THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


ALASKA EXTENDED FORECAST DISCUSSION




ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
201 PM EST THU NOV 27 2014

VALID 12Z MON DEC 01 2014 - 12Z FRI DEC 05 2014

DEEP BERING SEA LOW PRESSURE EXPECTED TO WORK ITS WAY TOWARD THE
ERN ALEUTIANS AND THEN NEAR KODIAK ISLAND WILL BE THE DOMINANT SFC
FEATURE OF INTEREST DURING THE FCST PERIOD.  SOME OF THE DETAILS
OF EXACTLY HOW THIS SYSTEM WILL EVOLVE/TRACK WILL DEPEND ON
TYPICALLY DIFFICULT TO RESOLVE ASPECTS OF ONE OR MORE PIECES OF
ENERGY FLOWING AROUND THE SERN SIDE OF A MEAN UPR HIGH WELL NWWD
OF THE MAINLAND... AS WELL AS ON TIMING OF FLOW FROM ERN ASIA INTO
THE WRN PAC.

FROM DAY 4 MON INTO EARLY DAY 6 WED CURRENT PREFS LEAN TOWARD A
MODEL/ENSEMBLE MEAN BLEND THAT GIVES MORE EMPHASIS TO THE 06Z GFS
PARALLEL/00Z ECMWF RELATIVE TO THE 06Z GEFS/00Z ECMWF MEANS IN
LIGHT OF DEPTH IN THE INDIVIDUAL MODEL RUNS FOR THE BERING SEA LOW
AND 06Z GFS PARALLEL TRACK THAT IS CLOSER TO THE NWD ECMWF/ECMWF
MEAN THAN THE 00Z/06Z OPERATIONAL GFS RUNS EARLY IN THE PERIOD. 
AFTER EARLY WED THE TIMING OF UPSTREAM ERN ASIA/WRN PAC FLOW
BECOMES THE LARGEST SCALE DIFFERENCE... WITH THE ECMWF/ECMWF MEAN
BECOMING FASTER THAN THE GFS/CMC AND THEIR RESPECTIVE MEANS.  THE
00Z ECMWF RAPIDLY STRAYS WELL SWD OF THE MAJORITY OF SOLNS WITH
THE BERING SEA/ALEUTIANS SYSTEM AFTER 12Z WED.  TOWARD THE END OF
THE PERIOD THE 06Z PARALLEL GFS HOLDS ONTO A DEEP SYSTEM NEAR
KODIAK ISLAND WHILE CONSENSUS MEAN FLOW SUGGESTS THE SYSTEM SHOULD
BE TRENDING WEAKER AT THAT TIME.  OTHERWISE MID-SMALLER SCALE
DETAILS ALOFT OVER AND N OF THE BERING SEA ARE QUITE DIVERSE SO
CONFIDENCE IS LOW FOR ANY PARTICULAR MODEL SOLN.  FAVORING A
SCENARIO MORE TOWARD THE SLOWER MAJORITY ACROSS THE NRN PAC...
WENT WITH 70 PCT TOTAL 06Z GEFS MEAN/PARALLEL GFS VERSUS THE 00Z
ECMWF MEAN DAY 7 THU AND 70/30 06Z GEFS MEAN/00Z ECMWF MEAN DAY 8
FRI.

RAUSCH





Last Updated: 201 PM EST THU NOV 27 2014