213
FXUS63 KDVN 181129
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
529 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 /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 529 AM CST WED DEC 18 2024
RECENT SATELLITE TRENDS PER GOES 16 NIGHTTIME MICROPHYSICS RGB
CHANNEL SHOWS SUB 2KFT CLOUDS BEGINNING TO SCATTER OUT. AS A
RESULT, HAVE UPDATED THE TAFS TO IMPROVE TO VFR QUICKER THAN
ANTICIPATED THIS MORNING. LOW VFR CLOUDS UPSTREAM ACROSS
SOUTHERN MN WILL ADVECT INTO THE REGION MID-TO-LATE MORNING,
WITH NORTHWEST WINDS REMAINING UNDER 12KTS. A RIDGE OF HIGH
PRESSURE WILL SLIDE EAST TONIGHT, WITH CLOUDS CLEARING AND WINDS
BECOMING CALM. IDEAL RADIATIONAL COOLING WILL ALLOW FOR SOME
PATCHY FOG TO DEVELOP AND HAVE ADDED THIS TO THIS TAF CYCLE.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
SHORT TERM...GROSS
LONG TERM...GROSS
AVIATION...GROSS
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