EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 144 AM EST FRI JAN 29 2016 VALID 12Z MON FEB 01 2016 - 12Z FRI FEB 05 2016 ...OVERVIEW... WITHIN A DEVELOPING WEST COAST RIDGE/DOWNSTREAM TROUGH MEAN PATTERN... A STRONG STORM SYSTEM EXPECTED TO TRACK FROM THE FOUR CORNERS REGION THROUGH THE PLAINS AND GREAT LAKES INTO ERN CANADA WILL BE THE DOMINANT FOCUS FOR NEXT WEEK'S FCST. THIS SYSTEM WILL LIKELY GENERATE A FULL ARRAY OF SIGNIFICANT WEATHER FROM SNOW IN THE COLD SECTOR TO LOCALLY HVY RNFL AND STRONG CONVECTION IN THE WARM SECTOR WITH SOME STRONG WINDS IN BOTH CASES. AREAL COVERAGE OF PCPN OVER THE LOWER 48 SHOULD DECREASE LATER IN THE WEEK WITH THE PASSAGE OF THE SFC LOW AND WAVY COLD FRONT. ...GUIDANCE EVALUATION/PREFERENCES... BASED ON GUIDANCE AVBL THROUGH THE 12Z/18Z CYCLE... OVERALL PREFERRED AN AVG OF LATEST OPERATIONAL SOLNS /INCLUDING VARIOUS WEIGHTS OF THE ECMWF..GFS..UKMET..CMC RUNS/ TO START THE DAYS 3-5 MON-WED PART OF THE FCST. FOR THE FOUR CORNERS TO GRTLKS SYSTEM IN PARTICULAR THE OPERATIONAL RUNS ARE FAIRLY AGREEABLE IN DEPICTING STRONGER DEVELOPMENT THAN SEEN IN THE ENSEMBLE MEANS. ALSO THE RELATIVELY FASTER/WEAKER 12Z ECMWF MEAN APPEARED TO BE ONE OF THE LESS LIKELY OPTIONS GIVEN THE STRONG SUPPORTING DYNAMICS ALOFT. EVEN MINUS THE ECMWF MEAN THERE REMAIN SOME TIMING DIFFS WITH GFS RUNS A LITTLE ON THE SLOW SIDE AS EARLY AS LATE IN THE SHORT RANGE PERIOD. COMPARING ENSEMBLE LOW SPREAD OVER THE PAST COUPLE DAYS THERE HAS BEEN A TREND TO TRIM AWAY THE SLOWER SIDE OF THE SPREAD BUT THE FASTER SIDE OF THE SPREAD IS HOLDING FAIRLY STEADY. THE FAVORED BLEND YIELDS RELATIVELY MODEST ADJUSTMENTS FROM CONTINUITY. MEANWHILE THIS BLEND PROVIDES A GOOD INTERMEDIATE SOLN BTWN THE STRONG GFS/WEAK 12Z ECMWF FOR THE SYSTEM REACHING ERN CANADA AS OF EARLY MON. FOR BOTH SYSTEMS CONSULT THE MODEL DIAGNOSTIC DISCUSSION PMDHMD FOR COMPARISONS/PREFS WITH RESPECT TO THE NEW 00Z MODEL RUNS THROUGH 12Z MON. DAYS 6-7 THU-FRI FCST RAPIDLY INCREASES ENSEMBLE MEAN WEIGHTING RELATIVE TO OPERATIONAL SOLNS WITH DAY 7 USING THE MEANS EXCLUSIVELY. AS OF THE END OF DAY 5 MODELS/ENSEMBLES STILL CLUSTER WELL WITH A WEST COAST RIDGE AND CNTRL/E-CNTRL CONUS TROUGH. THEN SOLNS DIVERGE IN WHAT HAPPENS TO ERN PAC ENERGY HEADING INTO THE MEAN RIDGE WITH THESE DIFFS THEN BEGINNING TO IMPACT TIMING/AMPLITUDE OF DOWNSTREAM FLOW. IT SEEMS THAT IN MORE CASES THAN NOT THIS SEASON WRN RIDGES HAVE TENDED TO ALLOW SOME DEGREE OF ENERGY TO PASS THROUGH RATHER THAN DEFLECTING IT AS TYPICAL BIASES MIGHT SUGGEST. THUS THE BLEND LEANS MORE TO THE ECMWF MEAN THAT HAS CONSISTENTLY BEEN ALLOWING A SHRTWV TO ENTER THE WEST ALBEIT WITH SOME TIMING/DEPTH DIFFS... IN CONTRAST TO THE MINIMAL REFLECTION IN 12Z/18Z GEFS MEAN RUNS. ...SENSIBLE WEATHER HIGHLIGHTS... TRACK/IMPACTS OF THE PRIMARY STORM OF INTEREST MAY BE CONSIDERED MORE TYPICAL OF A SPRING OR LATE FALL SYSTEM. HIGHEST PROBABILITY FOR SIGNIFICANT WINTER WEATHER WILL EXTEND FROM PORTIONS OF THE FOUR CORNERS STATES NEWD THROUGH THE CNTRL PLAINS AND INTO THE UPR GRTLKS. SOME SNOW MAY BE MDT-HVY WITH WINDS STRONG ENOUGH TO PRODUCE BLOWING/DRIFTING OF SNOW ALONG WITH LOW WIND CHILL VALUES. UPSLOPE FLOW ON THE ERN SLOPES OF THE ROCKIES AND LAKE ENHANCEMENT OVER THE WRN-NRN GRTLKS MAY PROVIDE LOCALLY HIGHER SNOW TOTALS AT SOME LOCATIONS IN THOSE AREAS. ALSO EXPECT A PERIOD OF SOME LAKE EFFECT SNOW IN THE COLD CYCLONIC FLOW BEHIND THE SYSTEM. IN THE WARM SECTOR ONE OR MORE BANDS OF MDT-HVY RNFL ARE PSBL AND RECENT SPC OUTLOOKS INDICATE SOME SEVERE POTENTIAL FROM THE LWR MS VLY EWD-NEWD TO JUST W OF THE SRN HALF OF THE APLCHNS. ONCE THE ABOVE SYSTEM DEPARTS FROM THE WEST... EXPECT PRIMARY EMPHASIS FOR PCPN OVER THE WRN STATES TO BE ALONG THE CNTRL-NRN WEST COAST INTO THE NRN ROCKIES. ONE OR MORE PERIODS OF ENHANCED PCPN ARE PSBL. HOWEVER SPREAD IN SHRTWV DETAILS DURING THE LATTER HALF OF THE WEEK LEADS TO DIFFICULTY IN PINPOINTING TIMING/LOCATION OF MAX AMTS. THE AMPLIFIED PATTERN WILL SUPPORT ANOMALOUS TEMPS AT MANY LOCATIONS. A SIZABLE AREA OF HIGHS 10-20F BELOW NORMAL SHOULD EXTEND FROM THE WRN STATES INTO CNTRL HIGH PLAINS DURING THE FIRST HALF OF THE WEEK WITH SOMEWHAT LESS EXTREME ANOMALIES EXTENDING EWD/NEWD. IN THE WARM SECTOR TO THE E THERE SHOULD BE ONE OR MORE DAYS WITH MIN TEMPS AS WARM AS 20-30F ABOVE NORMAL AND A SMALLER AREA OF PLUS 20F OR GREATER ANOMALIES FOR HIGHS. READINGS AT SOME LOCATIONS MAY APPROACH/REACH DAILY RECORD VALUES... MORE LIKELY FOR MIN TEMPS. RAUSCH