764  
FXUS63 KARX 241112  
AFDARX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LA CROSSE WI  
612 AM CDT SUN OCT 24 2021  
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 254 AM CDT SUN OCT 24 2021  
 
MID TO HIGH CLOUDS HAVE OVERSPREAD THE AREA AHEAD OF A DEVELOPING  
SYSTEM OVER THE CENTRAL PLAINS. UPPER TROUGHING CROSSING THE ROCKIES  
CONTINUES TO SUPPORT A ~997MB SURFACE LOW PRESENTLY OVER CENTRAL  
KANSAS. A WARM FRONT EXTENDS EASTWARD FROM THIS SYSTEM, MARKING A  
TIGHT BAROCLINIC ZONE FROM MISSOURI INTO SOUTHERN OHIO. AS THIS  
SYSTEM MAKES HEADWAY TOWARD THE LOCAL AREA LATER TODAY INTO TONIGHT,  
THE MAIN FORECAST CONCERNS WILL BE RAINFALL AMOUNTS AND NORTHERN  
EXTENT, AS WELL AS INCREASINGLY GUSTY WINDS HEADING INTO TONIGHT.  
 
ENSEMBLE AND DETERMINISTIC (INCLUDING HI-RES) GUIDANCE HAS GENERALLY  
LOCKED ONTO THE RAIN SHIELD REACHING ROUGHLY AS FAR NORTH AS THE I-  
90 CORRIDOR LATER TODAY. THERE'S STILL SOME SLIGHT NORTH OR SOUTH  
VARIANCE, BUT THIS I-90 TREND HAS REMAINED FAIRLY CONSISTENT OVER  
THE LAST 24 HOURS. THAT'S THANKS TO A STRONG SURFACE HIGH SITTING  
OVER ONTARIO KEEPING DRIER MID-LEVEL AIR IN PLACE NORTH OF I-90.  
SYNOPTIC LIFT WILL BEGIN TO SPREAD RAIN NORTHWARD INTO OUR AREA  
TOWARDS MID-MORNING AS THE LOW LEVELS MOISTEN UP. RAINFALL WILL PICK  
UP MORESO THIS AFTERNOON AND EVENING AS FORCING IS ENHANCED BY MID-  
LEVEL FRONTOGENESIS LIFTING JUST NORTH IF I-90. RAIN CONTINUES INTO  
THE OVERNIGHT AS THE SURFACE LOW CUTS EAST ACROSS CENTRAL ILLINOIS,  
AND THEN THE PRECIP QUICKLY PEELS EAST LATE TONIGHT AS THE SYSTEM  
DEPARTS. RAIN SHOULD BE COMPLETELY OUT OF OUR AREA BY DAYBREAK  
MONDAY. LOOKS LIKE AROUND 0.5 TO 1.25" ACROSS NORTHEAST IA AND  
SOUTHWEST WI, WITH LESSER AMOUNTS NORTHWARD TO I-90.  
 
THE OTHER CONCERN WITH THIS SYSTEM WILL BE AN INCREASE IN WINDS THIS  
AFTERNOON AND EVENING. THE PRESSURE GRADIENT WILL BEGIN TO TIGHTEN  
ACROSS OUR SOUTH THIS AFTERNOON AS THE SURFACE LOW REACHES THE IA/MO  
BORDER. WHILE THE LOW DOESN'T LOOK TO BE DEEPENING MUCH BY THAT TIME  
ANYMORE, AS IT CROSSES THE MISSISSIPPI RIVER THIS EVENING HIGH  
PRESSURE TO THE NORTH WILL BUILD SOUTHWARD AROUND THE BACK SIDE OF  
IT, FURTHER TIGHTENING THE GRADIENT. 0-1KM LAPSE RATES LOOK TO BE  
SUPPORTIVE FOR SOME CONTINUED LOW LEVEL MIXING EVEN INTO THE  
OVERNIGHT, AS WINDS IN THE 925-900MB LAYER INCREASE TO 40-45 KNOTS  
ACROSS OUR SOUTH. EXPECTING GUSTINESS THIS EVENING WILL BE MORE TIED  
TO GRADIENT WINDS, BUT EVEN LIMITED MIXING WILL LIKELY SUPPORT  
ENOUGH DOWNWARD MOMENTUM FOR A FEW GUSTS JUST OVER 40 MPH IN OUR FAR  
SOUTH. SEVERAL EPS MEMBERS SUPPORT GUSTS OF THIS MAGNITUDE, BUT  
CERTAINLY 30 TO 40 MPH WILL BE MORE COMMON. SIDE NOTE: FV3 IS AN  
OUTLIER WITH ITS GUSTS OF 45-50 MPH IN OUR SOUTH, WHICH RESULTED  
IN 24.00Z HREF MEAN/MAX GUSTS LOOKING OVERDONE. THUS, NOT  
ANTICIPATING NEED FOR A WIND ADVISORY AT THIS TIME. PRESSURE  
GRADIENT AND WINDS LOOK TO GRADUALLY RELAX AFTER MIDNIGHT.  
   
LONG TERM
 
(MONDAY THROUGH SATURDAY)  
ISSUED AT 254 AM CDT SUN OCT 24 2021  
 
EXPECT A RETURN TO SUNSHINE MONDAY AND TUESDAY AS AMPLIFYING RIDGING  
ALOFT CROSSES THE REGION. FOCUS WILL BE ON A DEEP LONGWAVE TROUGH  
MAKING ITS WAY THROUGH WESTERN CONUS. A SPLIT FLOW PATTERN WILL  
DEVELOP ONCE IT CROSSES THE ROCKIES, WITH A NORTHERN STREAM  
SHORTWAVE CROSSING THE DAKOTAS BY WEDNESDAY AND A SOUTHERN STREAM  
WAVE MORPHING INTO A CLOSED LOW OVER THE SOUTHERN PLAINS. MAIN  
FORECAST CONCERN IS HOW THESE FEATURES EVENTUALLY INTERACT WITH EACH  
OTHER TOWARDS THE END OF THE WEEK. GUIDANCE SEEMS TO BE COMING INTO  
BETTER AGREEMENT FOR THE CUTOFF LOW TO DEEPEN/EXPAND AS IT CROSSES  
THE MISSISSIPPI RIVER BY FRIDAY. OUR AREA IS PROGGED TO BE ON THE  
NORTHERN/NORTHWESTERN PERIPHERY OF THIS SYSTEM AS IT WOBBLES OVER  
THE MIDDLE MISSISSIPPI VALLEY INTO APPALACHIA. A FAVORABLE PLUME  
OF MOISTURE WILL GRADUALLY WORK INTO THE AREA ON WEDNESDAY. LOOKS  
LIKE WE WILL BE IN FOR AN UNSETTLED PERIOD LATE IN THE WEEK AS  
PERSISTENT SYNOPTIC FORCING INTERACTS WITH THIS MOISTURE, BUT  
CONFIDENCE IN SPECIFIC DETAILS REMAINS LOW. WEDNESDAY NIGHT  
THROUGH FRIDAY IN PARTICULAR LOOKS LIKE THE WETTEST PERIOD AT THIS  
TIME. TEMPERATURES WILL REMAIN NEAR OR JUST BELOW SEASONAL  
NORMALS WITH HIGHS IN THE 50S.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)  
ISSUED AT 612 AM CDT SUN OCT 24 2021  
 
MAIN TAF CONCERNS ARE THE POSSIBILITY OF MVFR CONDITIONS AT BOTH  
RST/LSE TAF SITES THIS AFTERNOON INTO TONIGHT. SURFACE LOW WILL MOVE  
INTO THE CENTRAL PLAINS STATES TODAY INTO TONIGHT AND SPREAD  
RAIN/STRATUS DECK OF CLOUDS INTO THE AREA. WITH A DRY AIRMASS ALONG  
AND NORTH OF INTERSTATE 90...THIS WILL INHIBIT ANY RAIN AND STRATUS  
DECK NORTH OF INTERSTATE 90. AT THIS TIME...VFR CONDITIONS WILL  
PREVAIL AT BOTH RST/LSE TAF SITES THROUGH THE PERIOD. HOWEVER...IF  
SURFACE LOW TRACKS SLIGHTLY FURTHER NORTH THAN WHAT IS  
FORECAST...THEN LOWER CEILINGS WILL MOVE OVER THE TAF SITES THIS  
AFTERNOON INTO TONIGHT AND POSSIBLY BE MVFR TO IFR. AS SURFACE LOW  
DEEPENS OVER THE CENTRAL PLAINS STATES...WINDS WILL INCREASE AND  
POTENTIALLY GUSTS UP 25 KNOTS AT TAF SITES THIS AFTERNOON INTO  
TONIGHT.  
 

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

 
 

 
 
SHORT TERM...KURZ  
LONG TERM...KURZ  
AVIATION...DTJ  
 
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