179
FXUS63 KDMX 200745
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
245 AM CDT TUE OCT 20 2026
KEY MESSAGES
- SEASONALLY WARM AND MOSTLY DRY CONDITIONS PERSIST THROUGH THE
WEEK.
- BREEZY CONDITIONS DEVELOP NORTH AND WEST FRIDAY AND SATURDAY.
- RAIN POTENTIAL (20 TO 30% CHANCE) RETURNS SATURDAY INTO
SATURDAY NIGHT, MAINLY OVER NORTHERN AND WESTERN IOWA.
SHORT TERM /THROUGH WEDNESDAY/
ISSUED AT 243 AM CDT TUE OCT 20 2026
- WARM TEMPERATURES AND DRY CONDITIONS CONTINUE THROUGH WEDNESDAY.
- BREEZY CONDITIONS ACROSS NORTHERN NORTHERN AND NORTHWEST IOWA
TUESDAY AFTERNOON.
- RAIN POTENTIAL (20 TO 30% CHANCE) RETURNS SATURDAY INTO
SATURDAY NIGHT, MAINLY OVER NORTHERN AND WESTERN IOWA.
CURRENT SYNOPTIC ANALYSIS PLACES A STRONG CANADIAN HIGH PRESSURE
NEAR THE GREAT LAKES, WHICH REMAINS THE PRIMARY DRIVER OF OUR
PERSISTENT DRY PATTERN. A FEW DIURNAL CLOUDS PRESENT EARLIER TODAY
HAVE CLEARED, SETTING UP STRONG RADIATIONAL COOLING OVERNIGHT.
EXPECT LOW TEMPERATURES THIS MORNING TO DIP INTO THE LOWER 40S, WITH
UPPER 30S POSSIBLE ACROSS NORTHERN IOWA. CURRENT GUIDANCE HINTS AT
PATCHY FOG DEVELOPMENT LATE TONIGHT; HOWEVER, DEW POINT DEPRESSIONS
REMAINING AROUND 2-3 DEGREES PAIRED WITH LIGHT 5-6 MPH SURFACE WIND
SHOULD KEEP BOUNDARY LAYER MIXING JUST SUFFICIENT ENOUGH TO LIMIT
WIDESPREAD DENSE FOG.
FOR TODAY, BOUNDARY LAYER MIXING AND DIURNAL HEATING WILL ALLOW
TEMPERATURES TO ONCE AGAIN CLIMB INTO THE UPPER 60S TO LOWER 70S.
THE PRIMARY FEATURE OF NOTE ACROSS NORTHERN IOWA, ESPECIALLY
NORTHWEST IOWA WILL BE TIGHTENING SURFACE PRESSURE GRADIENTS AS A
MID LEVEL SHORTWAVE DISTURBANCE TRAVERSES THE ROCKIES AND EMERGES
ONTO THE PLAINS. THIS WILL LEAD TO GUSTY SOUTHERLY WINDS REACHING UP
TO 20 MPH TUESDAY AFTERNOON. GUSTS WILL QUICKLY SUBSIDE TOWARD
SUNSET AS WE LOSE DIURNAL HEATING.
WEDNESDAY
AS WE SHIFT INTO WEDNESDAY, THE AFOREMENTIONED SHORTWAVE
DISTURBANCE WILL CONTINUE TO PROPAGATE EASTWARD ACROSS THE REGION.
MID-LEVEL MOISTURE ADVECTION AHEAD OF THE TROUGH AXIS WILL YIELD A
SLIGHT INCREASE IN CLOUD COVERAGE. WHILE A FEW GUIDANCE MEMBERS SHOW
LIGHT/SPOTTY SHOWERS ACROSS SOUTHWEST IOWA, SOUNDINGS REVEAL A
SUBSTANTIAL LAYER OF DRY AIR IN THE SUB-CLOUD LAYER. ANY
PRECIPITATION WILL STRUGGLE TO REACH THE GROUND DUE TO LOW LEVEL
EVAPORATION (VIRGA), KEEPING PRECIPITATION CHANCES BELOW 10%. WARM
AND DRY CONDITIONS WILL OTHERWISE PERSIST.
LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/
ISSUED AT 129 PM CDT MON OCT 19 2026
THE AFOREMENTIONED 500 MB RIDGING GENERALLY PERSISTS THROUGH THE
SECOND HALF OF THE WORK WEEK, KEEPING CONDITIONS DRY AND WARM
THROUGH AT LEAST THURSDAY. HOWEVER, AN APPROACHING NORTHERN STREAM
TROUGH LATE THIS WEEK WILL HELP RELEASE THE WESTERN CONUS CUTOFF LOW
THAT HAS BEEN BLOCKING OUR PATTERN THUS FAR. THIS AMPLIFIED
TROUGHING WILL PROGRESS EASTWARD INTO THE ROCKIES AND GREAT PLAINS
REGIONS THROUGH THE SECOND HALF OF THE WEEK, SHOVING THE RIDGE AND
COINCIDENT SURFACE HIGH OFF EASTWARD. THE AMPLIFIED FLOW PATTERN
WILL BRING A BETTER FETCH OF MOISTURE INTO AT LEAST THE WESTERN HALF
OF THE STATE FRIDAY INTO SATURDAY ALTHOUGH THE MAIN SURFACE LOW AND
BETTER SYNOPTIC FORCING GENERALLY STAYS NORTH AND WEST OF IOWA.
STILL, SOME RAIN/SHOWERS MAY DEVELOP ALONG THE TRAILING COLD FRONT
EXPECTED TO MOVE INTO IOWA SATURDAY INTO SATURDAY NIGHT. THESE RAIN
CHANCES AREN'T OVERLY HIGH (AROUND 20 TO 30% PER NBM) AND HEAVILY
FAVOR NORTHWESTERN IOWA GIVEN QUITE A BIT OF UNCERTAINTY WITH
HOW ROBUST THE BOUNDARY WILL BE SO FAR FROM THE PARENT LOW. EVEN
IF THE RAIN DOESN'T COME TO FRUITION, BREEZY CONDITIONS ARE
LIKELY TO DEVELOP FRIDAY AND SATURDAY WITH THE INCREASED
PRESSURE GRADIENTS, AGAIN OVER NORTHERN AND WESTERN IOWA. COOLER
TEMPERATURES BEGIN TO FILL IN SUNDAY INTO MONDAY, ALTHOUGH THE
MAGNITUDE OF COOLING WILL BE DEPENDENT ON HOW ROBUST THE COLD
FRONT IS ON SATURDAY.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 1023 PM CDT MON OCT 19 2026
VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD. WINDS REMAIN FROM
THE SOUTHEAST UNDER 10 KTS. VERY PATCHY FOG IS POSSIBLE IN
NORTHERN IOWA, HOWEVER DRY AIR WILL PREVENT MOST DEVELOPMENT AND
DID NOT INCLUDE AT THIS TIME.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...TDR
LONG TERM...DODSON
AVIATION...HAGENHOFF
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