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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