EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
137 PM EST SUN FEB 12 2012
 
VALID 12Z WED FEB 15 2012 - 12Z SUN FEB 19 2012
 
FINAL HPC SURFACE FRONTS/PRESSURE AND 500 MB PROGS REMAIN
PRIMARILY DERIVED FROM A 70-30% BLEND OF ECMWF ENSEMBLES AND GFS
ENSEMBLES...ALBEIT WITH SOME MANUAL FORECASTER ADJUSTMENTS.  THIS
SOLUTION MAINTAINS HPC CONTINUITY BY STILL LEANING HEAVILY UPON
ENSEMBLE GUIDANCE AS DETERMINISTIC GUIDANCE SOLUTIONS VARY
SIGNIFICANTLY FROM THE BEGINNING OF THE MEDIUM RANGE FORECAST
PERIOD...ESPECIALLY ACROSS WRN NORTH AMERICA.  THESE DIFFERENCES
QUICKLY SPREAD DOWNSTREAM ACROSS THE REST OF THE CONTINENT.

MODEL FORECAST SPREAD IS QUITE LARGE ALOFT WITH THE EVOLUTION OF
THE BULK OF NERN PACIFIC TROUGH ENERGY WORKING INLAND TOWARD WRN
NORTH AMERICA WITH SOLUTIONS FALLING INTO THREE CLUSTERS BY THU. 
RECENT GFS/UKMET/DGEX RUNS TEND TO DIG FLOW MORE SHARPLY ALONG THE
WEST COAST RESULTING IN A CLOSED LOW OFF BAJA. THE CANADIAN/NOGAPS
OFFER STARKLY LESS DIGGING ONLY INTO THE NRN ROCKIES THAT SEEMS
INSUFFICIENT CONSIDERING UPSTREAM FLOW.  MOST RECENT ECMWF AND
ECMWF ENSEMBLE RUNS AND THE 12 UTC NAM/JMA SHOW MORE OF AN INLAND
SLIDER INTO THE SWRN US.  THAT SAID...THE LATEST 12 UTC GFS/ECMWF
HAVE STARTED TO TREND TOWARD A MORE COMMON DIGGING CLOSER DOWN THE
WEST COAST THAN PRIOR RUNS.  OPT TO STAY THE COURSE FOR NOW
BLENDING INSTEAD ECMWF ENSEMBLES WITH A SMALLER PORTION OF GFS
ENSEMBLES TO AVOID DETERMINISTIC DETAIL WITH LOWER PREDICTABILITY.
 THESE ENSEMBLE MEAN SOLUTIONS ARE BOTH SLIGHTLY MORE SWD DIGGY
THAN THE 00 UTC ECMWF AND A SOLUTION IN THAT DIRECTION WITH A
MANUALLY FORECASTER ADJUSTED DEPTH TO MATCH SEEMS REASONABLE
CONSIDERING UPSTREAM RIDGE AMPLITUDE AND OVERALL 12 UTC GUIDANCE
TRENDS.

LATER IN THE WEEK THE GFS...GEFS MEAN...AND GEM GLOBAL ALL BREAK
FROM THE SPLIT FLOW CHARACTERISTIC OF THIS ENTIRE COLD SEASON WITH
A SUSPICIOUSLY CLEAN LOOKING POSITIVE PNA PATTERN.  THE ECMWF AND
ECMWF ENSEMBLES HONOR THE SPLIT THROUGH THE FORECAST.  ACCORDINGLY
AM AGAIN SHYING AWAY FROM INDIVIDUAL MODEL GUIDANCE WITH
PREFERENCE OF A SOLUTION CLOSEST TO ECMWF ENSEMBLES...BUT DID ADD
IN 30% GFS ENSEMBLES TO HEDGE UNCERTAINTY.

CISCO/SCHICHTEL