EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1106 AM EST TUE JAN 12 2016 VALID 12Z FRI JAN 15 2016 - 12Z TUE JAN 19 2016 ...OVERVIEW... THE FCST PERIOD WILL FEATURE TWO DOMINANT HGT ANOMALY CENTERS THAT MULTI-DAY MEANS HAVE BEEN SHOWING IN RECENT DAYS... A NEGATIVE CENTER OVER THE PAC A LITTLE NE OF 40N 150W AND A POSITIVE CENTER JUST NE OF HUDSON BAY. A COMPOSITE OF ASSOC TELECONNECTIONS YIELDS A CONSISTENT LOWER 48 MEAN PATTERN OF A WRN RIDGE AND ERN TROUGH. THIS PATTERN SHOULD YIELD WET CONDS FROM N-CNTRL CA NWD AND GENERALLY MILD CONDS OVER THE WRN STATES ALONG WITH BELOW NORMAL TEMPS AND A DRYING TREND OVER THE EAST. TELECONS RELATIVE TO EACH HGT ANOMALY FEATURE SHOW THE GREATEST DIFFS WITH NRN ROCKIES/NRN-CNTRL PLAINS TEMPS. ...MODEL EVALUATION AND PREFERENCES... OVER THE ERN PAC/WRN NOAM THE LATEST CYCLE OF GUIDANCE SHOWS NO LARGE SCALE DISCREPANCIES. PRIMARY FCST ISSUES INVOLVE AN ONGOING SERIES OF ERN PAC SHRTWVS THAT WILL PASS THROUGH THE WRN MEAN RIDGE AND CONTINUE INTO THE DOWNSTREAM MEAN TROUGH. THE 00Z/06Z GFS RUNS ARE A TAD STRONGER THAN CONSENSUS WITH THE IMPULSE REACHING THE WEST COAST ON DAY 4 SAT WITH THE 00Z RUN IN PARTICULAR BECOMING A STRONG SOLN DOWNSTREAM. THE 00Z GFS MAY ALSO BE A LITTLE STRONG WITH THE NEXT SHRTWV ARRIVING ON DAY 5 SUN. SHRTWVS OF INTEREST HAVE SUFFICIENTLY SMALL SCALE FOR PREDICTABILITY OF SPECIFICS TO BE BELOW AVG. OVER THE CNTRL-ERN STATES MODEL/ENSEMBLE MEANS SEEM TO BE IN THE PROCESS OF CONVERGING FOR THE DAYS 3-4 FRI-SAT PERIOD. GEFS MEANS ARE CATCHING UP TO OTHER SOLNS THAT MAINTAIN BETTER REFLECTION OF A SRN STREAM SHRTWV OVER THE PLAINS/MS VLY ON FRI AND EJECTS NEWD TO SUPPORT A DEEPENING SFC WAVE THAT TRACKS FROM THE GULF COAST TO JUST OFF THE MID ATLC/NERN COAST. BY SAT THE 06Z GEFS MEAN IMPROVES UPON THE 00Z RUN WITH DEPTH SIMILAR TO THE 00Z ECMWF MEAN... THOUGH OPERATIONAL SOLNS GENERALLY AGREE UPON A DEEPER SYSTEM THAN THE MEANS. LARGER SCALE FCST PROBLEM PERSISTS WITH TIMING OF AN UPPER LOW FCST TO TRACK FROM SRN CANADA ACROSS THE UPR GRTLKS/NEW ENGLAND. GFS RUNS REMAIN ON THE SLOW SIDE OF THE SPECTRUM. GEFS MEANS HAVE TENDED TO BE SOMEWHAT FASTER THAN OP GFS RUNS AND THE 06Z GEFS MEAN TRENDS FASTER LATE SUN ONWARD TO ADD SUPPORT FOR LEANING MORE TOWARD THE ECMWF CLUSTER. ENSEMBLE MEANS SUGGEST THE 00Z ECMWF COULD BE SOMEWHAT FAST WITH THE OVERALL ERN TROUGH BY DAYS 6-7 MON-TUE THOUGH. BASED ON THE ABOVE CONSIDERATIONS... OVERALL STARTING PREFS SIDE WITH THE 00Z ECMWF MEAN/06Z GEFS MEAN/00Z ECMWF IN ORDER OF HIGHEST TO LOWEST WEIGHTING. THE FCST INCLUDES SOME MANUAL ADJUSTMENTS TO THE INITIAL BLEND WHERE OPERATIONAL GUIDANCE DISPLAYED SUFFICIENT AGREEMENT IN PRINCIPLE. ...SENSIBLE WEATHER HIGHLIGHTS... AREAS FROM THE NRN HALF OF CA INTO THE PAC NW SHOULD SEE MULTIPLE EPISODES OF LOCALLY MDT-HVY PCPN. FOR THE 5-DAY PERIOD TELECONNECTIONS AND MOST GUIDANCE INDICATE HIGHEST TOTALS SHOULD BE FROM NRN CA INTO THE EXTREME SWRN CORNER OF OR. SOME OF THIS MSTR WILL LIKELY REACH THE NRN ROCKIES. EXPECT TEMPS OVER THE WEST TO BE ABOVE AVG DURING THE PERIOD WITH RELATIVELY HIGH SNOW LEVELS. SYSTEM TRACKING FROM THE GULF COAST NEWD OFF THE E COAST FRI-SAT MAY BRING A BRIEF PERIOD OF ENHANCED RNFL TO PARTS OF THE SOUTHEAST/E COAST. MOST SNOW FROM THE COMBINATION OF THIS SYSTEM AND INITIAL MIDWEST/GRTLKS SYSTEM SHOULD BE CONFINED TO AN AREA FROM THE UPR MS VLY/UPR GRTLKS INTO CNTRL-NRN NEW ENGLAND. BEHIND THESE SYSTEMS MOST OF THE ERN 2/3 OF THE U.S. SHOULD TREND COLDER/DRIER... WITH THE PRIMARY EXCEPTION BEING SIGNIFICANT LAKE EFFECT SNOW AT SOME LOCATIONS GIVEN COLD CYCLONIC FLOW AND MINIMAL ICE COVER THUS FAR. THERE MAY ALSO BE ONE OR MORE POCKETS OF SNOW/RAIN ASSOC WITH SHRTWVS EMBEDDED WITHIN THE MEAN FLOW ALOFT. THE MOST EXTREME ANOMALIES SHOULD BE CENTERED OVER THE NRN PLAINS-UPR MS VLY WITH HIGH TEMPS 15-25F BELOW NORMAL DURING THE WEEKEND. ALSO NOTE THAT BREEZY CONDS OVER SOME AREAS WILL PRODUCE DANGEROUSLY COLD WIND CHILL VALUES. THIS COLD SPELL FALLS NEAR THE CLIMATOLOGICALLY COLDEST TIME OF YEAR SO MOST LOCATIONS WOULD HAVE TO SEE COLDER TEMPS THAN FCST TO THREATEN ANY DAILY RECORDS. RAUSCH