EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1057 AM EST THU JAN 14 2016 VALID 12Z SUN JAN 17 2016 - 12Z THU JAN 21 2016 ...OVERVIEW... A DEEP/COLD ERN CONUS MEAN TROUGH WILL GRADUALLY RELAX WITH TIME AS SUPPORTING POSITIVE HGT ANOMALIES TO THE N/NE OF HUDSON BAY STEADILY ERODE. AS A RESULT EXPECT A GRADUAL TREND TOWARD MORE WEST TO EAST PROGRESSION OF INDIVIDUAL SHRTWV SYSTEMS THAT CONTINUE TO EJECT FROM A LONG TERM ERN PAC TROUGH AND PASS THROUGH A WRN CONUS MEAN RIDGE. LATEST MODELS/ENSEMBLES REFLECT THIS GENERAL EVOLUTION BUT DISPLAY SOME MEANINGFUL DETAIL AND TIMING/AMPLITUDE DIFFS WITH INDIVIDUAL FEATURES THROUGH THE PERIOD. ...GUIDANCE EVALUATION AND UNCERTAINTY ASSESSMENT/PREFERENCES... AMONG THE 00Z/06Z GUIDANCE THE 06Z GEFS AND 00Z ECMWF/NAEFS MEANS OFFERED THE BEST COMBINATION OF CLUSTERING AND CONTINUITY WITH MOST FEATURES AND THUS FORM THE BASIS OF THE LATEST FCST. THE ONE EXCEPTION IS THE INCLUSION OF A MODEST AMOUNT OF 06Z GFS/00Z ECMWF DATA FOR DAY 3 SUN TO ENHANCE THE SYSTEM OFF VANCOUVER ISLAND/PAC NW COAST AND IN THE CASE OF THE 06Z GFS ADD A LITTLE DEFINITION TO THE WAVE THAT MAY BE TRACKING NEWD FROM FL. REGARDING THIS WAVE ON SUN THE MOST NOTABLE TREND FROM THE PAST 12-24 HRS HAS BEEN A TRIMMING AWAY OF THE NWRN SIDE OF THE SPREAD THAT HAD BEEN OCCUPIED BY SOME GFS RUNS/GEFS MEMBERS. THERE IS STILL A BROADER THAN USUAL SPREAD FOR THE TIME FRAME INVOLVED AND THUS BELOW AVG CONFIDENCE IN ANY PARTICULAR SOLN. RECENT TRENDS SEEM TO FAVOR LEANING AT LEAST TOWARD A MODERATELY WEAK EVOLUTION AS PER THE ENSEMBLE MEANS/06Z GFS... AND OFFER POTENTIAL FOR EVEN THE WEAKER 00Z ECMWF TO BE A POSSIBILITY. CONSULT THE MODEL DIAGNOSTIC DISCUSSION PMDHMD FOR LATEST INFO REGARDING PREFS BASED ON NEW 12Z MODEL DATA THROUGH 00Z MON. UPSTREAM THE MOST PROBLEMATIC ASPECT OF THE FCST INVOLVES AMPLITUDE/PHASE DIFFS THAT ARISE AS EARLY AS DAY 4 MON WITH 00Z/06Z GFS RUNS AND SOME 00Z GEFS MEMBERS BEING MORE AMPLIFIED THAN MOST OTHER SOLNS WITH WEAK SHRTWV ENERGY CROSSING THE WEST. THIS STRONGER DEPICTION OF THE ENERGY LEADS TO DISCREPANCIES FROM CONSENSUS FOR DOWNSTREAM FLOW. THEN THERE ARE NOTABLE TIMING/AMPLITUDE DIFFS FOR STRONGER TROUGH ENERGY MOVING THROUGH THE WEST AND INTO THE PLAINS DAYS 5-7 TUE-THU. THE 06Z GFS/00Z CMC ARE FASTER THAN THE MAJORITY CLUSTER/CONTINUITY AS REPRESENTED BY THE FAVORED 06Z GEFS AND 00Z ECMWF/NAEFS MEANS. THE 00Z GFS ARRIVES INTO THE WEST A BIT ON THE SLOW SIDE BUT THEN CATCHES UP. SOME OPERATIONAL GFS/ECMWF RUNS HAVE BEEN SIGNALING POTENTIAL FOR SOME CLOSURE OF THE UPR TROUGH ENERGY BUT WOULD LIKE TO SEE BETTER STABILITY/AGREEMENT IN THE DETAILS BEFORE INCORPORATING ANY OPERATIONAL GUIDANCE WITH THE ENSEMBLE MEANS. FINALLY... UPSTREAM HGT FALLS WILL LIKELY APPROACH THE WEST COAST DAY 7 THU. ENSMEANS ARE SIMILAR AND CONSISTENT RELATIVE TO PAST RUNS WHILE THE 00Z/06Z GFS RUNS ARE FASTER THAN THE MEANS. ...SENSIBLE WEATHER HIGHLIGHTS... FAIRLY GOOD CONSENSUS STILL EXISTS FOR THE NRN HALF OR THIRD OF CALIFORNIA TO SEE THE HIGHEST PCPN TOTALS FOR THE SUN-THU PERIOD. THE PAC NW SHOULD ALSO SEE AT LEAST A COUPLE PERIODS OF ENHANCED PCPN BUT WITH SOMEWHAT LESSER AMTS. TOTALS SHOULD BE LIGHTER YET OVER THE SRN HALF OF CA. SOME OF THIS WEST COAST MSTR WILL EXTEND INTO FAVORED TERRAIN OF THE NRN-CNTRL INTERIOR WEST/ROCKIES. THE PATTERN WILL FAVOR NEAR TO ABOVE NORMAL TEMPS WITH MINS IN PARTICULAR BEING ON THE WARM SIDE WITH A DECENT AREA OF PLUS 10F OR GREATER ANOMALIES FOR MULTIPLE DAYS. ISOLD DAILY RECORDS FOR WARM MINS MAY BE PSBL. RELATIVELY HIGH SNOW LEVELS SHOULD DECLINE FOR A TIME WITH PASSAGE OF THE UPR TROUGH AROUND TUE-THU. VERY COLD TEMPS OVER THE CNTRL-ERN STATES EARLY IN THE PERIOD SHOULD MODERATE FROM WEST TO EAST. ON SUN-MON EXPECT A BROAD AREA OF TEMPS 10F OR MORE BELOW NORMAL WITH HIGHS IN THE NRN PLAINS/MIDWEST PSBLY 20-30F BELOW NORMAL AND MINS ONLY SOMEWHAT LESS EXTREME. IN SPITE OF SUCH ANOMALIES IT MAY BE DIFFICULT TO REACH DAILY RECORD VALUES SINCE THIS IS CLIMATOLOGICALLY THE COLDEST TIME OF YEAR. BREEZY CONDS OVER SOME AREAS WILL ALSO LEAD TO DANGEROUS WIND CHILL VALUES. PARTS OF FLORIDA MAY SEE A BRIEF PERIOD OF MDT-HVY RNFL ON SUN DEPENDING ON EVOLUTION OF SUPPORTING SFC WAVE. LOCALLY ENHANCED LAKE EFFECT SNOW SHOULD GRADUALLY TAPER OFF TOWARD MIDWEEK. ONE OR MORE SMALL POCKETS OF RAIN/SNOW MAY ACCOMPANY ONE OR MORE SHRTWVS CROSSING THE CNTRL-ERN STATES BUT A MORE ORGANIZED AREA OF PCPN WILL LIKELY DEVELOP OVER THE PLAINS/MS VLY TOWARD WED-THU AS THE UPR TROUGH CROSSING THE WEST APPROACHES THE PLAINS. THE FULL RANGE OF PRECIP TYPES SHOULD BE REPRESENTED WITH MEANINGFUL ENHANCEMENT AT SOME LOCATIONS DEPENDING ON EXACT EVOLUTION OF THE SYSTEM SFC/ALOFT. RAUSCH