162  
FXUS63 KGRB 161100  
AFDGRB  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREEN BAY WI  
600 AM CDT TUE JUL 16 2019  
 
UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE  
   
SHORT TERM...TODAY...TONIGHT
 
AND WEDNESDAY  
ISSUED AT 409 AM CDT TUE JUL 16 2019  
 
THE MAIN CONCERNS IN THE SHORT TERM PORTION OF THE FORECAST WILL BE  
THE CONTINUED VERY WARM AND HUMID CONDITIONS ACROSS THE AREA ALONG  
WITH ISOLATED TO SCATTERED SHOWER AND THUNDERSTORM POTENTIAL.  
 
TODAY AND TONIGHT: A WEAK COOL FRONT/WIND SHIFT, STRETCHING  
NORTHEAST TO SOUTHWEST, WILL SHIFT SOUTH AND BECOME EAST TO WEST  
ORIENTED THIS AFTERNOON BEFORE BECOMING NEARLY STATIONARY JUST SOUTH  
OF THE CWA THIS EVENING. MOST LOCATIONS WILL REMAIN PRECIPITATION  
FREE TODAY INTO THIS EVENING; HOWEVER, THERE MAY BE SOME ENHANCED  
CONVERGENCE ALONG/NEAR LAKE MICHIGAN (AHEAD OF THE FRONT) TO TOUCH  
OFF SOME SHOWERS AND THUNDERSTORMS LATE THIS AFTERNOON INTO EARLY  
THIS EVENING. INSTABILITY AHEAD OF THE FRONT IS EXPECTED TO BE  
AROUND 1000-2000 J/KG WITH DEEP LAYER SHEAR VALUES EXPECTED TO BE  
AROUND 25 KTS. THIS WOULD BE ENOUGH TO ALLOW FOR A FEW STRONG  
THUNDERSTORMS TO DEVELOP DURING THE LATE AFTERNOON AND EARLY EVENING  
HOURS. THE LACK OF ANY STRONG UPPER-LEVEL SUPPORT AND LACK OF  
ENHANCED SHEAR, WOULD TEND TO LEND LESS SUPPORT TO A MORE ORGANIZED  
STRONG TO SEVERE WEATHER THREAT. IN FACT, SPC ONLY HAS THE AREA  
PAINTED IN A GENERAL THUNDER THREAT. PWAT VALUES ARE PROGGED TO BE  
IN THE 1 TO 2 INCH RANGE, SO ANY THUNDERSTORM THAT DOES DEVELOP  
COULD DROP A LOT OF RAIN IN A SHORT PERIOD OF TIME. THE STORMS ARE  
EXPECTED TO DIMINISH FROM NORTH TO SOUTH OVERNIGHT. HIGHS TODAY WILL  
BE IN THE UPPER 80S WITH OVERNIGHT LOWS ONLY DROPPING INTO THE 60S  
TO AROUND 70 TONIGHT.  
 
WEDNESDAY: THE FIRST HALF OF THE DAY WILL LIKELY BE DRY ACROSS THE  
AREA AND CONTINUED VERY WARM AND HUMID. BY MID TO LATE AFTERNOON, A  
SHORTWAVE IS EXPECTED TO APPROACH THE AREA FROM THE WEST. THIS WILL  
STEADILY INCREASE THE CHANCES FOR SHOWERS AND THUNDERSTORMS INTO THE  
AFTERNOON AND EVENING HOURS. IN ADDITION, THE AFOREMENTIONED  
STATIONARY FRONTAL BOUNDARY WILL LINGER JUST SOUTH OF THE AREA. THE  
COMBINATION OF THESE FEATURES WILL SET THE STAGE FOR AN ACTIVE  
WEDNESDAY AFTERNOON INTO THE EVENING HOURS. TIMING AND PLACEMENT OF  
THE FEATURES WILL BE THE BIGGEST CHALLENGE AND POPS WILL LIKELY BE  
INCREASED AS CONFIDENCE INCREASES IN EACH OF THESE. INSTABILITY  
VALUES ARE EXPECTED TO BE AROUND 1000-2000 J/KG ONCE AGAIN;  
HOWEVER, SHEAR VALUES WITH SOME UPPER-LEVEL SUPPORT WILL INCREASE TO  
AROUND 35 TO 45 KTS. THIS WOULD INDICATE AN INCREASING POTENTIAL FOR  
SEVERE WEATHER BY LATE WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT.  
LARGE HAIL AND ESPECIALLY DAMAGING WINDS WILL BE THE MAIN THREATS  
FROM THE STORMS. IN ADDITION PWATS ARE EXPECTED TO REMAIN FAIRLY  
HIGH, IN THE 1 TO 2 INCH RANGE, THROUGH THIS TIME PERIOD. OTHERWISE,  
VERY WARM AND MUGGY CONDITIONS CAN BE EXPECTED WITH HIGHS IN THE MID  
TO UPPER 80S.  
   
LONG TERM
 
WEDNESDAY NIGHT THROUGH MONDAY  
ISSUED AT 409 AM CDT TUE JUL 16 2019  
 
FORECAST CONCERNS CONTINUE TO REVOLVE AROUND THUNDERSTORM CHANCES  
AND EXCESSIVE HEAT POTENTIAL INTO EARLY NEXT WEEK. MODELS HAVE A  
VARIETY OF DETAIL DIFFERENCES IN REGARDS TO THE THUNDERSTORM  
POTENTIAL, BUT APPEAR TO POINT TOWARDS TWO MAIN PERIODS, NAMELY  
WEDNESDAY NIGHT INTO EARLY THURSDAY AND ALSO LATE IN THE WEEKEND. AS  
SUB-TROPICAL RIDGING BUILDS NORTH, THE HOTTEST PERIOD APPEARS TO BE  
IN THE FRIDAY-SATURDAY TIME FRAME. WILL USE A GENERAL MODEL BLEND  
TO MITIGATE SMALL SCALE DIFFERENCES.  
 
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...SHORTWAVE ENERGY WILL BE  
MOVING ACROSS THE NORTHERN PLAINS AND THE LAKE SUPERIOR REGION IN  
THE WEDNESDAY NIGHT AND THURSDAY TIME FRAME. AS A MODEST 30-40 KT  
LOW LEVEL JET CRANKS UP AHEAD OF THE SHORTWAVE, ELEVATED MOISTURE  
TRANSPORT WILL INCREASE ACROSS THE REGION. MOST UNSTABLE CAPE WILL  
ALSO INCREASE AS WELL, IN THE 1500-2000 J/KG RANGE IN A REGION OF  
EFFECTIVE SHEAR UPWARDS OF 30 KTS. WITH THAT MAGNITUDE OF  
INSTABILITY AND DEEP LAYER SHEAR, COULD HAVE A SEVERE MCS THREAT ON  
WEDNESDAY NIGHT, THOUGH BEST DYNAMICS SHOULD REMAIN NORTH OF THE  
REGION. THE SIGNIFICANT SEVERE PARAMETER SUGGEST CENTRAL AND NORTH-  
CENTRAL WI HAS THE BEST CHANCE OF SEVERE STORMS AS INSTABILITY MOVES  
IN FROM THE WEST. A WEAK FRONT WILL THEN APPROACH THE AREA ON  
THURSDAY AFTERNOON. EVOLUTION OF THUNDERSTORM ACTIVITY ON WEDNESDAY  
NIGHT WILL HELP DETERMINE THE STORM POTENTIAL ON LATER THURSDAY.  
AMPLE MIXED LAYER CAPE UPWARDS OF 3000 J/KG AND DEEP LAYER SHEAR  
ESTIMATED AT 40 KTS ARE EXPECTED TO DEVELOP THURSDAY AFTERNOON.  
FORCING WILL BE RATHER WEAK AND SOME CAPPING WILL LIKELY BE PRESENT,  
BUT WITH THAT SORT OF INSTABILITY, IT WOULDNT TAKE MUCH TO DEVELOP  
STRONG STORMS. INSTABILITY SHOULD RAPIDLY DIMINISH ON THURSDAY  
NIGHT, BUT REMAIN SUFFICIENT FOR A SLIGHT CHANCE OF STORMS TO  
CONTINUE.  
 
REST OF THE FORECAST...SUB-TROPICAL RIDGING WILL THEN BUILD NORTH  
INTO THE AREA ON FRIDAY, PUSHING A LINGERING FRONT INTO FAR NORTHERN  
WI. THIS FRONT WILL LEAD TO LOW CHANCES OF STORMS AT TIMES ON  
FRIDAY AND SATURDAY, BUT LACK OF LARGE SCALE FORCING SHOULD LIMIT  
COVERAGE AND ORGANIZATION. THE BIGGER STORY SOUTH OF THE FRONT WILL  
BE THE HOT AND HUMID WEATHER. LOW LEVEL TEMPS SUPPORT HIGHS IN THE  
LOW TO MID 90S. COMBINED WITH DEWPOINTS IN THE UPPER 60S TO LOW  
70S, HEAT INDICES WILL APPROACH 100 DEGREES OVER CENTRAL AND EAST-  
CENTRAL WI ON FRIDAY AFTERNOON AND POSSIBLY SATURDAY AFTERNOON  
DEPENDING UPON STORM COVERAGE. THEN A COLD FRONT IS FORECAST TO MOVE  
ACROSS THE REGION SOMETIME ON SUNDAY. STRENGTH OF THE SYSTEM ALONG  
WITH MAGNITUDE OF INSTABILITY AHEAD OF THE FRONT SHOULD LEAD TO A  
GOOD CHANCE OF STORMS, AND A CHANCE OF SEVERE WEATHER. COOLER AND  
LESS HUMID AIR THEN IS EXPECTED TO MOVE IN BEHIND THE FRONT FOR  
EARLY NEXT WEEK.  

 
   
AVIATION
 
FOR 12Z TAF ISSUANCE  
ISSUED AT 559 AM CDT TUE JUL 16 2019  
 
VFR CONDITIONS CAN BE EXPECTED AT EACH OF THE TAF  
SITES THROUGH THIS EVENING. THERE COULD BE SOME SCATTERED SHOWERS  
AND THUNDERSTORMS OVER MAINLY THE EASTERN TAF SITES, BUT OVERALL  
CONFIDENCE IS LOW IN TIMING AND OCCURRENCE. OTHERWISE, LOOK FOR  
SOME SCATTERED TO BROKEN AFTERNOON CU. SOME PATCHY FOG MAY FORM  
OVERNIGHT TONIGHT IF ANY CLEARING OCCURS.
 
   
GRB WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SHORT TERM.....COOLEY  
LONG TERM......MPC  
AVIATION.......COOLEY  
 
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