009
FXUS63 KDMX 300747
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
247 AM CDT SAT MAY 30 2026
KEY MESSAGES
- BREEZY WITH SCATTERED, INTERMITTENT SHOWER CHANCES OF 30 TO
50% OVER WESTERN INTO CENTRAL IOWA TODAY. EMBEDDED
THUNDERSTORMS ARE ALSO POSSIBLE WITH THIS MOST LIKELY IN
WESTERN AND SOUTHERN IOWA. SEVERE WEATHER IS NOT FORECAST.
- LOCALLY HEAVY RAINFALL AND ISOLATED FLASH FLOODING POSSIBLE
LATE THIS AFTERNOON INTO TONIGHT OVER SOUTHERN IOWA AND
NORTHERN MISSOURI.
- CHANCES FOR SEVERE STORMS EXIST ON SUNDAY IN WESTERN IOWA,
THOUGH POTENTIAL IS LOW AT THIS TIME.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 247 AM CDT SAT MAY 30 2026
WHILE TWENTY FOUR HOURS LATER THE UPPER LEVEL PATTERN REMAINS IN AN
OMEGA BLOCK, FEATURES HAVE PROGRESSED TO VARYING DEGREES THIS
MORNING. THE POTENT SHORTWAVE TROUGH OVER SOUTHEASTERN CANADA HAS
MOVED OVER THE NORTHERN APPALACHIANS THIS MORNING. THE PLUME OF GULF
MOISTURE ON GOES-EAST UPPER LEVEL WATER VAPOR IMAGERY HAS SHIFTED
FARTHER NORTHEAST, THOUGH ONLY ABOUT 100 MILES OR SO IN THE 850 AND
925MB RAP ANALYSIS, WITH THE SHORTWAVE ENERGY ARRIVING OVER THE
STATE. AN AREA OF SHOWERS ON THE FRINGE OF THIS LOW LEVEL MOISTURE
GRADIENT IS SHIFTING INTO MINNESOTA THIS MORNING WHILE ANOTHER BAND
OF SHOWERS AND STORMS HAS DEVELOPED OVER SOUTHWESTERN IOWA INTO
NORTHWESTERN MISSOURI. THESE STORMS ARE IN AN AIRMASS WITH HIGHER
INSTABILITY AND PRECIPITABLE WATER (PWAT) VALUES. HOWEVER, THERE IS
A LACK OF SHEAR SO THE ONLY HAZARD WILL BE LIGHTNING EARLY THIS
MORNING.
AS THESE SLOWLY LIFT NORTHEASTWARD INTO CENTRAL IOWA THROUGH THE
MORNING, THE INSTABILITY LOOKS TO LAG BEHIND THROUGH EARLY AFTERNOON
STAYING MOSTLY SOUTHWEST OF DES MOINES PER LATEST HREF 1 HOUR
PROBABILITY OF THUNDER. EVEN AS THESE SHOWERS AND THE EMBEDDED
STORMS LIFT NORTHEASTWARD, THEY WILL BE SCATTERED AND FIGHTING
AGAINST DRIER AIR OVER EASTERN IOWA. IN FACT, PARTS OF OUR EASTERN
AND NORTHEASTERN FORECAST AREA, SUCH AS MASON CITY AND WATERLOO, ARE
UNLIKELY TO SEE ANY RAINFALL UNTIL SOMETIME SUNDAY. WHILE
INSTABILITY MAY BUILD OVER SOUTHWESTERN IOWA TO BETWEEN
1000-2000 J/KG, THE DEEP LAYER SHEAR IS UNREMARKABLE SO SEVERE
STORMS ARE NOT FORECAST. THAT SAID, THE ENVIRONMENT HAS SOME
REMINDERS OF A FUNNEL CLOUD SETUP WITH LOW CLOUD BASES, 0-3KM
MIXED LAYER CAPE OF 75 TO 150 J/KG PER CRESTON RAP SOUNDING, AND
WEAK SHEAR. A LACKING PIECE IS NO APPARENT WIND SHIFT OR
SURFACE BOUNDARY.
THE CONCERN AS WE HEAD THROUGH LATE THIS AFTERNOON INTO TONIGHT WILL
BE LOCALLY HEAVY RAINFALL AND THE POTENTIAL FOR FLASH FLOODING. THE
AIRMASS WILL BE ONE OF THE JUICER ONES SO FAR THIS YEAR WITH
PRECIPITABLE WATER VALUES WELL ABOVE NORMAL AND NEARING THE 90TH
PERCENTILE WITH SEASONALLY DEEP WARM CLOUD DEPTHS FOR EFFICIENT RAIN
PROCESS. THESE COMBINED WITH STORM MOTIONS OF AROUND 10 TO 15 MPH
POINT TO LOCALIZED AREAS OF HEAVY RAINFALL. INITIALLY, STORMS WILL
HAVE NEBULOUS FORCING, WHICH IS WHEN THE CONCERN MAY BE HIGHEST FOR
FLASH FLOODING DUE TO THE SLOW STORM MOTIONS. AS STRONGER SHORTWAVE
ENERGY LIFTS OVER THE REGION LATE THIS EVENING INTO THE OVERNIGHT, A
BAND OF STORMS IS FORECAST TO SWEEP THROUGH PORTIONS OF IOWA THAT IS
MORE PROGRESSIVE. RAINFALL BULLSEYES BY SUNDAY MORNING OF 3 TO 5
INCHES ARE SHOWN IN THE 0Z HRRR, WRF-ARW, AND REGIONAL CANADIAN OVER
FAR SOUTH CENTRAL IOWA, THE 0Z RRFS (FV3 CORE) OVER SOUTHWESTERN
IOWA, THE 0Z GFS/FV3 OVER SOUTHWEST IOWA INTO NORTHWESTERN MISSOURI,
AND THE 0Z RRFS (MPAS CORE) OVER NORTH CENTRAL MISSOURI ALONG WITH
THE 0Z NAMNEST, WHICH HAS AMOUNTS OVER 10 INCHES IN THAT AREA. THE
0Z HREF, WHICH IS INFLUENCED BY THE NAMNEST, SHOWS A SIMILAR
FOOTPRINT OVER NORTH CENTRAL INTO NORTHWESTERN MISSOURI WHILE THE 0Z
RRFS ENSEMBLE IS SPLIT BETWEEN POCKETS IN SOUTHERN IOWA AND NORTHERN
MISSOURI. WHILE MUCH OF IOWA HAS DRY SOILS PER NASA SPORT 0-10CM AND
10-40CM LAYERS GENERALLY AT THE 20TH PERCENTILE OR LOWER, THERE
REMAINS A MORE SUSCEPTIBLE AREA IN FAR SOUTH CENTRAL IOWA FROM RAINS
AROUND MAY 18 THAT IS IN THE 30TH TO 70TH PERCENTILE NOT TO
MENTION ANY AREAS THAT MAY BE PRIMED THIS MORNING OVER SOUTHWEST
IOWA. WITH THESE LESS DRY SOILS LINING UP WITH MODELED AREAS OF
HEAVY RAINFALL NOT TO MENTION HIGH RAIN RATES, FLASH FLOODING
IS POSSIBLE OVER SOUTHERN IOWA TONIGHT AND IS WITHIN THE
MARGINAL RISK OF EXCESSIVE RAINFALL. IF CONFIDENCE GROWS AND
NARROWS IN ON A MORE TARGETED AREA OF HEAVY RAINFALL, A FLOOD
WATCH MAY BE NECESSARY.
LONG TERM /SUNDAY THROUGH FRIDAY/
ISSUED AT 256 PM CDT FRI MAY 29 2026
SOME CONSENSUS IS COMING INTO VIEW ON SUNDAY'S SYNOPTIC PATTERN,
THOUGH CONVECTIVE EVOLUTION IS STILL HIGHLY VARIABLE ACROSS THE MID-
RANGE CAMS. THE WESTERN TROUGH WILL FINALLY PIVOT NORTHEAST OVER THE
HIGH PLAINS, WITH WAVES OF ENERGY PERHAPS FAR ENOUGH EAST TO
INFLUENCE STORMS IN IOWA SUNDAY. LEE CYCLOGENESIS TO THE WEST AND
ASSOCIATED SOUTHERLY FLOW WILL LIKELY ADVECT IN A WARM SECTOR WITH
UPPER 60S AND 70S DEWPOINTS. EPS/GEFS ENSEMBLES SHOW IOWA ON THE
EDGE OF MEANINGFUL 500 MB FLOW IN THE EXIT REGION OF THE TROUGH,
MEANING IMPROVED SHEAR MAY BE IN PLACE, THOUGH IT CERTAINLY ISN'T A
GUARANTEE. LATEST GEFS RUNS HAVE 50% CHANCE OF SUPERCELL COMPOSITES
>5 IN SOUTHERN IOWA. SPC NOW HAS A MARGINAL RISK IN WESTERN IOWA AS
A RESULT OF THESE TRENDS, AND SOME OF THE MACHINE LEARNING GUIDANCE
SUGGESTS LOW END SEVERE PROBABILITIES. CONVECTIVE EVOLUTION IN
NEBRASKA/KANSAS WILL BE IMPORTANT FOR SORTING OUT DETAILS FOR OUR
STORM CHANCES SUNDAY, AND CAMS SHOW TOO MUCH UNCERTAINTY TO DISCUSS
AT THIS TIME.
BY EARLY AND MID WEEK, ENSEMBLES SHOW SOME AGREEMENT THAT THE
WESTERN TROUGH WILL CONTINUE TO LIFT OUT TO THE NORTHEAST, AND
CENTRAL US RIDGING/EASTERN TROUGHING WILL HOLD THEIR POSITIONS. IF
THE LIFTING TROUGH CAN PULL MOISTURE ACROSS IOWA AND OVERCOME THE
DRY AIRMASS SITTING UNDER THE EASTERN TROUGHING/GREAT LAKES HIGH
PRESSURE, SCATTERED STORM CHANCES WILL CONTINUE THROUGH THE MID-
WEEK.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 1053 PM CDT FRI MAY 29 2026
SPOTTY LIGHT SHOWERS CONTINUE ACROSS CENTRAL IOWA THIS EVENING
AND ARE EXPECTED TO GRADUALLY LIFT NORTH AND DIMINISH OVER THE
NEXT FEW HOURS. SCATTERED SHOWERS REDEVELOP IN WESTERN IOWA BY
MORNING, SPREADING ACROSS CENTRAL IOWA THROUGH SATURDAY. THE
SCATTERED NATURE OF THE PRECIPITATION REMAINS A CHALLENGE FOR
TAFS, AS DOES TIMING. EXPECT MOST ACTIVITY TO MISS KMCW/KALO AND
HAVE KEPT FROM THOSE SITES. AT KDSM/KFOD/KOTM HAVE TRIED TO
TIME MOST LIKELY WINDOW FOR SCATTERED SHOWERS. A FEW RUMBLES OF
THUNDER ARE POSSIBLE, WITH BETTER CHANCES TOWARDS KOTM, BUT
CONFIDENCE IS TOO LOW AT THIS TIME AND HAVE KEPT TO -SHRA AT
THIS TIME.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...ANSORGE
LONG TERM...DE BRUIN
AVIATION...HAGENHOFF
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