042  
FXUS63 KGRB 160350 AAA  
AFDGRB  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREEN BAY WI  
1050 PM CDT THU MAY 15 2025  
   
KEY MESSAGES  
 
- GUSTY SOUTHWEST WINDS ARE EXPECTED FRIDAY, WITH HIGHEST GUSTS  
UP TO 40 MPH IN THE FOX VALLEY.  
 
- ANOTHER PERIOD OF SHOWERS AND THUNDERSTORMS ARE EXPECTED  
FRIDAY AFTERNOON. DAMAGING WIND GUSTS MAY BE POSSIBLE WITH ANY  
STRONGER STORM.  
 
 
   
DISCUSSION  
 
UPDATE...ISSUED AT 936 PM CDT THU MAY 15 2025  
 
THE LINE OF STORMS JUST EXITED NORTHEAST WI. SCATTERED SHOWERS  
WITH A FEW LIGHTNING STRIKES ARE STILL ONGOING OVER NORTH  
CENTRAL WI DUE TO CONTINUED VORTICITY ADVECTION WITH THE  
SPINNING CLOSED LOW THAT IS NOW OVER EASTERN NORTH DAKOTA.  
 
THE SOUTHWEST WINDS ARE GUSTY UPSTREAM WITH THAT LOBE OF  
VORTICITY PUSHING INTO CENTRAL WI, WHICH IS DUE TO MOMENTUM  
TRANSFER. IT LOOKS LIKE WINDS WILL TAPER OFF THROUGH THE  
OVERNIGHT HOURS WITH WEAKER MIXING. BUT AS SOON AS THE SUN  
RISES, EXPECT THE GUSTY WINDS TO KICK IN ONCE AGAIN.  
 
PREVIOUS DISCUSSION...ISSUED AT 304 PM CDT THU MAY 15 2025  
 
THE REST OF THIS AFTERNOON THROUGH FRIDAY NIGHT:  
 
A BROKEN LINE OF CELLULAR STORMS HAS BROKEN OUT, CURRENTLY FROM  
EAU CLAIRE DOWN TO MADISON WI. THIS IS LINE IS EXPECTED TO  
DEVELOP FURTHER AND RAMP UP IN INTENSITY THIS EVENING. HAIL AND  
GUSTY WINDS ARE EXPECTED, OWING TO SBCAPE AROUND 2500 J/KG AMID  
EFFECTIVE SHEAR AROUND 40 KNOTS. A COUPLE TORNADOES ALSO LOOK  
POSSIBLE, GIVEN EFFECTIVE SRH VALUES AROUND 200 M2/S2 OVER MUCH  
OF NE WI, AND AN EFFECTIVE WARM FRONT PARKED FROM THE FOX  
VALLEY UP THROUGH MARATHON AND LINCOLN COUNTY. THE PEAK TIMING  
FOR STORMS LOOKS TO BE FROM 5PM THROUGH 8PM THIS EVENING AS THE  
BROKEN LINE MOVES NORTHEAST. A TORNADO WATCH IS OUT FROM NOW  
THROUGH 10PM OVER MUCH OF OUR CWA.  
 
STORMS WILL QUICKLY MOVE THROUGH AND A DRY PUNCH ALOFT WILL  
CLEAR OUT SKIES FAIRLY QUICKLY BEHIND THE STORMS. THERE WILL BE  
A BIT OF A LULL OVERNIGHT, BUT TOMORROW, ENHANCED MIXING WILL  
LEAD TO GUSTY SOUTHWEST WINDS WITH SOME SCATTERED GUSTS TO 40  
MPH. A SECONDARY SHORTWAVE PIVOTING AROUND AN UPPER LEVEL LOW  
AND LINGERING MOISTURE WILL SQUEEZE OUT SOME MORE SCATTERED  
THUNDERSTORM ACTIVITY IN THE AFTERNOON. VERY DRY LOW LEVELS AND  
THE HIGH BASED NATURE OF THE STORMS WILL CAUSE THE POTENTIAL FOR  
GUSTY WINDS WITH ANY STORMS THAT GET ESTABLISHED ENOUGH IN THE  
ENVIRONMENT.  
 
SATURDAY THROUGH WEDNESDAY  
 
THE UPPER LOW WILL LINGER INTO SATURDAY. COOLER CONDITIONS ARE  
EXPECTED DUE TO CLOUDS AND THE COOLER AIR ALOFT AND HIGHS WILL  
TOP OUT IN THE LOW TO MID 60. DIURNALLY DRIVEN SCATTERED  
SHOWERS MAY OCCUR THROUGH THE DAY. THIS UPPER LOW SHOULD MOVE  
EAST ON SUNDAY, RESTORING RELATIVE HIGH PRESSURE, BUT CLOUDS  
WILL LIKELY LINGER ALONG WITH COOLER TEMPERATURES AS WINDS WILL  
COME AROUND TO NORTHEASTERLY. BY LATE IN THE EXTENDED PERIOD, A  
LARGE LOW PRESSURE SYSTEM IS EXPECTED TO APPROACH THE UPPER  
MIDWEST MONDAY INTO TUESDAY, BRINGING A PROLONGED PERIOD OF  
SHOWERY RAIN AND CLOUDS TO THE AREA. WINDS WILL REMAIN  
NORTHEASTERLY OFF OF THE LAKE, KEEPING OUR CWA COOL WITH HIGHS  
IN THE 50S.  
 
 
   
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/  
 
UPDATED AT 1050 PM CDT THU MAY 15 2025  
 
WHILE STRONG THUNDERSTORMS HAVE DEPARTED LATE THIS EVENING AND A  
LULL IN THE WEATHER IS EXPECTED OVERNIGHT, EXPECT FLIGHT CONDITIONS  
TO DETERIORATE ON FRIDAY AS LOW PRESSURE SLOWLY CROSSES THE REGION.  
 
SOUTH TO SOUTHWEST WINDS WILL BECOME STRONG AND GUSTY BY MID TO LATE  
FRIDAY MORNING WITH GUSTS OF 30 TO 35 KTS LIKELY. THESE GUSTY WINDS  
WILL DIMINISH ON FRIDAY EVENING.  
 
LOW LEVEL WIND SHEAR WILL LIKELY DEVELOP ACROSS THE REGION LATE  
TONIGHT AND CONTINUE THROUGH FRIDAY MORNING.  
 
SCATTERED SHOWERS AND THUNDERSTORMS ARE FORECAST TO DEVELOP ON  
FRIDAY AFTERNOON. A FEW STRONG STORMS ARE POSSIBLE THAT COULD  
PRODUCE WIND GUSTS IN EXCESS OF 45 KTS.  
 
CEILINGS ARE FORECAST TO FALL TO MVFR ON FRIDAY EVENING WITH ANOTHER  
ROUND OF SHOWERS MOVING ACROSS THE REGION.  
 
 
   
MARINE  
 
UPDATED AT 936 PM CDT THU MAY 15 2025  
 
A SMALL CRAFT ADVISORY CONTINUES INTO TONIGHT. THE SOUTHEAST  
WINDS ARE SWITCHING TO SOUTHWEST. THERE SHOULD BE A PERIOD OF  
GUSTY SOUTHWEST WINDS OVERNIGHT, BUT LOWER CONFIDENCE IN THEM  
OCCURRING OVER THE LAKESHORE VS. INLAND. THEREFORE, WE WILL  
PROBABLY ALLOW THE SMALL CRAFT ADVY EXPIRE. WE WILL NEED ANOTHER  
SMALL CRAFT ADVISORY FOR TOMORROW AS GUSTY SOUTHWESTERLY WINDS  
ARE EXPECTED TO BECOME GUSTY DURING THE DAYTIME HOURS.  
 
 
   
GRB WATCHES/WARNINGS/ADVISORIES  
 
WI...NONE.  
MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM CDT FRIDAY FOR LMZ522.  
SMALL CRAFT ADVISORY UNTIL 11 PM CDT THIS EVENING FOR LMZ542-  
543.  
 
 
 
 
 
DISCUSSION...MRC  
AVIATION...MPC  
MARINE...MRC  
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