436
FXUS63 KDMX 181725
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1125 AM CST SAT JAN 18 2025
...UPDATED FOR THE 18Z AVIATION DISCUSSION...
KEY MESSAGES
- BITTER COLD TEMPERATURES THROUGH THE WEEKEND INTO EARLY NEXT
WEEK. DANGEROUS WIND CHILLS OF -20F OR COLDER AT TIMES
BEGINNING TONIGHT THROUGH TUESDAY MORNING.
- WARM UP MID-WEEK AS HIGHS RETURN CLOSER TO AVERAGE.
- FORECAST REMAINS DRY AT THIS TIME, BUT TRENDS ARE POINTING
TOWARD A POSSIBLE PRECIP WINDOW WEDNESDAY AND/OR THURSDAY.
DISCUSSION
ISSUED AT 237 AM CST SAT JAN 18 2025
OUR WELL-ADVERTISED DIP INTO A COLD SNAP IS UNDERWAY AS A DEEP
LONGWAVE TROUGH CARVES OUT A HOME OVER MUCH OF THE CONUS. STRONG
COLD AIR ADVECTION EXTENDS ALMOST THE FULL LENGTH OF THE PLAINS
STATES AS BLUSTERY NORTH WINDS HAVE DELIVERED OUR FIRST ROUND
OF BITTER COLD AIR. WINDS HAVE BEEN QUITE GUSTY WITHIN THE CAA
REGIME BOOSTED BY ISALLOBARIC FORCING. GUSTS OF 30 TO 40 MPH
HAVE BEEN COMMON OVERNIGHT. SHALLOW HCRS HAVE BEEN OBSERVED IN
BOTH SATELLITE AND RADAR IMAGERY AND HAVE PRODUCED SCATTERED
SNOW FLURRIES AS THE CLOUD-BEARING LAYER COOLS THROUGH THE DGZ.
EVEN THE EFFICIENT CRYSTAL PRODUCTION HAS STRUGGLED TO OVERCOME
THE SUBSTANTIALLY DRY AIRMASS, WHICH SHOULD WIN OUT OVER THE
NEXT FEW HOURS AND EVENTUALLY CEASE LINGERING FLURRY ACTIVITY.
DIURNAL WARMING STRUGGLES TO OVERCOME COLD AIR ADVECTION TODAY AS
TEMPS ONLY MARGINALLY IMPROVE. HIGHS WILL BE IN THE TEENS TO LOW 20S
WITH BLUSTERY NORTH WINDS MAKING IT FEEL LIKE THE SINGLE DIGITS
ABOVE AND BELOW ZERO. WIND CHILL VALUES FALL TO -20F AND COLDER
TONIGHT INTO SUNDAY MORNING FOR ALL BUT THE SOUTHERN FRINGES OF
THE FORECAST AREA. THE INHERITED COLD WEATHER ADVISORY REMAINS
MOSTLY ON TRACK, BUT DID REFINE JUST A BIT BY ADDING ANOTHER ROW
OF COUNTIES SOUTH TO ACCOUNT FOR MARGINALLY COLDER WIND CHILL
VALUES COMPARED TO THE PREVIOUS FORECAST. LOW-AMPLITUDE
SHORTWAVES DIVING SOUTH THROUGH THE MEAN SYNOPTIC TROUGH DELIVER
REINFORCING SHOTS OF ARCTIC AIR, KEEPING THE BITTER COLD
AIRMASS FIRMLY IN PLACE TO START NEXT WEEK. HIGHS WILL ONLY BE
IN THE SINGLE DIGITS AND TEENS WITH LOWS FALLING BELOW ZERO,
ESPECIALLY ACROSS THE NORTH MONDAY NIGHT WHERE BOTH THE GEFS AND
ECENS FEATURE A >50% PROBABILITY OF TEMPS COLDER THAN -10F.
ADDITIONAL WIND CHILL HEADLINES ARE A NEAR CERTAINTY AND WILL BE
EVALUATED WITH FUTURE UPDATES.
TROUGH AND BITTER COLD AIRMASS ARE SHUNTED EAST MID-WEEK, REPLACED
BY A PERIOD OF SHORTWAVE RIDGING AND MODERATING TEMPERATURES BACK
CLOSER TO SEASONAL NORMS. MODELS CONTINUE TO DISAGREE A BIT ON
PATTERN EVOLUTION WITH THE GFS SHOWING A DEEPER WAVE DIGGING BACK
SOUTH AND ANOTHER STINT OF BELOW NORMAL TEMPS TOWARD THE END OF NEXT
WEEK, WHEREAS THE EURO IS MORE PROGRESSIVE AND ON THE WARMER SIDE OF
GUIDANCE. LATEST NBM REMAINS DRY THROUGH THE 7 DAY, HOWEVER ENSEMBLE
PROBABILITIES HAVE BEEN TRENDING UPWARD FOR MEASURABLE (>= 0.01"
LIQUID EQUIVALENT) PRECIPITATION TOWARD WED-THU. POPS MAY NEED
TO BE INTRODUCED IN FUTURE UPDATES IF TRENDS HOLD IN THAT
DIRECTION.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 1125 AM CST SAT JAN 18 2025
BREEZY WIND OUT OF THE NORTHWEST WILL GUST 20-25+ KTS THROUGH
THE TAF PERIOD, IN MOST CASES NOT DIMINISHING OVERNIGHT. AS
OCCURRED LAST EVENING, LOW STRATUS IS EXPECTED ACROSS NORTHERN
IOWA OVERNIGHT (INCLUDED AT KMCW/KALO AT THIS TIME). VERY
ISOLATED SNOW SHOWERS MAY DEVELOP BENEATH THE STRATUS IN THIS
BREEZY NORTHWEST FLOW SETUP OVERNIGHT. THESE SHOWERS ARE OFTEN
HIGHLY ISOLATED AND SHORT LIVED, THUS HAVE NOT INCLUDED IN TAFS
AT THIS TIME. SHOULD THEY OCCUR, A PERIOD OF MVFR VISIBILITY TO
ACCOMPANY THE LOWER CEILINGS WOULD BE THE MOST LIKELY SCENARIO.
DMX WATCHES/WARNINGS/ADVISORIES
COLD WEATHER ADVISORY FROM 3 AM TO NOON CST SUNDAY FOR
IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081-
082.
DISCUSSION...MARTIN
AVIATION...HAGENHOFF
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