580
FXUS63 KGRB 092339
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
639 PM CDT THU APR 9 2026
UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE
KEY MESSAGES
- LIGHT RAIN AND A BRIEF WINTRY MIX ARE POSSIBLE LATE THIS EVENING
AND TONIGHT.
- PERIODS OF HEAVY RAINFALL AND THUNDERSTORMS EXPECTED LATE THIS
WEEKEND THROUGH THE MIDDLE OF NEXT WEEK. THERE IS A 60-80%
CHANCE OF RAINFALL GREATER THAN 1 INCH FROM SATURDAY NIGHT
THROUGH TUESDAY NIGHT.
- STRONG OR SEVERE THUNDERSTORMS POSSIBLE MONDAY AFTERNOON AND
EVENING.
- MINOR FLOODING CONTINUES ALONG THE WOLF RIVER, THOUGH RUNOFF FROM
MELTING SNOW IN THE UPPER PENINSULA PAIRED WITH HEAVY RAIN MAY
RESULT IN MORE WIDESPREAD AND SIGNIFICANT FLOODING LATE THIS
WEEKEND INTO NEXT WEEK.
DISCUSSION
ISSUED AT 1234 PM CDT THU APR 9 2026
THE LATEST RAP ANALYSIS AND SATELLITE IMAGERY SHOW A COLD FRONT
DRAPED ACROSS THE CENTRAL PLAINS TO CENTRAL ILLINOIS EARLY THIS
AFTERNOON. COLD ADVECTION IS OCCURRING NORTH OF THE FRONT ACROSS
NORTHERN WISCONSIN. SHALLOW STRATOCUMULUS CLOUDS PUSHED AS FAR
SOUTHEAST AS CENTRAL WI LATE THIS MORNING, BUT THESE CLOUDS ARE
EXPECTED TO MIX OUT AND RETREAT NORTH THROUGH THE AFTERNOON.
MEANWHILE, MID AND HIGH CLOUDS WILL INCREASE FROM THE WEST AHEAD
OF THE NEXT SHORTWAVE TROUGH CURRENTLY MOVING ACROSS NORTHEAST
MONTANA. THIS SYSTEM IS POISED TO BRING THE NEXT CHANCE OF
PRECIPITATION TO THE REGION LATE THIS EVENING INTO TONIGHT.
PRECIPITATION CHANCES ARE THE MAIN FORECAST CONCERN IN THE SHORT
TERM. FLOW ALOFT WILL BACK AND PUSH AN ELEVATED FRONT INTO
SOUTHERN WISCONSIN THIS EVENING. WHILE THE HEAVIEST PRECIPITATION
WILL OCCUR SOUTH OF THE AREA, MID-LEVEL CONVERGENCE AND
FRONTOGENESIS WILL SUPPORT SUFFICIENT LIFT FOR LIGHT PRECIPITATION
FROM MID-EVENING THROUGH LATE OVERNIGHT. A LIGHT WINTRY MIX MAY
OCCUR ON THE BACK EDGE OF THE PRECIP AS TEMPERATURES FALL INTO THE
MIDDLE 30S. A DUSTING IS POSSIBLE ON GRASSY SURFACES, BUT LITTLE
TO NO ACCUMULATION IS EXPECTED. CLOUDS WILL BE SLOW TO DEPART ON
FRIDAY MORNING, BUT EXPECT DRIER AIR AND MIXING TO GRADUALLY ERODE
THE CLOUDS ON FRIDAY AFTERNOON. HIGH PRESSURE WILL BE CENTERED
ACROSS THE REGION FRIDAY NIGHT BEFORE SLIDING EAST, ALLOWING FOR A
BRIEF PERIOD OF QUIET WEATHER.
AN AMPLIFYING UPPER LEVEL PATTERN WILL DRIVE A STRONG FRONTAL
SYSTEM ACROSS THE MIDWEST LATE THIS WEEKEND INTO EARLY NEXT WEEK,
LEADING TO WIDESPREAD PRECIPITATION CHANCES. RETURN FLOW AND
STRONG MOISTURE ADVECTION WILL BRING RAIN INTO CENTRAL WI BY LATE
SATURDAY AFTERNOON, SPREADING ACROSS THE REST OF THE REGION
SATURDAY NIGHT. PRECIPITABLE WATER VALUES ARE FORECAST TO REACH
THE 99TH PERCENTILE BY SUNDAY MORNING AS A 50 KT LOW LEVEL JET
IMPINGES ON THE AREA. THESE INGREDIENTS FAVOR WIDESPREAD SHOWERS
AND THUNDERSTORMS. BUT WITH INSTABILITY ONLY 200-400 J/KG ON
SATURDAY NIGHT INTO SUNDAY MORNING, THE CHANCES OF SEVERE WEATHER
LOOKS LOW. A RELATIVELY LULL IN THE PRECIPITATION LOOKS POSSIBLE
FOR THE SECOND HALF OF SUNDAY THROUGH MONDAY MORNING.
THE PERIOD FROM MONDAY AFTERNOON INTO MONDAY NIGHT BEARS THE MOST
WATCHING FOR SEVERE WEATHER POTENTIAL. A COLD FRONT WILL SAG INTO
THE STATE FROM THE NORTHWEST ON MONDAY, FOLLOWING A BRIEF LULL IN
ACTIVITY SUNDAY NIGHT. INSTABILITY IS FORECAST TO SURGE UPWARDS
OF 1000 J/KG COMBINED WITH DEEP LAYER SHEAR OF 40-50 KTS. TUESDAY
ALSO BEARS SCRUTINY AS AN INSTABILITY RESERVOIR REMAINS IN CLOSE
PROXIMITY TO THE REGION. WHILE PREDICTABILITY REGARDING SPECIFIC
DETAILS REMAINS BELOW NORMAL AT THIS RANGE, THE COMBINATION OF
HEIGHT FALLS AND A PASSING SURFACE WAVE SHOULD SUPPORT ORGANIZED
CONVECTION. SHOWERS MAY LINGER INTO WEDNESDAY AS THE SYSTEM
EVENTUALLY DEPARTS.
GIVEN THE HIGH MOISTURE CONTENT AND MULTIPLE ROUNDS OF RAIN,
THERE IS A 60-80 PERCENT CHANCE OF RAINFALL GREATER THAN 1 INCH,
AND A 20-40 PERCENT CHANCE OF GREATER THAN 2 INCHES FROM SATURDAY
NIGHT THROUGH TUESDAY NIGHT. THIS POTENTIAL FOR HEAVY RAINFALL
WILL LEAD TO AN INCREASE IN RIVER FLOODING POTENTIAL, ESPECIALLY
WITH ONGOING ELEVATED WATER LEVELS ON AREA RIVERS.
AVIATION
FOR 00Z TAF ISSUANCE
ISSUED AT 638 PM CDT THU APR 9 2026
VFR EARLY THIS EVENING WITH LOWERING MID CLOUDS. A SHORTWAVE
TROUGH WILL THEN BRING A CHANCE FOR LIGHT PRECIPITATION FROM WEST
TO EAST LATE THIS EVENING THROUGH THE OVERNIGHT HOURS. LIGHT RAIN
IS EXPECTED FOR CENTRAL WI TO THE FOX VALLEY AND LAKESHORE
TERMINALS, WHILE A LIGHT WINTRY MIX OF RAIN AND SNOW MAYBE
SWITCHING TO SNOW, IS POSSIBLE FOR RHI. PRECIP WILL BE LIGHT AND
BRIEF. FLIGHT CONDITIONS ARE EXPECTED TO DETERIORATE WITH MVFR
CIGS DURING THE PRECIPITATION, WITH A LOWER RISK OF IFR CIGS FROM
CWA TO RHI. BRIEF MVFR VISIBILITIES ARE POSSIBLE AS WELL, ESPECIALLY
AT RHI.
MVFR CEILINGS WILL LINGER INTO FRIDAY MORNING AFTER THE PRECIPITATION
ENDS. A GRADUAL RETURN TO VFR IS EXPECTED ON FRIDAY AFTERNOON AS
DRY AIR MOVES INTO THE REGION.
WINDS FROM THE W EARLY ON WILL BECOME VARIABLE THIS EVENING, THEN
LIGHT FROM THE N/NW OVERNIGHT INTO FRIDAY. HOWEVER, A BOUNDARY
DROPPING SOUTH ACROSS THE BAY/NORTHERN LAKE MICHIGAN WILL SWITCH
WINDS TO NE AT GRB/ATW/MTW FOR A TIME LATER TONIGHT. THERE IS A
LOW POTENTIAL (<20%) OF GUSTS TO 20 KTS AT GRB AS THE BOUNDARY
MOVES THROUGH (06Z-08Z).
CONFIDENCE REMAINS HIGH REGARDING THE DEVELOPMENT OF MVFR CEILINGS
TONIGHT INTO FRIDAY MORNING, BUT LOWER REGARDING THE DEVELOPMENT
OF MVFR VISIBILITIES AND ANY IFR CEILINGS.
OUTLOOK...VFR FRIDAY EVENING THROUGH SATURDAY MORNING. WIDESPREAD
RAIN AND A FEW THUNDERSTORMS WITH MVFR/IFR CONDITIONS LIKELY SATURDAY
NIGHT THROUGH SUNDAY.
HYDROLOGY
ISSUED AT 1234 PM CDT THU APR 9 2026
NO SIGNIFICANT CHANGES TO THE PREVIOUS FORECASTERS THOUGHTS. MINOR
FLOODING CONTINUES ON THE WOLF RIVER EARLY THIS AFTERNOON. A
MAINLY DRY PERIOD IS ANTICIPATED THROUGH SATURDAY, WITH THE
EXCEPTION OF LIGHT RAIN OVER PARTS OF CENTRAL AND EAST CENTRAL WI
TONIGHT. PERIODS OF HEAVY RAIN AND THUNDERSTORMS ARRIVE LATER IN
THE WEEKEND AND CONTINUE THROUGH THE MIDDLE OF NEXT WEEK. DURING
THIS UPCOMING PERIOD, PROBABILITIES FOR RAINFALL IN EXCESS OF 1
INCH ARE 60-80%, WITH A 20-40% CHANCE OF AMOUNTS IN EXCESS OF 2
INCHES AND A 5-15% CHANCE OF 3 INCHES OR MORE. CURRENT FORECASTS
CALL FOR 1.5 TO 2 INCHES IN MOST AREAS. RUNOFF FROM THIS RAINFALL,
COMBINED WITH RAPID SNOWMELT IN THE UPPER PENINSULA AND FAR
NORTHERN WI, IS EXPECTED TO BRING POTENTIAL FOR MORE WIDESPREAD
AND SIGNIFICANT FLOODING HEADING INTO THE EARLY TO MIDDLE PART OF
NEXT WEEK. RIGHT NOW, IT APPEARS THE MOST SIGNIFICANT FLOODING
IMPACTS MAY OCCUR ON THE MENOMINEE RIVER AND ITS TRIBUTARIES.
GRB WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION.....MPC
AVIATION.......JLA
HYDROLOGY......MPC
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