314
FXUS63 KDVN 191109
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
509 AM CST THU DEC 19 2024
KEY MESSAGES
- A STRONG CLIPPER SYSTEM MOVES THROUGH THE AREA TODAY/TONIGHT,
BRINGING A CHANCE (40-70%) OF LIGHT ACCUMULATING SNOW
- TEMPERATURES NEAR OR ABOVE AVERAGE TODAY 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 351 AM CST THU DEC 19 2024
OUR ACTIVE WEATHER PATTERN CONTINUES THIS WEEK, WITH YET ANOTHER
POTENT SYSTEM EXPECTED TO MOVE THROUGH THE AREA LATER TODAY,
BRINGING MORE ACCUMULATING SNOW TO OUR NORTH. A BROAD UPPER-LEVEL
TROUGH AND ATTENDANT MID-LEVEL SHORTWAVE OVER THE DAKOTAS WILL DIVE
SOUTHEASTWARD TOWARDS THE AREA TODAY. THE ASSOCIATED 1005 MB SURFACE
LOW CURRENTLY SITUATED OVER WESTERN NORTH DAKOTA WILL FOLLOW.
CONFIDENCE REMAINS HIGH THAT THE BULK OF THE SNOW WITH THIS SYSTEM
WILL REMAIN NORTH OF THE AREA, WITH GENERALLY LIGHT AMOUNTS ACROSS
OUR NORTHEAST. FARTHER SOUTH, AS TEMPERATURES WARM ABOVE FREEZING,
PTYPES ALONG AND SOUTH OF INTERSTATE 80 WILL LIKELY FALL AS RAIN OR
DRIZZLE IF ANY ICE CRYSTAL GROWTH CEASES. WE COULD ALSO HAVE BREEZY
CONDITIONS AHEAD OF THE SURFACE LOW THIS MORNING INTO THE EARLY
AFTERNOON, WITH SOUTHERLY GUSTS BETWEEN 20 TO 30 MPH. HIGHS SHOULD
WARM TO THE LOWER 30S NORTH TO THE LOWER/MIDDLE 40S SOUTH.
AS WE HEAD TO TONIGHT, A FEW LOBES OF POSITIVE VORTICITY ADVECTION
EMBEDDED WITHIN THE PARENT TROUGH WILL CONTINUE CHANCES (30 TO 60%)
OF SNOW TONIGHT. AS THE SURFACE LOW DEPARTS THE REGION TO THE
SOUTHEAST, AN IMPRESSIVELY TIGHT SURFACE PRESSURE GRADIENT LOOKS TO
DEVELOP CONCURRENTLY WITH SOME ENHANCED LOW-LEVEL FGEN AND A
GRADUALLY SATURATING DENDRITIC GROWTH ZONE. SOME OF THE 00Z GUIDANCE
SUGGESTS A SATURATED DGZ DEPTH OF ~6000 FT, SO SNOW WOULD VERY MUCH
BE THE DRY/FLUFFY VARIETY. WITH WINDS TURNING MORE NORTHWESTERLY AND
STRENGTHENING WITH GUSTS BETWEEN 25 TO 35+ MPH AND THE DRY, FLUFFY
SNOW COMPOSITION SHOULD SUPPORT AT LEAST SOME PATCHY BLOWING SNOW
OVER FAR NORTHEASTERN IOWA INTO NORTHWESTERN ILLINOIS. SO, EXPECT
NOT ONLY SOME SLIPPERY CONDITIONS FOR THE FRIDAY MORNING COMMUTE,
BUT ALSO SOME REDUCED VISIBILITIES IN THE BLOWING SNOW. TEMPERATURES
WILL ALSO TAKE A DIVE TONIGHT IN THE CAA REGIME BEHIND THE LOW, WITH
LOWS IN THE LOWER TO MIDDLE 20S.
WHAT ABOUT SNOWFALL TOTALS? WE BOOSTED SNOW TOTALS ONLY SLIGHTLY,
GIVEN THE CONCERN FOR HIGHER SNOW RATIOS TONIGHT. STILL THINKING
BETWEEN 1-2 INCHES OF TOTAL SNOW NORTHEAST OF A PRINCETON, IL TO
DUBUQUE, IA LINE, WHICH MATCHES UP WELL WITH THE 19.00Z HREF
ENSEMBLE EXCEEDANCE PROBABILITIES OF 1" OF TOTAL SNOWFALL OF 40 TO
70%+. I WOULDN'T BE SURPRISED IF SOME ISOLATED LOCATIONS SAW JUST
OVER 2" BASED ON THE HREF PROBABILITY MATCHED-MEAN TOTAL
SNOWFALL.
LONG TERM /FRIDAY THROUGH WEDNESDAY/
ISSUED AT 351 AM CST THU DEC 19 2024
THE LONG-TERM PERIOD STARTS WITH ANY LINGERING SNOW FROM TONIGHT'S
CLIPPER EVENTUALLY ENDING FRIDAY MORNING AND BECOMING DRY BY FRIDAY
AFTERNOON. 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 /12Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 505 AM CST THU DEC 19 2024
EXPECT AREAS OF IFR/MVFR CEILINGS WITH THE SYSTEM MOVING ACROSS
NORTHERN IA/IL TODAY. ALSO EXPECT AREAS OF SNOW POSSIBLY MIXED
WITH SOME DZ OVER NORTHERN SECTIONS WITH KDBQ AND KCID BEING
THE MOST IMPACTED TAF LOCATIONS.
LATEST 1046Z IR SATELLITE IMAGE HAS PLENTY OF LOW AND MID LEVEL
CLOUDS ACROSS IOWA WITH THE SYSTEM. THE LATEST SATELLITE ALSO
SHOWS SOME BREAKS IN THE CLOUDS ACROSS PARTS OF WESTERN IOWA.
LATEST 1048Z MOSAIC RADAR IMAGE HAS SOME LIGHT SNOW ACROSS
PARTS OF FAR NORTHERN IOWA WITH THE HEAVIER SNOW FURTHER NORTH.
AS THE SYSTEM CONTINUES TO MOVE ACROSS THE REGION EXPECT AN
INCREASE IN SNOW DURING PART OF THE TAF PERIOD WITH THE HEAVIEST
AROUND 19/21Z-20/00Z TIME FRAME AND ENDING BY 20/03Z AT TAF
LOCATIONS. HAVE PLACED LOWER VISIBILITY RESTRICTIONS AT KDBQ
WITH THE SNOW FOR A BRIEF PERIOD BASED ON DATA. WINDS
SOUTHEASTERLY WILL INCREASE AND SHIFT SOUTH TO SOUTHWEST AND
BECOME NORTHWEST BY 20/05Z. KBRL IS EXPECTING TO BE BEST TAF
LOCATION TODAY WITH ONLY SOME MVFR CLOUDS MOVING IN LATER IN THE
TAF PERIOD.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
SHORT TERM...SCHULTZ
LONG TERM...SCHULTZ
AVIATION...HOLICKY
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