130
FXUS63 KDMX 162004
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
204 PM CST SUN FEB 16 2025
KEY MESSAGES
- ACCUMULATING SNOWFALL SOUTHWEST AND SOUTH LATE TONIGHT THROUGH
MONDAY. AMOUNTS OF 2-3" LIKELY IN OUR SOUTHWESTERN COUNTIES
AROUND BEDFORD AND MOUNT AYR. LIGHT SNOW MAY LINGER AT TIMES
ACROSS THE AREA TUESDAY INTO WEDNESDAY, BUT WITH LITTLE TO NO
ADDITIONAL ACCUMULATION.
- PERIOD OF VERY COLD WEATHER FOR MUCH OF THIS WEEK, WITH
TEMPERATURES FALLING BELOW ZERO EACH OF THE NEXT FIVE NIGHTS,
AND WIND CHILLS BOTTOMING OUT AROUND 20 BELOW ZERO (SOUTHEAST)
TO NEAR 40 BELOW ZERO (NORTHWEST) TUESDAY MORNING.
- WARMER WEATHER APPEARS LIKELY FOR NEXT WEEKEND INTO EARLY THE
FOLLOWING WEEK, PROVIDING A LIGHT AT THE END OF THE TUNNEL.
DISCUSSION
ISSUED AT 204 PM CST SUN FEB 16 2025
A PERIOD OF NOTABLY COLDER WEATHER THAT BEGAN LAST NIGHT WILL
PERSIST INTO MUCH OF THE COMING WEEK, WITH THE COLDEST PERIOD
COMING GENERALLY FROM MONDAY NIGHT THROUGH WEDNESDAY NIGHT.
BEFORE THAT, HOWEVER, ACCUMULATING SNOWFALL IS ANTICIPATED IN
SOUTHWESTERN IOWA ON MONDAY.
A LARGE RIDGE OF SURFACE HIGH PRESSURE IS SPILLING FROM SOUTHERN
CANADA DOWN ACROSS THE DAKOTAS AND IOWA THIS AFTERNOON, BRINGING
GUSTY NORTHWEST BREEZES AND COLD TEMPERATURES ONLY IN THE SINGLE
DIGITS TO LOWER TEENS ACROSS MOST OF OUR AREA AT THIS TIME.
WINDS WILL DIMINISH AFTER THIS EVENING AS THE CORE OF THE RIDGE
BUILDS CLOSER AND DECOUPLING TAKES PLACE, WHICH WOULD NORMALLY
FAVOR RAPID RADIATIONAL COOLING ESPECIALLY WITH FRESH SNOW ON
THE GROUND ACROSS MUCH OF THE AREA. HOWEVER, THIS WILL BE
COMPLICATED BY INCREASING CLOUDS FROM THE WEST/SOUTHWEST AS A
ZONE OF MODEST FRONTOGENETICAL FORCING APPROACHES IN THE BRISK
ZONAL STEERING FLOW ALOFT. HOURLY TEMPERATURE TRENDS TONIGHT
WILL THUS BE VERY TRICKY TO FORECAST AS NIGHTTIME COOLING MAY
INITIALLY BE SLOWED A BIT BY THE ORGANIZED WINDS, ACCELERATE AS
THE WINDS DIMINISH, BUT THEN TEMPERATURES MAY STABILIZE OR EVEN
RISE AS MID/HIGH LEVEL CLOUDS SPREAD IN LATE. GIVEN THESE
COMPETING FACTORS OPTED TO STAY VERY CLOSE TO PREVIOUS FORECAST
WHICH IS A LITTLE BELOW THE 50TH PERCENTILE OF THE GUIDANCE
ENVELOPE, BUT ANY CHANGES IN THE WIND OR SKY COVER FORECAST
COULD RESULT IN SIGNIFICANT TEMPERATURE VARIATIONS ACROSS OUR
SERVICE AREA OVERNIGHT.
AS THE AFOREMENTIONED FRONTOGENETICAL FORCING BUILDS IN AND
SLIDES ACROSS NEBRASKA, SOUTHERN IOWA, AND NORTHERN MISSOURI IT
WILL GENERATE SNOWFALL IN THESE AREAS BEGINNING LATE TONIGHT AND
CONTINUING THROUGH MONDAY. AGAIN, THERE ARE COMPETING FACTORS
SUPPORTING RELATIVELY HIGHER OR LOWER SNOWFALL AMOUNTS IN OUR
SOUTHWESTERN COUNTIES. FORECAST SOUNDINGS INDICATE A DEEP
SATURATED LAYER ALMOST ENTIRELY WITHIN THE DGZ (DENDRITIC GROWTH
ZONE) ON MONDAY MORNING, SUPPORTING HIGH SLRS (SNOW TO LIQUID
RATIOS) AND HIGHER SNOWFALL AMOUNTS. HOWEVER, THE FORCING IS
MODEST AND FORECAST QPF LIGHT, ONLY AROUND 0.10 INCH IN OUR
SOUTHWEST CORNER, PLUS NEAR-SURFACE DRY AIR FILTERING OUT OF THE
HIGH PRESSURE RIDGE MAY UNDERCUT THE SNOW A BIT AND RESULT IN
SOME FRAGMENTING/SUBLIMATION EFFECTS WHICH WOULD LOWER THE SLRS.
ONCE AGAIN MAINTAINED ESSENTIALLY A PERSISTENCE FORECAST, WITH
MAXIMUM ACCUMULATIONS DOWN AROUND RINGGOLD AND TAYLOR COUNTIES
OF AROUND 2-3 INCHES. THAT IS ACTUALLY ABOVE MUCH OF THE
GUIDANCE, RESPECTING THE DEEP DGZ DEPICTED IN FORECAST
SOUNDINGS. DID MAKE TWO ADJUSTMENTS TO THE ONGOING WINTER
WEATHER ADVISORY IN THE SOUTHWEST, ADDING ADAMS AND DECATUR
COUNTIES WHERE FORECAST SNOW AMOUNTS APPROACH 2.5" OR SO, AND
DELAYING THE START TIME OF THE ADVISORY TO 11Z/5AM MONDAY AS THE
PRECIPITATION ONSET TIME HAS DELAYED A BIT. ALSO TIGHTENED UP
THE POP GRADIENT ON THE NORTHERN EDGE OF THE SNOW, AS DRY AIR
ENTRAINMENT FROM THE NORTH SHOULD RESULT IN A PRETTY SHARP
CUTOFF WITH LITTLE TO NO ACCUMULATION EXPECTED NORTH OF A LINE
ROUGHLY FROM ATLANTIC TO BLOOMFIELD.
ASIDE FROM THE SNOW IN THE SOUTH/SOUTHWEST ON MONDAY, THE BIG
STORY WILL BE THE INTENSE COLD COMING FOR SEVERAL DAYS THIS
WEEK. THE PRIMARY GENERATOR OF THIS COLD SNAP WILL BE THE
AFOREMENTIONED SURFACE HIGH PRESSURE RIDGE BUILDING DOWN FROM
CANADA, WHICH WILL DOMINATE THE MIDWEST AND IOWA UNTIL AT LEAST
FRIDAY. THE SNOW PACK IN PLACE ACROSS MUCH OF THE AREA WILL ACT
AS A POSITIVE REINFORCEMENT AS WELL, HOWEVER, CLOUD COVER WILL
PROVIDE SOME MITIGATING EFFECTS AT TIMES. IN PARTICULAR, FROM
MONDAY NIGHT THROUGH WEDNESDAY A 500 MB TROUGH WILL ROTATE
SLOWLY INTO AND OVER THE UPPER MIDWEST, RESULTING IN MID/HIGH
LEVEL CLOUDS AT TIMES WHICH MAY DAMPEN DAYTIME "WARMING" A BIT
AND COULD LIMIT NIGHTTIME COOLING SOMEWHAT SIGNIFICANTLY. IN ANY
EVENT IT WILL BE VERY COLD, BUT THE COMBINED AND SOMETIMES
COMPETING EFFECTS OF SNOW COVER, WIND VARIATIONS, AND
INTERMITTENT CLOUDS WILL INFLUENCE COLD WEATHER WATCH, WARNING,
AND ADVISORY DECISIONS OVER THE NEXT SEVERAL DAYS. AT THIS TIME
HAVE NOT MADE ANY CHANGES TO THE ONGOING COLD WEATHER ADVISORY
FOR TONIGHT THROUGH MONDAY MORNING, OR THE EXTREME COLD WATCH
FOR MONDAY NIGHT THROUGH TUESDAY MORNING. IT STILL APPEARS
LIKELY WARNING CRITERIA WILL BE MET ACROSS AT LEAST PARTS OF THE
AREA, IF NOT MOST OF IT, EVEN IF MID/HIGH CLOUDS TO PERSIST
THROUGH MONDAY NIGHT. HOWEVER, THAT WOULD IMPACT WHICH PARTS OF
THE AREA MEET WARNING CRITERIA AND WHICH DO NOT, SO HAVE
DEFERRED THIS DECISION IN FAVOR OF MAINTAINING THE WATCH AT THIS
TIME. ON TUESDAY NIGHT AND WEDNESDAY NIGHT LOW TEMPERATURES
ACTUALLY FALL TO EVEN LOWER LEVELS, HOWEVER WINDS ARE LIGHTER SO
WIND CHILL VALUES ARE SLIGHTLY LESS COLD. EVEN SO, IT IS
ANTICIPATED THAT EITHER ADVISORIES OR WARNINGS WILL BE NEEDED
FOR THESE PERIODS AT SOME POINT AS WELL.
IN THE EXTENDED FORECAST PERIOD, AROUND NEXT WEEKEND INTO EARLY
THE FOLLOWING WEEK, IT APPEARS WE WILL SEE WEAKER AND MORE
BENIGN WEST NORTHWESTERLY 500 MB FLOW, RESULTING IN ALTERNATING
PERIODS OF MODEST THERMAL RIDGING AS WELL AS A RETURN OF
GENERALLY SOUTHWESTERLY SURFACE FLOW. THIS SHOULD SUPPORT
NOTABLY WARMER WEATHER AND CURRENTLY THE FORECAST HIGH
TEMPERATURES FOR NEXT SATURDAY AND SUNDAY ARE IN THE 20S AND
30S, SO THAT WILL PROVIDE SOMETHING TO LOOK FORWARD TO DURING
THE COLD DAYS AHEAD.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1113 AM CST SUN FEB 16 2025
SCATTERED CLOUDS BASED ANYWHERE FROM FL011 TO FL100 WILL AFFECT
THE AREA THIS AFTERNOON, PRODUCING BRIEF AND TRANSIENT MVFR
CEILINGS AT SOME SITES (MAINLY FOD/DSM/OTM) BEFORE BREAKING UP
LATER TODAY. VFR CONDITIONS ARE THEN FORECAST OVERNIGHT WITH
DIMINISHING WINDS. LOW CLOUDS AND LIGHT SNOW WILL MOVE INTO
SOUTHERN IOWA ON MONDAY AND MAY AFFECT DSM/OTM AFTER ABOUT 15Z,
BUT IMPACTS ARE MORE LIKELY AFTER 18Z AND HAVE HELD OFF MENTION
IN THE 18Z TAFS FOR NOW.
DMX WATCHES/WARNINGS/ADVISORIES
COLD WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON CST MONDAY
FOR IAZ004>007-015>017-023>028-035>039-050.
EXTREME COLD WATCH FROM LATE MONDAY NIGHT THROUGH TUESDAY
MORNING FOR IAZ004>007-015>017-023>028-033>039-044>050-057>062-
070>075-081>086-092>097.
WINTER WEATHER ADVISORY FROM 5 AM TO 6 PM CST MONDAY FOR
IAZ081-092>094.
DISCUSSION...LEE
AVIATION...LEE
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