821  
FXUS63 KDVN 172358  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
558 PM CST TUE DEC 17 2024  
   
KEY MESSAGES
 
 
- CHANCE (30-70+%) OF SNOW, WINTRY MIX AND RAIN IN PORTIONS OF THE  
CWA TONIGHT FROM NORTH TO SOUTH.  
 
- STRONG CLIPPER THURSDAY MAY BRING A CHANCE FOR ACCUMULATING SNOW  
FOR AREAS NORTH OF I-80.  
 
- COLDER AND MAINLY DRY FRIDAY, THEN A LOW CHANCE FOR LIGHT SNOW SOMEWHERE  
IN OR NEAR THE LOCAL FORECAST AREA LATE FRIDAY NIGHT INTO  
SATURDAY.  
 

 
   
SHORT TERM /THROUGH WEDNESDAY NIGHT/
 
 
ISSUED AT 251 PM CST TUE DEC 17 2024  
 
TONIGHT...PROGRESSIVE PATTERN WITH EMBEDDED WAVES CONTINUING ACRS  
THE CONUS, WITH WATER VAPOR IMAGERY SHOWING ONE UPSTREAM WAVE OF  
NOTE CURRENTLY ACRS NE, WITH AND ASSOCIATED LEESIDE BAROCLINIC LEAF  
FROM THE SOUTHWESTERN PLAINS TO ACRS IA. THIS FEATURE ALSO ALREADY  
PRODUCING SNOW ACRS SD, SOUTHWEST MN INTO NORTHWEST IA. THE DIGGING  
UPPER TROF AXIS WILL PRODUCE A SWATH OF PRECIP(SNOW) ACRS THE LOCAL  
AREA FROM NORTHWEST-TO-SOUTHEAST FROM THIS EVENING AND INTO THE  
OVERNIGHT, ALTHOUGH QUITE A BIT OF TOP-DOWN SATURATION TO GO WITH  
IT'S INITIAL LIFT BEFORE PRECIP REACHES THE SFC. ANOTHER ELEVATED WAA  
TYPE CONVEYOR FROM THE SOUTH WILL LOOK TO SPREAD SCTRD RAIN SHOWERS  
UP FROM THE SOUTH AND MAKE IT INTO THE SOUTHERN QUARTER TO THIRD OF  
THE DVN CWA. BACK TO THE SNOW IN THE NORTH, STRENGTH OF H8-H7 MB F-  
GEN FORCING AND SATURATION MAY LAY OUT NARROW OR CONFINED SWATHS OF  
HIGHER SNOW AMOUNT'S OF 1-2+ INCHES BY 12Z WED MORNING, BUT WHERE  
THESE "ENHANCED" SWATHS LAY OUT THE CHALLENGE OF COURSE. BUT LOOKING  
AT SOME OF THE F-GEN PROGS THAT SEEM TO BE HANDLING THE BETTER SNOW  
BANDS OFF TO THE NORTHWEST CURRENTLY, THEY LAY OUT GENERALLY IN THE  
VICINITY OF THE HWY 20 CORRIDOR, WITH SECONDARY FORCING BAND CLOSET  
TO HWY 30.  
 
AS THE SNOW BANDS SAG SOUTH TOWARD I80 AND SOME OF THE RAIN IN THE  
SOUTH TRIES TO PUSH NORTHWARD, FCST SOUNDINGS SUGGEST A BUILDING  
WARM WEDGE ALOFT ENOUGH TO PRODUCE A WINTRY MIX IN THE VICINITY OF  
THE I-80 CORRIDOR TOWARD MIDNIGHT AND A FEW HOURS PAST. THE VERTICAL  
PROFILES SUGGEST BOUTS OF SLEET, FREEZING RAIN AND SNOW POSSIBLE  
ALONG THIS CORRIDOR(A COUNTY OR TWO EITHER SIDE OF I-80)UNTIL  
NORTHERLY FLOW AND EVAPO-COOLING IN THE WARM LAYER COOL IT ENOUGH  
FOR A TREND BACK TO MAINLY LIGHT SNOW. WITH SFC TEMPS HOVERING AT  
OR A LITTLE BELOW FREEZING, SOME LIGHT ICE GLAZE MAY BE POSSIBLE IN  
BETWEEN THE SLEET AND SNOW. CURRENT HIRES PROGS SUGGEST MOST OF THE  
PRECIP EAST OF THE CWA BY THE TIME THE MORNING RUSH IS IN EARNEST,  
BUT THERE MAY BE SOME LINGERING SLICK SPOTS ON UNTREATED SURFACES.  
LOW TEMPERATURES TONIGHT BEHIND A PASSING SFC TROF INDUCED BY THE  
WAVE ALOFT, WILL LOOK TO RANGE FROM THE LOW 20S IN THE NORTHWEST, TO  
THE LOWER 30S IN THE SOUTHEAST.  
 
WEDNESDAY...A BREEZY NORTHWEST SFC FLOW COOLING DAY IN INCOMING  
RIDGE PRESSURE GRADIENT. EXTENT OF CLOUD COVER SOMEWHAT UNCERTAIN,  
BUT WOULD THINK THAT WITH INCOMING SUBSIDENCE FIELDS THAT THERE  
WOULD BE SOME BREAKS AT TIMES FOR AT LEAST PARTIAL SUN. COLD AND DRY  
WED NIGHT UNDER LINGERING RIDGE AXIS. MAY HAVE TO THINK ABOUT SOME  
PATCHY FOG, BUT TOO UNCERTAIN AT THIS POINT TO INCLUDE IN THE  
GRIDS.  
 

 
   
LONG TERM /THURSDAY THROUGH TUESDAY/
 
 
ISSUED AT 251 PM CST TUE DEC 17 2024  
 
THURSDAY...STEERING FLOW ENSEMBLES SHOW ANOTHER DIGGING CLIPPER  
SYSTEM IN THE MIDWEST FLOW, MORE VIGOROUS THAN THE ONE FOR TONIGHT.  
STILL SOME VARIANCE BETWEEN THE SOLUTIONS AND ENSEMBLES OF THE EXACT  
PATH OF THIS SYSTEM TAKES AND HOW FAR NORTH OR SOUTH IT JOGS. BUT THE  
LATEST TRENDS IN MOST OF THE RECENT MODEL RUNS HAVE TRENDED FURTHER  
SOUTH, THUS THE NORTHERN OR NORTHEASTERN THIRD TO HALF OF THE FCST  
AREA MAY BE MORE UNDER THE GUN FOR SNOW WITH THIS SYSTEM BY THU  
MORNING. A FEW SOLUTIONS EVEN HAVE ADVISORY LEVEL SNOW ACCUMULATIONS  
IN NORTHEAST PORTIONS OF THE DVN CWA. FOR NOW WILL RAISE POPS TO 30-  
60% IN THE NORTH, AND AWAIT FURTHER MODEL TRENDS/RUNS TO BETTER  
DEFINE OVER THE NEXT 24 HOURS OR SO. INTERESTING THAT SOUTH OF THE  
PRECIP, THE WARM DRAW OF THE PASSING CLIPPER SYSTEM MAY RAISE TEMPS  
INTO THE 40S IN THE SOUTH.  
 
FRIDAY THROUGH MONDAY...COOL CORE UPPER TROF WILL LOOK TO DEEPEN  
ACRS THE MS RVR VALLEY IN THE WAKE OF THE THU CLIPPER ON FRIDAY AND  
INTO THE START OF THE WEEKEND. THUS COLDER TEMP TRENDS LOOK ON TAP  
FOR FRIDAY AND SATURDAY. ALSO, THE NORTHWEST-TO-SOUTHEAST ALIGNED  
LLVL BAROCLINICITY MAY USHER A WEAK CLIPPER OR ISENTROPIC LIFT EVENT  
DOWN ACRS THE AREA EITHER LATE FRIDAY NIGHT OR SATURDAY FOR A  
POTENTIAL LIGHT SNOW EVENT IN OR NEAR THE LOCAL FCST AREA. BUT ANY  
RIPPLE WILL HAVE TO BATTLE DRY AIR AND IT'S PRECIP ERODING EFFECTS.  
LONGER RANGE UPPER JET FLOW AND MEAN STEERING PROGS SUGGEST A  
FLATTENED FLOW FOR TEMP MODERATION LATE IN THE WEEKEND AND INTO NEXT  
WEEK. OF COURSE THIS FLOW WILL ALSO LOOK TO USHER ANOTHER WAVE  
SOMEWHERE ACRS THE MIDWEST LATE SUNDAY INTO MONDAY WITH INCREASING  
PRECIP CHANCES AGAIN.  
 

 
   
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
 
 
ISSUED AT 548 PM CST TUE DEC 17 2024  
 
A FAST MOVING STOMR SYSTEM WILL MOVE ACROSS THE AREA TONIGHT  
THROUGH 12 UTC ON WEDNESDAY. THERE ARE VFR CONDITIONS AT ALL TAF  
TO START THE PERIOD WITH CEILINGS CURRENTLY BETWEEN 10 TO 12  
KFT AND THE RADAR RETURNS ACROSS EASTERN IOWA ARE CURRENTLY NOT  
REACHING THE GROUND. CEILINGS WILL GRADUALLY BECOME MVFR IN THE  
03 TO 06 UTC TIMEFRAME FROM NORTHWEST TO SOUTHEAST BEFORE  
PRECIPITATION BEGINS. PERIODS OF MVFR TO POSSIBLY IFR  
VISIBILITIES ARE POSSIBLE AT ALL TAF SITES BETWEEN 5 TO 10 UTC  
WITH MAINLY MVFR CEILINGS DURING THAT PERIOD. THE WINDOW FOR  
PRECIPITATION MAY BE SHORTER AT KBRL WITH PRECIPITATION FALLING  
IN A 1 TO 3 HOUR WINDOW. PRECIPITATION TYPES ARE EXPECTED TO BE  
ALL SNOW AT KDBQ AND ALL RAIN AT KBRL. A RASN OR FZRASN MIX IS  
POSSIBLE AT KCID AND KMLI BEFORE CHANGING TO ALL SNOW BUT  
CONFIDENCE IS LOW AT THIS TIME. CEILINGS WILL LIFT TO VFR WITH  
CLOUDS SLOWLY THINNING AFTER 12 UTC. WINDS WILL INCREASE TO 10  
TO 15 KNOTS AFTER 15 UTC AND BECOME MORE NORTHWESTERLY.  
 

 
   
DVN WATCHES/WARNINGS/ADVISORIES
 
 
IA...NONE.  
IL...NONE.  
MO...NONE.  
 

 
 

 
 
SHORT TERM...12  
LONG TERM...12  
AVIATION...COUSINS  
 
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