432  
FXUS63 KARX 200351  
AFDARX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LA CROSSE WI  
1051 PM CDT TUE OCT 19 2021  
   
SHORT TERM
 
(THIS EVENING THROUGH WEDNESDAY)  
ISSUED AT 154 PM CDT TUE OCT 19 2021  
 
HIGH PRESSURE CONTINUES IT'S REIGN OF TODAY'S SENSIBLE WEATHER WITH  
CLEAR SKIES AND UNSEASONABLY WARM TEMPERATURES. THE NATIONAL BLEND  
HAS BEEN HAVING A DIFFICULT TIME WITH SURFACE WARMING STRENGTH THE  
PREVIOUS FEW DAYS, AND HAVE SUBSEQUENTLY USED 90TH PERCENTILE MAX  
TEMPS FOR TODAY, WHICH LINES UP WITH HOW YESTERDAY'S MAX TEMPS  
PANNED OUT CONTAINING SIMILAR CONDITIONS.  
 
PRECIPITATION CHANCES BEGIN TOMORROW AS A CLOSED LOW CROSSES THE  
NORTHERN PLAINS. INITIAL PRECIPITATION CHANCES EARLY TOMORROW  
MORNING SEEM TO BE ELEVATED AND SHOWERY IN NATURE AS ISENTROPIC  
ASCENT RAMPS UP WITHIN THE WARM CONVEYOR BELT DOWNSTREAM OF THE LOW  
CENTER. THE NEXT CHANCE OF PRECIPITATION TOMORROW OCCURS DURING THE  
AFTERNOON AS THE LOW CENTER GETS DRY SLOTTED AND A NORTH-SOUTH BAND  
OF INSTABILITY WORKS ITS WAY ACROSS OUR FORECAST AREA. AS THIS  
HAPPENS AND THE LOW WRAPS ITSELF UP, A MID-LEVEL FRONTOGENETICAL  
DEFORMATION BAND SOAKS NORTH OF THE LOW CENTER, NORTH OF INTERSTATE  
94. THE THIRD AND FINAL PRECIPITATION CHANCE FOR OUR FORECAST AREA  
OCCURS TOMORROW NIGHT AS THE DEFORMATION BAND SWEEPS BEHIND THE LOW.  
 
SEVERE THREAT REMAINS LOW WITH A STOUT 800 MB CAP INHIBITING ANY  
SURFACE-BASED CAPE FOR MOST OF OUR AREA. THE BEST INSTABILITY OCCURS  
IN THE AFTERNOON, WITH MUCAPE VALUES NEAR 1000 J/KG IN BOTH THE RAP  
& NAM, ALONG A NORTH-SOUTH MISSISSIPPI RIVER BASED BAND. OVERALL,  
SMALL SEVERE THREAT REMAINS FOR POTENTIAL MARGINAL 1" HAILERS.  
PRECIPITATION AMOUNTS REMAIN 0.25"-0.50" FROM SOUTH TO NORTH WITH  
HIGHER AMOUNTS POSSIBLE WITHIN POTENTIAL MESOSCALE BANDING.  
   
LONG TERM
 
(WEDNESDAY NIGHT THROUGH TUESDAY)  
ISSUED AT 154 PM CDT TUE OCT 19 2021  
 
THE LOW CONTINUES EAST WEDNESDAY NIGHT WITH THE MAIN DEFORMATION  
RAIN BAND ALONG I-94, AND LOWERING RAIN CHANCES SOUTHWARD. THE  
RAIN WILL TAKE MUCH OF THE NIGHT TO CLEAR AND THIS IS A SLOWER  
EXIT THAN PREVIOUSLY FORECAST. BY SUNRISE THURSDAY, THE RAIN  
SHOULD BE ENDING IN CENTRAL WI.  
 
THE JUST-BELOW NORMAL AIR MASS THEN MOVES INTO THE AREA THROUGH  
SATURDAY WITH FROSTS/FREEZES LIKELY ACROSS MUCH OF THE AREA. THERE  
IS PRETTY GOOD AGREEMENT ON A STRONGER SHORTWAVE TROUGH /CURRENT  
WAVE OFF WEST COAST/ SHIFTING THROUGH THE NORTHWEST FLOW AND  
BRINGING IN SOME MID- LEVEL CLOUD LATE THURSDAY NIGHT WHICH MAY  
HINDER LOWS THAT MORNING FROM GETTING TOO COLD. BUT, SATURDAY  
MORNING SHOULD BE COLDER WITH CLEAR SKIES EXPECTED OVERNIGHT. AN  
END TO THE GROWING SEASON IS EXPECTED THIS WEEKEND IN MANY AREAS.  
 
STRONGER WARM ADVECTION AND MOISTURE TRANSPORT FROM THE SOUTH  
SHIFT IN FOR SUNDAY RAIN CHANCES. THE DETERMINISTIC ECMWF  
SOLUTIONS THE LAST 12 HOURS ARE AN OUTLIER DRY SOLUTION VERSUS  
THEIR ENSEMBLE AND ALSO THE GEFS MEMBERS. ABOUT 40% OF THE MEMBERS  
IN THE 19.00Z EC ENS RAIN SUNDAY AND IT IS A HIGHER NUMBER IN THE  
19.00Z GEFS. THE 19.00Z GEFS IS CERTAINLY THE NORTHERN OUTLIER ON  
THE MOISTURE SURGE'S NORTHWARD EXTENT. THE RAIN CHANCES CONTINUE  
INTO SUNDAY NIGHT.  
 
AS THE CONUS LONG WAVE PATTERN BECOMES MORE AMPLIFIED AGAIN WITH  
WEST COAST TROUGHING, EARLY NEXT WEEK LOOKS LIKE IT SHOULD BRING  
ABOVE NORMAL TEMPERATURES AFTER MONDAY.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)  
ISSUED AT 1051 PM CDT TUE OCT 19 2021  
 
VFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THIS COMING  
AFTERNOON, THEN RAINFALL AND ACCOMPANYING LOWER CEILINGS RETURN BY  
THE EVENING.  
 
EXACT TIMING OF THE INITIAL BAND OF SHOWERS IS UNCERTAIN, BUT  
CONFIDENCE INCREASES LATER IN THE DAY AS SHOWERS ARE ANTICIPATED TO  
BECOME MORE WIDESPREAD AROUND 18Z. THERE IS A CHANCE FOR  
THUNDERSTORMS, BUT WAS NOT CONFIDENT ENOUGH TO INCLUDE IN THE TAF AT  
THIS TIME. AT KRST, MVFR CEILINGS BECOME MORE LIKELY TOWARDS THE END  
OF THE FORECAST PERIOD AFTER 00Z. WINDS WILL BE FROM THE SOUTH INTO  
THE EARLY MORNING HOURS, FROM THE WEST THROUGH THE AFTERNOON, AND  
THEN BECOME MORE NORTHERLY AFTER 00Z REMAINING AROUND 10 KNOTS  
OR LESS.  
 

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

 
 

 
 
SHORT TERM...JAR  
LONG TERM...BAUMGARDT  
AVIATION...PETERS  
 
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