247
FXUS63 KDMX 031920
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
220 PM CDT THU APR 3 2025
KEY MESSAGES
- RAIN LIKELY (60+%) SOUTHEAST LATE FRIDAY, LESSER CHANCES
NORTHWEST
- COOL, BELOW NORMAL TEMPERATURES THIS WEEKEND AND EARLY NEXT
WEEK, INCLUDING A FEW NIGHTS WITH WIDESPREAD SUB-FREEZING LOWS
- DRY MUCH OF THE WEEKEND INTO TUE, THEN LOW CHANCES (<=30%) FOR
PRECIP RETURN TUE NIGHT-THU
DISCUSSION
ISSUED AT 219 PM CDT THU APR 3 2025
THE PARENT ROCKIES LONG WAVE TROUGH THAT BROUGHT WIDESPREAD
SHOWERS AND STORMS TO IOWA EARLY WEDNESDAY, AND WIDESPREAD
SEVERE WEATHER TO THE MID-MS AND OH RIVER VALLEYS LAST NIGHT
WILL EVOLVE SLOWLY OVER THE NEXT FEW DAYS WITH STRONGER NORTHERN
STREAM INFLUENCES EVENTUALLY CHANGING OUR REGIME TO A DRIER,
COOLER PATTERN BY THE WEEKEND. THERE WASN'T A WHOLE LOT GOING
ON THIS AFTERNOON WITH VARIABLE CLOUD COVER DRIVEN BY
CONFLICTING FACTORS. HIGH CLOUDINESS IN WEAK KINEMATIC LIFT
CONTINUED TO REACH SOUTHERN IA FROM THE ACTIVE SOUTHWEST FLOW
ALOFT, WHILE UNDERNEATH LOW LEVEL CYCLONIC FLOW AND NEGATIVE
THETA-E ADVECTION KEPT THINGS DRY WITH NOTHING BEYOND STRATUS
NORTH.
THE MID AND UPPER LEVEL KINEMATIC CONTRIBUTIONS WILL PERSIST
INTO TOMORROW, BUT THE THERMODYNAMIC SUPPORT WILL INCREASE AS
THE H85/H7 BAROCLINIC ZONE TO OUR SOUTH LIFTS NORTHWARD INTO IA.
THIS WILL INCREASE CHANCES FOR LIGHT RAIN, MAINLY SOUTHEAST
LATER INTO THE DAY AND EVENING, WITH MID-UPPER LEVEL LIFT
ASSOCIATED WITH THE APPROACHING DAKOTAS TROUGH ALSO ADDING LIGHT
RAIN CHANCES NORTHWEST. THERE COULD ALSO BE A VERY SMALL WINDOW
ON THE TRAIL END OF THAT SYSTEM WERE TEMPS COULD FAVOR A BIT OF
LIGHT SNOW, BUT THAT POTENTIAL IS QUITE MINIMAL AT THIS TIME.
BY SATURDAY, LARGE SCALE SUBSIDENCE SHOULD MOVE IN AS THE
NORTHERN STREAM TROUGH ADVANCES THROUGH THE NORTHERN PLAINS INTO
THE GREAT LAKES WITH BRISK NORTHWEST WINDS USHERING IN COOLER
TEMPERATURES. THIS WILL BE REINFORCED BY THE PASSAGE OF A GREAT
LAKES PV ANOMALY EARLY MONDAY WITH ANOTHER FRONTAL PASSAGE AND SHOT
OF COOLER AIR AND SOMEWHAT ANOMALOUSLY HIGH SURFACE HIGH
PRESSURE INTO THE UPPER MS VALLEY EARLY TUESDAY. HIGHS SATURDAY
AND MONDAY MAY NOT MAKE IT OUT OF THE 40S IN MOST PLACES, AND
WIDESPREAD SUB-FREEZING LOWS ARE ANTICIPATED SATURDAY AND
ESPECIALLY MONDAY NIGHTS. WITH CLEAR SKIES AND LIGHT WINDS, LOWS
IN THE UPPER TEENS MONDAY NIGHT ARE NOT OUT OF THE QUESTION
NORTH WITH WIDESPREAD 20S ELSEWHERE. THE LOCAL OFFICE CONSENSUS
IS THAT CONDITIONS ARE STILL CONSIDERED TOO EARLY IN THE
GROWING SEASON TO INITIATE FROST OR FREEZE HEADLINES, HOWEVER
THAT MAY BE RE-EVALUATED IN THE COMING DAYS, ESPECIALLY THE
SOUTH HALF OF THE STATE, DEPENDING ON PARTNER FEEDBACK.
THE PATTERN IS THEN EXPECTED TO TRANSITION TO SOME DEGREE OF
NORTHWEST FLOW ALOFT WITH LOW CONFIDENCE ON HOW ACTIVE IT WILL
BE AND OUR RESULTANT PRECIP POTENTIAL TUESDAY INTO WEDNESDAY.
RECENT GFS DETERMINISTIC RUNS HAVE REMAINED STRONGER WITH BOTH
THE WAVE ALOFT AND ITS SURFACE REFLECTION, WHILE RECENT ECMWF
RUNS HAVE BEEN WEAKER. PREVIOUS ENSEMBLE RUNS WERE STAYING
WITHIN THEIR PARENT MODEL CORE TRENDS (GEFS MORE BULLISH), BUT
12Z GEFS AND EPS 24HR MEDIAN QPF ARE CONVERGING SOMEWHAT AND NOW
MORE SIMILAR SUGGESTING A MIDDLE OF THE ROAD APPROACH WITH LIGHT
RAIN SOMETIME WEDNESDAY INTO THURSDAY BUT WITH TIMING
UNCERTAINTIES. THE NBM SEEMS TO GRASP THIS TREND ACCORDINGLY
WITH LOW CHANCES (<=30%) SPREAD OUT OVER 48 HOURS. THE FLIP TO
NORTHWEST FLOW IS ALSO EXPECTED TO RETURN TEMPERATURES TO NORMAL
OR ABOVE WITH HIGHS IN THE 60S BY WED AND THU.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1242 PM CDT THU APR 3 2025
CONFIDENCE IS LOW ON ITS TREND, BUT MVFR STRATUS IS EXPECTED TO
REMAIN FAIRLY STEADY STATE ACROSS NORTHERN IA INTO AT LEAST THE
EARLY EVENING HOURS AFFECTING KFOD, KMCW, AND KALO, AND
POSSIBLY LONGER AT KMCW. LOOKING INTO FRIDAY, WIDESPREAD HIGH
CLOUDINESS IS ANTICIPATED AHEAD OF THE SYSTEM WITH PRECIPITATION
POTENTIAL MAINLY HOLDING OFF SOUTHEAST NEAR KOTM UNTIL AFTER
THE VALID PERIOD (04/18Z).
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...SMALL
AVIATION...SMALL
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