778  
FXUS63 KARX 261201  
AFDARX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LA CROSSE WI  
701 AM CDT TUE MAR 26 2019  
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 305 AM CDT TUE MAR 26 2019  
 
MAIN FORECAST CONCERNS FOR TODAY ARE ON AFTERNOON RELATIVE HUMIDITY  
VALUES.  
 
ANOTHER QUIET WEATHER DAY IS EXPECTED ACROSS THE REGION AS HIGH  
PRESSURE SLIDES OFF TO THE SOUTHEAST. MOISTURE WILL START TO MAKE A  
VERY SLOW RETURN TODAY AS SOUTH/SOUTHWEST WINDS DEVELOP. WILL LIKELY  
SEE LOW RELATIVE HUMIDITY VALUES AGAIN TODAY ALONG AND EAST OF THE  
MISSISSIPPI RIVER, WHERE READINGS ARE EXPECTED TO DROP INTO THE 15  
TO 25 PERCENT RANGE. HAVE LOWERED RH VALUES TODAY, ANTICIPATING THAT  
WE SHOULD SEE MIXING TO AROUND 850 MB. OTHERWISE, PLAN ON SOME  
PASSING HIGH CLOUDS THROUGH THE DAY. CLOUDS WILL INCREASE TONIGHT AS  
SOUTHERLY FLOW ADVECTS STRATUS INTO THE AREA. THE INCREASING WINDS  
AND CLOUD COVER SHOULD HELP KEEP LOW TEMPERATURES IN THE 30S.  
   
LONG TERM
 
(WEDNESDAY THROUGH MONDAY)  
ISSUED AT 305 AM CDT TUE MAR 26 2019  
 
AN UPPER SHORTWAVE TROUGH PASSING TO THE NORTH ACROSS CANADA WILL  
DRAG A COLD FRONT TOWARDS THE AREA ON WEDNESDAY AND SOUTH OF THE  
AREA BY THURSDAY MORNING. AHEAD OF THE FRONT, A THERMAL RIDGE  
AXIS WILL NOSE INTO SOUTHERN MN AND WESTERN WI ON WEDNESDAY WITH  
925 MB TEMPS PROGGED TO RISE TO 12-15C, WITH HIGHS LIKELY  
NEAR OR ABOVE THE 60 DEGREE MARK FOR MUCH OF THE AREA. SOUTHERLY  
WINDS WILL BECOME GUSTY WITH A TIGHTENING SURFACE GRADIENT WHILE  
MOISTURE TRANSPORT INCREASES WITH STRENGTHENING SOUTHWESTERLY 925-850  
MB FLOW.  
 
DESPITE BROAD MODEST MID-LEVEL HEIGHT FALLS/WARM ADVECTION THE  
STRONGER SYNOPTIC LIFT WILL REMAIN NORTH OF THE AREA WEDNESDAY INTO  
THURSDAY CLOSER TO THE UPPER TROUGH. COULD NOT RULE OUT A SHOWER OR  
TWO IN NORTHERN WI ON WEDNESDAY AS A SHORTWAVE SWINGS ACROSS THE  
US/CANADIAN BORDER. OTHERWISE, CHANCES ARE LOW FOR MUCH IN THE WAY  
OF PRECIP WITH THE FRONTAL PASSAGE, WITH PERHAPS A SHOWER  
WEDNESDAY NIGHT OVER NORTHEAST IA/SOUTHWEST WI IF MOISTURE IS DEEP  
ENOUGH. AS THE FRONT SINKS SOUTH OF THE REGION THURSDAY, HIGH  
PRESSURE WILL APPROACH FROM THE NORTHERN PLAINS WITH LOW-LEVEL  
COLD ADVECTION HELPING TO COOL TEMPS DOWN A TOUCH FROM WEDNESDAY.  
HOWEVER, WITH LOWS WEDNESDAY NIGHT HOLDING IN THE 30S TO MID 40S,  
HIGHS STILL SHOULD REACH THE UPPER 40S TO UPPER 50S.  
 
FRIDAY INTO SATURDAY, AN AMPLIFYING UPPER TROUGH DIGGING SOUTHWARD  
INTO THE UPPER MIDWEST WILL INTERACT WITH A SHORTWAVE TROUGH COMING  
OUT OF THE PLAINS. OVERALL, THERE'S PRETTY GOOD MODEL AGREEMENT  
THAT A SURFACE CYCLONE WILL RIDE NORTHEAST ALONG THE MID-LEVEL  
BAROCLINIC ZONE FROM THE SOUTHERN PLAINS INTO THE LOWER GREAT  
LAKES. MODEL CONSENSUS WOULD STILL FAVOR AREAS SOUTH OF I-90 FOR  
THE HIGHER PRECIP CHANCES FRIDAY INTO EARLY SATURDAY (AND HIGHEST  
AMOUNTS SOUTH OF THE AREA). HOWEVER, THERE REMAINS SOME MODEL  
SPREAD IN THE PLACEMENT OF THE LOW/NORTHWARD EXTENT OF PRECIP,  
LARGELY DUE TO DIFFERENCES IN THE DEGREE OF PHASING BETWEEN THE  
NORTHERN/STREAM WAVES. THE 26.00Z ECMWF CONTINUES TO SHOW A BIT  
MORE PHASING THAN THE GFS, AND CONSEQUENTLY IS STRONGER/FARTHER  
NORTH WITH THE SYSTEM. ON THE NORTHERN PERIPHERY OF THE SYSTEM,  
THERE MAY BE ENOUGH COLD AIR IN PLACE FOR SOME SNOW, ESPECIALLY  
FRIDAY NIGHT. WITH THE SPLIT FLOW NATURE OF THE SYSTEM, CONFIDENCE  
IN DETAILS IS TEMPERED THOUGH AT THIS TIME RANGE.  
 
AFTER THIS SYSTEM EXITS ON SATURDAY HIGH PRESSURE WILL BUILD IN  
UNDER NORTHWEST FLOW ALOFT THROUGH THE WEEKEND WITH COOL HIGH TEMPS  
IN THE 30S AND 40S.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)  
ISSUED AT 701 AM CDT TUE MAR 26 2019  
 
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. HIGH CLOUDS  
WILL MOVE ACROSS THE REGION TODAY THEN WE WILL SEE AN INCREASE IN  
LOWER CLOUDS FROM THE SOUTHWEST TONIGHT INTO WEDNESDAY MORNING.  
CLOUD BASES LOOK TO REMAIN VFR BUT CANNOT RULE OUT SOME MVFR  
CEILINGS AT TIMES AT KRST. LLWS IS EXPECTED LATE TONIGHT INTO  
WEDNESDAY MORNING AS WINDS INCREASE INTO THE 35 TO 45 KT RANGE  
AT 2 KFT.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 305 AM CDT TUE MAR 26 2019  
 
THE DRIER AIRMASS GRADUALLY SHIFTS SOUTHEAST OF THE REGION TODAY,  
BUT EXPECT ANOTHER DAY OF LOW RELATIVE HUMIDITY. PLAN ON AFTERNOON  
RH VALUES FALLING INTO THE 15 TO 25 PERCENT RANGE ALONG AND EAST OF  
THE MISSISSIPPI RIVER. SOUTH/SOUTHWEST WINDS ARE EXPECTED TO INCREASE  
TO 10 TO 20 MPH WITH GUSTS TO AROUND 30 MPH ON WEDNESDAY.  
HOWEVER, MOISTURE RETURNS TO THE AREA LATE TONIGHT INTO WEDNESDAY  
SO MIN RH VALUES ON WEDNESDAY SHOULD BE IN THE 40 TO 50 PERCENT  
RANGE. IF THE MOISTURE DOESN'T RETURN TO CENTRAL WISCONSIN, WE  
COULD SEE MIN RH VALUES DROP INTO THE 30S OR POSSIBLY THE UPPER  
20S.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 305 AM CDT TUE MAR 26 2019  
 
RIVER LEVELS WILL CONTINUE TO RISE THROUGH LATE WEEK AND THEREAFTER  
ALONG THE MISSISSIPPI WITH GENERALLY MINOR TO MODERATE FLOODING  
EXPECTED THROUGH THE WEEKEND. WITH CONTINUED SNOWMELT RUNOFF, MINOR  
TO MODERATE FLOODING WILL PERSIST ON SEVERAL MS RIVER TRIBUTARIES IN  
WISCONSIN, GENERALLY NORTH OF INTERSTATE 90 OVER THE NEXT FEW  
DAYS, WITH RIVER LEVELS EXPECTED TO SLOWLY FALL THROUGH LATE WEEK.  
MOSTLY DRY WEATHER IS FORECAST THROUGH THURSDAY, WITH THE NEXT  
SYSTEM FRIDAY INTO SATURDAY FORECAST TO BRING PRECIP TO AREAS  
MAINLY NEAR OR SOUTH OF I-90, WITH THE HEAVIEST PRECIP AMOUNTS  
CURRENTLY EXPECTED MAINLY SOUTH OF THE AREA.  
 

 
   
ARX WATCHES/WARNINGS/ADVISORIES
 
 
WI...NONE.  
MN...NONE.  
IA...NONE.  

 
 

 
 
SHORT TERM...WETENKAMP  
LONG TERM...JM  
AVIATION...WETENKAMP  
FIRE WEATHER...WETENKAMP  
HYDROLOGY...JM  
 
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