564
FXUS63 KDMX 122345
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
645 PM CDT THU JUN 12 2025
...UPDATED FOR THE 00Z AVIATION DISCUSSION...
KEY MESSAGES
- ISOLATED SHOWERS AND STORMS THIS AFTERNOON AND EARLY EVENING. ANY
SEVERE CHANCES ARE LIMITED TO FAR NORTHERN IOWA.
- 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.
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 /00Z TAFS THROUGH 00Z SATURDAY/
ISSUED AT 638 PM CDT THU JUN 12 2025
A FEW THUNDERSTORMS ARE ONGOING ACROSS IOWA PRODUCING NUMEROUS
AREAS OF OUTFLOW THAT WILL KEEP WIND DIRECTION ERRATIC INTO
EARLY THIS EVENING. ONLY INCLUDED THUNDERSTORM MENTION AT KMCW
WITH A LACK OF CONFIDENCE ELSEWHERE. THE WIND WILL STEADY AND
BECOME CONSISTENT FROM THE SOUTH/SOUTHEAST. AN AREA OF STRATUS
MAY LIFT INTO IOWA ON FRIDAY AND WILL BRING THE POTENTIAL FOR
MVFR CIGS. AGAIN, OVERALL AREAL COVERAGE OF MVFR CIGS IS LOW AND
DID NOT INCLUDE AT MOST LOCATIONS.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...ANSORGE
AVIATION...DONAVON
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