000
FXUS63 KDVN 121135
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
535 AM CST THU DEC 12 2013

.SYNOPSIS...
ISSUED AT 339 AM CST THU DEC 12 2013

LATEST SURFACE ANALYSIS SHOWED THE ARCTIC HIGH FROM NE OK INTO
SOUTHERN IL. A WEAK TROUGH REACHED FROM SE ND TO SW MN. A
TIGHTENING PRESSURE GRADIENT AND AXIS OF PRESSURE FALLS AHEAD OF
THIS TROUGH WAS DEVELOPING OVER CENTRAL AND NE IA. RESULTING SOUTH
TO SOUTHWEST SURFACE WINDS AND WEAK WARM ADVECTION...ALONG WITH A
STREAM OF MID AND HIGH CLOUDS IN THE NW FLOW...WERE CAUSING
TEMPERATURES TO SLOWLY RISE EARLY THIS MORNING AFTER EVENING LOWS
FROM AROUND ZERO TO 10 BELOW. WIND CHILL INDEX READINGS WERE
HOVERING -20 MAINLY ALONG THE IA HIGHWAY 20 CORRIDOR...WITH
SUBZERO TEENS WIDESPREAD ELSEWHERE.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 339 AM CST THU DEC 12 2013

FOCUS IS ON THE INITIAL COLD TEMPERATURES AND BITTER COLD WIND CHILL
INDEX VALUES THIS MORNING. WARMING TREND TO THEN FOLLOW TODAY
UNTIL A COLD FRONT DROPS SOUTH INTO THE REGION TONIGHT.

SURFACE WINDS WILL CONTINUE TO SLOWLY INCREASE EARLY THIS MORNING AS
THE WEAK CLIPPER SYSTEM PASSES TO THE NORTH FROM MN INTO WI. AS
WINDS INCREASE...TEMPERATURES WILL ALSO BE SLOWLY RISING...FROM
AROUND ZERO TO 5 BELOW TO A ZERO TO 5 ABOVE RANGE OVER MUCH OF THE
FORECAST AREA BY SUNRISE. 5 TO 10 MPH S TO SW WINDS WILL KEEP WIND
CHILLS IN THE SUBZERO TEENS IN THE ADVISORY AREA NORTH OF I-80
EARLY THIS MORNING WITH ESPECIALLY THE HIGHWAY 20 CORRIDOR MOST
LIKELY TO SEE -20 OR COLDER FOR A FEW MORE HOURS...BASED ON HOURLY
TEMPERATURE AND WIND TRENDS. HAVE ALREADY ADJUSTED THE WIND CHILL
ADVISORY EXPIRATION TIME TO 6 AM BASED ON THESE TRENDS AND WILL LEAVE
AS IS FOR NOW. WHILE DANGEROUS WIND CHILLS NO LONGER EXPECTED
AROUND DAWN...IT WILL STILL BE BITTERLY COLD FOR THE MORNING
COMMUTE HOURS.

THROUGH THE REST OF TODAY...SOUTHWEST WINDS WILL PARTIALLY TAP INTO
STRONG WARM ADVECTION ALOFT. THIS WILL SUPPORT HIGHS IN THE 20S OVER
THE CENTRAL AND SOUTH...WITH LOWER 30S OVER THE SNOW-FREE AREAS OF
FAR NE MO INTO W CENTRAL IL. IN THE NORTH...DEEPER SNOW COVER...AND
OCCASIONAL CLOUDS IN THE NW FLOW ALOFT WILL LIMIT HIGHS TO THE TEENS
ALONG THE HIGHWAY 20 CORRIDOR.

TONIGHT...A DEVELOPING COLD FRONT AHEAD OF THE NEXT RESURGENCE OF
ARCTIC HIGH PRESSURE OVER CANADA IS EXPECTED TO DROP SOUTH TO NEARLY
BISECT THE FORECAST AREA FROM NORTH TO SOUTH BY SUNRISE. MOISTURE
WILL BE LACKING IN THE LOW TO MID LEVELS...SO NOTHING IN THE WAY OF
LOW CLOUDS OR PRECIPITATION IS SUPPORTED. IT WILL...HOWEVER...LEAD
TO A LARGE THERMAL GRADIENT SETTING UP BY MORNING...ENHANCED BY
THE DEEPER SNOW COVER ACROSS THE NORTH. THIS WILL RESULT IN LOWS
IN THE SINGLE DIGITS NORTH OF I-80...WITH TEENS TO NEAR 20 IN THE
SOUTH.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 339 AM CST THU DEC 12 2013

THE MAIN FOCUS IN THE EXTENDED FORECAST IS THE WINTER STORM SYSTEM
THAT WILL BRING ACCUMULATING SNOWS TO THE SE 2/3 OF THE CWFA FRI PM
THROUGH SATURDAY MIDDAY.  MODELS ARE IN GENERALLY GOOD AGREEMENT IN
SWEEPING A SFC LOW ACROSS THE LOWER MS RIVER VALLEY FRI NIGHT AND
SAT WITH AN INVERTED TROUGH NUDGING NORTHWARD INTO THE REGION.  THE
LATEST NAM HAS COME IN FURTHER NORTH AND WETTER THAN PREVIOUS RUNS
AND REMAINS AN OUTLIER.  GFS/ECMWF HAVE BEEN RELATIVELY CONSISTENT
WITH BOTH TIMING AND LOCATION.

FRI AM SHOULD REMAIN DRY AS THE ATMOSPHERE INITIALLY SATURATES A DRY
LAYER AROUND 85H. PRECIPITATION...IN THE FORM OF ALL SNOW...IS
EXPECTED TO THEN SPREAD NORTHWARD UP TO THE I 80 CORRIDOR DURING THE
AFTERNOON. HAVE BUMPED UP POPS FOR THE ENTIRE EVENT...WITH
LIKELY-CATEGORICAL POPS INTRODUCED AT SOME POINT FROM FRI AFTERNOON
THROUGH EARLY SAT FOR AREAS ALONG AND SE OF A LINE FROM OTTUMWA TO
FREEPORT. BY THE FRI EVENING COMMUTE...SNOWFALL AMOUNTS ALONG AND
SOUTH OF HIGHWAY 34 MAY REACH THE INCH...TO INCH AND A HALF RANGE.
NORTHWARD TO I 80...ONLY A DUSTING TO A HALF INCH IS EXPECTED.  SNOW
WILL SPREAD FURTHER NORTHWARD AND INTENSIFY DURING THE EVENING AND
OVERNIGHT...WHEN MOST OF THE EVENT WILL TAKE PLACE.  AT THIS TIME...
IT APPEARS THAT MOST AREAS SE OF A LINE FROM CEDAR RAPIDS TO
FREEPORT WILL SEE 1 TO 3 INCHES...WITH PARTS OF SOUTHEAST IA...
NORTHEAST MO...AND WEST CENTRAL IL SEEING UP TO 4-5 INCHES.  AT THIS
TIME...A WINTER WEATHER ADVISORY REMAINS LIKELY FOR AREAS SOUTH OF A
LINE FROM FAIRFIELD IA...TO PRINCETON IL...FOR A SOLID 2-4 INCHES...
WITH HIGHER AMOUNTS UP TO AROUND 5 INCHES IN SOUTHERN HANCOCK AND
MCDONOUGH COUNTIES. WILL HOLD OFF ON ISSUING ADVISORY AT THIS
TIME. LITTLE ADDITIONAL SNOWFALL IS EXPECTED SAT AS THE SYSTEM
MOVES OFF TO THE EAST.

NOT MUCH CHANGE TO TEMPERATURES THROUGH EXTENDED OTHER THAN TRENDING
A DEG/TWO LOWER HERE AND THERE.  SUN AM LOOK TO BE THE COLDEST...
WITH READINGS MAINLY IN THE SINGLE DIGITS.  THESE MAY NEED FURTHER
LOWERING IF SKIES CLEAR OUT MORE THAN CURRENTLY FORECAST.

A CLIPPER SYSTEM MAY SKIRT THE NE 1/5 OF THE CWFA SUN NIGHT...
OTHERWISE THE REMAINDER OF THE EXTENDED IS DRY AT THIS TIME. A
GRADUAL WARM UP IS EXPECTED EARLY NEXT WEEK...WITH HIGHS BY TUE
IN THE UPPER 20S TO MID-UPPER 30S.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 535 AM CST THU DEC 12 2013

VFR CONDITIONS WILL CONTINUE TODAY AND TONIGHT. SOUTHWEST WINDS
FROM 10 TO 15 KTS WILL DIMINISH TO LESS THAN 10 KTS TONIGHT...THEN
BECOME LIGHT EAST OR VARIABLE TOWARD MORNING AS SLOW MOVING COLD
FRONT STALLS ACROSS THE REGION.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...WIND CHILL ADVISORY UNTIL 6 AM CST EARLY THIS MORNING FOR BENTON-
     BUCHANAN-CEDAR-CLINTON-DELAWARE-DUBUQUE-IOWA-JACKSON-
     JOHNSON-JONES-LINN-MUSCATINE-SCOTT.

IL...WIND CHILL ADVISORY UNTIL 6 AM CST EARLY THIS MORNING FOR BUREAU-
     CARROLL-HENRY IL-JO DAVIESS-PUTNAM-ROCK ISLAND-STEPHENSON-
     WHITESIDE.

MO...NONE.
&&

$$

SYNOPSIS...SHEETS
SHORT TERM...SHEETS
LONG TERM...14
AVIATION...SHEETS