THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


EXTENDED FORECAST DISCUSSION




EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1059 AM EST FRI DEC 19 2014

VALID 12Z MON DEC 22 2014 - 12Z FRI DEC 26 2014

...AN ACTIVE HOLIDAY WEATHER PATTERN...

...OVERVIEW...
A DEEPENING AREA OF LOW PRESSURE IN THE MIDWEST WILL MIGRATE
ACROSS THE GREAT LAKES AND UPPER OHIO VALLEY---THEN SETTLE OVER
CENTRAL QUEBEC IN THE LATTER HALF OF THE FORECAST PERIOD. THE
BREATH AND DEPTH OF THE SURFACE LOW WILL PRODUCE BROAD-SCALE WINDY
CONDITIONS AND

...MODEL PREFERENCES/UNCERTAINTY ASSESSMENT...
IN THE EAST...
THE 19/00Z ECENS/ECMWF AND GEFS/GFS HAVE MAINTAINED DECENT
AGREEMENT ALOFT WITH THE NEGATIVE-TILT TROUGH MIGRATION ACROSS THE
NORTHEAST QUARTER OF THE NATION. THE SUBTLE DIFFERENCES---TIED TO
FRONTAL PROGRESSION AND LOCATION OF TRIPLE-POINT LOW FORMATION(S)
EMBEDDED WITHIN THIS NEGATIVE-TILT TROUGH. THE 19/00Z ECMWF WAS A
SLIGHTLY FASTER SOLUTION ACROSS THE EAST VERSUS THE GEFS/GFS WITH
THE INITIAL FRONTAL PASSAGE AND WIND SHIFT FROM SOUTHERLY THE
WESTERLY...BUT BOTH WERE ESSENTIALLY---SPOT ON---WITH THE TIMING
OF THE SECONDARY SURGE OF COLDER CANADIAN AIR SURGING ACROSS THE
GREAT LAKES AND NORTHEAST ON DAY 4-5.

IN THE WEST...
THE 19/00Z ECENS/GEFS SUPPORT A DIGGING NW-TO-SE MOVING
UPPER-LEVEL TROUGH FROM PUGET SOUND TO THE GREAT BASIN...AND
MIGRATING THIS DEEPENING SYSTEM---WEST OF THE DIVIDE BY DAY 5-6.
WE LIKED A BLEND OF THE ECENS/GEFS HERE. VOJTESAK

...SENSIBLE WEATHER HIGHLIGHTS...
AN AMPLIFIED MID-UPPER LEVEL TROUGH AND PCPN FOCUSING LEAD SURFACE
LOW/FRONTAL SYSTEM DEVELOPS OVER THE CENTRAL US BY EARLY NEXT WEEK
AS EMBEDDED IMPUSLES DIG TO THE LEE OF AN AMPLIFIED ERN PACIFIC
RIDGE ALOFT. THE SUPPORTING AND INCREASINGLY NEG-TILT TROUGH ALOFT
WORKS OVER THE ERN US AND OUT THROUGH THE NERN STATES INTO DAYS
5/6 WED/THU. SUSPECT A THREAT EXISTS FOR ORGANIZED WINTER WEATHER
IN LEAD FLOW OVER A COOLED NRN NEW ENG AIRMASS TUE WITH LOW
INDUCED WRAP-AROUND SNOWS SPREADING FROM THE UPPER MIDWEST AND
GREAT LAKE STATES/MIDWEST LINGERING PAST TUE/WED THAT WORK MORE IN
ERNEST OUT THROUGH THE APPALACHIANS AND MAINLY INTERIOR NRN
MID-ATLANTIC/NERN US ON CHRISTMAS EVE AND CHRISTMAS.

MEANWHILE...NRN/NERN PACIFIC MID-UPPER TROUGH ENERGIES SHOULD WORK
SHARPLY SEWD THROUGH AND TO THE LEE OF AN AMBIENT DOWNSTREAM MEAN
RIDGE POSITION TO SPREAD DYNAMICALLY DRIVEN PCPN INTO THE PAC NW
WED AND FURTHER INLAND ACROSS THE N-CENTRAL INTERMOUNTAIN
WEST/ROCKIES CHRISTMAS INTO NEXT FRI. THIS WILL INCLUDE A THREAT
FOR MODERATELY HEAVY SNOWS FOCUSING OVER FAVORED INLAND TERRAIN.
THIS WRN US SYSTEM REACHES THE CENTRAL US IN ABOUT A WEEK
PROMPTING CYCLO/FRONTOGENESIS AND PCPN/INFLOW RECOVERY OUT FROM
THE GULF OF MEXICO IN THE WAKE OF THE LEAD/EXITING ERN/NERN US
STRONG LOW SYSTEM INCLUDING SOME WINTERY PCPN THREAT ON THE NW
PERIPHERY OF THE OVERALL PCPN SHIELD SPREADING NEWD FROM THE
CENTRAL PLAINS TO THE GREAT LAKES STATES RIDING OVERTOP WARM
SECTOR CONVECTIVE RAINS.
SCHICHTEL





Last Updated: 1059 AM EST FRI DEC 19 2014