945
FXUS63 KDVN 170905
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
305 AM CST TUE DEC 17 2024
KEY MESSAGES
- WARM AND DRY TODAY, WITH INCREASING CLOUDS.
- CHANCE (30-50%) OF SNOW TONIGHT PRIMARILY NORTH OF I-80, WITH
SNOWFALL AMOUNTS LESS THAN AN INCH. SOME SLICK SPOTS MAY
DEVELOP PRIOR TO THE WED AM COMMUTE.
- STRONG CLIPPER THURSDAY MAY BRING LIGHT ACCUMULATING SNOW FOR
AREAS NORTH OF HIGHWAY 30.
- COLDER AND MAINLY DRY FRIDAY AND INTO THE WEEKEND, WITH ABOVE
NORMAL TEMPERATURES RETURNING NEXT WEEK.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 254 AM CST TUE DEC 17 2024
MOSTLY CLEAR SKIES WERE SEEN ACROSS MOST OF THE CWA EARLY THIS
AM PER GOES 16 NIGHTTIME MICROPHYSICS CHANNEL. THE EXCEPTION WAS
ALONG AND NORTH OF THE HIGHWAY 20 CORRIDOR, WHERE AN EXPANSIVE
DECK OF STRATUS OVER NORTHEAST IA AND SOUTHERN WI WAS MOVING
EAST SOUTHEAST. WATER VAPOR SATELLITE LOOPS SHOW SUBTLE
SHORTWAVES OVER SOUTHERN ID AND SOUTHERN ALBERTA. THESE WAVES
WILL MOVE EAST IN THE FLOW ALOFT BRINGING RAIN/SNOW CHANCES
TONIGHT AND INTO WEDNESDAY. TEMPERATURES AT 3AM, RANGED FROM 29
DEGREES IN INDEPENDENCE, TO 35 DEGREES IN BURLINGTON.
MID-HIGH LEVEL CLOUDS WILL INCREASE THROUGH THE DAY TODAY,
AHEAD OF THE APPROACHING WAVES. THIS WILL DAMPEN THE HIGHS
SOMEWHAT TODAY, WITH AFTERNOON READINGS ONLY REACHING THE UPPER
30S NORTH OF I-80, TO THE LOWER 40S SOUTH.
LATE EVENING/TONIGHT...A POSITIVELY TILTED SHORTWAVE TROUGH
WILL SWING THROUGH THE MIDWEST AND AIDED BY A STRONG 120KT JET
STREAK, WILL PROVIDE LARGE SCALE FORCING FOR ASCENT. MODELS
CONTINUE TO SUGGEST A STRONG FGEN BAND DEVELOPING IN NORTHERN IA
AND TRACKING EAST SOUTHEAST INTO EASTERN IA. THERMAL PROFILES
SUGGEST SNOW WILL BE THE DOMINANT PTYPE NORTH OF I-80, WITH THE
PRECIPITATION ARRIVING IN THE 00-10Z WED TIMEFRAME. SNOWFALL
AMOUNTS LESS THAN AN INCH ARE FORECAST, MAINLY ON ELEVATED AND
GRASSY SURFACES. THE LATEST NBM EXCEEDANCE PROBABILITIES OF A
TENTH OF AN INCH OF SNOW OR GREATER ALSO SUPPORT THIS NOTION AND
ARE ONLY IN THE 20-40% RANGE. THE STRENGTH OF THE FORCING AND
SUBSEQUENT SNOWFALL RATES, AND MARGINAL SUB-FREEZING PAVEMENT
TEMPS PER METRO FORECAST WILL BE THE LIMITING FACTORS FOR ANY
IMPACTS. HOWEVER WITH ALL THAT BEING SAID, A VERY NARROW BAND OF
1"+ AMOUNTS IS STILL A POSSIBILITY ALONG AND NORTH OF HIGHWAY
20. SOME SLICK SPOTS MAY OCCUR ON ROADS PRIOR TO AM COMMUTE AND
AN SPS MAY BE NEEDED. THIS IS SOMETHING WE WILL CLOSELY MONITOR
TODAY, AS THE SYSTEM MOVES ACROSS THE PLAINS. A RAIN/SNOW MIX OR
EVEN JUST RAIN IS FORECAST SOUTH OF I-80. RAIN AMOUNTS WILL BE
LIGHT AND UNDER A TENTH OF AN INCH. ALL PRECIPITATION SHOULD BE
EAST OF THE AREA BY 12Z WED.
LONG TERM /WEDNESDAY THROUGH MONDAY/
ISSUED AT 254 AM CST TUE DEC 17 2024
THURSDAY-THURSDAY NIGHT...THE LATEST 00Z DETERMINISTIC AND
ENSEMBLE MODELS HAVE COME INTO BETTER AGREEMENT ON THE TRACK OF
A RATHER POTENT CLIPPER SYSTEM PROGGED TO DROP SOUTHEAST TOWARDS
THE REGION THURSDAY AND THURSDAY NIGHT. WHILE TIMING AND
STRENGTH DIFFERENCES STILL EXIST, THE GENERAL TRACK OF THE
SURFACE LOW WOULD BE A PATH FROM THE DAKOTAS AT 12Z THU TO
NORTHEAST IA BY 00Z FRI. THIS WOULD KEEP THE BULK OF THE SNOW
AND THE GREATER IMPACTS TO OUR NORTH, WHICH IS ALSO SHOWN BY THE
TIGHTENING GRADIENT OF THE NBM EXCEEDANCE PROBABILITIES OF 1"
SNOW OR GREATER ACROSS NORTHEAST IA AND SOUTHERN WI. LOCALLY,
THE HIGHEST 1" PROBABILITIES (15-25%) IS ALONG AND NORTH OF
HIGHWAY 20. MEASURABLE SNOW PROBABILITIES FROM THE NBM (GREATER
THAN 0.1") ARE HIGHER AND ARE CURRENTLY IN THE 30- 50% RANGE
FROM INDEPENDENCE, IA TO STERLING, IL. STILL NOT THAT GREAT FOR
THOSE SNOW LOVERS OUT THERE.
FRIDAY-SUNDAY...ANY SNOW WILL QUICKLY EXIT THE AREA BEFORE SUNRISE
FRIDAY, REPLACED BY STRONG CAA. BRISK NORTH WINDS AND A RETURN TO
MORE SEASONABLE HIGH TEMPERATURES IN THE UPPER 20S IS FORECAST. A
LARGE AREA OF HIGH PRESSURE WILL BRING MAINLY DRY CONDITIONS FOR
THE REST OF THE WEEKEND.
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 IS LOOKING QUITE BLEAK.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 1039 PM CST MON DEC 16 2024
MVFR CLOUDS WILL MOVE ACROSS NORTHEAST IOWA AND ALONG THE WI/IL
BORDER THROUGH AT LEAST 17Z/17 WITH SOME BRIEF PERIODS OF VFR
ALONG THE SOUTHERN EDGE OF THE CLOUDS. VERY SHORT TERM MODELS
ARE STRUGGLING WITH THESE CLOUDS BUT NBM IS CAPTURING THE 2-3
KFT AGL CIGS. OTHERWISE LLWS PROGGED BY THE RAP MODEL IS NOW
MARGINAL WITH THE MAIN JUMP IN WINDS MAINLY ABOVE 2KFT AGL.
ELSEWHERE ACROSS THE REST OF EASTERN IOWA AND NORTHERN ILLINOIS
EXPECT VFR CONDITIONS AS CLOUDS SLOWLY LOWER THROUGH 06Z/18 WITH
THE APPROACH OF A STORM SYSTEM.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
SHORT TERM...GROSS
LONG TERM...GROSS
AVIATION...08
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