639  
FXUS63 KARX 180413  
AFDARX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LA CROSSE WI  
1113 PM CDT THU SEP 17 2020  
   
SHORT TERM
 
(THIS EVENING THROUGH FRIDAY)  
ISSUED AT 207 PM CDT THU SEP 17 2020  
 
ANOTHER QUIET DAY ACROSS THE REGION UNDER NORTHWEST FLOW ALOFT  
WITH SURFACE HIGH PRESSURE BUILDING IN. SATELLITE IMAGERY SHOWED  
SOME ADDITIONAL SMOKE MOVING INTO THE AREA, BUT EXPERIMENTAL HRRR  
INDICATED IT WOULD BE REMAINING ALOFT IN THE FORECAST AREA.  
 
OTHERWISE, THE MAIN ISSUE IN THE SHORT TERM IS THE COOLER  
TEMPERATURES AND FROST POTENTIAL TONIGHT. SKIES LOOK TO REMAIN  
CLEAR TONIGHT AS HIGH PRESSURE CONTINUES TO BUILD IN. THIS SETS UP  
FOR SOME PRETTY GOOD RADIATIONAL COOLING, WITH THE FAVORED COLD  
AREAS NEAR AND NORTH OF I-94 GETTING DOWN INTO THE LOWER 30S. A  
FROST ADVISORY HAS BEEN ISSUED FOR THOSE AREAS. EXPECT ANOTHER  
COOL, QUIET DAY ON FRIDAY, WITH HIGHS IN THE 50S AND 60S.  
   
LONG TERM
 
(FRIDAY NIGHT THROUGH THURSDAY)  
ISSUED AT 207 PM CDT THU SEP 17 2020  
 
EXPECT ANOTHER NIGHT WITH SOME FROST POTENTIAL IN THE FAVORED  
COLD AREAS FRIDAY NIGHT. OTHERWISE THE LONG TERM PERIOD STILL  
LOOKS PRETTY QUIET. HIGH PRESSURE WILL START PUSHING OFF TO THE  
EAST SATURDAY AS A TIGHTENING PRESSURE GRADIENT LEADS TO  
STRENGTHENING SOUTHERLY RETURN FLOW. BY SUNDAY, MODEL SOUNDINGS  
SHOW 35 TO 40 MPH WINDS AT THE TOP OF THE MIXED LAYER, SO WOULD  
EXPECT SOME FAIRLY GUSTY WINDS AT TIMES THROUGH THE WEEKEND,  
ESPECIALLY IN THE OPEN SPOTS. IN ADDITION TO THE SOUTHERLY FLOW,  
UPPER LEVEL RIDGING WILL BUILD IN, LEADING TO INCREASING  
TEMPERATURES INTO THE BEGINNING OF NEXT WEEK. EXPECT WIDESPREAD  
HIGHS IN THE 70S BY MONDAY OR TUESDAY FOLLOWED BY A FEW LOWER 80S  
ON WEDNESDAY.  
 
AS FAR AS PRECIPITATION CHANCES GO, MODELS CONTINUE TO TREND  
TOWARD THE DRY SIDE. A WEAK SURFACE BOUNDARY WILL APPROACH THE  
AREA FROM THE WEST SOMETIME SUNDAY INTO MONDAY, BUT GUIDANCE IS IN  
GOOD AGREEMENT OF ANY ASSOCIATED PRECIPITATION DISSIPATING AS IT  
MOVES IN, OWING TO DRY AIR IN THE LOWER LEVELS. ANOTHER BOUNDARY  
LOOKS LIKE IT MIGHT SLIDE THROUGH AND BRING SOME RAIN CHANCES  
SOMETIME WEDNESDAY OR THURSDAY PER SEVERAL GEFS MEMBERS AND THE  
17.00Z ECMWF. HOWEVER PLENTY OF OTHER GUIDANCE REMAINS DRY DURING  
THAT TIMEFRAME, SO CONFIDENCE IS QUITE LOW.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)  
ISSUED AT 1105 PM CDT THU SEP 17 2020  
 
VFR CONDITIONS THROUGH THE TAF PERIOD. SURFACE HIGH PRESSURE OVER  
THE UPPER MISSISSIPPI VALLEY WILL DRIFT TOWARD LAKE MICHIGAN  
DURING THE PERIOD. A PATCH OF MID-LEVEL CLOUDS WILL PUSH SOUTH,  
HOWEVER ADDITIONAL CLOUDS ARE FORECAST TO DEVELOP WESTWARD ACROSS  
WISCONSIN FL040-080. THERE IS NOT GOOD AGREEMENT ON THE COVERAGE  
PER SHORT RANGE MODELS AND FORECAST SOUNDINGS, SO FOR NOW WILL  
INCLUDED SCATTERED CLOUDS. NORTH WINDS UNDER 10 MPH WILL BECOME  
MORE EAST AND SOUTHEAST FRIDAY.  
 

 
   
ARX WATCHES/WARNINGS/ADVISORIES
 
 
WI...FROST ADVISORY UNTIL 8 AM CDT FRIDAY FOR WIZ017-029-034-042>044.  
 
MN...NONE.  
IA...NONE.  

 
 

 
 
SHORT TERM...CA  
LONG TERM...CA  
AVIATION...ZAPOTOCNY  
 
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