056
FXUS63 KDMX 121140
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
640 AM CDT SUN JUL 12 2026
...UPDATED FOR THE 12Z AVIATION DISCUSSION...
KEY MESSAGES
- WARM AND DRY CONDITIONS TODAY THROUGH AT LEAST MID-WEEK. HIGHS
IN THE UPPER 80S AND 90S THIS WEEK.
- SHALLOW, PATCHY FOG POSSIBLE EARLY THIS MORNING AND AGAIN
MONDAY MORNING.
SHORT TERM /THROUGH TUESDAY/
ISSUED AT 254 AM CDT SUN JUL 12 2026
A RATHER STAGNANT WEATHER PATTERN IS IN STORE OVER THE NEXT SEVERAL
DAYS. HEAT WILL CONTINUE TO INCREASE AND PRECIPITATION CHANCES
REMAIN LOW THROUGH THIS PERIOD. THE H500 RIDGE CONTINUES TO BUILD
ACROSS THE ROCKY MOUNTAIN WEST, POSITIONING US UNDER OVERALL
WEAK FLOW AS THE MAIN JET STREAM IS BEING ROUTED UP AND OVER THE
BUILDING RIDGE INTO CANADA. SURFACE HIGH PRESSURE WILL CONTINUE
TO BUILD THIS MORNING, AND SHOULD BRING IN WEAK AND A
RELATIVELY DRY AIRMASS. THIS AND HEIGHT RISES HAVE CLEARED OUT
ANY ATTEMPTS AT CLOUD COVER THIS MORNING. THE MOST PRESSING NEAR
TERM CHALLENGE IS WHETHER TO EXPECT ANY RADIATION FOG AS WE
APPROACH SUNRISE. IT APPEARS THE CALM WINDS AND CLEAR SKIES MAY
BE COUNTERED BY QUITE SHALLOW MOISTURE. FOG MAY STILL BE
POSSIBLE FOR A SHORT TIME AROUND SUNRISE, BUT IT IS EXPECTED TO
BE PATCHY AT BEST. SIMILAR CONDITIONS WILL RETURN SUNDAY NIGHT.
THE PATTERN OVER THE NEXT THREE DAYS HAS VERY LITTLE VARIATION. THE
SURFACE HIGH STALLS OVER IOWA WHILE THE THERMAL RIDGE BUILDS OVER
THE DAKOTAS. SFC-850MB FLOW WILL CONTINUE TO BE WEAK, MEANING
ADVECTION IS MINIMAL AND WE WILL JUST BE MODIFYING THE SAME AIRMASS
EACH DAY. 850MB TEMPS WILL BE SLIGHTLY WARMER TODAY, AND AGAIN ON
MONDAY, BUT THE WARMER >25C TEMPS LOOK TO REMAIN WEST AND NORTH OF
IOWA, SPARING US FROM A TRUE HEAT WAVE, AT LEAST FOR NOW. STILL, THE
AMPLE SUNSHINE IS EXPECTED TO WARM THE TEMPERATURES A COUPLE DEGREES
MORE EACH DAY. NBM SUGGESTS HIGHS JUST BELOW 90 TODAY, 89-92
TOMORROW, AND 91-94 TUESDAY.
FOR THE SAKE OF HEADLINE DISCUSSION, IT IS WORTH DIVING INTO
HUMIDITY EXPECTATIONS AS WELL. THE LETHARGIC SYNOPTIC PATTERN
WON'T DO MUCH TO ADVECT MORE OR LESS MOISTURE INTO IOWA, AND
AFTERNOON TDS WILL BECOME ALMOST ENTIRELY DEPENDENT ON MIXING,
SOIL MOISTURE, AND EVAPOTRANSPIRATION (ET). CORN IS NEARING
MATURITY AND ET IS BECOMING MORE SIGNIFICANT EACH DAY, WHICH MAY
KEEP DEWPOINTS AT LEAST IN THE 60S EACH DAY ACROSS MOST OF
IOWA. SECONDLY, NASA SPORT SHOWS SOIL MOISTURE IS HIGHEST ACROSS
NE IOWA WITH SOME POCKETS INTO SE IOWA. IT WILL BE MOST
FAVORABLE TO RETAIN LOW TO MID 70S TDS IN THESE AREAS (LOWER
BOWEN RATIOS) AND DIRECTLY BENEATH THE SFC HIGH WHERE TURBULENCE
IS LOWEST FOR OVERALL LESS MIXING OUT. THESE TDS WOULD BE HIGH
ENOUGH TO ADJUST THE APPARENT TEMPS UP A FEW DEGREES, BUT THIS
WILL BE COUNTERED BY DECREASED HEATING IN THESE AREAS. BY
TUESDAY WE MAY BE AT BORDERLINE HEADLINE CRITERIA, PARTICULARLY
IN EASTERN IOWA, BUT UNCERTAINTY IN HUMIDITY WILL MAKE THIS A
LATER DECISION.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
ISSUED AT 225 PM CDT SAT JUL 11 2026
THE WARM AND HUMID CONDITIONS GENERALLY STICK AROUND THROUGH THE
REMAINDER OF THE WEEK, ALTHOUGH THE INFLUENCE OF THE SURFACE HIGH
AND UPPER RIDGING BEGINS TO WEAKEN THROUGH THE SECOND HALF OF THE
WORK WEEK. AN AMPLIFIED CANADIAN TROUGH WILL BEGIN TO PUSH THE 500
MB RIDGE BACK WESTWARD, PUTTING IOWA ON THE PERIPHERY BETWEEN THE
NORTHWEST FLOW TO OUR NORTHEAST AND RIDGING TO OUR WEST. AT THE
SURFACE, THIS WILL EQUATE TO A MESSY SURFACE PATTERN WITH WEAK HIGH
PRESSURE OVERHEAD AND LOW PRESSURE TO OUR WEST, FAVORING SOUTH
SOUTHWESTERLY FLOW. THIS TRANSITION WILL TAKE PLACE WEDNESDAY AND
THURSDAY, ULTIMATELY NOT RESULTING IN MUCH NOTICEABLE CHANGE AT THE
SURFACE ASIDE FROM CONTINUED WARMING BOTH DAYS. HIGHS ARE EXPECTED
TO REACH THE MID-90S WITH DEWPOINTS AROUND 70, PUSHING HEAT INDICES
INTO THE UPPER 90S AND NEAR 100F. WITH THE WEAKENING HIGH,
SUBSIDENCE ALSO WON'T BE AS STRONG AND THE POTENTIAL FOR DIURNALLY-
DRIVEN THUNDERSTORMS COULD CREEP BACK INTO THE FORECAST THROUGH THE
SECOND HALF OF THE WEEK. WITH THE LACK OF ANY PROMINENT SYSTEMS,
GUIDANCE AND NBM ARE STRUGGLING TO RESOLVE THIS, BUT A SIGNAL DOES
EXIST WHEN LOOKING AT THE LONGER RANGE MODELS. THERE'S OF COURSE NO
SHORTAGE OF INSTABILITY THIS TIME OF YEAR BUT THE FLOW IN THIS
REGIME SHOULD BE FAIRLY WEAK, SO THE SEVERE RISK APPEARS LOW AT THIS
TIME. WITH THE LOW UNCERTAINTY, THE FORECAST REMAINS DRY THROUGH
MID-WEEK, BUT WILL BE SOMETHING TO WATCH FOR AS WE GET CLOSER.
AVIATION /12Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 637 AM CDT SUN JUL 12 2026
ASIDE FROM PATCHY FOG CURRENTLY CLEARING OUT ACROSS THE STATE, VFR
CONDITIONS PREVAIL TODAY THROUGH TONIGHT. THE FOG THIS MORNING WAS
RATHER ISOLATED, BUT STILL RESULTED IN BRIEF LIFR CONDITIONS AT
KMCW. SIMILAR CONDITIONS MAY BE IN PLACE TOMORROW MORNING, BUT
CONFIDENCE IS TOO LOW TO INCLUDE IN THIS ISSUANCE.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...DE BRUIN
LONG TERM...DODSON
AVIATION...DE BRUIN
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