032  
FXUS63 KGRB 260338  
AFDGRB  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREEN BAY WI  
1038 PM CDT TUE JUL 25 2017  
 
UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE  
   
SHORT TERM
 
TONIGHT AND WEDNESDAY  
ISSUED AT 325 PM CDT TUE JUL 25 2017  
 
RADAR ECHOES THAT WERE IN WESTERN WISCONSIN THIS MORNING  
CONTINUED TO MOVE SOUTHEAST INTO THE FORECAST AREA TODAY BUT  
SHOWERS/SPRINKLES GRADUALLY DIED OFF IN THE MUCH DRIER AIR MASS IN  
CENTRAL AND EASTERN WISCONSIN (AS SEEN ON THE 12Z GRB SOUNDING).  
A SEPARATE AREA OF SHOWERS AND STORMS ACROSS NORTHWEST WISCONSIN,  
WERE THE MUCAPE WAS MAINLY IN THE 500-1000 J/KG AND THERE WAS  
LITTLE OR NO CIN, WAS MOVING EAST-SOUTHEAST. THIS WILL IMPACT  
PARTS OF CENTRAL WISCONSIN, BUT WITH LITTLE OR NO CAPE IN EASTERN  
WISCONSIN IT SHOULD DIE OFF BEFORE REACHING THE FOX VALLEY.  
 
AN APPROACHING FRONTAL BOUNDARY COMBINED WITH MID LEVEL SHORT  
WAVE ENERGY WILL HELP TO BRING THUNDERSTORMS TO THE AREA FOR  
TONIGHT. THE STORMS WOULD IMPACT NORTHERN WISCONSIN FIRST BEFORE  
MOVING TO THE SOUTHEAST DURING THE NIGHT. SPC DAY 1 OUTLOOK HAS A  
MARGINAL RISK OF SEVERE STORMS ACROSS MUCH OF THE AREA (GENERALLY  
WEST OF THE FOX VALLEY) AND A SLIGHT RISK IN THE WESTERN REACHES  
OF ONEIDA COUNTY AND VILAS COUNTY. THOUGH THERE IS SOME CAPE IN  
THE WESTERN PART OF THE AREA, AND THERE IS A DECENT AMOUNT OF  
SURFACE TO 3 KM SHEAR IN WESTERN WISCONSIN ACCORDING TO  
MESOANALYSIS, THERE IS NOT SIGNIFICANT BOUNDARY AND HIRES MODELS  
DID NOT EVEN FORECAST THE CONVECTION THAT IS CURRENTLY MOVING INTO  
CENTRAL/NORTH CENTRAL WISCONSIN. WOULD THINK THE MAIN THREAT IS  
LATE TONIGHT WITH THE SURFACE BOUNDARY APPROACHING.  
 
AS THE FRONT CONTINUES NORTH TO SOUTH ON WEDNESDAY THE SHOWERS AND  
STORMS ARE EXPECTED TO CONTINUE. MODELS DO SEEM TO SHIFT THE  
FOCUS MORE TO THE WEST OF THE AREA DURING THE DAY, SO CONFIDENCE  
IN POP FORECAST FOR WEDNESDAY IS BELOW AVERAGE.  
   
LONG TERM
 
WEDNESDAY NIGHT THROUGH TUESDAY  
ISSUED AT 325 PM CDT TUE JUL 25 2017  
 
STORMS LIKELY TO BE ONGOING AT THE START OF WEDNESDAY EVENING  
OVER MOST LOCATIONS AS A COLD FRONT DROPS SOUTHWARD OVER THE AREA.  
INSTABILITY AND SHEAR PARAMETERS MAY BE ENOUGH FOR STRONG TO  
SEVERE STORMS OVER PARTS OF CENTRAL AND EAST CENTRAL WISCONSIN IN  
THE EVENING HOURS BEFORE THE FRONT DROPS SOUTH OF THE AREA  
OVERNIGHT. HIGH PRESSURE BUILDS INTO THE REGION FROM THE NORTH TO  
DECREASE CLOUDS.  
 
MEDIUM RANGE PROGS HINT OF A WEAK SHORT WAVE TROUGH DROPPING INTO  
AT LEAST NORTHERN WISCONSIN THURSDAY AFTERNOON. HEIGHT 500 TEMP  
DATA SHOWS THE NAM IS VERY QUICK WITH DROPPING THE COLD CORE OF  
AIR ALOFT INTO CENTRAL WISCONSIN THURSDAY AFTERNOON, WHILE THE  
ECMWF AND GFS STILL HAVE THE COLD CORE OVER THE MINNESOTA  
ARROWHEAD LATE THURSDAY AFTERNOON. WILL CONFINE ANY SMALL POPS TO  
NORTHERN WISCONSIN AT THIS TIME WITH DAYTIME HEATING. AS HEIGHTS  
INCREASE OVER THE PLAINS STATES THURSDAY NIGHT INTO FRIDAY, THE  
SHORT WAVE TROUGH IS PROGGED TO TURN INTO A NEARLY CLOSED LOW OVER  
NORTHERN LAKE MICHIGAN BY FRIDAY MORNING BEFORE DRIFTING INTO  
LOWER MICHIGAN IN THE AFTERNOON. WILL CONTINUE A DRY FORECAST WITH  
SURFACE DEWPOINTS IN THE LOWER 50S UNDER THE SURFACE HIGH  
PRESSURE REGIME.  
 
UPPER RIDGE THEN NUDGES INTO THE AREA FOR THE START OF THE  
WEEKEND WHILE THE SURFACE HIGH REMAINS SETTLED OVER THE GREAT  
LAKES REGION. PROGS ATTEMPT TO DROP A COLD FRONT INTO THE AREA  
LATER IN THE WEEKEND WITH A NORTHERN STREAM SHORT WAVE TROUGH.  
BUT COVERAGE APPEARS MINIMAL AND TIMING CHALLENGING, SO WILL  
HANDLE WITH LOWER END POPS FOR NOW.  

 
   
AVIATION
 
FOR 06Z TAF ISSUANCE  
ISSUED AT 1026 PM CDT TUE JUL 25 2017  
 
A COLD FRONT WILL PUSH ACROSS NORTHERN WI LATE TONIGHT AND  
CENTRAL WISCONSIN ON WEDNESDAY. DETAILS REMAIN ELUSIVE, BUT IT  
APPEARS THAT SHOWERS AND STORMS WILL ARRIVE OVER NORTHERN WI AFTER  
MIDNIGHT, WHILE CENTRAL TO NORTHEAST WI WILL SEE THE STORMS  
ARRIVE BY EARLY TO MID MORNING. MVFR CIGS WILL ARRIVE AHEAD OF THE FRONT,  
THOUGH SOME PATCHY IFR CIGS ARE POSSIBLE WHERE THE HEAVIER RAINS  
FALL. SHOWERS/STORMS TO EXIT DURING THE AFTERNOON HOURS ON  
WEDNESDAY.  
 

 
   
GRB WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SHORT TERM.....MG  
LONG TERM......TDH  
AVIATION.......MPC  
 
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