236
FXUS63 KDVN 191923
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
123 PM CST THU DEC 19 2024
KEY MESSAGES
- THE ONGOING "DOUBLE BARRELED" CLIPPER WILL CONTINUE THROUGH
TONIGHT, WITH A CONFIDENT TRANSITION TO COLD, WINDY CONDITIONS WITH
PASSING FLURRIES AND LIGHT SNOW OVERNIGHT.
- TEMPERATURES WILL COOL DOWN FRIDAY AND SATURDAY BEFORE WARMING UP
TO START THE CHRISTMAS WEEK
- PROSPECTS FOR A WHITE CHRISTMAS REMAIN QUITE UNFAVORABLE
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 120 PM CST THU DEC 19 2024
AN ELONGATED "DOUBLE BARRELED" CLIPPER IS MOVING SOUTHEAST
THROUGH MINNESOTA AND NORTHEAST IOWA TODAY. WARM ADVECTION SNOW
ASSOCIATED WITH A STRONG LEAD VORTICITY MAXIMUM (EVIDENT ON
RADAR AND SATELLITE), HAS BEEN PRODUCING ACCUMULATING SNOW OVER
MINNESOTA, WISCONSIN, AND IOWA NORTH OF HIGHWAY 20 TODAY. THIS
HAS JUST BARELY IMPACTED OUR NORTHERN COUNTIES AND A CLOSE
INSPECTION OF PLOW CAMERA INFORMATION SHOWS THAT THROUGH 1 PM,
WE'VE HAD A FEW TENTHS OR NOTHING SOUTH OF THE NORTHERN BORDERS
OF BUCHANAN THROUGH DUBUQUE COUNTIES, WHILE JUST TO THE NORTH,
1+ INCHES OF SNOW HAS OCCURRED. UPSTREAM, THE MAIN LOW AND
SECONDARY VORTICITY IS DROPPING INTO SOUTHWESTERN MN.
AS OF 1 PM, THE "WARM SECTOR" OF THE CLIPPER WITH TEMPERATURES IN
THE 30S AND 40S IS SPREADING INTO EASTERN IOWA. SOME SHOWERY SNOW
AND RAIN SHOWERS ARE BEGINNING TO DEVELOP IN THE WAA BAND FROM NEAR
IOWA FALLS THROUGH THE QUAD CITIES JUST AHEAD OF THIS WARMER AIR.
THIS PRECIPITATION APPEARS TO BE QUICKLY MOVING EAST, LIGHT,
AND WITH TEMPERATURES RISING ABOVE FREEZING DURING THE
AFTERNOON, LOW OR ZERO IMPACT FOR OUR CENTRAL CWA.
TONIGHT, WITH THE LOW PASSING VERY CLOSE TO DUBUQUE AROUND 5-7 PM,
WE'RE LIKELY TO AGAIN FOCUS MOST OF THE SNOW POTENTIAL TO THE
NORTHEAST OF THE CWA THIS EVENING. HOWEVER, GIVEN THE IMPROVING
SATURATION ALREADY NOTED NEAR HIGHWAY 20, SOME PERIODS OF LIGHT
TO MODERATE SNOW IS EXPECTED, AND ACCUMULATIONS OF 1 - 2 INCHES
CONTINUE TO BE SUPPORTED BY FRESH MODEL DATA, CONCEPTUAL
FORECASTS, AND UPSTREAM CONDITIONS/RADAR. WHILE SOME TRANSIENT
SNOW SHOWERS CAN BE EXPECTED FARTHER SOUTH THROUGH I-80, THE
MILD TEMPERATURES AND BRIEF NATURE OF THESE SHOULD KEEP IMPACTS
AND ACCUMULATIONS RATHER LOW. TOWARDS THE 4PM-7PM, WINDOW, A
FULL TRANSITION TO RAIN SHOWERS IS EXPECTED TO THE SOUTH OF
HIGHWAY 30, AGAIN WITH LIGHT AMOUNTS BEFORE THE LOW'S PASSAGE
EAST BRINGS IN COLDER CONDITIONS, FLURRIES/SNOW SHOWERS, AND
GUSTY WEST NORTH WEST WINDS FOR THE LATER EVENING AND OVERNIGHT
HOURS.
WINDS WILL BE ON THE INCREASE, THOUGH THE COUPLING OF STRONG WINDS
ALOFT AND DEEP MIXING FOUND TO THE WEST IS NOT EXPECTED TO MOVE
THROUGH OUR CWA IN THAT INTENSITY. WITH MORE MOISTURE,WE'LL BE
PLENTY WINDY, BUT MORE IN THE PEAK WIND RANGE OF 30-35 KTS FOR
GUSTS. THOSE WINDS WITH TEMPERATURES FALLING TO THE TEENS TO
LOWER 20S WILL BRING WIND CHILLS DOWN TO THE +SINGLE DIGITS
TONIGHT!
I'VE PAIRED BACK BLOWING SNOW IN THE GRIDS TO LOCATIONS IN THE
HIGHWAY 20 CORRIDOR DURING THE LATE EVENING TO OVERNIGHT, AS THIS
SHOULD BE THE ONLY LOCATION EXPECTED TO HAVE FRESH SNOW OVER 1 INCH.
STILL, ANY PASSING SNOW SHOWER WITH WINDS OF 20-30 MPH, WILL SEE
BRIEF LOWERED VISIBILITIES, AND THIS CAN BE ADDRESSED IN SPS AND
GRAPHICS TONIGHT.
LONG TERM /FRIDAY THROUGH WEDNESDAY/
ISSUED AT 120 PM CST THU DEC 19 2024
FRIDAY, COLD BRISK CONDITIONS WILL CONTINUE. THE TIGHT SURFACE
PRESSURE GRADIENT BEHIND THE SURFACE LOW SHOULD KEEP GUSTY NORTHWEST
WINDS GOING, ALONG WITH PLENTY OF CLOUD COVER FROM THE CYCLONIC
FLOW/CAA REGIME. HIGHS FRIDAY WILL COOL TO MORE SEASONAL VALUES -
INTO THE MIDDLE 20S NORTHWEST TO NEAR FREEZING SOUTHEAST. FRIDAY
NIGHT LOOKS TO BE QUITE COLD, WITH A SURFACE HIGH PRESSURE RIDGE
AXIS TRANSLATING THROUGH THE REGION, RESULTING IN LIGHT AND VARIABLE
WINDS. FOR LOCATIONS THAT RECEIVE ACCUMULATING SNOW TODAY/TONIGHT,
OVERNIGHT LOW TEMPERATURES COULD FALL INTO THE SINGLE DIGITS ABOVE
ZERO. FOR MOST, LOWS FRIDAY NIGHT WILL FALL TO THE TEENS, SO MAKE
SURE TO BUNDLE UP IF YOU PLAN TO BE OUT AND ABOUT. THE REMAINDER OF
THE WEEKEND REMAINS DRY, WITH A LITTLE BIT OF A WARM UP BY SUNDAY
THANKS TO THE SOUTHERLY RETURN FLOW AS THE HIGH PRESSURE RIDGE
DEPARTS. HIGHS SHOULD WARM ABOVE FREEZING FOR MOST LOCATIONS SUNDAY.
FOR MONDAY THROUGH CHRISTMAS DAY, NOT MUCH IN THE WAY OF
PRECIPITATION, EXCEPT FOR MONDAY INTO MONDAY NIGHT, WHEN A COOL
FRONT/MID-LEVEL IMPULSE MOVE THROUGH THE AREA. THE BULK OF THE QPF
APPEARS TO REMAIN TO OUR EAST, BUT WE COULD SEE A LIGHT RAIN/SNOW
MIXTURE, WITH SNOW POSSIBLE NORTH OF INTERSTATE 80.
LOOKING AHEAD TO CHRISTMAS DAY, CONFIDENCE IS VERY HIGH THAT THE
PROSPECTS FOR A WHITE CHRISTMAS ARE PRETTY BLEAK. THE LATEST NBM
EXCEEDANCE PROBABILITIES OF TEMPERATURES ABOVE FREEZING ARE OVER 90%
FOR MOST LOCATIONS IN OUR REGION, AND INDEED, THE NBM DETERMINISTIC
HIGH TEMPERATURES HAVE US WARMING INTO THE UPPER 30S NORTH TO THE
MIDDLE 40S SOUTH, SO BAD NEWS FOR THOSE THAT ARE LOOKING FOR SOME
SNOWINESS FOR CHRISTMAS.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1115 AM CST THU DEC 19 2024
A FAST MOVING CLIPPER TYPE STORM SYSTEM WILL MOVE FROM EASTERN
SOUTH DAKOTA THROUGH NORTHEAST IOWA BETWEEN 18Z AND 00Z THIS
EVENING. THIS WILL CONTINUE TO BRING VARIABLE VFR/MVFR
CONDITIONS WITH PASSING LOW CLOUDS IN SOUTHERLY FLOW OVER MOST
OF IOWA AND ILLINOIS THROUGH THIS AFTERNOON, AS THE SNOW REMAINS
ALONG AND NORTH OF HIGHWAY 20. THIS CONTINUE TO LOOK JUST NORTH
OF DBQ THROUGH MID AFTERNOON, BEFORE THE SNOW SHIFTS A BIT
SOUTH, AND MIXES WITH OR CHANGES TO RAIN ALONG INTERSTATE 80
AROUND 00Z, WHEN THE LOW PRESSURE CENTER MOVES BY. BEHIND THE
LOW ( THE 06Z TO 18Z TIME FRAME) WE WILL BE WINDY, AND COLDER,
WITH MVFR CLOUDS EXPECTED. SOME PASSING FLURRIES ARE ALSO
POSSIBLE AT TIMES OVERNIGHT.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
SHORT TERM...ERVIN
LONG TERM...SCHULTZ
AVIATION...ERVIN
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