FXUS63 KDVN 221010
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
410 AM CST TUE DEC 22 2009

.SYNOPSIS...
SHEARING SHORTWAVE MOVING EAST FROM SD/NE THROUGH IA COUPLED WITH
WARM ADVECTION/ISENTROPIC LIFT ABOVE H85 WARM FRONT ARCING FROM 
CENTRAL THROUGH SOUTHEAST IA RESPONSIBLE FOR SNOW OVER NORTHEAST
SECTIONS OF CWA EARLY THIS MORNING. NARROW RIBBON OF STRONG 
WAA AND MID LEVEL FRONTOGENETICAL FORCING ASSISTING 20-30+ MILE
WIDE BAND OF MOD/HVY SNOW FROM KDBQ-KVYS SLIDING EAST AT 10-15 MPH.
OOZ SUBJECTIVE UPPER AIR ANALYSIS SHOWS TROUGH MOVING INLAND OUT
WEST WITH COUPLE OF VIGOROUS ENERGY CENTERS... ONE OVER NORTHWEST
WA NEAR SEATTLE AND THE OTHER OVER SOUTH CENTRAL CA NEAR 
BAKERSFIELD. DOWNSTREAM RIDGING SHIFTING EAST INTO THE PLAINS
EARLY THIS AM UNDERGOING AMPLIFICATION IN RESPONSE TO DIGGING
ENERGY.   ..05..

&&

.SHORT TERM...TODAY AND TONIGHT... 
BAND OF SNOW NORTHEAST SECTIONS TO CONTINUE SHIFTING EAST THIS
MORNING ALONG WITH ATTENDANT SHEARING WAVE AND FORCING. 
CHALLENGE THEREAFTER IS PCPN CHCS/TYPE. MID LEVEL RIDGE IN THE
PLAINS TO BUILD IN BY TNGT THUS NO SHORTWAVE ENERGY TO FOCUS
PCPN. ONLY MECHANISM FOR PCPN APPEARS TO BE CONTINUED WEAK WARM
ADVECTION/ISENTROPIC LIFT. NAM/GFS BUFR SOUNDINGS SHOW LACK OF
ICE INTRODUCTION THUS ANTICIPATE PCPN MAINLY DZ/FZDZ DEPENDING
ON SFC TEMPS... WHICH COULD MEASURE ESPECIALLY TNGT WITH LLVL
SATURATION DEPTH INCREASING. THIS BRINGS ABOUT CONCERNS THAT 
COULD SEE VERY THIN GLAZE/ICING OVER PORTIONS OF AREA WHICH CUD
NECESSITATE ADVISORY. TEMPS TODAY NEAR TO ABOVE FREEZING ALL
BUT FAR NORTH. EXPECT ONLY SMALL DROP IN TEMPS TNGT WITH CLOUDS
AND INCREASING EASTERLY WINDS.  ..05..

.LONG TERM...WEDNESDAY THROUGH MONDAY...
ALL OPERATIONAL MODELS IN REASONABLE AGREEMENT ON MASSIVE WINTER
STORM TO IMPACT MUCH OF THE CENTRAL UNITED STATES THE REMAINDER OF
THE WEEK.

DEEPENING TROUGH NOW ONSHORE ALONG THE WEST COAST EXPECTED TO PUSH 
INTO THE SOUTHERN PLAINS BY WEDNESDAY. SURFACE LOW TO ORGANIZE IN 
THE TX PANHANDLE AND DEEPEN AS A CLASSIC PANHANDLE HOOK MAJOR WINTER 
STORM. MODELS AGREE ON TAKING THE CYCLONE WEST OF THE DVN CWA. THIS 
OBVIOUSLY RAISES CONCERNS FOR MIXED PRECIPITATION ON WEDNESDAY INTO 
THURSDAY...FOLLOWED BY POTENTIAL FOR HEAVY FLOODING RAINS...AND THEN 
BACK TO ALL SNOW BY FRIDAY. PRECIPITABLE WATERS ARE 2 TO 3 STANDARD 
DEVIATIONS ABOVE NORMAL FOR THIS EVENT SO RATHER REMARKABLE FOR LATE 
DECEMBER. ONCE THE OCCLUDED MASSIVE STORM LIFTS TOWARDS THE WESTERN 
GREAT LAKES IT RUNS INTO THE HUGE GREENLAND BLOCKING RIDGE. THIS 
FORCES THE STORM SYSTEM TO STALL SO WE WILL BE DEALING WITH THIS AT 
LEAST THROUGH THE WEEKEND...WITH COLD TEMPS AND SNOW SHOWERS.

WEDNESDAY...HAVE ISSUED A NEW WINTER STORM WATCH FOR AREAS SOUTH OF 
THE PREVIOUSLY ISSUED WATCH...AND WILL EXTEND IT TO THE I-80 
CORRIDOR. THIS NEW WATCH WILL RUN FROM 12Z WED TO 00Z FRI FOR 
POTENTIAL FOR A SIGNIFICANT ICE STORM OF AT LEAST 1/4 TO 1/2 INCH 
ICE ACCUMULATIONS. IF THE COLD AIR HOLDS ON LONGER THEN A MAJOR ICE 
STORM IS POSSIBLE. AS CYCLONE BEGINS TO DEEPEN ON WEDNESDAY 
STRENGTHENING LOW LEVEL JET WILL TRANSPORT A WIDE OPEN GULF 
MOISTURE. WITH A STRONG HIGH PRESSURE NORTH OF LAKE SUPERIOR FEEDING 
COLDER AND DRIER IN FROM THE EAST...EVAPORATIVE COOLING SHOULD KEEP 
SURFACE TEMPS BELOW FREEZING FROM NEAR I-80 NORTHWARD. FORECAST 
SOUNDINGS SUPPORT THIS SCENARIO WHILE WARM LAYER IN THE COLUMN WARMS 
TO +4C...A CLASSIC FREEZING RAIN SOUNDING. ALONG HIGHWAY 20 THE 
ENTIRE COLUMN IS STILL BELOW FREEZING SO HEAVY SNOWS A CONCERN. 
FARTHER SOUTH TOWARDS HIGHWAY 34 AND SOUTHWARD THIS SHOULD BE AN ALL 
RAIN EVENT. STRONG WINDS GUSTING TO AT LEAST 30 TO 35 MPH WEDNESDAY 
AND THURSDAY MAY CAUSE WIDESPREAD POWER OUTAGES WHERE ANY ICE 
ACCUMULATIONS OCCUR. THIS ALSO RAISES CONCERNS FOR FALLING BRANCHES.

THURSDAY...AS CYCLONE DEEPENS FURTHER AND LIFTS TO WESTERN IA THE 
LOW LEVEL JET WILL BE SCREAMING OUT OF THE SOUTH AT OVER 50 KNOTS. 
SURFACE WINDS WILL BE TURNING SOUTHEAST SO WARMER AIR AT THE SURFACE 
WILL CONTINUE TO BE TRANSPORTED NORTHWARD. THIS WILL CHANGE MIXED 
BAG TO ALL RAIN...POSSIBLY HEAVY. THIS RAISES HYDRO CONCERNS FOR 
FLOODING AS RAIN FALLS ON SNOW PACK/FROZEN GROUND. EVENTUALLY A 
FLASH FLOOD OR FLOOD WATCH MAY NEED TO BE ISSUED FOR THIS SITUATION.
WITH SUCH A STRONG SYSTEM THE THREAT OF ELEVATED THUNDERSTORMS EXIST.

THURSDAY NIGHT AND FRIDAY...SYSTEM BEGINS TO OCCLUDE WITH DYNAMIC 
COOLING DROPPING 850 MB TEMPS DRAMATICALLY. THIS CHANGES 
PRECIPITATION OVER TO ALL SNOW...POSSIBLY HEAVY IN SOME PORTIONS
OF THE DVN CWA. EVENTUALLY THOUGH THE BETTER MOISTURE WILL GET CUT 
OFF AND LIGHTER SNOWS WILL PREVAIL.

THIS WEEKEND...AS MENTIONED EARLIER THE STACKED SYSTEM STALLS OVER 
THE WESTERN GREAT LAKES/MIDWEST KEEPING US IN THE CLOUDS...COLD TEMPS
AND OCCASIONAL SNOW SHOWERS.

THE BOTTOM LINE...THIS IS A POTENTIALLY DANGEROUS WINTER STORM WITH 
HEAVY PRECIPITATION TOTALS COMING IN A VARIETY OF PRECIPITATION 
TYPES. IT SHOULD BE STRESSED THAT THE TIMING OF THE CHANGEOVER TO 
PRECIPITATION TYPES IS DIFFICULT AHEAD OF THIS EVENT. CHRISTMAS 
HOLIDAY TRAVEL WILL BE GREATLY IMPACTED ACROSS A LARGE PORTION OF 
THE MIDWEST SO YOU WILL NEED TO KEEP UP WITH THE LATEST FORECASTS 
AND STATEMENTS. AREAS FROM NEBRASKA TO MINNESOTA WILL EXPERIENCE A 
BLIZZARD WITH POTENTIAL SNOWFALL TOTALS OF 1 TO 2 FEET OF SNOW.  

..HAASE..

&&

.AVIATION...
CIGS CLIMBING INTO VFR MANY AREAS FOR A WHILE EARLY THIS MORNING
IN WAKE OF DEPARTING SNOW BAND... WITH IFR TO MVFR CONDITIONS
SPRINKLED IN. SNOW WILL BE DIMINISHING AT KDBQ THROUGH DAYBREAK.
CONTINUED WARM ADVECTION/ISENTROPIC LIFT NORTH OF SFC FRONT OVER
MO SHOULD RESULT IN CIGS LOWERING TO WIDESPREAD IFR TO POSSIBLY 
LIFR WITH POTENTIAL FOR AREAS OF DRIZZLE OR FREEZING DRIZZLE...
ESPECIALLY THIS AFTN AND TONIGHT. WINDS TO REMAIN EASTERLY AT
GENERALLY 10-20 KTS THROUGH THE PERIOD.  ..05..

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY 
     AFTERNOON FOR CEDAR-CLINTON-IOWA-JOHNSON-MUSCATINE-SCOTT.

     WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH FRIDAY 
     AFTERNOON FOR BENTON-BUCHANAN-DELAWARE-DUBUQUE-JACKSON-
     JONES-LINN.

IL...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY 
     AFTERNOON FOR CARROLL-ROCK ISLAND-STEPHENSON-WHITESIDE.

     WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH FRIDAY 
     AFTERNOON FOR JO DAVIESS.

MO...NONE.
&&

$$

05/HAASE