FXUS63 KDVN 252106 CCA
AFDDVN
AREA FORECAST DISCUSSION...CORRECTED TYPO
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
305 PM CST FRI DEC 25 2009
.SYNOPSIS...
12Z UA ANALYSIS SHOWS A FULLY OCCLUDED EXTRATROPICAL CYCLONE OVER
IOWA. A LLJ OF 40-50 KTS RAN FROM THE GULF COAST TO THE GREAT LAKES
WITH NUMEROUS SHORTWAVES ROTATING AROUND THE UPPER LOW ACROSS IOWA.
VERY IMPRESSIVE UPPER LEVEL WARM AND COLD FRONTS WERE ASSOCIATED
WITH THE H85 LOW. THE EXTRATROPICAL CYCLONE WAS AT ITS MAXIMUM
INTENSITY...JUST UNDER 986 MB...AT 15Z WITH A 270 DEGREE WRAPPING OF
THE COLD AIR AROUND IT. 18Z SFC ANALYSIS HAD THE SFC LOW AROUND KEBS
WITH AN OCCLUSION RUNNING WEST TO THE MISSOURI RIVER. THE COLD FRONT
RAN EAST SOUTHEAST TO KMLI AND THEN SOUTH INTO THE OHIO AND
TENNESSEE VALLEYS. SEVERAL TROFS ASSOCIATED WITH UPPER LEVEL
DISTURBANCES RADIATED OUT FROM THE SFC LOW. DEW POINTS WERE IN THE
TEENS AND SINGLE DIGITS ACROSS THE PLAINS AND MID MISSISSIPPI VALLEY
WITH 20S AND 30S ACROSS THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY.
&&
.SHORT TERM...TONIGHT AND SATURDAY...
RUC CONTINUES TO BE THE BEST IN THE IMMEDIATE SHORT TERM REGARDING
TEMPERATURE TRENDS. AREA RADARS ARE OVERSHOOTING A LARGE AMOUNT OF
THE LOW LEVEL PRECIPITATION...EVIDENT BY THE RADAR RETURN HOLE OVER
THE AREA FILLING IN THROUGH MID AFTERNOON. CONDENSATION PRESSURE
DEFICITS AND FORCING SUGGEST FLURRIES THROUGH THE NIGHT WITH PERIODS
OF -SN. RUC AND 18Z WRF SUGGEST THE POTENTIAL FOR SEVERAL BANDS OF
-SN TO DEVELOP AND ROTATE ACROSS THE AREA. THUS SNOW AMOUNTS WILL BE
ON THE LIGHT SIDE WITH ABOUT AN INCH SEEN BY SUNRISE OVER PARTS OF
THE AREA.
FLURRIES AND PERIODS OF LIGHT SNOW WILL CONTINUE SATURDAY AS SEVERAL
VORT MAXES ROTATE THROUGH THE AREA. FORCING SUGGESTS SEVERAL BANDS
OF LIGHT SNOW TO AGAIN DEVELOP AND ROTATE ACROSS THE AREA WITH UP
TO ANOTHER INCH OF ACCUMULATION BY SUNSET.
TEMPERATURES WILL CONTINUE TO FALL THIS EVENING AS THE COLD AIR
MOVES IN FROM THE SOUTHWEST. LATER THIS EVENING AND OVERNIGHT
TEMPERATURES SHOULD REMAIN NEARLY STEADY OR POSSIBLY RISE SLIGHTLY
AS THE WARMER AIR ALOFT WRAPS AROUND FROM THE SOUTH AND WEST.
..08..
.LONG TERM...FRIDAY NIGHT THROUGH NEXT FRIDAY...
...SEASONABLY COLD AND UNSETTLED...FLURRIES AND LIGHT SNOW INTO
SUNDAY NIGHT...THEN LIGHT SNOW POSSIBLE WEDNESDAY...
OVERVIEW...MODEL INITIALIZATION VERY GOOD. VERIFICATION AT 2 PM
SUPPORTS USING 12Z ECMWF WITH FORCING INPUTS FROM 80 KM NAM-WRF INTO
MONDAY. USED A 60/40 BLEND OF ECMWF AND GFS DAY 4 AND BEYOND BASED
ON RUN TO RUN CONTINUITY.
SATURDAY NIGHT THROUGH SUNDAY NIGHT...UPPER LOW TO SLIDE SLOWLY EAST
WITH PLENTY OF CLOUDS AND PERIODS OF LIGHT SNOW AND FLURRIES. LOCAL
TOOLS ALL INDICATE ADDITIONAL SNOW AMOUNTS SHOULD BE GENERALLY AN
INCH OR LESS. AGAIN KEPT MODEST DIURNAL TRENDS WITH LOWS IN THE TEENS
AND HIGHS IN THE LOWER 20S. KEPT WINDS MAINLY IN THE 10 TO 20 MPH
RANGE FOR SEASONABLY BRISK WEATHER. EXPECT AT LEAST A THIRD OF THE
TIME OVER THIS 36 HOUR PERIOD FLURRIES OR LIGHT SNOW TO BE FALLING.
KEPT CHANCE POPS...DECREASING TO FLURRIES SUNDAY NIGHT.
MONDAY THROUGH TUESDAY NIGHT...QUIET AND SEASONABLY COLD WITH SURFACE
HIGH MOVING IN. ENOUGH LOW LEVEL CONVERGENCE TO SUPPORT PARTLY
CLOUDY SKIES TO LIMIT MINS ATTM. MAIN ISSUE IS IF SKIES CLEAR THAN
MINS WILL NEED LOWERING BY UP TO 5 DEGREES OR MORE FOR LATER SHIFTS
TO REASSESS.
WEDNESDAY...UPPED POPS TO CHANCE FOR SNOW WITH WEAK SW PACIFIC SYSTEM
AHEAD OF NEXT REINFORCING SHOT OF COLD AIR FROM CANADA. ANALYSIS OF
MODEST MOISTURE AND LIMITED FORCING SUGGEST ANY AMOUNTS TO BE
LIGHT...GENERALLY A COUPLE INCHES OR LESS. SPECIFIC COVERAGE MOST
FAVORED LOCATIONS AND AMOUNTS SHOULD BE BETTER ASCERTAINED IN NEXT
12-24 HOURS. AMOUNT OF CLOUDS WILL IMPACT TEMPS AND WENT WITH MOSTLY
CLOUDY SKIES ATTM WITH HIGHER MINS.
THURSDAY INTO FRIDAY...TRIMMED TEMPS A FEW DEGREES AND KEPT DRY.
CLOSE INSPECTION SUPPORTS TEMPS WILL NEED FURTHER LOWERING BY 5 TO 10
DEGREES. THIS IS BASED ON AMOUNT OF REINFORCING ARCTIC AIR THAT IS
SUGGESTED TO ARRIVE AND AREA DOES GET 1 TO 4 INCHES OF NEW SNOW BY
LATE WEEK. SOME LOCAL TOOLS AND TECHNIQUES SUPPORT MINS WELL BELOW
ZERO FOR NEXT FEW SHIFTS TO EVALUATE AND CLARIFY. ..NICHOLS..
&&
.AVIATION...
FULLY OCCLUDED CYCLONE WILL SLOWLY FILL AND ROTATE ACROSS IA THROUGH
00Z/27. CONDENSATION PRESSURE DEFICITS AND FORCING INDICATE
WIDESPREAD --SN THROUGH 00Z/27. FORCING SUGGESTS BANDS OF -SN WILL
DEVELOP AND ROTATE ACROSS THE AREA AS WELL. CIGS MAY BRIEFLY RISE TO
2KFT BUT SHOULD DROP TO 1-2KFT AND REMAIN THERE AFT 06Z/26. VSBYS
SHOULD REMAIN 6SM OR NO WORSE THAN 3-5SM OUTSIDE OF ANY BANDED SN.
VSBYS/CIGS IN BANDS OF SN MAY DROP BLO 1SM AND BLO 1KFT. ..08..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
08/NICHOLS
