408
FXUS63 KDMX 140345
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1045 PM CDT SAT SEP 13 2025
...UPDATED FOR THE 06Z AVIATION DISCUSSION...
KEY MESSAGES
- MAIN CHANGE IS AN INTRODUCTION IN RAIN/STORM CHANCES SUNDAY
AFTERNOON AND EVENING, MAINLY CENTRAL AND EAST (35% AND LESS).
RAINFALL AMOUNTS WILL BE LIGHT.
- WARM WITH HIGHS AROUND 90 DEGREES UNTIL WEDNESDAY.
- NEXT BEST CHANCE OF STORMS WEDNESDAY.
DISCUSSION
ISSUED AT 148 PM CDT SAT SEP 13 2025
12Z UPPER AIR OBSERVATIONS HAD 22C TEMPERATURES AT 850MB AT BOTH TOP
AND ICT. MODELS INDICATE THE WARMEST BATCH OF AIR IS OVER NEBRASKA
AT THIS TIME. 850MB TEMPERATURES OVER 20C ARE A HIGH CONFIDENCE
NUDGER TOWARD HIGHS IN THE 90S, ESPECIALLY IN A DRY (THEREFORE
MIXABLE) AIRMASS SUCH AS THE ONE SEEN TODAY OVER THE STATE.
HIGHS IN THE LOW TO MID 90S WILL BE COMMONPLACE TODAY. THE
LONGWAVE TROUGH ENCAPSULATING THE WESTERN CONUS HAS SPLIT MAXIMA
OF HEIGHT FALLS TODAY: ONE IN THE INNER MOUNTAIN WEST AND THE
OTHER IN THE DESERT SOUTHWEST. THE DESERT FEATURE IS WHAT WILL
BE RESPONSIBLE FOR OUR SHOWERS AND STORMS LATE TOMORROW, BUT
BEFORE IT GETS HERE, IT WILL CONTINUE TO IGNITE CONVECTION IN
THE SOUTHERN AND CENTRAL GREAT PLAINS, STUNTING THE APPROACH OF
WARMER TEMPERATURES THAN SEEN TODAY. THIS IS WHY THE REST OF THE
FORECAST HAS LOWER HIGHS COMPARED TO TODAY, BUT STILL ABOVE
AVERAGE NONETHELESS.
THIS FEATURE WILL DEEPEN AND TILT NEGATIVELY OVER THE NEXT 48 HOURS,
DEVELOPING A CLOSED LOW AND STACKING BY THE END OF THE DAY SUNDAY.
ITS WARM CONVEYOR BELT WILL PULL THE MOISTURE AXIS INTO THE NORTHERN
GREAT PLAINS, BUT WITHOUT THE BULK OF THE INSTABILITY AXIS. MUCAPE
VALUES GREATER THAN 1500 J/KG WILL BE FOUND IN PORTIONS OF CENTRAL
AND EASTERN IOWA. HI RES GUIDANCE HAS TRENDED TOWARDS SHOWERS AND
STORMS TAKING ADVANTAGE OF THIS ENERGY ONCE CONVECTIVE TEMPERATURE
IS REACHED, OWED TO THE TRANSPORT OF MOISTURE FOUND OVER THE
OZARKS/MID SOUTH THIS MORNING. PRECIPITATION WOULD BE HIGH-BASED AS
THE SATURATED PARCELS WOULD LAUNCH AROUND 700MB, PER SOUNDING
PROFILES. THE THREAT FOR STRONG TO SEVERE STORMS IS LOW (<10%) DUE
TO LACK OF SHEAR AND MOISTURE DEPTH. ACTIVITY WOULD BE FOCUSED ON
THE GRADIENT OF INSTABILITY, STARTING IN MAINLY SOUTH CENTRAL IOWA
AND EXPANDING NORTHEAST. INTRODUCING POPS SUNDAY AFTERNOON IS THE
MAIN CHANGE IN THE SHORT TERM FORECAST, HIGH TEMPERATURES SUFFERING
SLIGHTLY FROM IT. TEMPERATURES COULD UNDERPERFORM IF STORMS
INITIATE EARLIER IN THE AFTERNOON. THIS SAME SCENARIO IS IN
PLAY MONDAY AND TUESDAY WITH THE FV3 CORES HAVING THE MOST
COVERAGE. THIS IS UNREALISTIC DUE TO THEIR TENDENCY TO OVERMIX
THIS TIME OF YEAR. THE AFOREMENTIONED TROUGH LOOMS JUST TO THE
NORTHWEST IN THE SECOND HALF OF NEXT WEEK AND IS RESPONSIBLE FOR
THE RAIN CHANCES AND COOLDOWN, ALTHOUGH TRENDING LESS
PROGRESSIVE.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 1040 PM CDT SAT SEP 13 2025
VFR CONDITIONS WITH LIGHT, SOMEWHAT VARIABLE WINDS PREVAIL OVER
THE AREA TONIGHT AND INTO THE MORNING HOURS. THERE REMAINS A
POTENTIAL FOR PATCHY FOG IN NORTHEAST IOWA FOR A FEW HOURS IN
THE MORNING, SO NO CHANGE TO VFR VISIBILITY RESTRICTIONS AT KDSM
AND KALO. WINDS INCREASE OUT OF THE SOUTH TOMORROW, WITH THE
STRONGEST GUSTS OVER THE WESTERN HALF OF THE STATE. THIS PUTS
KFOD AND KDSM RIGHT ON THE EDGE OF SOME OF THE BREEZIER WINDS,
SO HAVE STARTED TO TREND WINDS UPWARD FOR THESE SITES. IT'S
POSSIBLE GUSTS UP TO 20 KTS MAY BE NEEDED IN FUTURE ISSUANCES,
BUT CLOUD COVER IS LIMITING CONFIDENCE IN FULL MIXING TOMORROW.
SCATTERED SHOWERS AND THUNDERSTORMS ARE LOOKING POSSIBLE LATE
TOMORROW AFTERNOON AND THROUGH THE EVENING, POTENTIALLY
IMPACTING ALL SITES. HOWEVER, THE TIMING OF THIS PRECIPITATION
HAS BEEN TRENDING TOWARD THE END OF THIS TAF PERIOD, SO HAVE
LEFT MENTION OUT OF TAFS DUE TO LOW CONFIDENCE IN IMPACTS
AT TERMINALS SUNDAY AFTERNOON. THAT SAID, KEEP AN EYE ON FUTURE
FORECASTS AS SHOWER AND/OR THUNDER MENTION MAY NEED TO BE ADDED
TOMORROW AFTERNOON, SHOULD CONFIDENCE BECOME GREATER. ASIDE FROM
POTENTIAL PRECIPITATION, VFR CONDITIONS PREVAIL THROUGH THE END
OF THE TAF PERIOD.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...JIMENEZ
AVIATION...DODSON
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