Preliminary Forecasts
Issued by NWS

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FXUS02 KWNH 280555
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1254 AM EST SUN DEC 28 2014

VALID 12Z WED DEC 31 2014 - 12Z SUN JAN 04 2015


...BIG CHILL FOR THE WEST...

THE GLOBAL NUMERICAL MODELS UNANIMOUSLY INDICATE THAT THE MEDIUM
RANGE WILL OPEN WITH COLD AIR WELL ENTRENCHED IN THE WESTERN
UNITED STATES. BY THURSDAY MORNING, THE COLD AIR IS PROGGED TO
HAVE FILLED EVER EVERY NOOK AND CRANNY OF THE NATION WEST OF THE
HUNDREDTH MERIDIAN. SNOW LEVELS LOOK IMPRESSIVELY LOW OVER
SOUTHERN CALIFORNIA WEDNESDAY AND THURSDAY, WITH FREEZING
TEMPERATURES ALONG PARTS OF THE LOWER COLORADO RIVER VALLEY.
DAYTIME HIGHS WILL STAY FRIGID EARLY IN THE PERIOD WEST OF THE
CONTINENTAL DIVIDE IN WASHINGTON STATE--PROTECTED FROM THE
DEVELOPING CHINOOK OVER MONTANA VIA THE EXTREME POSITIVE TILT OF
THE UPPER TROUGH. STRONG RADIATIONAL COOLING OVER A FRESH UPSLOPE
SNOWPACK IN EASTERN COLORADO SHOULD HELP WEDNESDAY DAWN BITTERLY
COLD.

THE CRYSTAL BALL DARKENS CONSIDERABLY BY NEXT WEEKEND, WHEN THE
DEEP LOBE OF COLD AIR OVER THE SOUTHWEST FINALLY BEGINS TO KICK
EASTWARD. THE TIMING OF THE SHORTWAVES IN THE NORTHERN STREAM
VIS-A-VIS THE EJECTION OF THE SOUTHWESTERN VORTEX WILL HAVE GREAT
BEARING ON THE EXTENT AND TYPE OF PRECIPITATION OVER THE CENTRAL
AND EASTERN STATES. SLEET AND FREEZING RAIN WILL LIKELY TAKE UP
MORE REAL ESTATE THAN HERETOFORE THIS SEASON CONSIDERING THE HEFT
OF THE MODIFIED ARCTIC AIRMASS THAT SPREADS ACROSS THE MIDWEST AND
INTO THE MID ATLANTIC AND NORTHEAST MID- TO LATE WEEK. A
SIGNIFICANT NORTHERN STREAM SHORTWAVE DIPPING INTO THE GREAT LAKES
NEXT WEEKEND MAY VIE FOR DOMINANCE WITH THE HEART OF THE EJECTING
SOUTHWEST SYSTEM--SOMETHING BEST SORTED OUT AT THIS POINT BY A
HEAVY RELIANCE ON THE RECENT ENSEMBLE MEANS.


CISCO

$$





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