640
FXUS63 KDMX 030324
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1024 PM CDT SUN AUG 2 2026
...UPDATED FOR THE 06Z AVIATION DISCUSSION...
KEY MESSAGES
- DRY CONDITIONS THROUGH MONDAY WITH HIGHS IN THE 80S.
- FOG POSSIBLE IN EASTERN AND SOUTHEAST IOWA TONIGHT INTO MONDAY
MORNING.
- WIDESPREAD THUNDERSTORM CHANCES TUESDAY AND WEDNESDAY WITH A
SLIGHT RISK OF EXCESSIVE RAINFALL.
SHORT TERM /THROUGH TUESDAY NIGHT/
ISSUED AT 251 PM CDT SUN AUG 2 2026
HIGH PRESSURE DOMINATED THE WEATHER THIS AFTERNOON AND WILL KEEP
CONDITIONS DRY AND WINDS LIGHT. HIGHS THIS AFTERNOON WILL BE IN THE
LOW 80S WITH PLENTY OF SUN. FOG WILL MAKE A RETURN TONIGHT AND BE
MAINLY SHALLOW, BUT WILL FILL IN MORE IN THE EAST AND SOUTHEAST.
PLACES LIKE OTTUMWA MAY SEE SOME REDUCTIONS IN VISIBILITY FOR
THE MONDAY MORNING COMMUTE. LIGHT WINDS WILL BE REPLACED BY
STEADY SOUTHERLY FLOW MONDAY AFTERNOON. HIGHS WILL RETURN TO THE
MID AND UPPER 80S IN THE SOUTH AND WEST THROUGH TUESDAY.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
ISSUED AT 251 PM CDT SUN AUG 2 2026
A COLD FRONT WILL TRAIL ALONG A NEGATIVELY TILTED UPPER WAVE NEAR
THE US-CANADA BORDER AND HAS TRENDED SLOWER TO EXIT OVER IOWA. HEAVY
RAIN IS THE MAIN CONCERN AS PWATS RISE ABOVE 1.5" AND FLOW POINTS
PARALLEL TO THE FRONT'S ORIENTATION. WHILE CAPE TOTALS OVER 1000
J/KG BOTH TUESDAY AND WEDNESDAY AFTERNOON, THE SATURATION OF THE
PROFILE KEEPS LAPSE RATES CLOSER TO THE MOIST ADIABAT, PRESENTING AN
ELONGATED AND SKINNY CAPE PROFILE. UNIFORM PARCEL ACCELERATION WILL
FAVOR HEAVY RAIN OVER HAIL AND THE WEAK SHEAR PROFILE WILL MAKE ANY
WET MICROBURST POTENTIAL IN STORMS RELATIVELY SHORT-LIVED. THE
SEVERE WEATHER RISK IS LOW FOR THESE REASONS ON BOTH DAYS, BUT A
MARGINAL AND SLIGHT RISK ERO HAVE BEEN ISSUED. RAINFALL WILL PEAK IN
THE EVENING AND OVERNIGHT HOURS WITH DETERMINISTIC RUNS ALL PAINTING
A BAND OF 2"+ IN NORTHERN AND CENTRAL IOWA. GIVEN PRESENT CONVECTIVE
PROCESSES HIGHLIGHTED ABOVE, WOULD NOT BE SURPRISED IF LOCALIZED
AMOUNTS OVER 5" ARE REALIZED. AMOUNTS WILL BE BETTER UNDERSTOOD AS
THE SYSTEM ENTERS THE CAM WINDOW.
FOR HYDROLOGY IMPACTS, SOIL MOISTURE IN NORTHERN AND NORTHWEST IOWA
IS LOW (5-20%) AND CAN TAKE THE MOST RAIN. NATIONAL WATER MODEL
SIMULATIONS USING GFS QPF HAVE MOST OF THE RIVER RESPONSES IN
EASTERN IOWA WHERE ANTECEDENT CONDITIONS ARE COMPARATIVELY MORE
WET. ONLY THE HIGH-END BASIN QPF OUTPUTS BRING BASINS SUCH AS
THE CEDAR INTO FLOOD STAGE, SO THE CHANCE FOR THIS IS LOW (5%).
FOR FLASH FLOOD POTENTIAL, IOWA IS IN PEAK CROP MATURITY WHICH
FURTHER DIMINISHES CONCERNS FOR RURAL PARTS OF THE STATE.
CONCERNS INCREASE IF THE AXIS OF HEAVY RAIN FALLS ON AN URBAN
AREA.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 1021 PM CDT SUN AUG 2 2026
FOG REMAINS A CHALLENGE FOR THE OVERNIGHT FORECAST WITH THE
GREATEST POTENTIAL REMAINING AT KOTM. KALO MAY HAVE PATCHES OF
FOG AS WELL AND WILL CONTINUE TO MONITOR. CUMULUS WILL DEVELOP
AGAIN ON MONDAY AND THERE REMAINS A CHANCE FOR A PERIOD OF BKN
MVFR CIGS BELOW 3 KFT. THE WIND WILL INCREASE FROM THE
SOUTH/SOUTHEAST WITH A FEW SITES IN NORTHERN IOWA INCLUDING KMCW
REACHING SUSTAINED 12 KTS WITH GUST NEAR 20 KTS DURING THE
AFTERNOON HOURS.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...JIMENEZ
LONG TERM...JIMENEZ
AVIATION...DONAVON
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