671
FXUS63 KDMX 302340
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
640 PM CDT SAT MAY 30 2026
...UPDATED FOR THE 00Z AVIATION DISCUSSION...
KEY MESSAGES
- BREEZY WITH SCATTERED, INTERMITTENT SHOWERS THROUGH THIS
AFTERNOON. IF NEW ACTIVITY CAN DEVELOP, A FEW THUNDERSTORMS
ARE ALSO POSSIBLE IN MAINLY WESTERN AND SOUTHERN IOWA THIS
EVENING. MORE WIDESPREAD STORMS MOVE THROUGH OVERNIGHT. A FEW
GUSTY WINDS ARE POSSIBLE OVERNIGHT, BUT SEVERE WEATHER IS NOT
FORECAST.
- LOCALLY HEAVY RAINFALL AND ISOLATED FLASH FLOODING ARE
POSSIBLE INTO TONIGHT OVER SOUTHERN IOWA AND NORTHERN
MISSOURI.
- CONDITIONAL THREAT FOR STRONG TO SEVERE STORMS ON SUNDAY, IN
MAINLY WESTERN IOWA, THOUGH POTENTIAL IS LOW AT THIS TIME.
SHORT TERM /THROUGH SUNDAY NIGHT/
ISSUED AT 239 PM CDT SAT MAY 30 2026
UPPER LEVEL PATTERN CONTINUES TO FEATURE AN OMEGA BLOCK BUT BOTH THE
EASTERN AND WESTERN UPPER LOWS UNDERGO SOME AMOUNT OF NORTHERLY
MOVEMENT OVER THE NEXT FEW DAYS. THIS STILL LARGELY KEEPS UPPER
RIDING OVER THE CENTRAL U.S. BUT A LEE SIDE SURFACE LOW WILL DEVELOP
AND MOVE NORTHWARD INTO THE DAKOTAS INTO SUNDAY. HAVE CONTINUED TO
SEE SHOWERS LIFT NORTHWARD INTO EARLY THIS AFTERNOON AFTER THEY
DEVELOPED THIS MORNING WITH ADDITIONAL ACTIVITY DEVELOPING IN
ESPECIALLY PORTIONS OF NORTH CENTRAL INTO EASTERN IOWA ALONG THE
THETA-E GRADIENT. SHEAR CONTINUES TO BE WEAK WITH THE MAIN AREA OF
INSTABILITY IN SOUTHWEST IOWA SO LARGELY EXPECTING ANY OF THIS
DEVELOPING ACTIVITY TO BE MAINLY SHOWERS WITH THE ONLY HAZARD
LIGHTNING FOR THE MOST PART, WHICH GIVEN WHERE THE MAIN INSTABILITY
AXIS IS AND THESE SHOWERS ARE DEVELOPING, IS ON THE LOWER SIDE TOO.
HOWEVER, AS NOTED IN THE PREVIOUS DISCUSSION, THE NON-SUPERCELL
TORNADO PARAMETER IS PICKING UP ON AN AREA IN MAINLY WESTERN IOWA
WHERE AROUND 100 J/KG OF 0-3 CAPE OVERLAPS WITH SURFACE VORTICITY
WHICH COULD POTENTIALLY LEAD TO THE DEVELOPMENT OF A FEW FUNNEL
CLOUDS THOUGH AGAIN SHEAR IS QUITE WEAK AND THERE IS NO NOTABLE
BOUNDARY. WILL CONTINUE TO MONITOR THIS CLOSELY THROUGH THE
REST OF THE AFTERNOON HOURS.
AS WE GET INTO TONIGHT, THERE CONTINUES TO BE DISAGREEMENT BETWEEN
THE CAMS AND GLOBAL MODELS ON NEW SHOWERS/STORMS THAT CAN DEVELOP
AHEAD OF AN EXPECTED APPROACHING MCS WHICH LOOKS TO REACH FAR
SOUTHWEST IOWA AROUND 06Z. ALTHOUGH CANNOT RULE OUT A FEW GUSTY
WINDS IN FAR WEST/SOUTHWEST IOWA AS THIS MCS ARRIVES, IT WILL
ENCOUNTER A MORE STABLE ENVIRONMENT SO THE EXPECTATION IS THE LINE
OF STORMS WILL WEAKEN AS THEY CROSS AND MOVE THROUGH IOWA OVERNIGHT.
HOWEVER, AS ALSO NOTED IN THE PREVIOUS DISCUSSION, IT MAY BE ABLE TO
MAINTAIN A HEAVY RAIN THREAT WITH PWAT VALUES BETWEEN 1.5 TO 2" IN
SOUTHERN IOWA AND FAVORABLE WARM CLOUD DEPTHS. SEVERAL GUIDANCE
SOURCES CONTINUE TO SUGGEST AN AREA OF 1-2" WITH AN EVEN MORE HIGHLY
LOCALIZED AREA OF 2-4". WITH THE OVERNIGHT ACTIVITY, THESE HIGHEST
RAIN TOTALS LOOK TO BE IN NORTHERN MISSOURI WITH THE SLIGHTLY
LIGHTER AMOUNTS INTO SOUTHERN IOWA. PRIOR TO THAT, CENTERED AROUND
THIS EVENING, THE NAMNEST, HRW NSSL AND TO A LESSER DEGREE ARW ALL
KICK OFF EXCEPTIONAL RAIN TOTALS WITH ANY STORMS THAT CAN
DEVELOP IN SOUTHERN TO SOUTHWEST IOWA PRIOR TO THE MCS. WILL
AGREE THAT ANYTHING THAT CAN DEVELOP AHEAD OF THE MCS WOULD
STILL BE IN AN ENVIRONMENT FOR EFFICIENT RAINFALL AND WOULD BE
SLOW MOVING, WHAT REMAINS MORE UNCLEAR IF THERE IS ENOUGH
FORCING TO KICK OFF THESE NEW SHOWERS/STORMS (OTHER THAN THE
AREAS ALREADY DISCUSSED ABOVE). WITH THIS UNCERTAINTY,
CONFIDENCE WAS NOT HIGH ENOUGH TO ISSUE A FLOOD WATCH THOUGH
AREAS IN ESPECIALLY TAYLOR AND RINGGOLD COUNTIES ARE ESPECIALLY
PRIMED GIVEN HEAVY RAINFALL A COUPLE WEEKS AGO AND IN TAYLOR
COUNTY, THIS MORNING. WPC MAINTAINED THE MARGINAL RISK (LEVEL 1
OF 4) FOR EXCESSIVE RAINFALL GIVEN THE POSSIBILITY FOR HEAVY
RAIN AND LOCALIZED FLASH FLOODING TO OCCUR WHICH WAS SUPPORTED
LOCALLY AND WITH NEIGHBORING OFFICES GIVEN THE ENVIRONMENT BUT
UNCERTAINTY IN STORM DEVELOPMENT AND COVERAGE. WILL CONTINUE TO
MONITOR THE HYDRO THREAT INTO THIS EVENING AS WELL.
BEHIND THE DEPARTING MCS ON SUNDAY, THE MESOSCALE DETAILS REMAIN
MORE UNCERTAIN WITH ADDITIONAL STORM DEVELOPMENT. SPC MAINTAINED THE
MARGINAL RISK (LEVEL 1 OF 5) FOR SEVERE WEATHER OVER THE SOUTHWEST
HALF OF THE STATE BUT REMOVED THE SLIGHT (LEVEL 2 OF 5) IN WESTERN
IOWA WITH THE OVERALL SETUP CONDITIONAL. IF STORMS CAN DEVELOP,
LARGE HAIL AND STRONG WINDS COULD BE POSSIBLE IN A STRONG TO SEVERE
STORM, AS WELL AS ADDITIONAL HEAVY RAIN, WITH WEAK, BUT OVERALL
BETTER SHEAR THAN TODAY AND PLENTY OF INSTABILITY. HOWEVER,
SOUNDINGS LOOKED CAPPED WITH MIDLEVEL DRY AIR THROUGH A GOOD PORTION
OF THE DAY AND THERE ISN'T A DISCERNIBLE MECHANISM TO KICK OFF
NEW ACTIVITY EITHER THUS RELIANT ON ANY FEATURES LEFT FROM THE
MCS OVERNIGHT.
IT WILL BE WARM AND MUGGY IN THE 70S TO 80S WITH DEW POINTS IN
THE 50S TO 60S THROUGH SUNDAY.
LONG TERM /MONDAY THROUGH SATURDAY/
ISSUED AT 239 PM CDT SAT MAY 30 2026
UPPER RIDGING IS MAINTAINED TO START THE NEW WORK WEEK WITH
MOISTURE LARGELY SHUNTED TO THE SOUTH AND WEST UNTIL CLOSER TO
MIDWEEK WHEN SHOWER AND STORM CHANCES AGAIN RETURN TO THE
FORECAST. DETAILS AT THIS TIME RANGE REMAIN UNCERTAIN WITH A
SURFACE HIGH OVER THE GREAT LAKES TO CONTEND WITH. TEMPERATURES
REMAIN IN THE 80S THROUGH THE WEEK.
AVIATION /00Z TAFS THROUGH 00Z MONDAY/
ISSUED AT 640 PM CDT SAT MAY 30 2026
DAYTIME SCATTERED SHOWER ACTIVITY IS TAPERING OFF AND A LULL IS
EXPECTED THROUGH THIS EVENING. AFTER MIDNIGHT A LINE FOR STORMS
IS EXPECTED TO MOVE INTO SOUTHWEST IOWA, PUSHING ACROSS IOWA
THROUGH SUNDAY MORNING. THIS IS EXPECTED TO WEAKEN AS IT MOVES
INTO CENTRAL IOWA, THOUGH THUNDERSTORMS ARE STILL POSSIBLE. HAVE
INCLUDED PREVAILING MENTIONS AT KFOD/KDSM/KOTM ON THE MOSTLY
LIKELY WINDOW FOR SHOWERS WITH A PROB30 GROUP TO TIME OUT THE
THUNDER CHANCES. ADJUSTMENTS TO BOTH THE -SHRA AND -TSRA ARE
LIKELY AS WE FINE TUNE THE TIMING AND SPEED OF THE CONVECTION AS
IT REACHES IOWA LATER TONIGHT. THERE IS LESS CERTAINTY ON THIS
REACHING NORTHERN AND EASTERN IOWA, SO FOR NOW HAVE KEPT FROM
KALO/KMCW, HOWEVER ADDITIONS OF AT LEAST -SHRA ARE POSSIBLE AT
THE 06Z ISSUANCE.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...05
LONG TERM...05
AVIATION...HAGENHOFF
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