Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 181152
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
552 AM CST THU DEC 18 2014

.SYNOPSIS...
ISSUED AT 321 AM CST THU DEC 18 2014

SNOW FAIRLY WIDESPREAD FROM WESTERN MO INTO NE AND KS AHEAD OF AN
UPPER LEVEL SHORTWAVE OVER THE PLAINS. REPORTS OF ACCUMS FROM
1-3 INCHES FROM NORTHERN KS THROUGH THE KC METRO WITH OBS SUGGESTING
THE LEADING EDGE OF SNOW BETWEEN CHILLICOTHE MO AND KC METRO
MOVING N/E. TRENDS SUPPORT SYSTEM AND ATTENDANT SNOW TO GRADUALLY
WEAKEN TODAY AS IT ENCOUNTERS RIDGING OVER THE REGION... BUT
BEFORE DOING SO IS EXPECTED BRING SOME LIGHT ACCUMS TO SOUTHERN
PORTIONS OF CWA.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 321 AM CST THU DEC 18 2014

SHORTWAVE WILL MOVE ACROSS REGION TODAY AND DEAMPLIFY/WEAKEN WHILE
RUNNING INTO THE RIDGE. THIS ALONG WITH COPIOUS DRY AIR PER 00Z
DVN AND ILX RAOBS SHOULD RESULT IN STEADY WEAKENING OF SNOW AS IT
SPREADS INTO FAR SOUTHERN CWA THIS AM. FORCING PEAKS OVER NORTHERN
MO 10Z-15Z THEN QUICKLY DIMINISHING THROUGH 18Z. OVERALL GOING
WITH 0.05 TO 0.1 INCH OF LIQUID QPF WITH SLR OF 12-14:1 TO YIELD
AROUND AN INCH OR SO OF ACCUM VERY FAR SOUTHERN CWA MAINLY NORTHEAST
MO INTO PORTIONS OF WEST CENTRAL IL TAPERING OFF TO TRACE HWY 34.
GIVEN DRY AIR AND ALIGNMENT OF FORCING COULD ENVISION SCENARIO
WHEREBY THIS OCCURS OVER MUCH SHORTER DISTANCE OF 25+ MILES NORTHEAST
MO. CANT RULE OUT POSSIBILITY OF SOME FREEZING DRIZZLE FAR SOUTH
FOR A WHILE THIS AFTERNOON IF CLOUD BEARING LAYER BECOMES SUFFICIENTLY
SHALLOW/WARM.. BUT CONFIDENCE NOT HIGH ENOUGH TO INCLUDE MENTION
ATTIM. ASIDE FROM THE LIGHT SNOW FAR SOUTHERN CWA... EXPECT PTSUNNY
TO CLOUDY SKIES TODAY WITH TEMPS SIMILAR TO THOSE OF YSTDY IN
RELATIVELY NEUTRAL THERMAL ENVIRONMENT... WITH READINGS MAINLY IN
UPPER 20S TO LOWER 30S. WINDS NEGLIGIBLE AND GENERALLY 5 MPH OR LESS
WITH SURFACE RIDGING.

TONIGHT... GENERALLY PT-MOCDLY SKIES WITH SFC RIDGING BECOMING
RE-ESTABLISHED AS THE DOMINANT FEATURE. BANKING ON SUFFICIENT
CLOUDINESS TO PRECLUDE TEMPS FROM BOTTOMING OUT DESPITE NEAR
CALM/CALM WINDS... AND EXPECT GENERALLY UPPER TEENS TO MID 20S FOR
LOWS. SHOULD SOME AREAS SEE MORE IN WAY OF CLEARING THEN POTENTIAL
TO BE IN MID TEENS FOR LOWS.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 321 AM CST THU DEC 18 2014

FORECAST FOCUS ON ACTIVE WEATHER PATTERN ESPECIALLY CHRISTMAS WEEK.

FRIDAY THROUGH SUNDAY...ZONAL FLOW OVER THE REGION WITH A SERIES OF
SHORT WAVES MOVING ACROSS. THIS LOOKS TO BE ANOTHER RATHER CLOUDY
PERIOD WITH FORECAST SOUNDINGS INDICATING WEAK LOW LEVEL WARM
ADVECTION AND A STRONG INVERSION SETTING UP AROUND 850 MB...WITH MOISTURE
TRAPPED BELOW. SATURDAY NIGHT I HAVE INTRODUCED A SLIGHT CHANCE OF
FREEZING DRIZZLE IN OUR FAR NW CWA...AS A SHORT WAVE/VORT MAX
TRAVERSES NORTHERN IA. FORECAST SOUNDINGS INDICATE A WARM LAYER JUST
ABOVE FREEZING WITH DRY AIR IN THE MID LEVELS WITH MOISTURE BELOW.
MAXIMUM TEMPERATURES DURING THIS PERIOD WILL BE IN THE 30S TO NEAR
40 WITH LOWS IN THE 20S TO NEAR 30.

MONDAY THROUGH WEDNESDAY...THIS IS WHEN THE WEATHER GETS ACTIVE BUT
ALSO COMPLICATED AND CHALLENGING. UPPER LOW DEEPENS AS IT TRACKS
FROM THE NORTHERN PLAINS (MONDAY) INTO EASTERN IA (TUESDAY) AND THEN
LIFTING INTO THE WESTERN GREAT LAKES (WEDNESDAY). THE PATH OF THIS
SYSTEM WOULD SUGGEST MAINLY A RAIN/SNOW MIX BUT WILL NEED TO KEEP AN
EYE ON TUESDAY WHERE IT MAY CHANGE TO ALL SNOW...GIVEN THE COLD
POCKET ALOFT AND DYNAMIC COOLING. WAY TOO EARLY TO OFFER ANY
ACCUMULATION AMOUNTS IF ANY. MAXIMUM TEMPERATURES ON MONDAY SHOULD
PUSH INTO THE 40S FROM ABOUT I-80 SOUTHWARD...AND IN THE 30S TUESDAY
AND WEDNESDAY. THE ECMWF HAS NOW THROWN A CURVE BALL IN REGARD TO
THE WHOPPER STORM EARLIER INDICATED TO BE IN THE GREAT LAKES REGION
CHRISTMAS EVE. IT NOW IS NOT QUITE THE BOMB SHOWN THE PAST COUPLE
RUNS AND IS ALSO INTENSIFYING THE CYCLONE FARTHER EAST...IN NEW
ENGLAND! THIS IS WHAT THE GFS HAS BEEN INDICATING ALL ALONG. SUFFICE
TO SAY CONFIDENCE IS LOW AS PHASING ISSUES CONTINUE TO HAUNT THE
MODELS. SO MORE CHANGES IN THE MODELS CAN BE EXPECTED OVER THE NEXT
SEVERAL DAYS AND THE IMPACTS IF ANY ON OUR AREA REMAIN TO BE SEEN.

CHRISTMAS DAY AND FRIDAY...MANY UNCERTAINTIES REGARDING THE
POTENTIAL WINTER STORM OFFERED BY THE ECMWF ON FRIDAY. DEPENDING ON
WHERE THE HUGE UPPER LOW TO OUR NORTHEAST IS LOCATED WILL PLAY A
ROLE IN THE STRONG ENERGY COMING OUT OF THE SOUTHWEST. CONFIDENCE IN
THE TRACK/TIMING/INTENSITY OF THIS SYSTEM IS LOW BUT CERTAINLY THERE
IS THE POTENTIAL FOR A WINTER STORM SOMEWHERE IN THE MIDWEST...SO
ANYONE TRAVELING AROUND CHRISTMAS DAY OR THEREAFTER SHOULD CONTINUE
TO MONITOR LATER FORECASTS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 536 AM CST THU DEC 18 2014

WEAKENING STORM SYSTEM WILL SPREAD LIGHT SNOW ACROSS NORTHEAST MO...
FAR SOUTHEAST IA AND PORTIONS OF WEST CENTRAL IL THROUGH MIDDAY
BEFORE DIMINISHING. LIGHT SNOW COULD BRUSH THE BRL TERMINAL 15Z-18Z
BUT LOW CONFIDENCE DUE TO DRY AIR AND WEAKENING SYSTEM THUS ONLY
HAVE MENTION OF FLURRIES WITH VSBYS AOA 6SM. OTHERWISE... EXPECT
VFR CONDITIONS WITH MID/HIGH CLOUDINESS AND LIGHT WINDS. THE
POTENTIAL EXISTS FOR PATCHY FOG WITH MVFR TO LOCALIZED IFR VSBYS
LATE TONIGHT... BUT WITH MID/HIGH CLOUDINESS NOT CONFIDENT ENOUGH
ON DEVELOPMENT/IMPACT AT TERMINALS FOR MENTION AT THIS TIME.

&&

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

$$

SYNOPSIS...05
SHORT TERM...05
LONG TERM...HAASE
AVIATION...05





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