127
FXUS63 KDMX 141955
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
255 PM CDT SUN SEP 14 2025
KEY MESSAGES
- MARGINAL RISK UP INTO CRAWFORD COUNTY. DAMAGING WINDS WILL BE
THE PRIMARY THREAT, BUT THE THREAT WILL DIMINISH AFTER SUNSET.
- THUNDERSTORMS WITH GUSTY WINDS POSSIBLE TONIGHT (<30%) AND
AGAIN TOMORROW NIGHT (<20%) MAINLY CENTRAL AND EAST.
- RAIN BECOMES MORE LIKELY (>50% CHANCE) BY WEDNESDAY.
DISCUSSION
ISSUED AT 252 PM CDT SUN SEP 14 2025
OUT OF THE SEQUENCE OF TROUGHS SEEN OVER THE WESTERN CONUS AND
PACIFIC TODAY, THE FIRST FEATURE CONTINUES ITS NEGATIVE TILT INTO
THE UPPER MIDWEST TODAY. MODERATE HEIGHT FALLS ON THE ORDER OF -5 TO
-6 DAM WILL STAY JUST TO THE WEST OF THE STATE LATER TODAY. AN UPPER
JET WILL ROUND THE BASE OF THE FEATURE THROUGH TODAY, BOOSTING DEEP-
LAYER SHEAR VALUES OVER 40KTS IN WESTERN IOWA. CONVECTIVE TRENDS
HAVE SLOWED WITH TIME, MEANING THAT LESS STORMS WILL INCH INTO
WESTERN IOWA TONIGHT AND, WHEN THEY DO, LESS OF THE SHEAR WILL BE
UTILIZED THANKS TO THE NOCTURNAL INVERSION. WITH THE SYNOPIC-DRIVEN
CONVECTION GETTING HELD TO THE WEST, THERE'S ANOTHER REGION OF LIFT
TO WATCH TONIGHT: THE AIRMASS BOUNDARY OVER EAST-CENTRAL IOWA.
CONVERGENCE IS DRIVEN BY THE CLASHING OF THE EASTERLIES FROM THE
ONTARIO HIGH AND THE WARM CONVEYOR BELT OF THE AFOREMENTIONED LOW TO
THE WEST. THIS BOUNDARY CAN BE SEEN THIS AFTERNOON IN THE SOUTHWEST
TO EASTERLY SURFACE WINDS CREATING A CUMULUS FIELD.
WHILE SHEAR THIS FAR EAST WILL BE LOW, MUCAPE VALUES OVER 1000 J/KG
RESIDE OVER EASTERN IOWA. OVERNIGHT CAM RUNS, MAINLY THE HRRR,
PRODUCED 40KT WINDS. THIS OCCURS IN THE POCKET OF THE HIGHEST DCAPE
VALUES (AROUND 400 J/KG, BUT DECREASING THROUGH THE NIGHT). CLOUD
LAYER SHEAR IS VALUED AT LESS THAN 20KTS, SO STORMS THAT DO BECOME
STRONG WILL BE SHORT-LIVED. THIS GRADIENT HANGS AROUND MONDAY AND
MONDAY NIGHT AND MAY ONCE AGAIN PROVIDE ENOUGH SUPPORT FOR SHOWERS
AND STORMS, ALTHOUGH THIS TIME WITH LESS MOISTURE AT PLAY. MOST ALL
HREF MEMBERS HAVE CONVECTION ACROSS NORTH CENTRAL IOWA MONDAY
AFTERNOON, BUT KEEP IN MIND THAT EARLIER RUNS THAT COVERED
TODAY/TONIGHT PERIOD HAD CONVECTION GOING BY NOW, SO IT'S POSSIBLE
THAT COVERAGE IS OVERDONE AGAIN IN A SIMILAR SETUP. HAVE AT LEAST
KEPT NON-ZERO POPS IN TO COVER POTENTIAL.
BROAD TROUGHING SWIRLS OVER THE WESTERN CONUS AND THE UPPER RIDGE
WILL ANGLE INTO THE GREAT LAKES REGION BY MIDWEEK. GIVEN THE
PROXIMITY TO THE FORCING, RAIN AND STORM CHANCES ARE NOT FAR AWAY
WITH SOME POTENTIAL BEGINNING ONCE CONVECTIVE TEMPERATURE IS
REACHED. THE MASS OF SYNOPTIC FORCING GETS CLOSE ENOUGH TO HAVE
HIGHER CONFIDENCE RAIN AND STORMS FOR THE SECOND HALF OF THE
WEEK. IT WILL BE WRAPPED UP ENOUGH AT THAT POINT TO ONLY HAVE
HEIGHT FALLS AROUND -2 DAM, SO LESS DYNAMIC.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1233 PM CDT SUN SEP 14 2025
HAVE PRESERVED NO PRECIP MENTIONS THIS ISSUANCE, ALTHOUGH <30%
OF SHOWERS AND STORMS REMAINS TONIGHT FOR SITES LIKE KALO, KMCW,
AND KOTM. TIMING WOULD BE BETWEEN 06Z AND 12Z WITH PEAK TIMES
TOWARDS THE LATTER HALF OF THAT TIME PERIOD. CONFIDENCE REMAINS
LOW IN SPATIAL COVERAGE AND LOCATION. WILL CONTINUE TO EVALUATE
TRENDS AHEAD OF THE NEXT ISSUANCE.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...JIMENEZ
AVIATION...JIMENEZ
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