EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 122 AM EST SUN JAN 29 2017 VALID 12Z WED FEB 01 2017 - 12Z SUN FEB 05 2017 ...OVERVIEW AND GUIDANCE EVALUATION... MULTI-DAY MEANS CONTINUE TO SHOW A TENDENCY TOWARD ERN NOAM MEAN TROUGHING WHILE A MODEST MEAN RIDGE PRESIDES NEAR THE WEST COAST. INCREASING PROGRESSION OF UPSTREAM PACIFIC FLOW WILL ACCELERATE AN INITIALLY SLOW MOVING ERN PAC TROUGH/EMBEDDED UPR LOW THROUGH THE LONG-TERM WRN RIDGE AROUND FRI-SAT AND ONWARD ACROSS THE LOWER 48 THEREAFTER. TELECONNECTIONS RELATIVE TO THE VERY STRONG RIDGE/UPR HIGH OVER ALASKA/ERN SIBERIA AND NERN ATLC TROUGHING GENERALLY SUPPORT THE FCST ERN NOAM TROUGH AND OFFER A FAINT HINT OF A MEAN RIDGE ALONG THE WEST COAST. HOWEVER THEY ARE IN CONFLICT OVER THE NERN PAC/WRN CANADA AND EVOLUTION TO THE S/E OF CLOSED HIGHS TENDS TO HAVE BELOW AVG PREDICTABILITY SO THIS AREA BEARS CLOSE WATCHING AS A POTENTIAL SOURCE OF FCST UNCERTAINTY. DURING DAYS 3-5 WED-FRI UPDATING THE BLEND WITH 18Z GFS/12Z ECMWF RUNS AND TO A LESSER EXTENT 12Z CMC/UKMET MAINTAINED A GOOD REPRESENTATION OF CONSENSUS OR AN INTERMEDIATE SOLN WHERE SPREAD HAS PERSISTED. OF PARTICULAR NOTE THE FCST FOR SHRTWV ENERGY OVER SWRN CANADA/EXTREME NWRN U.S. HAS BEEN PROBLEMATIC FOR DAYS WITH GUIDANCE THROUGH THE 12Z/18Z CYCLES STILL NOT AS AGREEABLE AS DESIRED. MULTI-DAY TRENDS/CONTINUITY SEEM TO BE POINTING TOWARD A MIDDLE GROUND FOR THIS ENERGY. THE FCST DID NOT INCLUDE THE 12Z GFS WHICH BROUGHT THIS ENERGY FARTHER SWD THAN MOST OTHER SOLNS AND WAS ALSO ON THE SRN SIDE WITH THE SYSTEM NEARING THE WEST COAST. MEANWHILE SPREAD DEVELOPS WITH THE SWD EXTENT OF THE SFC FRONT THAT SETTLES OVER THE SRN TIER OF STATES E OF THE ROCKIES... WITH SOME INFLUENCE FROM EVOLUTION NEAR THE WRN CANADIAN BORDER. DAYS 6-7 SAT-SUN STARTED WITH A BLEND AMONG THE 18Z GFS/12Z ECMWF AND THEIR ENSEMBLE MEANS ALONG WITH A LITTLE 12Z CMC INPUT. SPREAD WITH THE SRN TIER FRONT CONTINUES INTO THIS TIME FRAME WHILE COMBINED UNCERTAINTIES OF TIMING/EVOLUTION OF THE EJECTING ERN PAC/WRN TROUGH PLUS SPECIFICS OF NRN STREAM FLOW AND PSBL INTERACTION WITH THE TROUGH PROVIDE ADDED COMPLEXITY TO THE FCST. THE MOST DISCERNIBLE TREND BY THIS TIME FRAME IS IN THE ECMWF MEAN WITH THE PAST 1-2 DAYS BECOMING FASTER AS THE ERN PAC TROUGH CROSSES THE LOWER 48. THE 12Z ECMWF WAS MORE DIFFUSE WITH THE TROUGH THAN IN PRIOR RUNS. ALSO TO SOME DEGREE... AVERAGING OUT RUN TO RUN VARIABILITY OVER RECENT DAYS THERE HAS BEEN A GENERAL TREND IN THE GUIDANCE TOWARD A MORE SUPPRESSED SFC PATTERN OVER THE ERN HALF OF THE COUNTRY. THUS IT SEEMED REASONABLE TO START WITH A SOLN PARTWAY BTWN THE 18Z GFS/GEFS MEAN AND MORE SUPPRESSED 12Z ECMWF/ECMWF MEAN/CMC. ALONG THE WEST COAST THE ONLY FEATURE OF NOTE IS A WEAK SHRTWV THAT MOST GUIDANCE SHOWS APPROACHING THE PAC NW DAY 7 SUN. ...WEATHER HIGHLIGHTS/THREATS... ACROSS THE WEST THE GUIDANCE CONTINUES TO SHOW THE BEST SIGNAL FOR A PERIOD OF HVY RAIN/HIGHER ELEV SNOW OVER NRN CA/SIERRA NEVADA RANGE DURING THE LATTER HALF OF THE WEEK AS THE SLOW MOVING ERN PAC SYSTEM APPROACHES. CONTINUED UNCERTAINTY WITH SPECIFICS OF FLOW ALOFT CLOSER TO THE CANADIAN BORDER TEMPERS CONFIDENCE IN DETERMINING HOW MUCH MSTR REACHES THE PAC NW. ISSUES ALOFT ALSO AFFECT SPECIFICS OF THE PCPN FCST OVER THE NRN ROCKIES ALONG/N OF A STNRY FRONT. EXPECT SNOW LEVELS TO BE FAIRLY LOW FROM THE CASCADES EWD. AS THE ERN PAC SYSTEM WEAKENS/MOVES INLAND THERE WILL BE A DRYING TREND DURING THE WEEKEND. TEMPS OVER THE WEST SHOULD BE WITHIN 10F OF NORMAL MOST DAYS... AVERAGING BELOW NORMAL NORTH AND NEAR TO MODESTLY ABOVE NORMAL CENTRAL/SOUTH. LOCALIZED AREAS WITH HIGHS A LITTLE MORE THAN 10F BELOW NORMAL ARE PSBL NRN AREAS WED-THU. LAKE EFFECT SNOW WILL LIKELY PERSIST THROUGH MUCH OF THE PERIOD BUT SHOULD GRADUALLY DECREASE IN COVERAGE/INTENSITY WITH TIME. FROM MIDWEEK ONWARD ONE MORE MORE AREAS OF MOSTLY LGT PCPN ARE PSBL BTWN THE PLAINS AND E COAST IN ASSOC WITH IMPULSES ALOFT. THE CNTRL PLAINS TO CNTRL MID ATLC STILL APPEARS TO BE THE MOST LIKELY TRANSITION BTWN RAIN AND SNOW WHERE ANY PCPN OCCURS. DURING THE WEEKEND PCPN SHOULD EXPAND OVER THE ERN HALF OF THE COUNTRY AS ERN PAC/WRN ENERGY APPROACHES. GUIDANCE HAS NOT YET LOCKED ONTO SYSTEM DETAILS SO CONFIDENCE IS FAIRLY LOW IN COVERAGE/INTENSITY/PCPN TYPE AT THIS TIME. TEMPS SHOULD BE BELOW NORMAL ACROSS THE NRN TIER AND ABOVE NORMAL ACROSS THE SOUTH. IN BOTH CASES ANOMALIES MAY EXCEED 10F AT SOME LOCATIONS. RAUSCH