EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 115 AM EST FRI FEB 13 2015 VALID 12Z MON FEB 16 2015 - 12Z FRI FEB 20 2015 ...OVERVIEW... AS HAS TENDED TO BE THE CASE WITH WEST COAST/ERN PAC RIDGE AND DOWNSTREAM TROUGH PATTERNS THAT HAVE EXISTED OVER THE PAST COUPLE WINTERS... LATEST GUIDANCE SUGGESTS ABOVE AVERAGE PREDICTABILITY FOR THE LARGE SCALE FLOW. HOWEVER QUESTION MARKS EXIST FOR MULTIPLE EMBEDDED SHRTWVS SO SOME IMPORTANT ASPECTS OF THE FCST HAVE SIGNIFICANTLY LOWER CONFIDENCE. ...GUIDANCE EVALUATION... WITH THE DANGEROUSLY COLD/WINDY SYSTEM AFFECTING THE NORTHEAST ON SUN NOW IN THE SHORT RANGE AND REACHING THE CANADIAN MARITIMES BY EARLY MON... THE NEXT FOCUS FOR ATTENTION WILL BE AMPLIFYING WRN-CNTRL CONUS SHRTWV ENERGY WHICH SHOULD PROGRESS INTO THE EAST BY THE MIDDLE OF NEXT WEEK WITH ASSOC SFC LOW PRES REACHING THE WRN ATLC AT THAT TIME. CURRENT CONFIDENCE IN ANY SPECIFIC SOLN IS BELOW AVG GIVEN THE MULTIPLE SOURCES OF ENERGY INVOLVED... INCL AN INITIALLY WEAK PIECE OF ENERGY FROM THE NERN PAC AND NOT REACHING WRN CANADA UNTIL SUN... AN EJECTING COMPACT UPR LOW INITIALLY NEAR BAJA CALIF... AND FLOW DIGGING SEWD FROM NWRN CANADA. THUS FAR THE MODELS HAVE BEEN INCONSISTENT IN HOW THESE FEATURES INTERACT AND WITH THE RESULTING SFC PATTERN. ENSEMBLE SFC LOW PLOTS ALSO SHOW CONSIDERABLE SPREAD. THE MOST NOTABLE TREND OVER RECENT RUNS AND IN PARTICULAR THE 12Z/18Z CYCLE IS ONE TOWARD GREATER SUPPRESSION AT THE SFC FROM THE SRN PLAINS THROUGH THE ERN STATES. AMONG THE NEW 00Z SOLNS THUS FAR THE 00Z GFS/CMC SUPPORT OR EVEN EXTEND THE RECENTLY ESTABLISHED TREND WHILE THE UKMET STRAYS FROM CONSENSUS ALREADY IN THE SHORT RANGE. THE 18Z GFS LEANED ON THE FASTER SIDE OF GUIDANCE LEAVING A COMPROMISE BTWN THE 12Z GFS/18Z GEFS MEAN AND SLOWER 12Z ECMWF/ECMWF MEAN AS THE BEST INTERMEDIATE SOLN TO REFLECT LATEST TRENDS THROUGH DAY 5 WED. UPSTREAM SIGNIFICANT SPREAD IN SFC DETAILS DEVELOPS OVER THE ROCKIES/PLAINS BY WED IN RESPONSE TO DIFFS IN HOW SHRTWV ENERGY ROUNDING THE MEAN RIDGE FLOWS SEWD... WHILE GUIDANCE ALSO DIVERGES WITH RESPECT TO THE EVOLUTION/TIMING OF ERN PAC ENERGY THAT MAY TRY TO PASS THROUGH OR AROUND THE MEAN RIDGE. AN AVG OF LATEST ENSEMBLE MEANS OFFERS A REASONABLE SOLN NEAR THE WEST COAST WITH MAINTENANCE OF A STRONGER RIDGE THAN 12Z ECMWF/18Z GFS/00Z CMC RUNS BUT NOT TO THE EXTENT OF THE 00Z GFS THAT HOLDS MORE UPR LOW ENERGY BTWN 30-35N THAN OTHER SOLNS BY WED. THE GENERAL MODEL/ENSEMBLE MEAN BLEND USED THROUGH WED AND COMBINATION OF THE 18Z GEFS/12Z NAEFS/12Z ECMWF MEANS MEANS THEREAFTER KEEPS ERN ROCKIES/PLAINS FEATURES ILL DEFINED UNTIL BETTER CLUSTERING DEVELOPS. ...SENSIBLE WEATHER HIGHLIGHTS... THE FCST IS RATHER UNCERTAIN REGARDING WINTER WEATHER POTENTIAL FROM THE ROCKIES/PLAINS THROUGH THE EAST MON-WED. LATEST TRENDS TOWARD A MORE SUPPRESSED SFC SYSTEM WOULD LIMIT THE NWD/NWWD EXTENT OF PCPN VERSUS PRIOR CONSENSUS. SOURCES OF UPR SUPPORT FOR THIS SYSTEM SUGGEST IT MAY TAKE UNTIL AT LEAST SUN TO GAIN DECENT CONFIDENCE IN REFINING PCPN TYPES AND DURATION/INTENSITY. CURRENTLY THE SRN TIER STATES HAVE THE BEST POTENTIAL TO SEE LOCALLY HVY TOTALS... MOSTLY RAIN WHERE HEAVIEST ACTIVITY OCCURS. DEPENDING ON UPSTREAM SHRTWV IMPULSES ONE OR MORE AREAS OF MOSTLY LGT SNOW MAY CROSS NRN AREAS. SOME LAKE EFFECT SNOW IS ALSO PSBL TO THE LEE OF PORTIONS OF THE GRTLKS NOT YET COVERED BY ICE. LGT PCPN MAY REACH THE NORTHWEST LATE IN THE PERIOD AS ERN PAC ENERGY PASSES INTO THE LARGE SCALE MEAN RIDGE. OVERALL THE MEAN PATTERN SHOULD SUPPORT WARM TEMPS OVER THE WEST... VARIABLE READINGS OVER THE PLAINS... AND BELOW TO MUCH BELOW NORMAL TEMPS OVER THE EAST. EXPECT WARMEST ANOMALIES OF PLUS 10-20F OVER THE INTERIOR WEST WED TO FRI WHILE MINUS 15-30F ANOMALIES ARE PSBL ON MULTIPLE DAYS OVER PARTS OF THE ERN HALF OF THE CONUS. RAUSCH