Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 242059
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
259 PM CST WED DEC 24 2014

.SYNOPSIS...
ISSUED AT 255 PM CST WED DEC 24 2014

DEEPENING LOW PRESSURE NEAR DETROIT MI WAS SPREADING A LARGE SHIELD
OF RAIN ACROSS THE OHIO VALLEY AND EASTERN GREAT LAKES. WITH A LONG
WAVE TROUGH LOCATED FROM THE UPPER MIDWEST TO THE LOWER MS VALLEY
A LARGE AREA OF LOW STRATUS WAS FOUND. THE BACK (WEST) EDGE OF THE
CLOUDS EXTENDED FROM THE EASTERN DAKOTAS TO EASTERN TEXAS. PATCHY
DRIZZLE OR SPRINKLES HAVE BEEN OBSERVED IN THE DVN CWA TODAY.

2 PM TEMPERATURES IN THE DVN CWA WERE IN THE MID TO UPPER 30S WITH
MID TO UPPER 20S NOTED IN THE DAKOTAS AND NORTHEAST NEBRASKA.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 255 PM CST WED DEC 24 2014

FORECAST FOCUS ON A MILD BUT QUIET CHRISTMAS.

TONIGHT...LOW PRESSURE DEEPENS AND TRACKS NORTH OF OTTAWA ONTARIO
CANADA WHILE SURFACE RIDGE PUSHES INTO THE CWA THIS EVENING. MEANWHILE...
FORECAST SOUNDINGS INDICATE THAT LOW LEVEL WARM AIR ADVECTION WILL
STRENGTHEN AN INVERSION AT AROUND 900 MB OVERNIGHT. LOW LEVEL MOISTURE
TRAPPED BELOW THE INVERSION WILL MAKE FOR A RATHER CLOUDY NIGHT.
AFTER MIDNIGHT THE WINDS TURN SOUTHWEST AS THE RIDGE SHIFTS TO OUR
EAST AND THERE MAY BE SOME BREAKS IN THE OVERCAST LATE TONIGHT AS
WE GET INTO A MORE ANTI-CYCLONIC FLOW. DUE TO EXPECTING MORE CLOUDS
I HAVE KEPT TEMPERATURES CLOSER TO THE WARMER MET GUIDANCE...IN
THE MID TO UPPER 20S. IF ANYTHING I MAY STILL BE A BIT TOO COOL.

CHRISTMAS DAY...THOSE WANTING A COLD AND WHITE CHRISTMAS ARE OUT OF
LUCK THIS YEAR BUT INSTEAD THIS WILL BE A MILD DAY. DEVELOPING STORM
SYSTEM IN THE ROCKIES WILL PUMP A DRY SOUTHERLY FLOW INTO THE CWA.
WITH HIGH PRESSURE IN THE GULF STATES THE GULF MOISTURE IS CUT-OFF.
WITH CONTINUED WARMING THE INVERSION WILL WEAKEN IN THE MORNING
ALLOWING FOR MORE SUNSHINE THE REMAINDER OF THE DAY. THERE SHOULD
BE AN INCREASE IN CIRRUS AS THE AFTERNOON PROGRESSES. THE COMBINATION
OF SOME SUNSHINE...SOUTH WINDS AND BARE GROUND WILL ALLOW AFTERNOON
TEMPERATURES TO SOAR INTO THE LOWER TO MID 40S. THIS IS AT LEAST
10 DEGREES ABOVE NORMAL FOR CHRISTMAS DAY.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 255 PM CST WED DEC 24 2014

MAIN HIGHLIGHTS OF THE EXTENDED FORECAST CONSIST OF THE NEXT STORM
SYSTEM TO AFFECT THE AREA EARLY IN THE WEEKEND...THEN A CHANGE TO A
COLDER...MORE WINTRY REGIME NEXT WEEK.

AHEAD OF THE WEEKEND SYSTEM...THU NIGHT INTO FRIDAY WILL SEE MORE OF
THE SAME WITH ABOVE NORMAL TEMPERATURES. THE DEVELOPING SOUTHERLY
FLOW AND LOW LEVEL MOISTURE WILL LIKELY RESULT IN MORE WIDESPREAD
STRATUS...WITH ONLY THE TIMING IN QUESTION AFTER THE PARTIAL
CLEARING EXPECTED CHRISTMAS DAY. FOR NOW...HAVE THIS RETURN TO
OVERCAST CONDITIONS TAKING PLACE BY MIDDAY FRIDAY. THIS WILL LIMIT
THE AMOUNT OF WARMING AND HAVE STRAYED TOWARD THE LOWER END OF
GUIDANCE WITH FRIDAY HIGHS FROM AROUND 40 NORTH TO NEAR 50 IN THE
FAR SOUTH.

THE NEXT SIGNIFICANT WEATHER FEATURE TO AFFECT THE REGION WAS
SHOWING UP AS A STRONG SHORTWAVE TROUGH ON SATELLITE WV IMAGERY
MOVING INTO NRN CA AND OR EARLY THIS AFTERNOON. THIS WAS PRECEDED BY
IMPRESSIVE 150 PLUS DECAMETER HEIGHT FALLS AT 500 MB OUT AHEAD ON
12Z UPPER AIR ANALYSIS. WHILE THIS FEATURE IS PROGGED TO BE A HEAVY
SNOWFALL MAKER FOR CHRISTMAS DAY ACROSS THE CENTRAL AND NORTHERN
ROCKIES...ITS IMPACTS WILL BE MUCH LESS AS IT PUSHES THROUGH THE
CENTRAL U.S. AND WEAKENS FRIDAY AND SATURDAY. HIGH PRESSURE THAT
REBOUNDS OVER THE SOUTHEAST U.S. BY THIS TIME WILL RESULT IN A SW TO
NE BAROCLINIC AXIS EXTENDING FROM OK TO UPPER MI...UPON WHICH THE
UPPER WAVE WILL SEND A WAVE OF LOW PRESSURE.

12Z MODELS HAVE SLOWED SOME WITH THE TIMING OF THE MAIN LOW AND
ASSOCIATED PRECIPITATION...WITH THE GFS AND ECMWF NOW IN SLIGHTLY
BETTER AGREEMENT DEPICTING THE WEAKENING UPPER WAVE FORMING A WEAK
SURFACE LOW OVER NORTHERN IL OR SOUTHERN LAKE MI BY SATURDAY
MORNING. THE GEM IS SOMEWHAT OF AN OUTLIER...WITH A SECONDARY LOW
EVENTUALLY TAKING OVER FURTHER SOUTH...WHICH WOULD RESULT IN AN
OVERALL SLOWER SYSTEM...AND ALSO MORE FAVORABLE FOR MEASURABLE SNOW
OVER THE FORECAST AREA. HOWEVER...WHILE WORTH WATCHING...HAVE KEPT
THE FORECAST CLOSER TO CONTINUITY AND THE MORE STABLE GFS/ECMWF
SCENARIO.

PRECIPITATION IN THE FORM OF RAIN OR DRIZZLE SHOULD BREAK OUT AHEAD
OVER MUCH OF THE AREA FRIDAY NIGHT...CHANGING LIGHT SNOW FROM NW TO
SOUTHEAST BY SATURDAY MORNING AS THE LOW LIFTS NORTHEAST AND PULLS
COLDER AIR SOUTHWARD INTO IA AND IL IN ITS WAKE. HAVE MADE ONLY
MINOR TWEAKS TO THE PREVIOUS FORECAST...ADDING DRIZZLE INTO THE MIX
IN THE WARM SECTOR FRIDAY NIGHT...WITH SNOW ACCUMULATIONS FROM FROM
A DUSTING TO HALF INCH BEFORE THE SYSTEM EXITS SATURDAY AFTERNOON.
WHILE NOT CURRENTLY MENTIONED IN THE FORECAST...THIS SETUP WITH A
WEAK SURFACE TROUGH AND DEEP LOW LEVEL MOISTURE CONVERGENCE...MAY
LEAD TO WIDESPREAD FOG WHICH COULD POSSIBLY BE DENSE FRIDAY NIGHT.

THE SOMEWHAT COLDER AIR THAT SPILLS INTO THE AREA OVER THE WEEKEND
WILL LINGER THROUGH MUCH OF NEXT WEEK AS A BROAD...POSITIVE TILT
UPPER TROUGH SETS UP OVER NORTH AMERICA. MODEL CONSENSUS HAS A
REINFORCING COLD FRONT ARRIVING AROUND MONDAY NIGHT...WHICH WOULD
SEND TEMPERATURES BELOW NORMAL THROUGH AT LEAST THE MIDDLE OF NEXT
WEEK. THERE IS A POTENTIAL FOR LIGHT SNOW WITH THIS FEATURE...
REFLECTED IN SLIGHT CHANCE POPS FOR MONDAY NIGHT INTO TUESDAY. MODEL
GUIDANCE IS SOMEWHAT CONSISTENT WITH WEDNESDAY HIGHS LIMITED TO ONLY
IN THE TEENS WITH LOWS IN THE SINGLE DIGITS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 255 PM CST WED DEC 24 2014

MVFR/LCL IFR CIGS BUT P6SM VISIBILITY THE REMAINDER OF THIS AFTERNOON
AND TONIGHT. CONDS BECOMING VFR CHRISTMAS DAY. NORTHWEST WINDS 10
TO 20 KNOTS THIS AFTERNOON THEN BECOMING SOUTHWEST LATE TONIGHT
AROUND 10 KNOTS. SOUTH WINDS CHRISTMAS DAY AT 10 TO 15 KNOTS.

&&

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

$$

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




















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