010  
FXUS63 KGRB 131956  
AFDGRB  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREEN BAY WI  
256 PM CDT MON JUL 13 2020  
 
FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE  
   
SHORT TERM
 
TONIGHT AND TUESDAY  
ISSUED AT 256 PM CDT MON JUL 13 2020  
 
HIGH PRESSURE THAT KEPT US DRY THE PAST COUPLE DAYS IS ON ITS WAY  
OUT THIS EVENING. AS RETURN FLOW SETS UP ON THE LEE SIDE OF THE  
HIGH TONIGHT, SOUTHERLY FLOW WILL DEVELOP A 30-40 KNOT LOW LEVEL  
JET ACROSS CENTRAL WISCONSIN. RISING DEWPOINTS OVERNIGHT COMBINED  
WITH THE LLJ WITH BRING THE DEVELOPMENT OF SOME UPPER LEVEL  
SHOWERS LATE TONIGHT. DEEP LAYER SHEAR AROUND 30 TO 35 KNOTS  
COULD ORGANIZE A FEW OF THE ELEVATED STORMS LONG ENOUGH TO PRODUCE  
A FEW AREAS OF SMALL HAIL, MAINLY ACROSS CENTRAL TO NORTH-CENTRAL  
WI. ONCE THE LLJ BEGINS TO WEAKEN TUESDAY MORNING HOWEVER, MOST  
OF THE CONVECTIVE STORMS ARE EXPECTED TO DIMINISH INTO SHOWERS BY  
LATE MORNING, LEADING TO A BREAK BEFORE STORMS REDEVELOP LATER ON  
TUESDAY. LOW TEMPERATURES TONIGHT WILL FALL INTO THE LOWER TO  
MIDDLE 60S.  
 
TUESDAY...A FEW SHOWERS MAY STILL BE IN PLACE ACROSS THE REGION,  
ALONG WITH A FEW AREAS OF UPPER LEVEL CLOUD COVER. THE MAIN EVENT  
WILL BE IN THE AFTERNOON AS A COLD FRONT MOVES INTO NORTH-CENTRAL  
AND CENTRAL WI. PRECIPITATION WILL BE MAINLY FOCUSED AWAY FROM THE  
FOX VALLEY THROUGH THE EVENING, BEFORE THE FRONT FINALLY MAKES ITS  
WAY EASTWARDS TUESDAY NIGHT. PWATS WILL PUSH UPWARDS OF 1.5-2  
INCHES, MAKING HEAVY RAINFALL A GOOD POSSIBILITY FOR MUCH OF THE  
AREA. THE STRENGTH OF SEVERE WEATHER REMAINS SOMEWHAT UNCERTAIN  
FOR THE REGION HOWEVER. DEEP LAYER SHEAR REMAINS 35 TO 50 KNOTS  
THROUGH THE LATE AFTERNOON, WHICH WILL PROVIDE SOME ORGANIZATION  
TO DEVELOPING STORMS. LOW LEVEL HELICITY AROUND 200-300 WILL  
SUPPORT DEVELOPING MESOCYCLONES AND ALSO SUGGESTS THE POTENTIAL  
FOR A BRIEF SPIN UP OR ISOLATED TORNADO IN ANY STRONGER STORMS  
THAT DEVELOP, AS LOW LEVEL VORTICITY WILL BE FAIRLY AVAILABLE TO  
DEVELOPING UPDRAFTS AS WELL. THE MAIN UNCERTAINTY REMAINS THE  
AVAILABILITY OF INSTABILITY, AS MODELS CONTINUE TO DIVERGE ON HOW  
THE MORNING SHOWERS AND CLOUD COVER WILL IMPACT THE REGION AHEAD  
OF THE FRONT. OVERALL, EXPECT HEAVY RAINFALL TO BE VERY LIKELY,  
WITH THE POTENTIAL FOR SEVERE HAIL AND WIND TO DEVELOP IN STRONGER  
CELLS. THE TORNADO THREAT IS ALSO PRESENT, BUT WILL BE MORE  
ISOLATED. SPC KEEPS US IN THE MARGINAL RISK FOR MOST OF THE  
REGION, WITH THE SLIGHT RISK EXTENDING INTO CENTRAL WI FROM THE  
SOUTHWEST, WHERE THE BEST CAPE IS, WHICH SEEMS VERY REASONABLE.  
THE SEVERE THREAT SHOULD BEGIN TO DIMINISH IN THE LATE EVENING TO  
EARLY OVERNIGHT HOURS, AS THE FRONT CROSSES THE REGION AND DIURNAL  
INSTABILITY BEGINS TO DISSIPATE. HIGH TEMPERATURES FOR TUESDAY  
ARE EXPECTED TO BE IN THE LOWER 70S UP NORTH TO THE LOWER 80S NEAR  
THE FOX VALLEY.  
   
LONG TERM
 
TUESDAY NIGHT THROUGH MONDAY  
ISSUED AT 256 PM CDT MON JUL 13 2020  
 
THE THREAT FOR STRONG TO SEVERE STORMS WILL CONTINUE INTO TUESDAY  
EVENING AHEAD OF AN APPROACHING COLD FRONT, WITH THE MAIN THREAT  
TRANSITIONING TO HEAVY RAINFALL DURING THE OVERNIGHT HOURS WITH  
THE LOSS OF DAYTIME HEATING AND THE BULK OF THE INSTABILITY.  
 
THE FRONT WILL STALL OUT OVER THE AREA ON WEDNESDAY, PROVIDING A  
FOCUS FOR ADDITIONAL SHOWERS AND THUNDERSTORMS THROUGH WEDNESDAY  
EVENING AS A MID LEVEL SHORTWAVE RIDES ALONG THE FRONTAL BOUNDARY.  
UNLIKE TUESDAY, THESE STORMS ARE NOT EXPECTED TO BE SEVERE AS  
ABUNDANT CLOUD COVER ALONG THE FRONT IS EXPECTED TO PUT A LIMIT ON  
THE AMOUNT OF INSTABILITY THAT IS AVAILABLE DURING THE AFTERNOON  
AND EVENING HOURS.  
 
HIGH PRESSURE WILL THEN BRING A PERIOD OF DRY WEATHER TO THE  
WESTERN GREAT LAKES LATE WEDNESDAY NIGHT, LASTING THROUGH FRIDAY  
MORNING. A LOW PRESSURE SYSTEM APPROACHING THE REGION FROM THE  
WEST WILL BRING THE CHANCE OF SHOWERS AND THUNDERSTORMS BACK TO  
THE AREA LATE IN THE WEEK AND INTO EARLY NEXT WEEK. TEMPERATURES  
DURING THIS PERIOD WILL ONCE AGAIN RISE WELL INTO THE 80S, WITH  
HIGHS THIS WEEKEND APPROACHING OR EXCEEDING 90 DEGREES ACROSS MUCH  
OF CENTRAL, EAST-CENTRAL AND NORTHEAST WISCONSIN. DEPENDING ON  
HOW MUCH CLOUD COVER LINGERS ACROSS THE AREA WITH THE  
AFOREMENTIONED SHOWERS AND THUNDERSTORMS, HEAT INDICES ARE  
EXPECTED TO RISE WELL INTO THE 90S WITH A FEW 100 DEGREE READINGS  
POSSIBLE THIS NEXT WEEKEND. WHILE THE HOT TEMPERATURES WILL BRING  
AN INCREASE IN INSTABILITY, IT IS TOO EARLY TO DETERMINE IF THESE  
STORMS ARE EXPECTED TO BE SEVERE.  

 
   
AVIATION
 
FOR 18Z TAF ISSUANCE  
ISSUED AT 1255 PM CDT MON JUL 13 2020  
 
VFR CONDITIONS WILL CONTINUE THROUGH THE BEGINNING OF THE TAF  
PERIOD AND INTO THE EARLY OVERNIGHT HOURS. THE MAIN AVIATION  
CONCERN FOR THE TAF PERIOD WILL BE RAIN AND THUNDERSTORMS  
DEVELOPING ACROSS CENTRAL AND NORTHERN WISCONSIN TONIGHT AS A LOW  
LEVEL JET DEVELOPS. THE RAIN AND STORMS WILL BRING MVFR AND  
POSSIBLY IFR CONDITIONS TO CENTRAL WISCONSIN AFTER 06Z, AS CLOUD  
DECKS AND VISIBILITY DROP. THIS WILL MAINLY IMPACT RHI, BUT IS  
EXPECTED TO SPREAD TO AUW AND CWA BY THE MID MORNING HOURS. THE  
LOW LEVEL JET WILL ALSO BUILD LOW LEVEL WIND SHEAR INTO THE REGION  
OVERNIGHT. THUNDERSTORMS WILL THEN DIMINISH TOWARDS THE END OF THE  
TAF PERIOD, LEAVING RAIN IN CENTRAL TO NORTHERN WISCONSIN.  
 
ANOTHER ROUND OF STRONGER STORMS IS POSSIBLE AFTER THE CURRENT  
TAF PERIOD, TUESDAY EVENING.  

 
   
GRB WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SHORT TERM.....UHLMANN  
LONG TERM......KURIMSKI  
AVIATION.......UHLMANN  
 
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