EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1059 AM EST MON JAN 19 2015 VALID 12Z THU JAN 22 2015 - 12Z MON JAN 26 2015 ...OVERVIEW AND GUIDANCE PREFERENCES... LATEST GUIDANCE OFFERS GOOD CONTINUITY IN PRINCIPLE... WITH A STRONG RIDGE BUILDING TOWARD THE WEST COAST THEN WEAKENING SLIGHTLY AS IT DRIFTS INLAND BY NEXT MON... WHILE TROUGHING OVER THE ERN HALF OF THE CONUS GRADUALLY AMPLIFIES. THE MAJORITY OF FCST UNCERTAINTIES INVOLVE SHRTWVS EMBEDDED WITHIN THE MEAN TROUGH AND THE ASSOC SFC SYSTEMS. FOR THE UPDATED FCST THE BEST BALANCE OF CONTINUITY AND LATEST GUIDANCE IS REPRESENTED BY A BLEND OF THE 00Z ECMWF/UKMET AND 06Z GEFS/00Z ECMWF MEANS INTO DAY 5 SAT... FOLLOWED BY A 50/30/20 BLEND OF THE 00Z ECMWF MEAN/00Z NAEFS MEAN/06Z GEFS MEAN. EARLY IN THE PERIOD LATEST ENSEMBLE LOW PLOTS SUGGEST THE 00Z/06Z GFS RUNS MAY BE A LITTLE TOO FAR EWD WITH THE SYSTEM OFF THE NERN COAST ON THU. ALSO CONSENSUS SHOWS MINIMAL SUPPORT FOR A COUPLE 06Z GFS FEATURES IN THE NRN TIER/UPR GRTLKS... A WAVE THAT REACHES THE NRN MN BORDER BY LATE THU AND A QUESTIONABLY SRN TRACK FOR THE TRAILING STRONGER SFC LOW OVER CANADA. CONSULT THE MODEL DIAGNOSTIC DISCUSSION PMDHMD FOR UPDATED PREFS FROM NEW 12Z GUIDANCE THROUGH 00Z FRI. THE NEXT FCST PROBLEM INVOLVES ENERGY EJECTING FROM THE SWRN CONUS/SRN PLAINS AND ASSOC SFC SYSTEM LIKELY TO TRACK FROM THE GULF OF MEXICO THEN OFFSHORE THE SERN COAST AND CONTINUING NEWD OVER THE WRN ATLC. CURRENT CONFIDENCE WOULD BE CONSIDERED BELOW AVG GIVEN MODEL SPREAD SFC/ALOFT... AND TYPICAL DIFFICULTIES IN RESOLVING IMPORTANT DETAILS OF ENERGY ALOFT IN THE TYPE OF EVOLUTION INVOLVED. GIVEN CURRENT UNCERTAINTY AND WIDE ENSEMBLE SPREAD FOR THE SFC SYSTEM PREFER TO COMPROMISE BETWEEN CONTINUITY AND THE 00Z ECMWF/06Z GFS WHICH HAVE COME IN WITH A SFC TRACK CLOSER TO THE SERN COAST AS OF EARLY SAT. BY DAYS 6-7 SUN-MON UPSTREAM ENERGY FEEDING INTO THE MEAN TROUGH SHOULD SUPPORT A SFC SYSTEM TRACKING INTO THE MS VLY/ERN STATES. RECENT ECMWF MEANS HAVE BEEN MORE CONSISTENT WITH THIS SYSTEM SO THE 00Z ECMWF MEAN DESERVES GREATEST WEIGHTING AMONG THE ENSEMBLE MEANS. INCLUSION OF THE 00Z NAEFS/06Z GEFS MEANS GIVES PARTIAL ACCOUNT FOR CONTINUITY. THE 00Z ECMWF IS A SUPPRESSED EXTREME COMPARED TO MOST OTHER SOLNS. FINALLY THE 06Z GFS HAS FAVORABLY TRENDED TOWARD CONSENSUS VERSUS THE 00Z GFS THAT IS QUICKER TO BRING SHRTWV ENERGY AROUND THE WEST COAST RIDGE ALOFT ON MON. ...SENSIBLE WEATHER HIGHLIGHTS... HEAVIEST PCPN SHOULD BE CONFINED TO LOCATIONS FROM THE WRN GULF COAST TO THE EXTREME SOUTHEAST/NRN FL DURING THE FIRST HALF OF THE PERIOD IN ASSOC WITH SHRTWV ENERGY CROSSING THE SRN TIER AND SFC WAVE TRACKING NEWD FROM THE GULF. FEATURES EMBEDDED WITHIN THE MEAN TROUGH ALOFT SHOULD BRING ONE OR MORE AREAS OF LGT-MDT SNOW TO AREAS FROM THE NRN TIER INTO THE GRTLKS/INTERIOR NEW ENGLAND LATE THIS WEEK WITH THE FAVORED AXIS THEN SHIFTING SWD TO SOME DEGREE THEREAFTER. PCPN ACROSS THE NRN PAC NW/NRN ROCKIES SHOULD LIGHTER IN THE SECOND HALF OF THE PERIOD AS HGTS ALOFT RISE. THE PATTERN ALOFT WILL FAVOR ABOVE TO MUCH ABOVE NORMAL TEMPS FROM THE WEST INTO THE PLAINS... PSBLY REACHING DAILY RECORDS FOR MIN AND/OR MAX READINGS AT SOME LOCATIONS. OVER THE EAST ANOMALIES SHOULD BE FAIRLY MODEST WITH MORE OF A NRN PAC ORIGIN FOR FLOW FEEDING INTO THE ERN CONUS MEAN TROUGH. LOCALIZED MINUS 5-10F ANOMALIES ARE PSBL DEPENDING ON EXACT EVOLUTION OF INDIVIDUAL SYSTEMS. RAUSCH