361
FXUS63 KDMX 020926
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
326 AM CST MON DEC 2 2024
KEY MESSAGES
- LIGHT SNOW ENDING THIS MORNING. EXPECT THIS SNOW TO IMPACT THE
MORNING COMMUTE OVER CENTRAL IOWA.
- STRONG AND GUSTY WINDS STILL EXPECTED BY WEDNESDAY AFTERNOON
AND EVENING. WIND GUSTS OF 40 TO 50 MPH ARE POSSIBLE.
- COLD THURSDAY FOLLOWED BY A WARMING TREND TO END THE WEEK AND
INTO NEXT WEEKEND.
DISCUSSION
ISSUED AT 323 AM CST MON DEC 2 2024
A DOUBLE PV ANOMALY STRUCTURE IS DESCENDING SOUTHEAST ACROSS THE
REGION THIS MORNING WITH THE INITIAL ASSOCIATED SHORT WAVE MOVING
INTO CENTRAL IOWA AND THE STRONGER MAIN SYSTEM OVER MINNESOTA. THERE
IS A NARROW FOCUSED RIBBON OF THETA-E ADVECTION AROUND 850 MB OVER
CENTRAL AND SOUTH CENTRAL IOWA. THE COMBINATION OF THE THERMODYNAMIC
AND KINEMATIC FORCING HAS LED TO AN AREA OF LIGHT TO EVEN MODERATE
SNOW OVER CENTRAL IOWA. ROADWAYS ARE BECOMING QUICKLY SNOW COVERED
OVER THE DES MOINES METRO AND TO AREAS NORTH AND WEST AND HAVE
HAD A FEW ROUNDS OF SNOW GLOBE SNOW HERE AT THE OFFICE ALREADY.
THIS WILL BE THE PRIMARY BAND OF SNOW THIS MORNING AND WILL
PRODUCE ONE HALF TO ONE INCH OF SNOW AS IT MOVES SOUTHEAST THIS
MORNING. A FEW LOCATIONS MAY STILL RECEIVE UP TO 1.5 INCHES OF
SNOW. THIS WILL COMPLICATE THE MORNING COMMUTE THIS MORNING AS
IT IS THE FIRST POTENTIAL WINTER DRIVING FOR MANY SINCE LAST
WINTER. THE IA DOT SNOW PLOWS HAVE BEEN OUT EARLY THIS MORNING
THOUGH SO KUDOS TO THEM!
FURTHER UPSTREAM, A STRATUS FIELD REMAINS OVER EASTERN SOUTH DAKOTA
AND INTO CENTRAL MINNESOTA WITH CLOUD BASES IN THE 1500 FT RANGE.
THAT CLOUD LAYER DOES RESIDE WITHIN THE DENDRITIC GROWTH ZONE
TEMPERATURES AND IF YOU ARE GUESSING THAT THE RESULT IS PERSISTENT
FLURRIES TO VERY LIGHT SNOW ACROSS THAT STRATUS DECK THEN YOU ARE
CORRECT! WHILE THE ACCUMULATING SNOW MAY BE DONE BY SUNRISE OR
SHORTLY AFTER, MAY NEED TO EXTEND FLURRIES UNTIL THAT STRATUS PASSES
THROUGH.
SURFACE HIGH PRESSURE OVER WESTERN NORTH DAKOTA NOW WILL MOVE ACROSS
IOWA TONIGHT. THERE IS A LOT OF STRATUS CLOUD COVER WITH THE HIGH
PRESSURE NOW AND THERE IS A STREAM OF INCREASING MID-LEVEL
CLOUDINESS MOVING SOUTHEAST THROUGH MONTANA. THE CLOUD DEBRIS SHOULD
KEEP MOST AREAS FROM BOTTOMING OUT TONIGHT AND WILL ACT MORE AS A
BLANKET THOUGH TEMPERATURES MAY FLUCTUATE AS THEY GO IN AND OUT OF
THE CLOUDS. WARM ADVECTION WILL COMMENCE ON THE BACKSIDE OF THE HIGH
OVER WESTERN IOWA AFTER MIDNIGHT AND THAT WILL ALSO LIMIT THE
TEMPERATURE DROP AS WELL.
TUESDAY WILL BE A BIT WARMER YET BREEZY WITH A FEW GUSTS OVER 25 MPH
POSSIBLE. TEMPERATURES WILL REACH THE LOW TO MID 30S MOST LOCATIONS
EXCEPT THE FAR NORTHEAST NEAR MASON CITY WHERE HIGHS MAY LINGER IN
THE UPPER 20S.
BEYOND TODAY, THE MAIN WEATHER FOCUS REMAINS WEDNESDAY AND WEDNESDAY
NIGHT AS AN UPPER LOW DESCENDS INTO THE WESTERN GREAT LAKES AND
DRAGS STRONG COLD ADVECTION INTO THE AREA. THE THERMAL RIDGE WILL
MOVE ACROSS IOWA TUESDAY NIGHT WHICH WILL KEEP OVERNIGHT IN THE 20S.
AN INITIAL BOUNDARY WILL PASS ACROSS CENTRAL IOWA LATE TUESDAY NIGHT
AND EARLY WEDNESDAY MORNING. THAT BOUNDARY WILL MAINLY BRING COLD
ADVECTION AROUND 925 MB WHICH WILL HELP WITH MIXING THE BOUNDARY
LAYER IN THE MORNING AND HELP WITH SURFACE WARMING. STILL CONTINUING
WITH HIGH TEMPERATURES IN THE 30S NORTH TO 40S SOUTH. THE STRONGER
COLD FRONT WILL REACH NORTHERN IOWA BY EARLY AFTERNOON AND CURRENT
TIMING WILL PLACE IT NEAR INTERSTATE 80 BY 6 PM. EXPECT FALLING
TEMPERATURES AND GUSTY TO STRONG NORTHWEST WINDS BEHIND THIS BOUNDARY
PASSAGE. THE WIND POTENTIAL STILL LOOKS ON TRACK FOR HEADLINE
CRITERIA WIND. MIXED LAYER WINDS ARE INCHING HIGHER OVER THE PAST 24
HRS AND NOW IN THE UPPER 30 TO UPPER 40 KT RANGE. THE INGREDIENTS
ARE STILL THERE WITH STRONG COLD ADVECTION, GOOD SUBSIDENCE WITH THE
UPPER SHORT WAVE PASSAGE, GOOD SURFACE PRESSURE RISES AND INCREASING
PRESSURE GRADIENT. THIS SHOULD RESULT IN SUSTAINED WINDS NEAR 30 MPH
AND WIND GUSTS NEAR TO ABOVE 45 MPH ACROSS MUCH OF CENTRAL AND
NORTHERN IOWA INTO THE EVENING HOURS.
THE WIND WILL DIMINISH LATE WEDNESDAY NIGHT AND INTO THE DAY
THURSDAY AS ANOTHER AREA OF HIGH PRESSURE ARRIVES. THURSDAY WILL BE
COLD AGAIN WITH HIGHS IN THE TEENS TO LOW 20S. ANOTHER SYSTEM IS
PROJECTED TO MOVE THROUGH THE REGION FRIDAY AND THIS SYSTEM
CONTINUES TO LOOK DEPRIVED OF MOISTURE. WARMER AIR WILL FOLLOW THE
SYSTEM WITH A WARMING TREND INTO NEXT WEEKEND.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 1124 PM CST SUN DEC 1 2024
LIGHT SNOW IS MOVING IN FROM NORTHWEST IOWA AND WILL AFFECT ALL
TERMINALS FOR SEVERAL HOURS OVERNIGHT INTO MONDAY MORNING. THIS
WILL RESULT IN A PERIOD OF MVFR VISIBILITY AND CEILINGS, WITH
BRIEF SPELLS OF IFR POSSIBLE ESPECIALLY AT FOD/MCW. HAVE MADE
BEST ESTIMATE ON TIMING THESE CONDITIONS BUT AMENDMENTS ARE
LIKELY OVERNIGHT. THE SNOW WILL END WITHIN A COUPLE HOURS BEFORE
OR AFTER SUNRISE MONDAY, WITH CEILINGS THEN STEADILY IMPROVING
LATER IN THE MORNING TO VFR FOR MOST OF THE DAY.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...DONAVON
AVIATION...LEE
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