147
FXUS63 KDMX 040001
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
601 PM CST TUE DEC 3 2024
...UPDATED FOR THE 00Z AVIATION DISCUSSION...
KEY MESSAGES
- SCATTERED SNOW SHOWERS POSSIBLE (30-40% CHANCE) ACROSS THE
NORTH AND NORTHEAST WEDNESDAY. LOW CONFIDENCE (~20%) IN
VISIBILITY RESTRICTIONS WITH SNOW.
- WIND ADVISORY IN EFFECT ACROSS THE NORTHERN HALF OF THE AREA
FROM NOON TO 9PM WEDNESDAY. GUSTS UP TO 50 MPH (LOCALLY 55
MPH) LIKELY (90% CONFIDENCE) ESPECIALLY ACROSS THE FAR NORTH.
- COLD THURSDAY MORNING WITH WIND CHILLS IN THE NEGATIVE TEENS
ACROSS THE NORTH.
DISCUSSION
ISSUED AT 218 PM CST TUE DEC 3 2024
A SCATTERED DECK OF UPPER LEVEL CLOUDS MOVED ACROSS THE STATE THIS
AFTERNOON, PRIMARILY IN THE NORTHERN HALF. SOUTHERLY WINDS WILL WORK
TO RECOVER TEMPERATURES SLIGHTLY TODAY WITH AREAS ACROSS THE SOUTH
JUST REACHING ABOVE FREEZING. TONIGHT, A DESCENDING TROUGH TO THE
NORTHEAST WILL DRAG WITH IT A FRONT. THE ARRIVAL OF THE FROPA HAS
TRENDED SLIGHTLY FASTER THIS FORECAST UPDATE WHICH WILL LIMIT HIGHS
ACROSS ESPECIALLY THE NORTH TOMORROW. HAVE LOWERED HIGHS, KEEPING
NORTHERN IOWA RIGHT AT FREEZING WHICH IT SHOULD REACH IN THE MORNING
HOURS JUST BEFORE THE FROPA. SOUNDINGS SHOW THE POTENTIAL FOR SOME
CONVECTIVE SNOW SHOWERS WITH STEEP LAPSE RATES IN THE PBL. THIS
POTENTIAL WILL BE ACROSS THE NORTH IN THE MORNING, FOCUSING IN THE
NORTHEAST THROUGH THE DAYTIME. QUICK BURSTS OF SNOW WILL BE POSSIBLE
AS MIXING MAXIMIZES, BUT SNOW WILL BE BLOWN AROUND ENOUGH IN THE
WIND TO LIMIT ACCUMULATION. ONE WOULD BE CONCERNED THAT WITH
EXPECTED GUSTS TOMORROW (MORE ON THE WINDS SHORTLY), BURSTS OF SNOW
COULD LEAD TO VISIBILITY RESTRICTIONS. FOR THIS AREA, THE HI-RES
GUIDANCE DOES HIGHLIGHT NARROW BANDS OF VSBY RESTRICTIONS ASSOCIATED
FROM SIMULATED HCR SNOW SHOWERS, SO REDUCTIONS OF 2SM OR LESS CANNOT
BE COMPLETELY RULED OUT. HOWEVER, A LIMITING FACTOR WILL BE THE LACK
OF SATURATION IN THE DGZ, HINDERING THE FORMATION OF MORE STELLAR
DENDRITES, LEAVING A SNOW PALLET CONSISTING OF SMALLER, LESS
OBSTRUCTIVE SHAPES. ALL THIS BEING SAID, CONFIDENCE THEN BECOMES LOW
(~20%) FOR SIGNIFICANT VISIBILITY REDUCTIONS IN THE NORTH.
NOW, FOR THE WINDS: HAVE ISSUED A WIND ADVISORY ACROSS THE NORTH FOR
WEDNESDAY AFTERNOON AND EVENING. IT IS LIKELY (90% CONFIDENCE) TO
SEE SUSTAINED WINDS OF 25-30 MPH WITH WIND GUSTS UP TO 50 MPH. IT
CANNOT BE COMPLETELY RULED OUT TO SEE 55+ MPH GUSTS IN THE PEAK
MIXING HOURS OF THE AFTERNOON. THIS IS SUPPORTED BY THE MAGNITUDE OF
WINDS AT THE TOP OF THE MIXED LAYER, WHICH EASED SLIGHTLY THIS
ISSUANCE, BUT STILL HIT 50 KTS FOR AN HOUR OR TWO IN THE FAR NORTH.
PAIR THIS WITH STEEP PBL LAPSE RATES, A TIGHT PRESSURE GRADIENT,
CAA, AND SUBSIDENCE FROM PRONOUNCED HEIGHT RISES, INGREDIENTS ARE
CERTAINLY IN PLACE TO MAXIMIZE MIXDOWN OF HIGHER WIND SPEEDS. TRENDS
WILL BE MONITORED TO SEE WHAT MAGNITUDE OF WINDS WILL BE REALIZED.
FOR NOW, THE WIND ADVISORY IS REPRESENTATIVE. CAA PRESERVES MIXING
THROUGH THE NIGHT, KEEPING GUSTY, BUT SUB-ADVISORY WINDS GOING UNTIL
THURSDAY. CLEARING SKIES WILL ALSO WORK TO PLUMMET TEMPERATURES INTO
THE SINGLE DIGITS FOR THURSDAY MORNING. THE AFOREMENTIONED WINDS
WILL PRODUCE WIND CHILLS IN THE NEGATIVE TEENS NORTH OF HIGHWAY 20.
HIGHS WILL ONLY WARM TO NEAR 20 DEGREES.
IN THE EXTENDED, AN UPPER LEVEL TROUGH WILL STALL OVER THE SOUTHWEST
CONUS AND BRING IN A WAA REGIME FOR THE WEEKEND. A REINFORCING OPEN
WAVE ENHANCES THIS REGIME FOR SUNDAY, PUSHING HIGHS IN THE 50S THAT
DAY. THE FORECAST FOR THE FOLLOWING WEEK REMAINS UNCERTAIN AS MODELS
DIVERGE ON HOW THEY HANDLE THE EASTWARD EVOLUTION OF THESE
WAVES.
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 601 PM CST TUE DEC 3 2024
VFR CONDITIONS AND BREEZY WINDS FROM THE SOUTHWEST WILL PREVAIL
INTO THIS EVENING. HOWEVER, WINDS WILL INCREASE AND TURN GUSTY
AS THEY BECOME FROM THE NORTHWEST WEDNESDAY MORNING WITH STRATUS
ARRIVING FROM NORTH TO SOUTH OVER THE STATE. CEILINGS WILL LOWER
INTO MVFR AT MCW, FOD, AND ALO FOR A SEVERAL HOUR PERIOD AROUND
MIDDAY. FARTHER SOUTH AT DSM AND OTM, CEILINGS MAY ALSO NEAR
MVFR, BUT CONFIDENCE IS TOO LOW TO INCLUDE SO HOLDING ONTO VFR
CONDITIONS FOR NOW. NARROW SNOW SHOWER BANDS MAY ALSO DEVELOP
LATE IN THE MORNING INTO THE AFTERNOON, BUT IT IS NOT POSSIBLE
TO PINPOINT WHETHER THESE WILL IMPACT A TERMINAL AT THIS TIME.
IF ONE OF THESE BANDS HAPPENS TO PASS OVER A TERMINAL, IFR
VISIBILTIES MAY OCCUR. WIND GUSTS OVER 35 KNOTS WILL BE COMMON
FROM LATE MORNING THROUGH THE END OF THE PERIOD AND THERE IS A
CHANCE THAT A FEW SITES IN NORTHERN IOWA MAY TICK OFF A WIND
GUST OF AROUND 50 KNOTS ONCE OR TWICE.
DMX WATCHES/WARNINGS/ADVISORIES
WIND ADVISORY FROM NOON TO 9 PM CST WEDNESDAY FOR IAZ004>007-
015>017-023>028-033>039-044>050-057>061.
DISCUSSION...JIMENEZ
AVIATION...ANSORGE
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