137  
FXUS63 KGRB 150131  
AFDGRB  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREEN BAY WI  
ISSUED BY NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI  
831 PM CDT WED MAY 14 2025  
   
KEY MESSAGES  
 
- MARINE DENSE FOG ADVISORY FOR THE NEARSHORE AREAS OF LAKE  
MICHIGAN THROUGH THURSDAY.  
 
- A DENSE FOG ADVISORY HAS BEEN ISSUED FOR THE EASTERN LAKE  
SHORE COUNTIES THIS EVENING INTO THURSDAY MORNING. FOG MAY  
CONTINUE TO ADVECT WEST TOWARD CENTRAL WISCONSIN AFTER DARK.  
 
- SCATTERED SHOWERS AND THUNDERSTORMS ARE OCCURRING IN CENTRAL  
AND NORTH CENTRAL WI THIS AFTERNOON. ISOLATED STORMS ARE POSSIBLE  
ALONG THE LAKE BREEZE AS WELL.  
 
- A BROKEN LINE OF STRONG THUNDERSTORMS WILL CROSS NORTHERN WI  
BETWEEN 4 AND 9 PM THURSDAY. SOME SEVERE STORMS ARE LIKELY  
WITH THE PASSAGE OF A COLD FRONT. ALL HAZARDS POSSIBLE OVER  
CENTRAL WI AND LARGE HAIL POSSIBLE OVER EASTERN WI.  
 
 
   
DISCUSSION  
 
UPDATE...ISSUED AT 835 PM CDT WED MAY 14 2025  
 
LIGHT WINDS ALONG THE LAKE SHORE AND SMALL DEWPOINT DEPRESSIONS  
HAVE ALLOWED FOG TO MOVE INLAND OFF LAKE MICHIGAN. AS THE SUN  
CONTINUES TO SET THIS EVENING, FOG IS EXPECTED TO EXPAND  
WESTWARD. LOW STRATUS WILL ALSO BE MOVING IN AND DEVELOPING  
ACROSS EAST CENTRAL AND NORTHEASTERN WISCONSIN. UNCERTAINTY  
REMAINS ON HOW FAR INLAND THE FOG WILL ADVECT AND DEVELOP. WITH  
A SET UP SIMILAR TO THE PREVIOUS NIGHT THERE IS SOME BETTER  
CONFIDENCE (MODERATE TO HIGH ROUGHLY 60 TO 80%) THAT THE FOG AND  
LOW STRATUS WILL NOT MOVE ANY FURTHER WEST THAN IT DID  
YESTERDAY. A DENSE FOG ADVISORY HAS BEEN ISSUED FOR THE EASTERN  
LAKE SHORE COUNTIES THROUGH MID THURSDAY MORNING. WILL CONTINUE  
TO MONITOR TEMPERATURES, DEWPOINTS AND WINDS THROUGH THIS  
EVENING FOR ANY EXPANSIONS WESTWARD.  
 
ISSUED AT 327 PM CDT WED MAY 14 2025  
 
TONIGHT THROUGH THURSDAY MORNING...  
 
SCATTERED SHOWERS AND THUNDERSTORMS DEVELOPED OVER CENTRAL AND NORTH  
CENTRAL WI THIS AFTERNOON, WHICH IS IN AN AREA WITH SOME WEAK MID  
LEVEL VORTICITY ADVECTION. MAIN THREAT IS LIGHTNING, BUT THERE IS A  
SMALL CHANCE FOR SMALL HAIL. THERE ARE A FEW SHOWERS POPPING UP  
ALONG THE LAKE BREEZE FROM GREEN BAY TO SOUTHERN CALUMET COUNTY.  
THERE IS WEAK INSTABILITY SO THE SHOWERS CAN DEVELOP ALONG WEAK  
FORCING, BUT NO SHEAR, SO THE UPDRAFTS CANNOT BE SUSTAINED.  
 
WE WILL CONTINUE TO HAVE LOW LEVEL MOISTURE FLOWING OVER THE  
RELATIVELY COOL LAKE MICHIGAN AND THEREFORE A CONTINUED FOG THREAT  
FOR THE OVERNIGHT HOURS. THE SETUP IS SIMILAR TO LAST NIGHT WHERE  
THE MARINE FOG WILL SPILL INLAND DURING THE LATE EVENING HOURS. IT  
SHOULD NOT GET QUITE AS FAR INLAND AS LAST NIGHT, BUT I WOULD  
SUSPECT THAT WE WILL HAVE TO ISSUE DENSE FOG ADVISORY ONCE AGAIN FOR  
AT LEAST THE LAKESHORE TO THE FOX VALLEY AREA.  
 
FOG AND LOW CLOUDS WILL DISSIPATE QUICKLY DURING THE MID MORNING AS  
WINDS START TO INCREASE OUT OF THE SOUTHEAST. THIS IS IN RESPONSE TO  
LOW PRESSURE APPROACHING FROM THE NORTHERN PLAINS. SYNOPTIC FORCING  
WILL REMAIN WEAK DURING THE MORNING HOURS, AND THERE WILL BE A LOT  
OF MID LEVEL DRY AIR IN PLACE. SUNSHINE WILL HELP TEMPS QUICKLY WARM  
TO AROUND 80 IN CENTRAL WI, BUT THE ONSHORE BREEZE WILL KEEP  
LAKESHORE TEMPS IN THE 60S. SOUTHEAST WINDS WILL BE IN THE 20 TO 30  
MPH RANGE FOR INLAND AREAS.  
 
THURSDAY AFTERNOON AND NIGHT  
 
A MID LEVEL TROUGH SWINGING ACROSS MT AND WY WILL CLOSE OFF OVER THE  
NORTHERN PLAINS EARLY THURSDAY MORNING. THE ASSOCIATED SURFACE LOW  
CENTERED OVER EASTERN SOUTH DAKOTA WILL QUICKLY OCCLUDE, AND THE  
FRONTAL BOUNDARY EXTENDING FROM THE LOW (ACROSS SOUTHERN MN AND INTO  
WEST CENTRAL WI) WILL SET UP BY MIDDAY THU AND WAIT FOR FURTHER  
FORCING. THAT FORCING WILL ARRIVE WITHIN A FEW HOURS WHEN THE NEXT  
FRONT ROUNDS THE BASE OF THAT LOW AND PUSHES INTO SOUTHWEST WI. THIS  
IS THE WHERE THE INITIAL STORMS (FOR WI) ARE EXPECTED TO DEVELOP.  
 
MOST MESO MODELS AGREE ON THERE BEING A LINE OF STORMS EXTENDING  
FROM CENTRAL MN TO THE TWIN CITIES AT 2 PM AND THEN THAT LINE  
QUICKLY EXPANDS EAST-SOUTHEAST AS THE FRONT LIFTS INTO CENTRAL WI  
BETWEEN 2 AND 4 PM. BY 5 PM, THERE SHOULD BE A LINE OF STORMS  
(POSSIBLY A SECOND LINE BEHIND IT) THAT GOES FROM NORTHWEST WI TO  
WISCONSIN RAPIDS, AND POTENTIALLY DOWN THROUGH MADISON AND  
JANESVILLE. STORMS SHOULD BE FAIRLY CLOSE TOGETHER ALONG THAT FRONT  
(IN A LINE) IN THE NORTHWEST AND CENTRAL PORTIONS OF WI, BUT MUCH  
FARTHER APART (DISCRETE) IN SOUTHERN PORTIONS.  
 
A LINE OF STRONG STORMS WILL QUICKLY TRACK ACROSS NORTHERN WI  
BETWEEN 4 PM AND 8 PM, ALTHOUGH THEY MAY BE JUST EXITING DOOR  
COUNTY AT 9 PM. AS STORMS ROLL INTO CENTRAL WI BETWEEN 4 AND 5 PM,  
ALL SEVERE HAZARDS WILL BE POSSIBLE. THE SYNOPTIC FORCING WITH  
STRONG VORTICITY ADVECTION AND LOW LEVEL FRONT WILL BE PLENTY TO GET  
STORMS TO DEVELOP AND PUNCH THROUGH THAT EML CAP. WITH DEWPOINTS IN  
THE LOWER 60S, CAPE AROUND 2000 J/KG, AND DEEP LAYER SHEAR AT AN  
IMPRESSIVE 40 KT (THANKS TO SOUTHEAST WINDS AND THE SURFACE AND  
SOUTHWEST WINDS PUSHING IN JUST ABOVE), THE ENVIRONMENT IS CONDUCIVE  
FOR SUPERCELLS. LARGE HAIL, DAMAGING WINDS, AND TORNADOES WILL ALL  
BE POSSIBLE AS THESE STORMS MOVE INTO OUR AREA. AS THE LINE SPEEDS  
EASTWARD, IT WILL START TO ENCOUNTER THE STOUT MARINE LAYER (FOX  
VALLEY UP TO IRON MOUNTAIN) AND STORMS WILL START TO BECOME ELEVATED.  
THERE WILL STILL BE A LARGE HAIL THREAT, BUT THE THREATS FOR  
DAMAGING WINDS AND TORNADOES WILL START TO DIMINISH.  
 
QUIET WEATHER WITH FAIRLY MILD TEMPERATURES IN THE 50S AND LIGHTER  
SOUTH-SOUTHWEST WINDS WILL OCCUR FOR THE OVERNIGHT HOURS.  
 
FRIDAY THROUGH SATURDAY...  
 
THE CLOSED UPPER LOW AND ASSOCIATED WEAKENING SURFACE LOW WILL TRACK  
FROM CENTRAL MN TO THE MN ARROWHEAD DURING THE DAY FRIDAY, AND  
STRAIGHT ACROSS UPPER MICHIGAN FRIDAY NIGHT THROUGH SATURDAY  
MORNING. A PIECE OF ENERGY (500MB VORTICITY) IS EXPECTED TO RIPPLE  
UP ACROSS THE EAST HALF OF WI ON FRIDAY OUT AHEAD OF THAT UPPER LOW.  
IN ADDITION, THE LOW LEVEL JET WILL ALSO BE STREAMING ACROSS THE  
REGION AND THERE WILL BE SOME UPPER DIVERGENCE PRESENT FROM THE  
LEFT EXIT REGION OF A STRONG UPPER JET.  
 
THE MAIN CONCERN WITH THIS WILL BE THE VERY STRONG WINDS AVAILABLE  
TO MIX DOWN TO THE SURFACE DURING THE DAY FRIDAY. GUSTS IN THE 35 TO  
45 MPH RANGE ARE LOOKING LIKELY FOR THE EARLY AFTERNOON HOURS IN THE  
FOX VALLEY, AND THIS WOULD MEET WIND ADVISORY CRITERIA. IN ADDITION,  
A FEW THUNDERSTORMS ARE POSSIBLE FRIDAY AFTERNOON, MAINLY SOUTH OF  
APPLETON TO SHEBOYGAN. CONTINUED GUSTY WINDS AND A FEW SHOWERS ARE  
POSSIBLE OVER THE REST OF THE AREA FRIDAY EVENING.  
 
WE WILL REMAIN IN CYCLONIC FLOW SATURDAY, SO DIURNAL SHOWERS ARE  
POSSIBLE ACROSS ALL OF NORTHERN WI. GUSTY NORTHWEST WINDS UP TO 30  
MPH WILL ALSO BE POSSIBLE.  
 
SUNDAY THROUGH TUESDAY...  
 
HIGH PRESSURE WILL CROSS ONTARIO SUNDAY AND NORTHERLY WINDS WILL  
USHER COLDER TEMPS INTO THE REGION. SUNDAY NIGHT LOOKS THE COLDEST  
WITH NORTH/CENTRAL AREAS DROPPING INTO THE LOWER 30S, THUS A FROST  
POTENTIAL. QUIET WEATHER WILL CONTINUE MONDAY. OUR NEXT CHANCE FOR  
SHOWERS AND SOME THUNDERSTORMS WILL ARRIVE MONDAY NIGHT AS AN UPPER  
TROUGH APPROACHES FROM THE PLAINS AND WE GET INTO THE WARM AIR  
ADVECTION AREA TO GIVE US SOME ELEVATED CONVECTION.  
 
CRONCE  
 
 
   
AVIATION /00Z TAFS THROUGH 00Z FRIDAY/  
 
ISSUED AT 645 PM CDT WED MAY 14 2025  
 
SCATTERED SHOWERS AND THUNDERSTORMS CONTINUE ACROSS NORTH  
CENTRAL AND CENTRAL WISCONSIN THROUGH THIS EVENING. SHOWERS AND  
STORMS WILL QUICKLY DIMINISH AFTER SUNSET. SIMILAR TO YESTERDAY  
LOW LEVEL CLOUDS AND FOG ARE EXPECTED TONIGHT. LAKE SHORE ARES  
ARE LIKELY TO SEE THE LOW LEVEL CLOUDS/FOG FIRST AS BOTH MOVE  
INLAND OFF LAKE MICHIGAN. FOG AND LOW CLOUDS ARE EXPECTED ONCE  
WINDS DECREASE AND THE SUN HAS SET BY MID TO LATE THIS EVENING  
INTO EARLY TOMORROW MORNING FOR THE LAKE SHORE AND FOX VALLEY  
AREAS.  
 
VISIBILITY OF A HALF MILE OR LESS AND IFR CEILINGS AROUND 200 TO 500  
FT ARE EXPECTED AGAIN. SOME AREAS COULD SEE CEILINGS DROP SLIGHTLY  
LOWER, ESPECIALLY WHERE FOG IS DENSE. UNCERTAINTY REMAIN IN HOW  
FAR WESTWARD FOG AND LOW STRATUS WILL PROGRESS. IF WINDS REMAIN  
LIGHT AND SKIES CLEAR, THEN IT IS POSSIBLE FOG WILL EXPAND JUST  
AS FAR AS IT DID LAST NIGHT. FOG AND STRATUS WILL QUICKLY  
DIMINISH BY MID THURSDAY MORNING.  
 
A LINE OF STORMS IS EXPECTED TO MOVE THROUGH CENTRAL AND NORTHERN  
WISCONSIN BETWEEN 4 AND 10PM THURSDAY AFTERNOON/EVENING. ALL HAZARDS  
WILL BE POSSIBLE FOR NORTHERN AND CENTRAL WISCONSIN. LARGE HAIL  
LOOKS TO BE THE MAIN CONCERNS FOR LAKE SHORE AREAS.  
 
LIGHT SOUTHEAST TO EAST WINDS ARE EXPECTED THIS EVENING THROUGH  
TONIGHT. THURSDAY AFTER SUNRISE WINDS WILL INCREASE AGAIN BECOMING A  
BIT BREEZY BY THE EARLY AFTERNOON. SOUTHEAST WINDS WILL QUICKLY  
SWITCH TO SOUTHWESTERLY BEHIND THE FRONT. SOUTH TO SOUTHWEST WINDS  
ARE EXPECTED THURSDAY NIGHT INTO FRIDAY.  
 
PATTERSON  
 
 
   
MARINE  
 
ISSUED AT 327 PM CDT WED MAY 14 2025  
 
GIVEN THAT THE ENVIRONMENT WILL CONTINUE TO REMAIN FAVORABLE  
(MOIST AIR OVER THE COOL OPEN WATERS) FOR DENSE FOG UNTIL THIS  
PATTERN BREAKS, THE MARINE DENSE FOG ADVISORY IS IN EFFECT UNTIL  
7PM THURSDAY. WE MAY BE ABLE TO EXPIRE THAT A LITTLE EARLIER ON  
THURSDAY AS SOUTHEAST WINDS KICK IN, SO THERE IS UNCERTAINTY IN  
THE END TIME. THIS INCLUDES THE BAY AREA, ALTHOUGH WE MAY SEE  
LESS FOGGY CONDITIONS DURING THE DAYLIGHT HOURS THERE.  
 
CRONCE  
 
 
   
GRB WATCHES/WARNINGS/ADVISORIES  
 
WI...DENSE FOG ADVISORY UNTIL 10 AM CDT THURSDAY FOR WIZ022-039-040-  
050.  
MARINE...DENSE FOG ADVISORY UNTIL 7 PM CDT THURSDAY FOR LMZ521-522-  
541>543.  
 
 
 
 
 
DISCUSSION...  
AVIATION...  
MARINE...  
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