806  
FXUS63 KGRB 262337  
AFDGRB  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREEN BAY WI  
637 PM CDT FRI MAY 26 2017  
 
UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE  
   
SYNOPSIS
 
 
ISSUED AT 251 PM CDT FRI MAY 26 2017  
 
SCATTERED SHOWERS AND GRADUALLY TURNING COOLER DURING THE HOLIDAY  
WEEKEND.  
 
NORTHWEST UPPER FLOW WILL DEVELOP ACROSS THE REGION AS A RIDGE  
SETS UP OVER WESTERN NORTH AMERICA AND AN UPPER TROUGH SETTLES IN  
OVER ONTARIO. THE PATTERN DOES NOT APPEAR AS THOUGH IT WILL BE  
EXCEPTIONALLY LONG-LIVED, AS DEAMPLIFICATION IS LIKELY TO BEGIN BY  
LATE IN THE PERIOD.  
 
TEMPERATURES WILL START THE PERIOD NEAR SEASONAL NORMALS, THEN  
DROP BACK TO A LITTLE BELOW NORMAL IN THE DEVELOPING NORTHWEST  
FLOW. THERE WILL BE SEVERAL OPPORTUNITIES FOR PRECIPITATION, BUT  
MOST PRECIPITATION EVENTS LOOK TO BE COMPOSED OF SCATTERED TO  
NUMEROUS SHOWERS SO AMOUNTS ARE LIKELY TO END UP NEAR NORMAL FOR  
THE 7 DAY PERIOD.  

 
   
SHORT TERM
 
TONIGHT AND SATURDAY  
ISSUED AT 251 PM CDT FRI MAY 26 2017  
 
PRECIPITATION CHANCES REMAIN SOMEWHAT UNCERTAIN DUE TO WEAK  
FORCING. TRENDED POPS UPWARD THIS EVENING AND THEN DOWN AFTER  
MIDNIGHT, FOLLOWING THE MOST RECENT HRRR RUNS. REMNANTS OF A WEAK  
BOUNDARY WILL LINGER ACROSS THE AREA SATURDAY, AGAIN LEADING TO  
RATHER NEBULOUS FORCING. STUCK WITH MAINLY CHANCE POPS WITH THE  
BEST CHANCE IN THE AFTERNOON.  
 
DENSE FOG OVER LAKE MICHIGAN HAS PRIMARILY REMAINED OFFSHORE, BUT  
SOUTHEAST LOW-LEVEL FLOW COULD BRING IT INLAND. THE MAIN CONCERN  
IS HIGHWAYS NEAR THE LAKE WHICH ARE LIKELY TO HAVE A HIGH TRAFFIC  
VOLUME AT THE START OF THE HOLIDAY WEEKEND. PLAN TO HANDLE THE  
SITUATION WITH SPSS UNLESS FOG MAKES A MORE AGGRESSIVE SURGE  
INLAND. WINDS MAY TURN OFFSHORE LATER TONIGHT AND PUSH THE FOG  
FARTHER OUT INTO THE LAKE, BUT AGAIN MODELS DIFFERED IN THE  
DETAILS OF THAT IN THE WEAK LOW-LEVEL PATTERN.  
   
LONG TERM
 
SATURDAY NIGHT THROUGH FRIDAY  
ISSUED AT 251 PM CDT FRI MAY 26 2017  
 
NORTHWEST FLOW ALOFT WILL CONTINUE THROUGH MUCH OF NEXT WEEK AS  
500MB RIDGE REMAINS ENTRENCHED ACROSS WESTERN NORTH AMERICA WITH A  
DOWNSTREAM TROUGH ACROSS EASTERN NORTH AMERICA. UPPER LEVEL  
DISTURBANCES AND ASSOCIATED WEAK COLD FRONTS WILL BRING PERIODIC  
CHANCES OF SHOWERS AND A FEW THUNDERSTORMS FROM TIME TO TIME  
THROUGH MUCH OF THE PERIOD.  
 
FOR SATURDAY NIGHT, WEAK FRONTAL BOUNDARY ACROSS THE AREA,  
COMBINED WITH DAYTIME HEATING WILL ALLOW FOR SCATTERED SHOWER TO  
LINGER INTO THE EVENING HOURS. A THUNDERSTORM COULD NOT BE RULED  
OUT. AFTER MIDNIGHT, TWO SYSTEMS WILL APPROACH THE AREA. THE FIRST  
SYSTEM WILL PASS TO THE SOUTH OF THE AREA WHILE THE SECOND SYSTEM  
WILL APPROACH FROM THE NORTHWEST. THESE TWO SYSTEMS WILL BRING  
INCREASING CHANCES OF SHOWERS OVERNIGHT INTO SUNDAY MORNING. THE  
NEXT WEAK COLD FRONT WILL MOVE ACROSS THE AREA SUNDAY AFTERNOON.  
THIS FEATURE WILL BRING CONTINUED CHANCES OF SHOWERS WITH A FEW  
THUNDERSTORMS EXPECTED. MOST OF THE SHOWER ACTIVITY WILL END  
DURING THE EVENING HOURS. WITH NORTHWEST FLOW ALOFT, COULD NOT  
RULE OUT AN ISOLATED SHOWER AFTER MIDNIGHT.  
 
NEXT SHORTWAVE ENERGY AND UPPER TROUGH SWING ACROSS THE AREA  
ON MEMORIAL DAY. WITH DAYTIME HEATING, INSTABILITY SHOWERS WILL  
BE ON THE INCREASE DURING THE LATE MORNING AND AFTERNOON. A FEW  
THUNDERSTORMS ARE POSSIBLE. DUE TO EXPECTED CLOUD COVER AND RAIN,  
LOWERED HIGH TEMPERATURES ON MEMORIAL DAY. ALSO, GUSTY WESTERLY  
WINDS ARE EXPECTED WITH GUSTS AROUND 30 MPH POSSIBLE.  
 
MORE INSTABILITY SHOWERS ARE EXPECTED TUESDAY, AND AGAIN WEDNESDAY  
AND THURSDAY. MOST OF THE TIME WILL BE DRY, HOWEVER THE BEST  
CHANCES OF RAIN APPEAR TO BE DURING THE AFTERNOON HOURS.  
TEMPERATURES DURING THE PERIOD WILL BE AT OR SLIGHTLY BELOW  
AVERAGE.  

 
   
AVIATION
 
FOR 00Z TAF ISSUANCE  
ISSUED AT 629 PM CDT FRI MAY 26 2017  
 
SCATTERED SHOWERS SHOULD EDGE OUT OF NORTHERN WI LATER TONIGHT,  
AND THE SCATTERED LINE OF THUNDERSTORMS OVER THE NORTHWEST PART  
OF THE STATE SHOULD DISSIPATE AS DAYTIME INSTABILITY WANES.  
PARTIAL CLEARING, LIGHT SURFACE WINDS, BOUNDARY LAYER WINDS OF  
15 KNOTS OR LESS AND LOW-LEVEL MOISTURE WILL LIKELY LEAD TO AREAS  
OF FOG AND LOW CLOUDS LATE TONIGHT, WITH LOCALIZED LIFR/VLIFR  
FLIGHT CONDITIONS POSSIBLE. DENSE FOG IS ALSO POSSIBLE ALONG THE  
LAKESHORE, BUT WHETHER OR NOT THIS WILL REACH THE MTW TAF SITE IS  
UNCERTAIN. THE FOG SHOULD MIX OUT EARLY SATURDAY MORNING. DAYTIME  
HEATING AND THE PRESENCE OF A WEAK BOUNDARY IN EASTERN WI MAY  
RESULT IN SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS LATE IN THE  
AFTERNOON. WILL MENTION VCSH AT GRB/ATW, BUT CONFIDENCE IS NOT  
HIGH ENOUGH TO MENTION THUNDERSTORMS AT THIS TIME.  
 

 
   
MARINE
 
 
ISSUED AT 251 PM CDT FRI MAY 26 2017  
 
DENSE FOG WILL CONTINUE TONIGHT INTO SATURDAY ON LAKE MICHIGAN.  
PATCHY DENSE FOG IS ALSO POSSIBLE ON THE BAY OF GREEN BAY. THE  
FOG MAY LINGER INTO SATURDAY NIGHT ON LAKE MICHIGAN. THERE IS  
A SLIGHT CHANCE OF THUNDERSTORMS DURING THE AFTERNOON AND  
EARLY EVENING HOURS SATURDAY, SUNDAY AND MEMORIAL DAY THAT MAY  
POSE A HAZARD TO MARINERS.  
 
GUSTY WESTERLY WINDS ARE EXPECTED ON MEMORIAL DAY WITH GUSTS  
AROUND 25 KNOTS POSSIBLE MAKING FOR HAZARDOUS CONDITIONS FOR  
SMALL CRAFT.  

 
   
GRB WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SYNOPSIS.......SKOWRONSKI  
SHORT TERM.....SKOWRONSKI  
LONG TERM......ECKBERG  
AVIATION.......KIECKBUSCH  
MARINE.........ECKBERG  
 
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