017
FXUS63 KDMX 131136
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
636 AM CDT FRI JUN 13 2025
...UPDATED FOR THE 12Z AVIATION DISCUSSION...
KEY MESSAGES
- DRIER PERIOD FRIDAY INTO SATURDAY WITH CHANCES NO HIGHER THAN 30%
OVER EASTERN OR NORTHERN IOWA.
- ACTIVE PERIOD OF WEATHER STARTING LATER SUNDAY INTO NEXT WEEK.
WHILE LACKING SPECIFICS (TIMING, LOCATION, HAZARDS) DUE TO
LOW PREDICTABILITY, STRONG TO SEVERE STORMS AND LOCALLY HEAVY
RAINFALL WILL BE POSSIBLE AT TIMES OVER THE REGION.
- STAYING WARM AND HUMID THROUGH THE PERIOD.
UPDATE
ISSUED AT 251 AM CDT FRI JUN 13 2025
PRIMARY WEATHER CONCERNS TODAY AND SATURDAY WILL BE ANCHORED ON THE
WARM FRONT THAT WILL WAVER ALONG AND NORTH OF THE IOWA/MINNESOTA
BORDER. THIS AFTERNOON THAT BOUNDARY IS EXPECTED TO BE PUSHED NORTH
OF THE AREA WHEN DIURNAL HEATING DESTABILIZES THINGS ENOUGH FOR
CONVECTIVE DEVELOPMENT, THOUGH A FEW THUNDERSTORMS MAY SKIM FAR
NORTHERN IOWA. THESE STORMS SHOULD REMAIN SUB-SEVERE WITH
MODEST INSTABILITY AND LITTLE SHEAR TO HELP ORGANIZE STORMS.
SATURDAY WILL BE A NEAR REPEAT WITH STORMS DEVELOPING ALONG THE
BOUNDARY WITH DIURNAL HEATING. THE BOUNDARY WILL NEED TO BE
WATCHED CLOSELY FOR WHERE THIS SETS UP, BUT THE NORTHERN COUPLE
ROWS OF IOWA COUNTIES ARE EXPECTED TO SEE A FEW SCATTERED
STORMS. INSTABILITY IS MARGINALLY INCREASE ON SATURDAY BUT
OVERALL SEVERE CHANCES REMAIN LOW.
A SHORTWAVE BRINGS A MORE ORGANIZED CHANCE FOR SHOWERS AND STORMS TO
NORTHWEST IOWA ON SUNDAY. THIS WILL KICK OFF WHAT IS SHAPING UP TO
BE AN ACTIVE WEEK ACROSS IOWA. AFTER WHAT HAS BEEN A QUIET START TO
THE WARM SEASON LOCALLY, NOW IS A GOOD TIME TO DUST OFF THOSE SEVERE
WEATHER PREPAREDNESS SKILLS. SEVERAL ROBUST SHORTWAVES WILL
MOVE ACROSS THE AREA, RIDING THE NORTHERN WARM FRONT, AS IS
OFTEN THE CASE WITH THIS SET UP. RIGHT NOW WAVES LOOK TO BE
TIMES AS MONDAY INTO THE MONDAY OVERNIGHT, TUESDAY INTO THE
TUESDAY OVERNIGHT AND WEDNESDAY, AND A FINAL QUICK MOVING WAVE
ON FRIDAY. MONDAY AND ESPECIALLY TUESDAY INTO WEDNESDAY ARE THE
MOST ROBUST WAVES AT THIS TIME AND WILL LIKELY BRING SEVERE
WEATHER TO THE STATE. WITH THIS SEVERAL DAYS OUT THERE ARE A
NUMBER OF DETAILS THAT ARE UNCERTAIN. WHAT IS KNOWN IS THAT
SEVERE STORMS AND HEAVY RAIN LOOK LIKELY THROUGH THIS WINDOW.
MULTIPLE ROUNDS OF HEAVY RAIN COULD PRESENT HYDROLOGIC CONCERNS
IF THEY SET UP OVER SIMILAR LOCATIONS ON CONSECUTIVE NIGHTS.
THIS FORECAST WILL BE FINE TUNED WITH ADDITIONAL DETAILS
SUPPLIED AS MORE DATA COMES AVAILABLE IN THE COMING DAYS.
DISCUSSION
ISSUED AT 208 PM CDT THU JUN 12 2025
IOWA RESIDES BETWEEN TWO AREAS OF FORCING EARLY THIS AFTERNOON WITH
A SHORTWAVE TROUGH PASSING NORTH OF THE STATE AND A BROAD, CLOSED
LOW MOVING EVER SO SLOWLY NEAR THE OZARKS. THE PASSING NORTH
SHORTWAVE TROUGH IS ALSO LOCATED CLOSER TO THE SURFACE WARM FRONT,
WHICH IS CURRENTLY FROM NEAR ESTHERVILLE TO SOUTH OF WATERLOO,
THOUGH THE EFFECTIVE WARM FRONT IS A BIT NORTH OF THAT. THERE IS
SOME SPEED AND DIRECTIONAL SHEAR OVER NORTHERN IOWA IN THE FORECAST
SOUNDINGS THAT RESULTS IN MARGINAL AT BEST AMOUNTS OF DEEP AND
EFFECTIVE SHEAR. FORECAST SOUNDINGS ALSO SHOW A BIT MORE SURFACE
BASED INSTABILITY (SBCAPE) TO AROUND 1500 J/KG PER LATEST SPC
MESOANALYSIS. THIS MAY ALLOW FOR A FEW STRONGER STORMS AROUND SEVERE
LIMITS TO DEVELOP MID-AFTERNOON AROUND THE IOWA-MINNESOTA BORDER
THAT MAY SCRAPE THE FAR NORTHERN PART OF OUR FORECAST AREA. THE
SEVERE WIND GUST SIGNAL THAT WAS SEEN YESTERDAY IN THE CONVECTIVE
ALLOWING MODELS (CAMS) IS NOT PRESENT TODAY SO THE MARGINAL RISK
FROM THE STORM PREDICTION CENTER SEEMS QUITE REASONABLE. ANY
ACTIVITY IS EXPECTED TO DISSIPATE BY MID-EVENING.
FARTHER SOUTH OVER CENTRAL AND SOUTHERN IOWA, THE FLOW BELOW 500MB
IS QUITE WEAK WITH SPEEDS GENERALLY AROUND OR LESS THAN 10 KNOTS
RESULTING IN LITTLE IF ANY DEEP OR EFFECTIVE SHEAR. CAPE PROFILES
ARE SKINNY, BUT YIELD AROUND 500 TO 1000 J/KG OF INSTABILITY WITH
STEEP LOW LEVEL LAPSE RATES. AS WAS THE CASE YESTERDAY, SOUNDINGS
SHOW PLENTY OF DRY AIR IN THE MID-LEVELS AS WELL AS SUB-CLOUD
RESULTING IN DOWNDRAFT CAPE VALUES BETWEEN 800 AND 900 J/KG. AS
TEMPERATURES RISE TO NEAR THE CONVECTIVE TEMPERATURE IN THE NEXT
HOUR OR TWO, ISOLATED STORMS ARE EXPECTED TO DEVELOP. STORMS MAY
GROW SOMEWHAT QUICKLY DUE TO THE LOW LEVEL LAPSE RATES, BUT WILL BE
UNABLE TO ORGANIZE WITH THE WEAK SHEAR AND BE OF AN AIRMASS VARIETY.
THUS, ANY HAIL WILL BE SMALL, SUB-SEVERE WITH DRY AIR ENTRAINING
INTO THE DOWNDRAFT RESULTING IN GUSTY, SUB-SEVERE WINDS OF AROUND 30
TO 35 KNOTS PER CAMS. THIS ACTIVITY SHOULD DIMINISH AFTER SUNSET IN
THE EARLY EVENING HOURS.
MID-LEVEL RIDGING WILL BUILD INTO IOWA FRIDAY INTO THIS WEEKEND AS
THE SHORTWAVE TROUGH MOVES EAST AND THE CLOSED LOW OVER THE OZARKS
CONTINUES ITS SLOW TRUDGE INTO THE OHIO VALLEY. AT THE SURFACE, A
FRONT WILL PASS AND STALL SOUTH OF THE STATE. THIS SHOULD PROVIDE A
PERIOD OF DRIER CONDITIONS FRIDAY INTO THE DAY SATURDAY WITH CHANCES
FOR SHOWERS AND STORMS AT NO MORE THAN 30% AND MAINLY OVER EASTERN
OR NORTHERN IOWA. THE RIDGE BEGINS TO RETREAT LATE THIS WEEKEND INTO
EARLY NEXT WEEK WITH INITIALLY NORTHWESTERLY FLOW THAT BECOMES MORE
FLATTENED ALLOWING SHORTWAVES TO OVERTOP IT. THIS WILL ALLOW THE
STALLED BOUNDARY SOUTH OF THE STATE TO RETURN NORTHWARD AND PLACE
IOWA BACK INTO THE WARM SECTOR EARLY NEXT WEEK. WHILE LACKING
SPECIFICS ON HAZARD TYPES (E.G. HAIL, WIND, TORNADO, FLASH FLOOD),
TIMING, AND LOCATION, IT DOES LOOK LIKE THERE WILL BE APPRECIABLE
INSTABILITY AND SHEAR PLUS FAVORABLE EFFICIENT RAINFALL PARAMETERS
FOR STRONG TO SEVERE STORMS AND AT LEAST LOCALLY HEAVY RAINFALL
SOMEWHERE OVER THE REGION AT TIMES FROM LATER SUNDAY INTO A GOOD
CHUNK OF NEXT WEEK. THE SEVERE POTENTIAL CONTINUES TO BE SUPPORTED
BY VARIOUS MACHINE LEARNING/ARTIFICIAL INTELLIGENCE (ML/AI)
PROBABILITIES WITH THE HIGHER PROBABILITIES AROUND TUESDAY AND
WEDNESDAY. WHILE NOT AS HIGH, THE MACHINE LEARNING PROBABILITIES FOR
EXCESSIVE RAINFALL ALSO POINT TO SOME RISK OVER THE REGION WITH
WPC'S DAYS 4 AND 5 EXCESSIVE RAINFALL OUTLOOKS COVERING SOME
PORTION OF IOWA. BEYOND THE STORM CHANCES, IT WILL BE A MID-
JUNE WEEK WITH HIGHS WELL INTO THE 80S AND DEWPOINTS IN THE 60S.
AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 636 AM CDT FRI JUN 13 2025
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. AN ISOLATED
SHOWER MAY NEAR KMCW/KOTM THIS MORNING BUT ACTIVITY HAS BEEN
VERY SPOTTY AND HAVE OPTED NOT TO INCLUDE IN THE TAFS AT THIS
TIME. LATER THIS AFTERNOON THUNDERSTORMS ARE EXPECTED TO
DEVELOP IN FAR NORTHERN IOWA. THIS IS EXPECTED TO REMAIN NORTH
OF KMCW HOWEVER WILL NEED TO MONITOR FOR ADJUSTMENTS. LOW CLOUDS
APPROACHING MVFR OR LOWER ARE POSSIBLE IN EASTERN IOWA AT THE
END OF THE TAF PERIOD ON SATURDAY MORNING. THIS WILL BE
ADDRESSED IN FUTURE UPDATES.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...HAGENHOFF
DISCUSSION...ANSORGE
AVIATION...HAGENHOFF
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