268  
FXUS63 KGRB 220359  
AFDGRB  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREEN BAY WI  
1059 PM CDT THU SEP 21 2017  
 
UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE  
   
UPDATE
 
 
ISSUED AT 932 PM CDT THU SEP 21 2017  
 
UPDATED FORECAST GRIDS TO INCLUDE WIDESPREAD DENSE FOG OVER THE  
EAST, LAKE AND BAY. THIS MATCHES THE DENSE FOG/MARINE DENSE FOG  
ADVISORY AREAS. ALSO DOWNPLAYED THE POPS FOR AT LEAST THE NEXT  
SEVERAL HOURS.  

 
   
SHORT TERM
 
TONIGHT AND FRIDAY  
ISSUED AT 258 PM CDT THU SEP 21 2017  
 
A WARM FRONT WAS LIFTING INTO SOUTHERN MN AND SOUTHWEST WI  
THIS AFTERNOON. A BAND OF LOW CLOUDS WAS PERSISTING NORTH  
OF THIS BOUNDARY, AND MOVING NORTHWARD THROUGH GRB CWA.  
TEMPERATURES WERE IN THE LOW TO MID 70S WITHIN THE CLOUD BAND, BUT  
IN THE UPPER 70S TO LOWER 80S WHERE THERE WAS SUNSHINE. DESPITE  
SBCAPE OF 1000-1500 J/KG ACROSS THE REGION, CINH OF 75-100 J/KG  
WAS CAPPING OFF ANY CONVECTION.  
 
THE WARM FRONT IS EXPECTED TO LIFT NORTH ACROSS THE REGION TONIGHT  
AND FRIDAY MORNING. THE FRONT, COMBINED WITH A DEVELOPING 30-35 KT  
LOW-LEVEL JET, SHOULD TRIGGER ISOLATED ELEVATED THUNDERSTORMS  
NORTH OF THE BOUNDARY, AS H8 LI'S OF -3 TO -5 C ADVECT INTO THE  
REGION. STORMS MAY BE A BIT MORE NUMEROUS OVER NORTH CENTRAL WI,  
AS SOME WEAK SHORT-WAVE ENERGY AND THE RRQ OF 50-60 KT JET BRUSH  
PAST LATER TONIGHT. SPC STILL HAS A SMALL PART OF NORTH CENTRAL WI  
IN THE MARGINAL RISK FOR SEVERE STORMS TONIGHT, AND THIS SEEMS  
REASONABLE, AS DEEP-LAYER SHEAR IS STRONGEST THERE (AROUND 30  
KTS). HAVE ADDED PATCHY FOG ACROSS MOST OF THE REGION OVERNIGHT,  
WITH AREAS OF FOG IN FAR NORTHEAST WI AND ON LAKE MICHIGAN, WHERE  
MARINE FOG IS ALREADY OCCURRING.  
 
THE WARM FRONT WILL LIFT INTO THE UPPER PENINSULA OF MICHIGAN  
ON FRIDAY, ENDING THE THREAT OF THUNDERSTORMS. THE RESULTING  
CLEARING AND GUSTY SOUTHWEST WINDS WILL LEAD TO STRONG HEATING,  
WITH MIXING THROUGH 900-875 MB SUPPORTING HIGH TEMPERATURES  
IN THE MIDDLE 80S TO LOWER 90S, MUCH ABOVE NORMAL.  
   
LONG TERM
 
FRIDAY NIGHT THROUGH THURSDAY  
ISSUED AT 258 PM CDT THU SEP 21 2017  
 
AN AMPLIFIED PATTERN WILL BE IN PLACE FOR THE CONUS UNTIL EARLY NEXT  
WEEK, THANKS TO A DEEP TROUGH OVER THE WESTERN U.S., AND A RIDGE  
OVER THE EAST. THE PATTERN DOES TRANSLATE EAST, WHICH WILL SIGNAL A  
PATTERN CHANGE BY THE MIDDLE OF NEXT WEEK ACROSS THE REGION.  
ALTHOUGH THERE ARE SOME TIMING DIFFERENCES IN REGARDS TO WHEN THIS  
PATTERN CHANGE OCCURS, MODELS ARE GENERALLY IN GOOD AGREEMENT THIS  
FAR OUT, SO WILL CONTINUE TO USE A MULTI MODEL BLEND FOR THIS  
FORECAST.  
 
FRIDAY NIGHT THROUGH SUNDAY...WITH A COLD FRONT NEARLY STATIONARY  
OVER MINNESOTA, AND A WARM FRONT EXTENDING EAST OVER LAKE SUPERIOR,  
THE ENTIRE REGION IS EXPECTED TO BE LOCATED IN THE WARM SECTOR  
DURING THIS PERIOD. WITH MOSTLY CLEAR CONDITIONS AND A BREEZY SOUTH  
WIND, TEMPERATURES WILL LIKELY RANGE FROM 15 TO 20 DEGREES ABOVE  
NORMAL. SATURDAY SHOULD BE WARMER THAN SUNDAY, WHEN A FEW 90S ARE  
POSSIBLE IN THE WARM SPOTS. HEAT INDICES IN THE LOW TO MID 90S ON  
SATURDAY WILL FALL BACK TO THE UPPER 80S ON SUNDAY.  
 
REST OF THE FORECAST...SUNDAY NIGHT CONTINUES TO LOOK QUIET AND  
WARM. THEN PRECIP CHANCES WILL GRADUALLY INCREASE FROM WEST TO EAST  
ON MONDAY AND TUESDAY WHEN A COLD FRONT DRIFTS CLOSER TO THE REGION.  
STORM CHANCES LOOK THE HIGHEST ON TUESDAY ALONG THIS FRONT, BUT ITS  
TOO EARLY TO ASSESS A SEVERE THREAT. MORE SEASONABLE TEMPS RETURN  
BEHIND THE FRONT FOR MIDWEEK.  

 
   
AVIATION
 
FOR 06Z TAF ISSUANCE  
ISSUED AT 1059 PM CDT THU SEP 21 2017  
 
PLENTY OF ISSUES JUST IN THE SHORT TERM MAKE THIS A LOW CONFIDENCE  
FORECAST. RAIN THAT MOST OF THE SYNOPTIC SCALE MODELS HAD REACHING  
THE AREA BY 06Z AT THE LATEST, HAS NOT YET DEVELOPED. HRRR HAD A  
FEW SPECS IN CENTRAL/NORTH CENTRAL WISCONSIN ON THE SIMULATED  
REFLECTIVITY PRODUCT, BUT JUST FOR A COUPLE OF HOURS AND THEN  
NOTHING MOVES IN UNTIL AROUND 14Z WHEN SHOWERS AND STORMS REACH  
VILAS COUNTY. IN THE MEAN TIME MOSTLY CLEAR SKIES PREVAILED, BUT  
DEW POINTS WERE WELL INTO THE 60S AND IT WILL NOT TAKE MUCH FOR  
TEMPERATURES TO DROP ENOUGH FOR FOG DEVELOPMENT. IFR/LIFR  
CONDITIONS IN DENSE FOG PREVAILED CLOSE TO LAKE MICHIGAN AND THE  
FOG COULD ADVECT FARTHER INLAND OVERNIGHT.  
 
WILL GO WITH MOSTLY MVFR AND/OR IFR CONDITIONS IN FOG AT MOST  
LOCATIONS OVERNIGHT. SOME LOW CEILINGS MAY ALSO DEVELOP. PLAN TO  
BRING SHOWERS AND STORMS IN DURING THE MORNING AND CONTINUE THEM  
EAST INTO THE AFTERNOON.  

 
   
GRB WATCHES/WARNINGS/ADVISORIES
 
 
DENSE FOG ADVISORY UNTIL 10 AM CDT FRIDAY FOR WIZ022-040-050.  

 
 

 
 
UPDATE.........MG  
SHORT TERM.....KIECKBUSCH  
LONG TERM......MPC  
AVIATION.......MG  
 
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