072
FXUS63 KDMX 022018
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
218 PM CST MON DEC 2 2024
KEY MESSAGES
- STRENGTHENING AND GUSTY WINDS FROM THE NORTHWEST WEDNESDAY
INTO WEDNESDAY NIGHT. GUSTS APPROACHING 45 MPH OVER NORTHERN
IOWA.
- NO WIDESPREAD PRECIPITATION CHANCES THROUGH THE END OF THE WEEK.
- UP AND DOWN TEMPERATURE SWINGS - COLD TONIGHT, MODERATING INTO
WEDNESDAY, COLDER ON THURSDAY, THEN TURNING MILDER INTO THE
WEEKEND
DISCUSSION
ISSUED AT 218 PM CST MON DEC 2 2024
STRONG SHORTWAVE TROUGH IS SLIPPING AWAY FROM THE STATE AFTER
DELIVERING AS MUCH AS 1 TO 2 INCHES OF SNOWFALL OVER PORTIONS OF
CENTRAL IOWA. THIS SHORTWAVE DEPARTS WITH HIGH PRESSURE
DROPPING INTO IOWA TONIGHT. THERE REMAINS UNCERTAINTY ON HOW
MUCH THE SKY WILL CLEAR WITH THE HREF SHOWING VARYING CLOUD
DECKS OVER THE STATE, THOUGH THE BEST CHANCE FOR ANY CLEARING
WOULD BE OVER SOUTHERN IOWA AFTER MIDNIGHT. WHEREVER THE SKY IS
CLEAR, THE LIGHT WINDS AND FRESH SNOW WOULD RESULT IN A COLDER
THAN INITIAL NATIONAL BLEND OF MODELS (NBM) FORECAST. FOR NOW,
HAVE BLENDED IN LOWS A DEGREE OR TWO LOWER THAN THE NBM GIVEN
THE CLOUD COVER UNCERTAINTY.
THE HIGH PRESSURE WILL MOVE INTO THE SOUTHEASTERN US ON TUESDAY.
WITH SURFACE FLOW BEING DIRECTED AROUND THIS HIGH AND AN APPROACHING
LOW PRESSURE, WILL SEE TEMPERATURES TICK UPWARD TO WITHIN A FEW
DEGREES EITHER SIDE OF FREEZING WITH BREEZY WINDS ON TUESDAY. THE
LOW PRESSURE WILL PASS NORTH OF THE GREAT LAKES, BUT THE FIRST COLD
FRONT WILL MOVE THROUGH IOWA EARLY ON WEDNESDAY AND THIS WILL CAUSE
AN INCREASE IN WINDS AND GUSTS FROM THE NORTHWEST. TEMPERATURES ARE
STILL FORECAST TO PEAK IN THE MIDDLE 30S TO LOW 40S WITH MUCH OF
THIS INITIAL COLD AIR ADVECTION (CAA) BEING ALOFT. AS THE SURFACE
COLD FRONT MOVES INTO IOWA IN THE AFTERNOON AND OUT OF THE STATE IN
THE EVENING, A STRONGER SURFACE PUSH OF CAA WILL OCCUR. THIS WILL
BRING THE STRONGEST WINDS AND GUSTS AS A HIGH PRESSURE RISE COUPLET
AND SUBSIDENCE MOVES THROUGH. THE LATEST ECMWF EXTREME FORECAST
INDEX HAS INCREASED WITH 70 TO 80% OF ITS MEMBERS HIGHLIGHTING AN
UNUSUALLY WINDY PERIOD COMPARED TO ITS MODEL CLIMATOLOGY OVER MUCH
OF IOWA. FORECAST SOUNDINGS AT EST AND MCW ALSO SHOW THE POTENTIAL
OF 45 TO PERHAPS 50 KNOTS AT THE TOP OF THE MIXED LAYER IN THE
AFTERNOON. THIS WOULD PUT US IN THE POSITION OF NEEDING A WIND
ADVISORY. THEREFORE, HAVE INCREASED WIND AND WIND GUSTS ABOVE
GUIDANCE TO ACCOUNT FOR THIS WINDY PERIOD. SO WHILE WEDNESDAY WILL
BE MILDER, IT WON'T FEEL LIKE IT IN THE AFTERNOON WITH THE APPARENT
TEMPERATURES BEING IN THE TEENS AND 20S. ALSO OF NOTE IN THE
SOUNDINGS WITH THE CAA, LAPSE RATES WILL STEEPEN ALLOWING FOR
ELEVATED INSTABILITY TO DEVELOP. THIS HAS THE HALLMARKS OF BEING
CONVECTIVELY INDUCED RAIN OR SNOW SHOWERS AND HAVE CONTINUED THE LOW
POP MENTION WITH SPRINKLES AND FLURRIES IN THE AFTERNOON OVER
NORTHERN IOWA FOR NOW.
CONDITIONS WILL BE MUCH COLDER ON THURSDAY BEHIND THESE COLD FRONTS
AS HIGH PRESSURE PASSES THROUGH. TEMPERATURES WILL BEGIN TO REBOUND
ON FRIDAY INTO THE WEEKEND WHEN HIGHS WILL BE NEAR IF NOT ABOVE
NORMAL. PRECIPITATION CHANCES REMAIN SLIM AS IOWA REMAINS BENEATH
NORTHWESTERLY FLOW. DETERMINISTIC MODELS SHOW SPURIOUS CHANCES
THURSDAY NIGHT OR FRIDAY NIGHT LARGELY, BUT OVERALL THERE IS NO
CONSISTENT PERIOD FOR PRECIPITATION. THIS IS ALSO REFLECTED IN THE
NBM AND MUCH OF THE PROBABILISTIC, CLUSTER ANALYSIS, AND AI MODELS
AND SO OUR FORECAST GOES FORWARD DRY AS WELL INTO THE WEEKEND.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 1131 AM CST MON DEC 2 2024
MAIN CONCERN IS OVER THE NEXT 6 HOURS OR SO AS LOW STRATUS IS
BEING PESKY WITH WIDESPREAD MVFR CEILINGS. THIS STRATUS AND
FLURRIES WILL EVENTUALLY DISSIPATE WITH THE EARLIEST BEING OVER
NORTHERN IOWA EARLY TO MID AFTERNOON AND MID TO LATE AFTERNOON
OVER SOUTHERN IOWA. HOWEVER, EXACT TIMING IN THE TAFS ARE LOW
CONFIDENCE WITH HOW THE STRATUS IS BEHAVING. MONITORING UPSTREAM
SATELLITE IMAGERY, THE UPSTREAM IFR STRATUS OVER MINNESOTA AND
NORTH DAKOTA DOES NOT SEEM TO BE MOVING THIS DIRECTION SO HAVE
KEPT OUT ANY MENTION. ONCE CONDITIONS RETURN TO VFR BY THIS
EVENING, WINDS WILL BECOME LIGHT AND FROM THE SOUTHWEST AS HIGH
PRESSURE PASSES THROUGH TONIGHT.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...ANSORGE
AVIATION...ANSORGE
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