410
FXUS63 KDMX 181803
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
103 PM CDT SUN OCT 18 2026
KEY MESSAGES
- SLOW WARMING TREND THIS WEEK, WITH HIGHS IN THE MID/UPPER 60S
TODAY AND MONDAY EVENTUALLY CLIMBING INTO THE MID/UPPER 70S
BY THURSDAY AND FRIDAY.
- THE FORECAST IS DRY THROUGH THE WORK WEEK, WITH RAIN CHANCES
RETURNING SOMETIME NEXT WEEKEND.
SHORT TERM /THROUGH TUESDAY NIGHT/
ISSUED AT 103 PM CDT SUN OCT 18 2026
A BROAD 500 MB RIDGE COVERS MOST OF THE CENTRAL AND SOUTHERN U.S.
TODAY, WITH A TROUGH PASSING BY FAR TO THE NORTH ACROSS CANADA
AND FLATTENING THE RIDGE A BIT OVER IOWA. MEANWHILE, A WEAK
SOUTHERN STREAM TROUGH IS CROSSING THE SOCAL/ARIZONA/FAR
NORTHWESTERN MEXICO REGION. AT THE SURFACE, A LARGE HIGH
PRESSURE AREA IS CENTERED ROUGHLY OVER THE OHIO RIVER VALLEY
WHILE A BROAD LOW PRESSURE TROUGH HAS DEVELOPED ALONG THE HIGH
PLAINS TO OUR WEST. THE PRESSURE GRADIENT BETWEEN THESE SYSTEMS
LIES ACROSS IOWA, RESULTING IN GUSTY SOUTHERLY BREEZES THIS
AFTERNOON. SKIES REMAIN CLEAR UNDER THE INFLUENCE OF THE 500 MB
RIDGE AND WITH GULF MOISTURE CUT OFF, WHILE DIURNAL MIXING IS
MAINTAINING LOW DEWPOINTS IN THE UPPER 30S. WITHIN THIS REGIME
TEMPERATURES ARE ONCE AGAIN OVERACHIEVING A BIT TODAY, AND ARE
LIKELY TO PEAK IN THE MID TO UPPER 60S THIS AFTERNOON.
TONIGHT, THE SURFACE TROUGH OVER THE HIGH PLAINS WILL GET
SQUEEZED OUT BY A SUCCEEDING HIGH PRESSURE AREA MOVING ALONG THE
U.S./CANADA BORDER. THIS WILL SLACKEN THE PRESSURE GRADIENT
OVER IOWA, ALONG WITH DIURNAL DECOUPLING, AND ALLOW OUR WINDS TO
DIMINISH AFTER SUNSET BUT NOT GO COMPLETELY CALM FOR THE MOST
PART. EVEN SO, WITH CLEAR SKIES OVERNIGHT RADIATIONAL COOLING
WILL ALLOW TEMPERATURES TO FALL INTO THE LOWER 40S IN MOST OF
OUR AREA BY SUNRISE MONDAY, AND A FEW SPOTS COULD DIP INTO THE
UPPER 30S. ON MONDAY THE NORTHERN SURFACE HIGH WILL MERGE WITH
THE OHIO RIVER VALLEY HIGH TO FORM AN EVEN LARGER RIDGE OVER
THE GREAT LAKES REGION THAT WILL DOMINATE THE SURFACE PATTERN
FOR A COUPLE OF DAYS. DURING THIS TIME, THE 500 MB SOUTHERN
STREAM TROUGH CURRENTLY OVER THE EXTREME SOUTHWESTERN U.S. WILL
BECOME SOMEWHAT DISCOMBOBULATED AS IT DRIFTS SLOWLY
NORTHEASTWARD TOWARD THE MIDWESTERN STATES. AS IT DOES SO, IT
WILL SPIT OUT SHREDS OF VORTICITY AND BRING INCREASED MOISTURE
ALOFT, RESULTING IN MID/HIGH LEVEL CLOUDS SPREADING OVER IOWA
FROM LATE MONDAY ONWARD. THESE MAY HAVE A SLIGHT DAMPENING
EFFECT ON TEMPERATURES, BOTH DAYTIME WARMING AND OVERNIGHT
COOLING, HOWEVER THE CLOUDS ARE LIKELY TO BE BOTH HIGH AND
GENERALLY THIN, MITIGATING THESE EFFECTS. MEANWHILE, A FEW
MODEL SOLUTIONS STILL TRY TO PUT OUT SPOTTY SPRINKLES OR LIGHT
SHOWERS, BUT FORECAST SOUNDINGS INDICATE A DEEP AND SUBSTANTIAL
DRY LAYER ABOVE THE SURFACE AND HAVE MAINTAINED POPS BELOW 10%
FOR NOW.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
ISSUED AT 103 PM CDT SUN OCT 18 2026
BETWEEN WEDNESDAY AND WEDNESDAY NIGHT THE WEAKENED 500 MB
TROUGH AXIS WILL FINALLY CROSS IOWA, BRINGING SOMEWHAT THICKER
MID/HIGH LEVEL CLOUDS. HOWEVER, THE TROUGH WILL BE LARGELY
WASHED OUT BY THAT TIME AND A DEEP NEAR-SURFACE DRY LAYER WILL
PERSIST, ONCE AGAIN REDUCING ANY RAIN CHANCES. THEREAFTER, A
HIGH-AMPLITUDE RIDGING PATTERN WILL BUILD ACROSS THE CENTRAL
U.S., WITH THE AXIS STRETCHING ALL THE WAY FROM MEXICO UP TO
HUDSON BAY BY THURSDAY EVENING. THIS WILL MAINTAIN DRY AND
NOTABLY WARMER WEATHER AT THE END OF THE WORK WEEK. BOTH
THURSDAY AND FRIDAY HIGH TEMPERATURES WILL LIKELY RANGE IN THE
MID TO UPPER 70S, AND A FEW AREAS COULD EVEN TOUCH 80 DEGREES.
BY FRIDAY, EVEN AS THE 500 MB RIDGE AXIS MOVES OVER IOWA, A
DEEP TROUGH WILL BUILD OVER THE WESTERN U.S. AND SUBSEQUENTLY
SLIDE NORTHEASTWARD INTO THE UPPER MIDWEST, SHUNTING THE
PRECEDING RIDGE SOUTHEASTWARD AND BRINGING A RETURN OF RAIN
CHANCES FOLLOWED EVENTUALLY BY A SURFACE TROUGH/COOL FRONT
THROUGH IOWA. WHILE THIS GENERAL SCENARIO IS LIKELY TO OCCUR,
LONG-RANGE MODELS STILL VARY CONSIDERABLY IN THE DETAILS OF THE
EVOLUTION, TIMING AND MAGNITUDE OF ANY RAIN CHANCES, STRENGTH
OF THE SURFACE TROUGH, ETC. AS SUCH, PERSISTENT LOW (20-30%)
RAIN CHANCES ARE FORECAST NEXT WEEKEND BUT IT IS LIKELY THESE
WILL EVENTUALLY NARROW TO A SHORTER PERIOD OF HIGHER POPS AS
CONFIDENCE IN TIMING INCREASES LATER THIS WEEK.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1221 AM CDT SUN OCT 18 2026
VFR CONDITIONS WILL CONTINUE FOR THE FORESEEABLE FUTURE. GUSTY
BREEZES THIS AFTERNOON WILL DIMINISH AROUND SUNSET AND BE LIGHT
FROM THE SOUTH TONIGHT THROUGH MONDAY.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...LEE
LONG TERM...LEE
AVIATION...LEE
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