933
FXUS63 KDMX 051148
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
648 AM CDT SAT SEP 5 2026
...UPDATED FOR THE 12Z AVIATION DISCUSSION...
KEY MESSAGES
- PATCHY FOG OVER MUCH OF NORTHERN/NORTH-CENTRAL IOWA THIS
MORNING, WITH POCKETS OF ISOLATED DENSE FOG AT TIMES.
- HOT AND HUMID CONDITIONS CONTINUE THROUGH TODAY, WITH A HEAT
ADVISORY IN EFFECT FOR MUCH OF SOUTHERN AND CENTRAL IOWA UNTIL
THIS EVENING. TEMPERATURES LOWER SLIGHTLY SUNDAY/MONDAY,
REDUCING OVERALL HEAT IMPACTS SOMEWHAT.
- VERY LOW POTENTIAL (<15%) FOR A FEW ISOLATED STORMS IN
NORTHWEST IOWA TODAY, OTHERWISE DRY. MORE WIDESPREAD SHOWERS
AND THUNDERSTORMS POSSIBLE ON SUNDAY, WITH A LOW POTENTIAL FOR
SEVERE WEATHER.
SHORT TERM /THROUGH SUNDAY NIGHT/
ISSUED AT 302 AM CDT SAT SEP 5 2026
PATCHY FOG HAS DEVELOPED ACROSS PORTIONS OF NORTHERN AND NORTH-
CENTRAL IOWA THIS MORNING, WITH LOCALIZED AREAS OF DENSE FOG THAT
HAS BEEN MORE TRANSIENT IN NATURE OVER THE LAST HOUR OR TWO. THE
CONTINUATION OF LIGHT WINDS AND MOSTLY CLEAR SKIES WILL LIKELY ALLOW
FOR FURTHER DEVELOPMENT OF THIS FOG GENERALLY NORTH OF HIGHWAY 30
THROUGH SUNRISE, BEFORE DISSIPATING. WHILE MOST OF THIS FOG IS
EXPECTED TO BE PATCHY, THERE IS A POSSIBILITY FOR INCREASED COVERAGE
OF DENSE FOG GIVEN THE AFOREMENTIONED CONDITIONS, SO WILL BE
MONITORING THIS CLOSELY. BESIDES THE FOG, A SHORTWAVE PASSING
THROUGH THE DAKOTAS WITHIN THE PERSISTENT BROAD MID-LEVEL RIDGE
OVERHEAD, PAIRED WITH AN INCREASING LOW LEVEL JET AND DEEP MOISTURE
CONVERGENCE HAS LED TO THUNDERSTORM DEVELOPMENT OVER EASTERN SOUTH
DAKOTA, WHICH IS LIFTING NORTHEAST. THIS SHORTWAVE WILL GRADUALLY
SHIFT INTO MINNESOTA THROUGH THE DAY, WITH SHOWERS AND STORMS
EXPECTED TO CONTINUE DURING THE MORNING AND INTO THE AFTERNOON.
GENERAL CONSENSUS VIA CAM GUIDANCE AND MOST DETERMINISTIC MODELS
INDICATE THIS ACTIVITY STAYING NORTH AND WEST OF IOWA TODAY, THOUGH
A FEW MODELS TRY TO EXPAND COVERAGE INTO NORTHWEST IOWA BY LATE
MORNING INTO THE AFTERNOON. A CLOSER LOOK AT SOUNDINGS FEATURE HIGH
INSTABILITY VALUES AROUND 4000-5000 J/KG AND STEEP LAPSE RATES
AROUND 7.5-8 C/KM, BUT WITH GENERALLY WEAK FLOW AND LOW LEVEL DRY
AIR, AS WELL AS A LACK OF FORCING OVERHEAD. IF STORMS CAN MAKE IT
INTO IOWA AND ARE ABLE TO MAINTAIN THEMSELVES, THE PRIMARY CONCERN
WOULD BE GUSTY WINDS. HAVE LEANED TOWARD THE DRIER SOLUTIONS, BUT
WILL MONITOR TRENDS ON RADAR IN CASE AN INCREASE IN POPS IS NEEDED
INTO NORTHWEST IOWA. ONE MORE DAY OF THE OPPRESSIVE HEAT AND
HUMIDITY IS ANTICIPATED TODAY AS THE HEAT DOME REMAINS NEARBY, WITH
FORECAST HIGHS EXPECTED TO TOP OUT IN THE LOW TO MID 90S ACROSS MUCH
OF IOWA, WHERE A HEAT ADVISORY REMAINS IN EFFECT UNTIL THIS EVENING.
ANOTHER SHORTWAVE WITHIN THE THERMAL RIDGE IS ANTICIPATED TO TRAVEL
IN CLOSER PROXIMITY TO IOWA LATE TONIGHT AND ESPECIALLY SUNDAY, WITH
LOW LEVEL MOISTURE TRANSPORT INCREASING OUT OF THE SOUTHEAST INTO
THE STATE THAT WILL POOL AGAINST AN ARRIVING BOUNDARY INTO WESTERN
IOWA. SHOWERS AND THUNDERSTORMS ARE EXPECTED AS A RESULT TO DEVELOP
AND INCREASE IN COVERAGE THROUGH THE DAY. A RIBBON OF INSTABILITY
AROUND 1000-2000+ J/KG OVER WESTERN IOWA, ALONG WITH SHEAR VALUES
AROUND 25-35 KNOTS SUGGEST AT LEAST AN ISOLATED POTENTIAL FOR STRONG
TO SEVERE STORMS WITH THIS ACTIVITY INTO THE AFTERNOON. DAMAGING
WINDS AGAIN WOULD BE THE PRIMARY POTENTIAL HAZARD, THOUGH PWATS NEAR
2 INCHES AND WARM CLOUD DEPTHS COULD ALSO LEAD TO LOCALIZED AREAS OF
HEAVY RAINFALL. ANOTHER FEATURE TO NOTE AT THE SAME TIME IS AN AREA
OF SURFACE HIGH PRESSURE OVER THE UPPER MIDWEST THAT IS FORECAST TO
SINK FURTHER SOUTH, WITH ITS INFLUENCE LOOKING TO INCLUDE PORTIONS
OF EASTERN IOWA. THIS KEEPS CHANCES OF SHOWER/STORM ACTIVITY IN
THESE AREAS LOWER, WHERE ANY CHANGES IN EXPECTED LOCATION OF THIS
FEATURE, SUCH AS A FURTHER EASTERN SHIFT COULD INCREASE SHOWER AND
STORM COVERAGE OVER IOWA, SO SOMETHING TO CONTINUE WATCHING. THICKER
CLOUD COVER OVERHEAD AND THE SHOWER/STORM ACTIVITY WILL AID TO KEEP
TEMPERATURES NOTICEABLY COOLER THAN IN RECENT DAYS, WITH FORECAST
HIGHS EXPECTED IN THE 80S THAT WILL ESSENTIALLY END THE LONG STREAK
OF HEAT HEADLINES, AT LEAST FOR A SHORT TIME.
LONG TERM /MONDAY THROUGH FRIDAY/
ISSUED AT 234 PM CDT FRI SEP 4 2026
EARLY NEXT WEEK THE WESTERN US TROUGH WILL DEEPEN AND ORGANIZE,
PUSHING EAST. THIS WILL CREATE AN OPPORTUNITY FOR MORE ORGANIZED
CONVECTION EARLY IN THE WEEK WITH INCREASED SHEAR AND UPPER LEVEL
SUPPORT ACROSS THE AREA. THE MAIN COOL FRONT ASSOCIATED WITH THE
SYSTEM PUSHES ACROSS IOWA TUESDAY AND WEDNESDAY, BRINGING
TEMPERATURES DOWN A FEW DEGREES BY LATE WEEK.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 648 AM CDT SAT SEP 5 2026
PATCHY FOG WITH ISOLATED AREAS OF LOCALLY DENSE FOG ARE ONGOING
THIS MORNING, ESPECIALLY IMPACTING KMCW, WHICH SHOULD GRADUALLY
IMPROVE OVER THE NEXT FEW HOURS AS THIS FOG DISSIPATES.
MONITORING IS ALSO ONGOING OF A CLUSTER OF STORMS OVER NORTHWEST
IOWA, WITH A LOW POTENTIAL OF TRACKING E/SE INTO PORTIONS OF
NORTH/CENTRAL IOWA THROUGH THE MORNING. CONFIDENCE IS NOT HIGH
THAT THIS ACTIVITY WILL HOLD TOGETHER, SO HAVE NOT INCLUDED
SPECIFICALLY INTO THE TERMINALS AT THIS TIME BUT MAY NEED TO
AMEND KFOD AND KMCW FOR INCLUSION IF THESE STORMS CAN HOLD
TOGETHER. VFR CONDITIONS OTHERWISE SHOULD RETURN FOR ALL SITES
BY MID-MORNING, WITH LIGHT WINDS OUT OF THE E/SE TODAY. MORE
WIDESPREAD FOG IS SIGNALED ACROSS NORTH/EAST IOWA INTO SUNDAY,
SO HAVE INCLUDED AT LEAST 6SM BR AT KALO, KMCW, AND KOTM AND
WILL ADJUST TIMING AND POTENTIAL VISIBILITY RESTRICTIONS IN
FUTURE ISSUANCES AS NEEDED.
DMX WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR IAZ033>039-
044>050-057>062-070>075-081>086-092>097.
SHORT TERM...BURY
LONG TERM...HAGENHOFF
AVIATION...BURY
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