883  
FXUS63 KDVN 180908  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
308 AM CST WED DEC 18 2024  
   
KEY MESSAGES
 
 
- RAIN AND SNOW TO MOVE EAST OF THE AREA BEFORE THE AM COMMUTE.  
SOME SLICK SPOTS WILL STILL POSSIBLE, ESPECIALLY ON UNTREATED  
ROADS NORTH OF HIGHWAY 30.  
 
- STRONG CLIPPER THURSDAY TO BRING A CHANCE OF ACCUMULATING  
LIGHT SNOW MAINLY NORTH OF I-80.  
 
- COLDER AND MAINLY DRY FRIDAY AND INTO THE WEEKEND, WITH ABOVE  
NORMAL TEMPERATURES RETURNING NEXT WEEK.  
 

 
   
SHORT TERM /THROUGH TONIGHT/
 
 
ISSUED AT 255 AM CST WED DEC 18 2024  
 
A NARROW AND INTENSE BAND OF SNOW TRACKED EAST SOUTHEAST ACROSS  
EASTERN IA AND NORTHERN IL LATE TUESDAY EVENING AND INTO THE  
EARLY MORNING HOURS TODAY. THIS FGEN BAND DEVELOPED IN THE  
700-600MB LAYER AND WAS AIDED BY A 120KT JET STREAK, AHEAD OF A  
POSITIVELY TILTED SHORTWAVE TROUGH. AREA WEBCAMS SHOWED A FEW  
SNOW COVERED ROADS UNDER THE BAND, GENERALLY NORTH OF A LINE  
FROM CEDAR RAPIDS TO MT CARROLL. MOST AREAS SAW LESS THAN AN  
INCH, HOWEVER SOME LOCATIONS UNDER THE BAND FOR THE LONGEST  
LIKELY SAW 1-3 INCHES. THE HIGHEST REPORT RECEIVED OVERNIGHT  
WAS 2.6" IN DAVIS, IL (STEPHENSON COUNTY). ABOVE FREEZING  
SURFACE AND SUB-CLOUD TEMPS SOUTH OF THIS BAND, ALLOWED FOR A  
WINTRY MIX OF RAIN, FREEZING RAIN, AND EVEN BRIEF PERIOD OF  
SLEET AT OUR OFFICE. THIS SHOWED UP NICELY IN THE RADAR DUAL  
PRODUCTS TONIGHT. THANKFULLY, PAVEMENT TEMPS WERE ABOVE  
FREEZING LEADING TO JUST WET ROADS.  
 
TODAY...ANY PRECIPITATION WILL EXIT THE AREA INTO NORTHEAST IL  
OVER THE NEXT 1-2 HOURS. HOWEVER, SOME SLICK SPOTS HAVE  
DEVELOPED PER DOT ROAD CONDITIONS AND ARE LIKELY TO REMAIN  
DURING THE AM COMMUTE, AS AIR TEMPERATURES AND PAVEMENT TEMPS  
DROP INTO THE UPPER 20S. PLEASE TAKE YOUR TIME AND LEAVE PLENTY  
OF SPACE BETWEEN YOU AND THE NEXT VEHICLE THIS MORNING. CLOUD  
COVER WILL MAKE FOR A CHALLENGING TEMPERATURE FORECAST TODAY.  
FORECAST SOUNDINGS SUGGEST CLOUDS MAY REMAIN TRAPPED UNDER AN  
INVERSION, WHICH WILL KEEP TEMPS FROM RISING MUCH DURING THE  
DAY. KEPT HIGHS ON THE LOWER SIDE OF GUIDANCE TODAY, WHICH  
RESULTS IN READINGS IN THE LOWER 30S.  
 
TONIGHT...A SURFACE RIDGE WILL SLIDE EAST ACROSS THE CWA, WITH  
CLEARING SKIES AND WINDS BECOMING CALM. THIS WILL SET THE STAGE  
FOR SOME FOG DEVELOPMENT AND I HAVE ADDED PATCHY FOG WORDING  
INTO THE FORECAST. LOWS TO DROP INTO THE LOWER 20S.  
 

 
   
LONG TERM /THURSDAY THROUGH TUESDAY/
 
 
ISSUED AT 255 AM CST WED DEC 18 2024  
 
THURSDAY-THURSDAY NIGHT...A STRONG CLIPPER REMAINS ON TRACK TO  
DROP SOUTHEAST ACROSS THE DAKOTAS INTO NORTHEAST IA ON THURSDAY.  
THIS KEEPS THE BULK OF THE SNOW AND THE GREATER IMPACTS TO OUR  
NORTH. THE NBM EXCEEDANCE PROBABILITIES OF 1" SNOW OR GREATER  
HAVE DECREASED IN THE PAST 24 HRS AND IS ONLY IN THE 10-20%  
RANGE ALONG AND NORTH OF HIGHWAY 20. MEASURABLE SNOW  
PROBABILITIES FROM THE NBM (GREATER THAN 0.1") HAVE REMAINED  
UNCHANGED AND ARE THE 30-50% RANGE FROM INDEPENDENCE, IA TO  
STERLING, IL. AN INTERESTING NOTE IN THE 00Z GUIDANCE TONIGHT IS  
THAT THE 00Z DETERMINISTIC GFS AND ECMWF ARE MUCH FURTHER SOUTH  
THAN THEIR ENSEMBLES, WHICH WOULD BRING HIGHER SNOWFALL AMOUNTS  
(2+ INCHES) TO OUR NORTHEAST THIRD OF COUNTIES. CONVERSELY, THE  
00Z NAM IS MUCH FURTHER NORTH LEADING TO LIGHTER AMOUNTS. STILL  
SOME TRACK AND STRENGTH DIFFERENCES TO IRON OUT IN THE NEXT  
24-36 HOURS. STAY TUNED.  
 
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.  
 
EARLY NEXT WEEK...RETURN FLOW DEVELOPS WITH HIGH CONFIDENCE  
(GREATER THAN 70%) OF ABOVE NORMAL TEMPERATURES PER CPC 8-14 DAY  
TEMPERATURE OUTLOOK. THE PROSPECTS FOR A WHITE CHRISTMAS THIS  
YEAR ARE LOOKING QUITE BLEAK.  
 

 
   
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
 
 
ISSUED AT 1124 PM CST TUE DEC 17 2024  
 
BAND OF SNOW HAS MOVED JUST TO THE EAST OF THE CID/DBQ TERMINALS  
AND WILL CONTINUE TO PROGRESS EAST OVER THE NEXT 1-3 HOURS. HAVE  
MAINTAINED RASN AT MLI AS THE BAND MOVES EAST, WITH MVFR VSBYS.  
PERIODS OF MVFR AND BRIEF IFR CIGS ARE EXPECTED THIS MORNING,  
AS THE SURFACE TROUGH SLIDES EAST. CONFIDENCE REMAINS LOW ON  
WHEN CONDITIONS IMPROVING BACK TO VFR, WITH MOST MODEL GUIDANCE  
STRUGGLING WITH CURRENT CONDITIONS. CEILINGS SHOULD IMPROVE  
TO VFR LATE MORNING AND EARLY AFTERNOON, WITH NORTHWEST WINDS  
INCREASING OVER 10 KTS.  
 

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

 
 

 
 
SHORT TERM...GROSS  
LONG TERM...GROSS/12  
AVIATION...GROSS  
 
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