ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 PM EDT MON MAY 13 2013

VALID 12Z FRI MAY 17 2013 - 12Z TUE MAY 21 2013

MAINTAINING A BLEND OF THE GEFS/EC ENSEMBLES THROUGH THE MEDIUM
RANGE FORECAST ALLOWS FOR A SMOOTH TRANSITION FOR DAYS 4-6 THAT
REASONABLY HANDLES THE SPLITTING UPPER-LEVEL TROUGH AND FRONTAL
PROGRESSION ACROSS WESTERN ALASKA AND INTO THE GULF OF ALASKA.
GFS-BASED STANDARDIZED TEMPERATURE ANOMALIES (FOR H85-H7 LEVELS)
SUGGEST 2-3 STANDARD DEVIATIONS BELOW NORMAL FOR MUCH OF WESTERN
AND CENTRAL ALASKA INTO DAY 7...BEFORE THE BULK OF THE COLD VORTEX
EXITING ALASKA FOR THE ARCTIC CIRCLE...ALLOWS FOR SUBSTANTIAL
HEIGHT RISES AND SHORTWAVE RIDGING ALOFT TO WORK INTO ALASKA FROM
THE WEST.

THE DAY 7-8 FORECAST CONTINUES TO FOLLOW THE GFS/ECMWF GUIDANCE
PACKAGE WITH A BROAD AND INTENSE CYCLONE MOVING OFF THE COAST OF
ASIA. WITH A SUBSTANTIAL RIDGE AT THE SURFACE AND ALOFT AHEAD OF
THIS SYSTEM...BELIEVE THE DETERMINISTIC 13/12Z GFS AND 13/00Z
ECMWF ARE HEADED IN THE CORRECT DIRECTION WITH THIS SYSTEM
TRACKING THE BULK OF ITS DYNAMICS AND PRECIPITATION THROUGH THE
BERING SEA FROM SOUTHWEST TO NORTHEAST.

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