180  
FXUS63 KDMX 231137  
AFDDMX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DES MOINES IA  
637 AM CDT SAT OCT 23 2021  
   
..UPDATED FOR THE 12Z AVIATION DISCUSSION
 
 
   
DISCUSSION
 
/TODAY THROUGH FRIDAY/  
ISSUED AT 420 AM CDT SAT OCT 23 2021  
 
THE PRIMARY MESSAGING HIGHLIGHTS THROUGH THE PERIOD INCLUDE...  
 
* AREAS OF FOG AND FROST EARLY THIS MORNING  
* WET PERIOD OVERNIGHT THROUGH SUNDAY NIGHT WITH WIDESPREAD 1-2"  
RAINS CENTRAL AND SOUTH  
* SOME SEVERE WEATHER POTENTIAL OVERNIGHT AND AGAIN INTO PEAK HEATING SUNDAY  
* ANOTHER WINDOW WITH LOW CONFIDENCE RAIN CHANCES MIDWEEK  
 
THE CURRENT WEATHER IS HIGHLIGHTED BY AREAS OF FOG ALONG THE  
HIGHWAY 20 AND 30 CORRIDORS WITH LIGHT WINDS AND CLEAR SKIES,  
WHICH SHOULD SLOWLY DISSIPATE SHORTLY AFTER SUNRISE. THE FREEZE  
AND FROST HEADLINES WILL BE UNCHANGED, AND LIKELY THE LAST OF THE  
SEASON FOR CENTRAL AND NORTHERN SECTIONS DUE TO CLIMATOLOGY AND  
CURRENT TEMPERATURES VERIFYING WITH WIDESPREAD SUB-FREEZING TEMPS  
OVER THE NORTHERN HALF OF THE STATE, WHICH BASED ON TEMP/DEW  
SPREADS ALSO INCLUDES PLENTY OF FROST. FAIR WEATHER IS ANTICIPATED  
TODAY WITH SOME CLOUDS PRODUCED BY WARM ADVECTION ALOFT, AND A  
HINT OF WHAT'S TO COME LATER THIS WEEKEND.  
 
THE PRIMARY WEATHER CONCERNS WILL BE PRECIP AND CONVECTIVE TRENDS  
STARTING LATER TONIGHT. THE LOW LEVEL BAROCLINIC ZONE OF CONCERN  
WAS ALREADY PRODUCING THUNDERSTORMS FROM EASTERN KS INTO SOUTHERN  
MO, AND THIS IS EXPECTED TO SURGE NORTHWARD THROUGH THE DAY INTO  
TONIGHT WITH THE WARM FRONT ACROSS NORTHERN MO APPROACHING  
DAYBREAK SUNDAY. STRONG WARM AND MOIST ADVECTION DRIVEN BY  
40-50 KTS OF LOW LEVEL JET FLOW ALONG THE 300K ISENT SURFACE AND  
ITS ASSOCIATED CONVERGENCE NEAR 850MB IS EXPECTED TO BLOSSOM  
ELEVATED CONVECTION CENTRAL AND SOUTH. A FEW STRONG TO SEVERE  
STORMS, MAINLY WITH HAIL, WILL BE POSSIBLE WITH 40+ KTS OF  
EFFECTIVE SHEAR AND 100-200 M2/S2 ESRH AT TIMES AS WELL. ALTHOUGH  
THE HIGHEST RAINFALL SHOULD REMAIN JUST SOUTH OF THE BORDER CLOSER  
TO THE WARM FRONT, THIS MOISTURE TRANSPORT AND SEASONALLY HIGH  
PRECIPITABLE WATER VALUES MAY STILL PRODUCE MODERATE RAINFALL INTO  
SOUTHERN IA AT TIMES.  
 
THESE THERMODYNAMIC FORCING MECHANISMS WILL CONTINUE INTO SUNDAY  
AND BE AIDED BY ADDITIONAL KINEMATIC FORCING AS THE MO VALLEY  
SHORT WAVE AMPLIFIES. THERE IS STILL SOME UNCERTAINTY WHETHER THE  
WARM SECTOR WILL REACH IA WITH THE GFS/FV3 SUITE OF PARAMETERIZED  
AND CONVECTION ALLOWING GUIDANCE STILL SUGGESTING A BIT WARMER,  
FARTHER NORTH SOLUTION THAN ITS NMMB/ARW COUNTERPARTS. THERE WILL  
STILL BE A POTENTIAL FOR STRONG TO SEVERE STORMS, STILL MAINLY  
HAIL, ALONG AND AHEAD OF THE TRIPLE POINT THROUGH THE DAY AND  
POSSIBLY EARLY EVENING DUE TO CONTINUED HIGH VALUES OF EFFECTIVE  
SHEAR. THE GFS/FV3 SUITE WOULD SUGGEST THIS COULD BRIEFLY BECOME  
SURFACE BASED FAR SOUTH WITH A NON-ZERO WIND AND TORNADO POTENTIAL  
IN MORE FAVORABLE MLCAPE/CIN CONDITIONS. WHILE IT CANNOT BE RULED  
OUT, THE PRIMARY MESSAGING WILL STILL FOCUS ON THE HAIL POTENTIAL  
WHETHER IT BE ELEVATED OR SURFACE BASED. THIS EXTENDED PERIOD OF  
RAINFALL MAY ALSO LEAD TO WIDESPREAD 1-2" RAINS CENTRAL AND SOUTH  
BEFORE THE SYSTEM EXITS LATER SUNDAY NIGHT. THE LATEST RFC  
CONTINGENCY FORECASTS FROM YESTERDAY, WITH SIMILAR QPF  
EXPECTATIONS TO TODAY, SUGGEST NO RIVER FLOODING WITH JUST WITHIN  
BANK RISES. THE RAINFALL RATES AND WANING VEGETATIVE INFLUENCES  
WILL PRODUCE PLENTY OF SOGGY FIELDS, WATER RISES IN SMALL STREAMS,  
AND PONDING WATER HOWEVER. THE MATURING SURFACE LOW AT OR NEAR  
THE IA/MO BORDER WILL ALSO PRODUCE SOME GUSTY E/NE WINDS NORTH OF  
ITS TRACK ACROSS NORTHERN AND/OR CENTRAL IA LATER SUNDAY INTO  
EARLY MONDAY.  
 
AFTER A DRY START TO THE NEXT WORK WEEK, CONFIDENCE IS HIGH THAT  
THERE WILL BE ANOTHER PRECIP WINDOW OF SOME DEGREE TOWARD THE  
MIDDLE PORTIONS OF NEXT WEEK AS A LARGE LONG WAVE TROUGH  
APPROACHES THE WESTERN CONUS MONDAY AND A PV ANOMALY FROM ITS BASE  
REACHES THE CENTRAL OR SOUTHERN PLAINS MIDWEEK. DETERMINISTIC  
GUIDANCE IS IN POOR AGREEMENT WITH THE TIMING AND MERIDIONAL  
PLACEMENT SO THE CONFIDENCE IN THE PERIOD OF HIGHEST CHANCES AND  
RAINFALL MAGNITUDE IS LOW. THE TRACK OF THESE NEXT TWO SYSTEMS  
WILL ALSO BE UNFAVORABLE FOR MUCH OF A TEMP REGIME CHANGE KEEPING  
TEMPS NEAR SEASONAL VALUES THROUGH THE PERIOD.  
 

 
   
AVIATION
 
/FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING/  
ISSUED AT 637 AM CDT SAT OCT 23 2021  
 
ALTHOUGH IT HAD RECENTLY ERODED SOMEWHAT NE-SW, AREAS OF FOG AND  
STRATUS WERE STILL IN PLACE FROM KCIN TO JUST SOUTH AND WEST OF  
KDSM AT 12Z. CONFIDENCE IN TRENDS IS LOW IN THE SHORT TERM, BUT  
MOST TAF SITES ARE EXPECTED TO REMAIN VFR FOR THE NEXT FEW HOURS  
UNTIL VFR CONFIDENCE INCREASES LATER THIS MORNING THROUGH THE  
AFTERNOON. LATER TONIGHT, LOWERING CEILINGS AND CONVECTION ARE  
EXPECTED TO ADVANCE INTO IA FROM MO, WITH MVFR TO IFR TRENDS AT  
KDSM AND KOTM. THUNDER IS POSSIBLE AS WELL, BUT HAS NOT BEEN  
MENTIONED YET AT THIS LEAD TIME.  
 

 
   
DMX WATCHES/WARNINGS/ADVISORIES
 
 
FROST ADVISORY UNTIL 9 AM CDT THIS MORNING FOR IAZ057>062-  
070>075.  
 
FREEZE WARNING UNTIL 9 AM CDT THIS MORNING FOR IAZ004>007-  
015>017-023>028-033>039-044>050.  
 

 
 

 
 
DISCUSSION...SMALL  
AVIATION...SMALL  
 
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