207
FXUS63 KDMX 020617
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
117 AM CDT WED SEP 2 2026
KEY MESSAGES
- ONGOING THUNDERSTORMS ACROSS NORTHERN/NORTHWESTERN IOWA EARLY
THIS MORNING WILL CARRY A SLOWLY DIMINISHING SEVERE WEATHER
THREAT. ADDITIONAL THUNDERSTORMS ARE THEN FORECAST ACROSS
ROUGHLY THE NORTHWESTERN HALF OF IOWA WEDNESDAY NIGHT AND
THURSDAY MORNING, WITH A LOW SEVERE WEATHER THREAT.
- HEAT AND HUMIDITY WILL PERSIST ESPECIALLY ACROSS SOUTHERN AND
SOUTHEASTERN IOWA, WHERE A HEAT ADVISORY REMAINS IN EFFECT
THROUGH THURSDAY AFTERNOON. HEAT INDEX VALUES WILL PEAK NEAR
100 DEGREES EACH DAY.
- ADDITIONAL HEAT AND STORM CHANCES CONTINUE THROUGH THE END OF
THE WEEK INTO LABOR DAY WEEKEND.
SHORT TERM /THROUGH THURSDAY/
ISSUED AT 117 AM CDT WED SEP 2 2026
A LARGE 500 MB RIDGE LIES JUST TO OUR SOUTHEAST, SMOTHERING MUCH
OF THE COUNTRY IN A HEAT WAVE THAT HAS ALREADY AFFECTED PARTS OF
IOWA FOR THE LAST FEW DAYS. MEANWHILE, WEAK RIDGING EXTENDS UP
THE HIGH PLAINS, BUT IS BEING PENETRATED AND FLATTENED BY A
COUPLE OF SUBTLE SHORTWAVE IMPULSES. AT THE SURFACE, A WEAK
TROUGH EXTENDS FROM THE LEE OF THE COLORADO ROCKIES
NORTHEASTWARD TO NEAR THE SOUTH DAKOTA/IOWA/MINNESOTA
INTERSECTION. THIS IS PROVIDING A FOCUS MECHANISM FOR VIGOROUS
THUNDERSTORM DEVELOPMENT AT THE CURRENT TIME, WHICH IS BEING
AIDED BY ONE OF THE AFOREMENTIONED 500 MB IMPULSES AS WELL AS A
GRADUALLY STRENGTHENING NOCTURNAL LOW-LEVEL JET. AS THE IMPULSE
CONTINUES TO TRACK EASTWARD AWAY FROM OUR AREA, THE STORMS WILL
LIKELY LINGER IN OUR NORTHERN AND NORTHWESTERN COUNTIES
OVERNIGHT BUT WITH GRADUALLY DIMINISHING INTENSITY. SEVERE
WEATHER REMAINS POSSIBLE FOR SEVERAL HOURS BEFORE THAT OCCURS,
AND A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 5 AM
ACCORDINGLY. IT IS LIKELY THAT AT LEAST ISOLATED SHOWERS AND
THUNDERSTORMS WILL CONTINUE DRIBBLING NEAR THE BOUNDARY AFTER
SUNRISE TODAY, BUT AS THE LOW-LEVEL JET FADES OUT LATER THIS
MORNING AND WARMER AIR ALOFT REBUILDS INTO THE AREA WITH THE
EXPANDING RIDGE, LINGERING ACTIVITY SHOULD BE INCREASINGLY
SUPPRESSED AND HAVE LARGELY REMOVED RAIN CHANCES FROM THE
FORECAST FOR THIS AFTERNOON AND EVENING.
THE NEXT 500 MB SHORTWAVE WILL OVERTOP THE RIDGE IN THE HIGH
PLAINS LATER TODAY, IN WHAT WILL BE SOMEWHAT OF A REPEAT OF WHAT
HAS OCCURRED IN THE LAST SEVERAL HOURS. THUNDERSTORMS WILL ONCE
AGAIN GENERATE SOMEWHERE NEAR THE NEBRASKA/SOUTH DAKOTA BORDER
THIS EVENING, THEN TRACK ROUGHLY EASTWARD TOWARD SOUTHERN
MINNESOTA AND NORTHERN IOWA INTO THURSDAY MORNING BEFORE FADING
OUT AGAIN. HOWEVER, WITH THIS SECOND ROUND THE SHORTWAVE APPEARS
WEAKER AND FORCING FOR ASCENT IS MORE MODEST. ALSO, THE LOW-
LEVEL JET WEDNESDAY NIGHT WILL BE ORIENTED SOMEWHAT MORE TO OUR
WEST RATHER THAN PIVOTING DIRECTLY OVERHEAD. THE COMBINATION OF
THESE EFFECTS IS A REDUCED SEVERE WEATHER THREAT DURING THIS
TIME, HOWEVER, GIVEN THE INSTABILITY ALOFT AND GENERALLY
FAVORABLE DEEP-LAYER SHEAR PROFILES, A COUPLE OF STRONG TO
SEVERE STORMS CANNOT BE RULED OUT.
ASIDE FROM THUNDERSTORM AND SEVERE WEATHER CHANCES THE NEXT
COUPLE OF DAYS, THE OTHER PRIMARY WEATHER IMPACT IS A
CONTINUATION OF HEAT AND HUMIDITY THAT REALLY RAMPED UP ON
TUESDAY. GIVEN OUR CONTINUING PROXIMITY TO THE LARGE HEAT DOME
OVER THE OHIO/MISSISSIPPI RIVER VALLEYS, LITTLE RELIEF FROM THE
HEAT IS ANTICIPATED THROUGH THURSDAY - AT LEAST IN THE SOUTHERN
HALF OR SO OF IOWA. IN NORTHERN IOWA, LINGERING COLD POOL AND
CONVECTIVE CLOUD DEBRIS EFFECTS SHOULD BLUNT THE HEAT SOMEWHAT,
WITH HIGHS MORE IN THE MID TO UPPER 80S IN THAT AREA. FARTHER
SOUTH HOWEVER, HEAT INDEX VALUES ARE STILL EXPECTED TO PEAK NEAR
100 DEGREES EACH DAY WITH LITTLE OVERNIGHT RELIEF, AND THE HEAT
ADVISORY REMAINS IN EFFECT THROUGH THURSDAY.
LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/
ISSUED AT 300 PM CDT TUE SEP 1 2026
AS WE HEAD INTO THE END OF THE WORK WEEK AND LABOR DAY WEEKEND,
ADDITIONAL SHOWERS AND STORMS WILL BE POSSIBLE AGAIN THURSDAY NIGHT
INTO FRIDAY MORNING. HIGHS ON FRIDAY WILL ONCE AGAIN CLIMB INTO THE
LOWER 90S, COUPLED WITH OPPRESSIVE DEW POINTS IN THE 70S. THE
ONGOING HEAT ADVISORY MAY EVENTUALLY NEED TO BE EXTENDED THROUGH
FRIDAY. HOWEVER, WE OPTED TO HOLD OFF ON ANY EXTENSIONS WITH THIS
FORECAST PACKAGE DUE TO LINGERING UNCERTAINTY REGARDING THE
SOUTHWARD EXTENT OF FRIDAY MORNING CONVECTION. ADDITIONAL SHOWERS
AND THUNDERSTORMS CHANCES WILL REMAIN IN THE FORECAST THROUGH THE
WEEKEND, ALONGSIDE CONTINUED WARM HIGHS IN THE UPPER 80S AND LOWER
90S.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1237 AM CDT WED SEP 2 2026
KDSM RADAR PROFILES SHOW 0-2KFT WIND SHEAR IS ONGOING ACROSS CENTRAL
PARTS OF THE STATE ALREADY NEAR 30 KNOTS, AND MAY STRENGTHEN TO 35
OR 40 KNOTS IN THE NEXT SEVERAL HOURS BEFORE WEAKENING JUST BEFORE
SUNRISE. STORMS HAVE LARGELY AVOIDED THE TERMINALS THIS OVERNIGHT,
THOUGH KMCW PROBABILITIES STILL REMAIN AT OR JUST OVER 50%.
UNCERTAINTY REMAINS IN HOW MUCH STORM ACTIVITY LINGERS THROUGH THE
DAYTIME HOURS TOMORROW, WITH A FEW SOLUTIONS SHOWING SPOTTY WEAK
STORMS AT VARIOUS POINTS TOMORROW.
DMX WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY FROM 1 PM THIS AFTERNOON TO 7 PM CDT THURSDAY
FOR IAZ057-058-070-071-081-092.
HEAT ADVISORY UNTIL 7 PM CDT THURSDAY FOR IAZ059>062-072>075-
082>086-093>097.
SHORT TERM...LEE
LONG TERM...TDR
AVIATION...DE BRUIN
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