Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 170952
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
352 AM CST WED DEC 17 2014

.SYNOPSIS...
ISSUED AT 348 AM CST WED DEC 17 2014

REGION REMAINS ENTRENCHED IN COLD CYCLONIC FLOW WITH STRATUS AND
A FEW FLURRIES ON BACKSIDE OF EASTERN CONUS LONGWAVE TROUGH
AND EMBEDDED SHEARING CLOSED CIRCULATION OVER THE UPPER MIDWEST.
TEMPS RUNNING ON AVERAGE 20-25 DEGS COLDER FROM 24 HRS AGO WITH
READINGS IN THE UPPER TEENS TO MID 20S... WITH NW WIND 10-15+ MPH
MAKING IT FEEL EVEN COLDER AND MORE LIKE THE SINGLE DIGITS TO
LOWER TEENS. WATER VAPOR IMAGERY SHOWS ACTIVE SOUTHERN BRANCH OF
JET STREAM WITH SEVERAL EMBEDDED PERTURBATIONS MOVING THROUGH THE
SOUTHWESTERN CONUS. PRIMARY DISTURBANCE OF INTEREST WAS LOCATED
NEAR BAJA CA AND EXPECTED TO LIFT OUT ACROSS THE SOUTHERN PLAINS
AND MID-MISSISSIPPI VLY TONIGHT AND THURSDAY... AND MAY BRUSH THE
SOUTHERN CWA WITH SOME LIGHT SNOW OR FLURRIES.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 348 AM CST WED DEC 17 2014

MAIN CHALLENGES ARE CLOUD TRENDS WITH IMPACT ON TEMPS... AND THE
POTENTIAL FOR LIGHT SNOW ACROSS THE SOUTHERN CWA LATE TONIGHT.

FOG ENHANCEMENT SATL IMAGERY SHOWS THE BACK EDGE OF THE STRATUS
MAINLY ALONG AND EAST OF I-35 PROGRESSING SLOWLY E/SE WITH
MORE EXPANSIVE AREA OVER SOUTHEAST MN MOVING NEARLY DUE SOUTH
AHEAD OF SHEARING CLOSED CIRCULATION. THE LATEST RAP SOUNDINGS
SUGGEST STRATUS MAY REMAIN TRAPPED UNDER INVERSION FOR MOST OF
THE DAY... WHILE NAM WOULD MAINTAIN STRATUS THROUGH MID AM BEFORE
BREAKING UP FROM WEST TO EAST. MODELS IN GENERAL HAVE BEEN TOO
OPTIMISTIC WITH CLEARING TRENDS... BUT WITH FLOW BECOMING MORE
ANTICYCLONIC TO NEARLY NEUTRAL AHEAD OF PLAINS SFC RIDGE BUILDING
IN AND AS MID LEVEL SUBSIDENT REGION SOUTH OF SHEARING CLOSED
CIRCULATION OVERSPREADS THE AREA TODAY BELIEVE PROSPECTS GOOD
FOR AT LEAST PARTIAL CLEARING LATER TODAY AND INTO THIS EVENING.
WHERE STRATUS BREAKS UP EXPECT SOME HIGH THIN CIRRUS ESPECIALLY
SOUTH HALF AHEAD OF SOUTHWEST SYSTEM. AS CLOUDS GO... SO GO THE
TEMPS AND HAVE STAYED NEAR GUIDANCE BLEND OR ON THE COLD SIDE WITH
HIGHS FROM MID 20S TO LOWER 30S. IF STRATUS REMAINS TRAPPED
UNDER THE INVERSION ALL DAY PER RAP SOUNDINGS THEN TEMPS STRUGGLE
WITH WIDESPREAD MID TO SOME UPPER 20S. GRADIENT TO WEAKEN TODAY
ESPECIALLY THIS AFTERNOON SO WINDS BECOMING MUCH LESS OF A FACTOR
ON THE CHILLS.

TONIGHT... SHORTWAVE TROUGH PROGGED TO LIFT FROM SOUTHERN PLAINS
TOWARD THE MID-MISSISSIPPI VLY BY 12Z ALTHOUGH IT LOOKS TO
DAMPEN/WEAKEN MARKEDLY AS IT MOVES INTO UPPER RIDGING OVER THE
MIDWEST. MODEL TIME-HEIGHT PLOTS AND SOUNDINGS DEPICT INCREASING
MID-HIGH LEVEL MOISTURE OVERNIGHT MAINLY SOUTHWESTERN 1/3-1/2 OF
THE CWA. GEM...GFS AND ECMWF ALL GENERATE SOME VERY LIGHT QPF
ACROSS THE FAR SOUTHWEST CWA LATE TONIGHT... BUT CLOSER INSPECTION
OF SOUNDINGS SHOW LOW LEVELS REMAIN DRY AND SATURATION INCOMPLETE
FOR MORE THAN JUST FLURRIES. GIVEN THAT THIS WILL BE VERY LATE
(AFT 09Z) DEVELOPING AND LOW CONFIDENCE WITH SATURATION COMPOUNDED
BY WEAKENING SYSTEM HAVE OPTED TO KEEP FCST DRY FAR SOUTH AND OMIT
ANY MENTION OF FLURRIES FOR NOW. LOWS QUITE CHALLENGING DUE TO
CLOUD COVER TRENDS. HAVE KEPT LOWS WITH GUIDANCE BLEND OR ON THE
COOL SIDE AND IN THE TEENS TO AROUND 20 DEGS. 850 MB TEMPS OF
AROUND -5C COUPLED WITH NEAR CALM WINDS AND ANY CLEARING WOULD
SUPPORT COLDEST MINS OF MID TEENS 13-16F.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 348 AM CST WED DEC 17 2014

FORECAST FOCUS ON A CHANCE OF LIGHT SNOW IN OUR FAR SOUTH THURSDAY
THEN ANOTHER CHANCE OF PRECIPITATION EARLY NEXT WEEK.

THURSDAY...OPERATIONAL MODELS DISAGREE ON MOISTURE/SATURATION AS A
SHORT WAVE TRACKS FROM THE SOUTHERN ROCKIES INTO THE MID MS VALLEY
IN THE MORNING. THE ECMWF/GEM ARE THE MOST AGGRESSIVE WITH LIGHT QPF
IN OUR SOUTHERN CWA WHILE THE AMERICAN MODELS ARE ESSENTIALLY DRY.
FORECAST SOUNDINGS INDICATE DRY LOW LEVELS SO IT WILL REMAIN TO BE
SEEN HOW MUCH THE LOW LEVELS CAN SATURATE. FOR COLLABORATION REASONS
I HAVE BUMPED UP POPS TO 40 IN EXTREME NORTHEAST MO...WITH SLIGHTS
AS FAR NORTH AS A FAIRFIELD TO MACOMB LINE. FARTHER NORTH IN THE CWA
THE DRY AIR IS FIRMLY ENTRENCHED WITH HIGH PRESSURE CENTERED IN THE
UPPER MIDWEST. ANY ACCUMULATIONS WILL BE MINOR AND WE ARE TALKING
ONLY A COUPLE OF TENTHS OF AN INCH IN EXTREME NORTHEAST MO. THE WAVE
MOVES QUICKLY INTO THE OHIO VALLEY DURING THE AFTERNOON WITH
LINGERING FLURRIES POSSIBLE. I HAVE LOWERED POPS IN THE AFTERNOON IN
OUR FAR SOUTH TO LESS THAN 20. MAXIMUM TEMPERATURES WILL RANGE FROM
THE UPPER 20S NORTH TO THE LOWER 30S SOUTH.

FRIDAY THROUGH SUNDAY...STORM SYSTEM IN THE SOUTHERN STREAM IS STILL
INDICATED BY MODELS TO REMAIN WELL SOUTH OF THE CWA. AN UPPER LEVEL
TROUGH MOVES ACROSS THE MIDWEST BUT AIRMASS IS TOO DRY TO MENTION
ANY MEASURABLE PRECIPITATION...AS THE DEEPER MOISTURE IS TIED TO THE
SOUTHERN STREAM STORM. HIGH TEMPERATURES DURING THIS PERIOD WILL BE
MAINLY IN THE 30S WITH LOWS IN THE 20S.

MONDAY AND TUESDAY...NEXT IN YOUR HIT PARADE IS A DEEPENING TROUGH
THAT DIGS INTO THE MIDWEST. OPERATIONAL MODELS ARE FAIRLY SIMILAR
WITH THIS FEATURE. HIGH END CHANCE POPS ARE IN THE GRIDS FOR THIS
SITUATION BUT PLENTY OF ROOM TO GO HIGHER OVER THE NEXT SEVERAL DAYS.
WITH THE SURFACE LOW REMAINING TO OUR NORTH THIS SETS UP THE
POTENTIAL FOR RAIN OR A RAIN/SNOW MIX BUT THEN TURNING TO ALL SNOW
BY THE TIME WE GET TO TUESDAY AFTERNOON AND TUESDAY NIGHT.

REMAINDER OF CHRISTMAS WEEK...MODELS HAVING DIFFICULTY WITH PHASING
ISSUES AS THE 00Z/17 ECMWF CRANKS UP A WHOPPER OF A WINTER STORM
(BOMBOGENESIS) TRACKING FROM THE LOWER MS VALLEY TO THE GREAT LAKES
CHRISTMAS EVE...WITH ARCTIC AIR PLUNGING QUICKLY INTO THE COUNTRY
BEHIND THE SYSTEM. THE GFS IS FARTHER EAST AND DEEPENS THE STORM IN
NEW ENGLAND INSTEAD. BEING A WEEK AWAY THERE LIKELY WILL BE MORE
CHANGES BUT CHRISTMAS TRAVELERS WILL WANT TO STAY TUNED.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1131 PM CST TUE DEC 16 2014

LINGERING LOW CLOUDS OVER IL AND THE EASTERN HALF OF IA WILL BE
SLOW TO MOVE OUT LATE TONIGHT AND WEDNESDAY MORNING...RESULTING IN
CONTINUED MVFR CONDITIONS DUE TO CIGS. SCATTERED FLURRIES WILL
REMAIN POSSIBLE ESPECIALLY AT CID AND MLI LATE TONIGHT. THE
UPDATED FORECASTS CONTINUE A GRADUAL CLEARING TREND...LIFTING
CLOUD BASES TO WELL ABOVE MVFR THRESHOLDS...IN A LOW CONFIDENCE
12Z TO 18Z TIMEFRAME. THERE IS HIGHER CONFIDENCE THAT ALL SITES
WILL BE VFR FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING. NW
WINDS WILL DIMINISH THROUGHOUT AND BECOMING LIGHT FROM THE NORTH
WEDNESDAY NIGHT AS HIGH PRESSURE BUILDS INTO THE UPPER MS VALLEY.

&&

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

$$

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





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