOLATION IS NOT A FACTOR ACROSS NORTHERN WI. THAT'S A
LITTLE EARLY FOR WARNINGS. BUT CONSIDERING THE INCREASING
CONFIDENCE AND POTENTIAL FOR HIGH IMPACTS, WILL ISSUE AN ICE
STORM WARNING FOR NORTH-CENTRAL TO FAR NORTHEAST WI AND A WINTER
STORM WARNING FOR VILAS COUNTY WHERE 2-4 INCHES OF SNOW IS
EXPECTED. THIS WILL NEED TO GET BRACKETED BY ADVISORIES, BUT WILL
LET LATER SHIFTS DETERMINE WHERE AND WHEN TO ISSUES THOSE AND
LEAVE THE WINTER STORM WATCH IN PLACE.
LONG TERM...MONDAY THROUGH FRIDAY
LIGHT SNOW WILL LIKELY LINGER ACROSS THE AREA ON SUNDAY NIGHT THAT
COULD LEAD TO A COUPLE INCHES OF SNOW AND PROLONG THE HAZARDOUS
TRAVEL ACROSS THE REGION. AFTER THE LOW EXITS, BELOW NORMAL
TEMPERATURES ARE EXPECTED ON MONDAY AND TUESDAY.
THE NEXT SYSTEM REMAINS ON TRACK TO IMPACT THE REGION DURING THE
TUESDAY NIGHT THROUGH WEDNESDAY NIGHT. A MIX OF RAIN AND SNOW IS
FORECAST WITH THIS SYSTEM AND SOME ACCUMULATIONS APPEAR POSSIBLE,
PARTICULARLY OVER FAR NORTHERN WI.
AVIATION
FOR 06Z TAF ISSUANCE
ISSUED AT 1055 PM CDT FRI MAR 28 2025
LOW PRESSURE MOVING EAST ALONG A STATIONARY FRONT AND A BAND OF
FRONTOGENETIC FORCING OVER NORTHERN WI WAS PRODUCING AREAS OF
SHOWERS AND EMBEDDED THUNDERSTORMS LATE THIS EVENING. EXPECT MOST
OF THE THUNDERSTORM ACTIVITY TO BE EAST OF THE TAF SITES AT THE
BEGINNING OF THE TAF PERIOD. MOST OF THE REGION WILL SEE LIGHT TO
OCCASIONALLY MODERATE RAIN SHOWERS OVERNIGHT, BUT NORTHERN WI WILL
LIKELY SEE SOME FREEZING RAIN, WITH ICE ACCUMULATIONS UP TO ONE
TO TWO TENTHS OF AN INCH.
THE SHOWERS SHOULD TAPER OFF FROM NW TO SE LATER TONIGHT INTO
EARLY SATURDAY, BUT LOW CLOUDS, LIGHT SHOWERS, DRIZZLE AND SOME
FOG SHOULD PREVAIL THROUGH SATURDAY MORNING. LIGHT FREEZING
PRECIPITATION MAY LINGER EARLY IN THE NORTH. MODERATE TO HEAVY
PRECIPITATION WILL LIFT NORTH ACROSS THE AREA SATURDAY AFTERNOON
AND EVENING. MOST OF THE REGION WILL SEE RAIN, BUT FREEZING RAIN
AND SLEET IS EXPECTED BY EVENING OVER MUCH OF NORTH CENTRAL AND
FAR NE WI, WHERE SIGNIFICANT ICING IS ANTICIPATED.
OVERALL, EXPECT MAINLY IFR FLIGHT CONDITIONS TO PREVAIL.
GRB WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL 7 AM CDT SATURDAY FOR WIZ005-
010>013-019-021.
WINTER STORM WARNING FROM 7 PM SATURDAY TO 7 PM CDT SUNDAY FOR
WIZ005.
ICE STORM WARNING FROM 7 PM SATURDAY TO 7 PM CDT SUNDAY FOR
WIZ010>013-018>021.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY EVENING
FOR WIZ030-031.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR WIZ073-074.
UPDATE.........KIECKBUSCH
DISCUSSION.....MPC/MPC
AVIATION.......KIECKBUSCH
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