478
FXUS63 KDMX 131732
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1232 PM CDT SAT SEP 13 2025
...UPDATED FOR THE 18Z AVIATION DISCUSSION...
KEY MESSAGES
- TODAY WILL BE THE HOTTEST DAY ACROSS THE STATE WITH MANY
LOCATIONS REACHING THE LOW TO MID-90S. THEREAFTER,
TEMPERATURES EACH SUCCESSIVE DAY THROUGH TUESDAY WILL BE
SIMILAR IF NOT JUST SLIGHTLY LOWER THAN THE PREVIOUS DAY.
- 20-35% CHANCE OF STORMS LATER SUNDAY INTO EARLY MONDAY.
ADDITIONAL 20% STORM CHANCES EXIST BOTH MONDAY AND TUESDAY
AFTERNOON WITH MORE WIDESPREAD STORM CHANCES AT TIMES
WEDNESDAY INTO THURSDAY.
- HEAT WILL BREAK LATE IN THE WEEK WITH MORE SEASONAL
CONDITIONS.
UPDATE
ISSUED AT 238 AM CDT SAT SEP 13 2025
NIGHTTIME MICROPHYSICS RGB FROM GOES-EAST SHOWS AN AREA OF MID-
LEVEL CLOUDS OVER CENTRAL INTO PARTS OF EASTERN IOWA EARLY THIS
MORNING, WHICH CORRESPONDS TO THE WARM AIR ADVECTION OVER IOWA.
OUTSIDE OF A FEW PASSING SPRINKLES CURRENTLY, THERE IS NO RAIN
IN THE STATE. THESE CLOUDS WILL SLIDE OFF TO THE EAST LEAVING A
GOOD DEAL OF SUNSHINE AS THE THERMAL RIDGE CENTERS OVER THE
REGION. WITH WARM TEMPERATURES ALOFT WITH RAP 850MB ANALYSIS
SHOWING 22C SPLITTING THE STATE AT THIS HOUR, THIS WILL SUPPRESS
ANY DEVELOPMENT LEAVING A HOT SEPTEMBER DAY. TEMPERATURES WILL
PEAK IN THE LOW AND MIDDLE 90S WITH THE EXCEPTION OF
NORTHEASTERN IOWA. WINDS WILL NOT BE AS BREEZY AS YESTERDAY, BUT
ONCE AGAIN DEWPOINTS WILL STAY IN THE 60S RESULTING IN HEAT
INDEX VALUES JUST A FEW DEGREES HIGHER THAN THE AIR TEMPERATURE.
AS MENTIONED YESTERDAY, HEATRISK IS PICKING UP ON THE LATE
SEASON HEAT INDICATING WIDESPREAD MODERATE IMPACTS WITH PATCHY
MAJOR IMPACTS. AS WITH ANY HEAT, TYPICAL PRECAUTIONS OF TAKING
REST BREAKS AND HYDRATING SHOULD BE PERFORMED.
THE LONGWAVE TROUGH OVER THE WESTERN US WILL BEGIN TO LIFT
NORTHEASTWARD AND BEGIN TO NEGATIVELY TILT AS IT DOES SO SATURDAY,
WHICH WILL BEGIN TO PUSH THE THERMAL RIDGE EASTWARD AS WELL. THUS,
SUNDAY'S HIGHS WILL BE SIMILAR TO IF NOT JUST A TAD LOWER THAN
SATURDAY'S, WITH THIS TREND MORE OR LESS CONTINUING THROUGH TUESDAY.
NAM AND RAP SOUNDINGS FOR SUNDAY AFTERNOON SHOW A VARYING DEGREE OF
A CAPPING LAYER TOO. WHILE THE RAP SHOWS A WEAKER CAP, BOTH THE NAM
AND RAP ARE FAIRLY DRY FOR THE OVERALL SOUNDING. ON THE OTHER SIDE
LOOKING AT HIGH RESOLUTION MODELS, STARTING TO SEE A FEW TRY TO
DEVELOP ISOLATED STORMS IN THE AFTERNOON HOURS SUCH AS THE FV3 AND
HRRR. GIVEN THE SPLIT SIGNAL AT THIS TIME, WILL BE WATCHING THIS
PERIOD TO SEE IF WE NEED TO PHASE IN HIGHER POPS SOONER SUNDAY
AFTERNOON. MUCH OF THE AFOREMENTIONED TROUGH'S ENERGY WILL STAY
FOCUSED OVER THE DAKOTAS WITH A GLANCING SHOT OF WEAK KINEMATIC AND
THERMODYNAMIC FORCING SUNDAY NIGHT, WHICH RESULTS IN BROAD 20 TO 35%
SHOWER AND STORM CHANCES. ANY STORMS OVERNIGHT WOULD BE ELEVATED
WITH WEAK SHEAR AROUND 25 KNOTS LIMITING THE SEVERE CHANCES.
WITH THE VERY WARM CONDITIONS LINGERING INTO EARLY NEXT WEEK, WILL
HAVE TO KEEP AN EYE ON THE DEGREE OF CAPPING THAT REMAINS. RIGHT
NOW, EACH MONDAY AND TUESDAY AFTERNOON COULD FIRE A FEW ISOLATED
STORMS WITH CHANCES 20% OR LESS. ADDITIONAL CLOUD COVER FROM WHAT IS
CURRENTLY FORECAST COULD ALSO WRECK HIGH TEMPERATURE FORECASTS
SIMILAR TO YESTERDAY/FRIDAY. AS ANOTHER LOBE OF VORTICITY SWINGS
DOWN FROM THE NORTHERN ROCKIES MID TO LATE WEEK, THIS WILL HELP TO
SLOWLY BRING A SURFACE FRONT INTO THE REGION. THIS WILL PROVIDE A
FOCUS FOR STORM CHANCES IN THIS TIME FRAME WITH CONDITIONS RETURNING
TO MORE SEASONAL LEVELS FOR THIS TIME OF SEPTEMBER.
DISCUSSION
ISSUED AT 241 PM CDT FRI SEP 12 2025
UPPER-LEVEL RIDGING CONTINUES TO USHER IN UNSEASONABLY WARM AIR
TODAY. A SHORTWAVE IS MOVING ACROSS THE TOP OF THE RIDGE THIS
AFTERNOON WITH THETA-E ADVECTION PROVIDING ENOUGH MOISTURE TO
FIRE OFF SOME SHOWERS AND STORMS ALONG THE MOISTURE AXIS. WARMER
AIR IS YET TO COME UPSTREAM, NOTICING THE 22C 850MB
TEMPERATURES IN THE 12Z RAOBS. THESE VALUES SIT AT THE 90TH
PERCENTILE FOR THE CENTRAL PLAINS SITES OBSERVING THESE
TEMPERATURES (SITES SUCH AS OUN), AND 22C WOULD EXCEED THE 90TH
PERCENTILE AT OAX. ALL THIS TO SAY, WE'LL BE APPROACHING RECORD
HIGHS TOMORROW IN CENTRAL IOWA. HIGHS TOMORROW IN THE SOUTH WILL
REACH THE MID 90S UNDER A MIX OF SUN AND CLOUDS. HEAT INDICES
WILL REMAIN CLOSE TO ACTUAL TEMPERATURES DUE TO THE LOWER DEW
POINTS. NONETHELESS, IT WILL BE IMPORTANT TO STAY HYDRATED AND
COOL AMIDST A LATE SEASON ROUND OF HEAT.
THE 850MB HIGH WILL REMAIN CENTERED OVER THE OZARKS/MID SOUTH,
LIMITING THE AMOUNT OF GULF MOISTURE THIS WEEKEND AND STALLING IT
INTO NEXT WEEK. THE LACK OF LOW-LEVEL MOISTURE ALREADY SHOWS TODAY
WITH CONVECTIVE PRECIP LOADING JUST MANAGING TO GET SOME SHOWERS OUT
OF THE 8KFT CLOUD BASES. THE THETA-E AXIS WILL PIVOT AROUND
NORTHEAST IOWA THROUGH THE NIGHT AND INTO SATURDAY. DEEPER
SATURATION LOOKS TO BE FAR ENOUGH EAST TO SPARE OUR AREA FROM MORE
RAIN, BUT CLOUD COVER MAY LINGER IN NORTHEAST IOWA. THEREFORE, HIGH
TEMPERATURES HAVE BEEN ADJUSTED SATURDAY, WITH PARTS OF NORTHEAST
IOWA BEING HELD CLOSER TO 90 DEGREES. SUNDAY WILL BE SIMILAR IN
HIGHS.
THE EXTENDED FORECAST REMAINS WARM WITH HIGHS IN THE 90S. A COLORADO
LOW WILL HINDER WAA AND MOISTURE TRANSPORT INTO THE UPPER MIDWEST AT
LEAST UNTIL WEDNESDAY, MEANING THAT HIGH TEMPERATURES WILL STAY
CLOSER TO 90 DEGREES. THE NEXT CLOSEST ROUND OF PRECIPITATION WILL
BE SUNDAY NIGHT AS A NEGATIVELY TILTED TROUGH SWINGS INTO THE
REGION. CONFIDENCE IS LOW IN THIS RAIN REACHING CENTRAL IOWA DUE
TO MOISTURE ISSUES MENTIONED EARLIER (<25% CHANCE). A CAPE
GRADIENT PARKS OVER EASTERN IOWA WHICH MAY BRING ENOUGH LIFT FOR
SHOWERS AND STORMS IN THE PEAK MIXING HOURS IN THE LATE
AFTERNOON, BUT CONFIDENCE IS LOW (<20%) SINCE HIGH PRESSURE
HOLDS THE DRY AIR. FINALLY, A LONG WAVE TROUGH FROM SOUTHWEST
CANADA INVADES THE UPPER RIDGE, OPENING THE REGION UP TO RAIN
CHANCES AND COOLER WEATHER IN THE SECOND HALF OF NEXT WEEK.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 1227 PM CDT SAT SEP 13 2025
LITTLE TO NO CHANGE IN THE NEXT 6 HOURS. VFR CONDITIONS TO
PREVAIL WITH WINDS FROM THE SOUTHWEST UNDER 20KTS. HAVE ADDED IN
PATCHY FOG TO KMCW FOR 2 HOURS NEAR SUNRISE AS TRENDS CONTINUE
TO INDICATE THIS POTENTIAL. NOT ENOUGH CONFIDENCE AT THIS TIME
TO ADD IN VSBY RESTRICTIONS, AND CHANCE OF FOG OVERALL AT KALO
HAS DECREASED, HENCE IT IS NOT MENTIONED THERE. WILL CONTINUE TO
EVALUATE IN LATER ISSUANCES.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...ANSORGE
DISCUSSION...JIMENEZ
AVIATION...JIMENEZ
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