383  
FXUS63 KGRB 160031  
AFDGRB  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREEN BAY WI  
ISSUED BY NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI  
731 PM CDT THU MAY 15 2025  
   
KEY MESSAGES
 
 
- MARINE DENSE FOG ADVISORY FOR THE NEARSHORE AREAS OF LAKE  
MICHIGAN THROUGH THE EARLY EVENING. A SMALL CRAFT ADVISORY  
 
- A BROKEN LINE OF STRONG THUNDERSTORMS WILL CROSS NORTHERN WI  
BETWEEN 4 AND 9 PM TODAY. 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.  
 
- ANOTHER PERIOD OF SHOWERS AND WEAK STORMS EXPECTED FRIDAY WITH  
SOME POTENTIAL FOR GUSTY WINDS WITH SOME OF THESE  
SHOWERS/STORMS.  
 

 
   
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 /00Z TAFS THROUGH 00Z SATURDAY/
 
 
ISSUED AT 724 PM CDT THU MAY 15 2025  
 
SCATTERED STORMS ARE PRESENT MOST EVERYWHERE OVER NORTHEAST WI.  
THESE STORMS WILL FEATURE GUSTY WINDS AND LARGE HAIL. AN  
ISOLATED TORNADO ALSO CAN'T BE RULED OUT THROUGH THE REST OF THE  
EVENING. THESE STORMS SHOULD CONTINUE TO LIFT NORTHEAST AND  
EXIT NORTHEAST WI BY 03 TO 04Z. FOLLOWING STORMS, SKIES ARE  
EXPECTED TO QUICKLY CLEAR AND REMAIN CLEAR OVERNIGHT AS A DRY  
SLOT MOVES IN, WITH LIGHTER WINDS THAT WILL TURN FROM SOUTHEAST  
TO SOUTHWEST OVERNIGHT.  
 
VFR CEILINGS RETURN TOMORROW THROUGH THE MORNING INTO THE  
AFTERNOON WITH SFC WIND GUSTS BECOMING STRONG OUT OF THE  
SOUTHWEST TO 35 KNOTS IN SPOTS, ESPECIALLY THE FOX VALLEY.  
THERE MAY BE ADDITIONAL SCATTERED THUNDERSTORM DEVELOPMENT IN  
THE AFTERNOON WITH GUSTY WINDS BEING THE PRIMARY THREAT.  
 

 
   
MARINE
 
 
ISSUED AT 304 PM CDT THU MAY 15 2025  
 
MARINE DENSE FOG WILL CONTINUE INTO THIS EVENING UNTIL  
THUNDERSTORMS AND A FRONT PASS DURING THE EARLY EVENING HOURS. A  
SMALL CRAFT ADVISORY WILL ALSO CONTINUE INTO TONIGHT ON  
SOUTHEAST WINDS. FOLLOWING THE PASSAGE OF THE FRONT, WINDS  
SHOULD EASE FOR A TIME OVERNIGHT AND THEN COME AROUND TO  
SOUTHWESTERLY BY TOMORROW AT DAWN. GUSTY SOUTHWESTERLY WINDS ARE  
THEN EXPECTED TO PICK UP LEADING TO A POTENTIAL SECOND PERIOD OF  
SMALL CRAFT ADVISORY CONDITIONS DURING TOMORROW AFTERNOON.  
 

 
   
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...  
AVIATION...  
MARINE...  
 
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