EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1256 AM EST WED JAN 28 2015 VALID 12Z SAT JAN 31 2015 - 12Z WED FEB 04 2015 ...GUIDANCE/UNCERTAINTY EVALUATION AND PATTERN OVERVIEW... THE WPC MEDIUM-RANGE PRODUCT SUITE IS PRIMARILY DERIVED FROM A BLEND OF THE 12 UTC GFS/ECMWF AND GFS/ECMWF/NAEFS ENSEMBLE MEANS ALONG WITH CONTINUITY. THESE GUIDANCE CHOICES OVERALL OFFER FAVORABLE SOLUTION CLUSTERING...BUT FORECAST SPREAD AND RUN TO RUN GUIDANCE VARIANCE SUGGEST ONLY AVERAGE TO BELOW NORMAL PREDICTABILITY. THE FAVORED WPC GUIDANCE COMPOSITE SHOWS THAT LARGE SCALE FLOW WILL EVOLVE TOWARD A BROAD CONUS MEAN TROUGH DOWNSTREAM FROM A RIDGE NEAR/JUST OFFSHORE THE WEST COAST. WITHIN THIS DEVELOPING MEAN PATTERN THE MOST SIGNIFICANT FCST PROBLEM THIS PERIOD APPEARS TO BE THE TIMING/DEPTH OF AMPLIFYING WRN CANADA FLOW AND DEGREE OF INTERACTION WITH SRN STREAM FLOW INITIALLY CONTAINING AN UPPER LOW OVER THE EXTREME SOUTHWEST. DETAILS OF THESE FEATURES AND INTERACTIONS WILL AFFECT THE SFC EVOLUTION AND PCPN TYPE/INTENSITY/COVERAGE FROM THE SWRN STATES THROUGH MUCH OF THE CNTRL-ERN U.S. FROM LATE THIS WEEK INTO THE START OF NEXT WEEK. MEANWHILE SOME ERN PAC ENERGY PUSHING THROUGH THE WEST COAST MEAN RIDGE WILL SPREAD SOME MOISTURE/PCPN SEWD OVER THE NW QUARTER OF THE NATION SUN-NEXT WED. ...SENSIBLE WEATHER HIGHLIGHTS... THE EXIT OF A VIGOROUS SYSTEM OFF THE NORTHEAST SATURDAY WILL BRING AN END TO A PERIOD OF WINTRY WEATHER AND STRONG WINDS. AN UPPER LOW BY THIS WEEKEND OVER THE SWR US/MEXICO WILL SUPPORT VARIOUS PCPN TYPES FROM THE FOUR CORNERS REGION INTO THE HIGH PLAINS. THE PCPN SHIELD WILL CONTINUE ACROSS THE PLAINS THEN NEWD TO THE ERN US AS NRN STREAM ENERGY GAINS INFLUENCE. GUIDANCE HAS STILL NOT YET STABILIZED ON A PARTICULAR SOLUTION SO CONFIDENCE REMAINS LOWER THAN DESIRED WITH EXACT PLACEMENT OF PCPN TYPES FOR THIS SYSTEM...BUT FULLY EXPECT A SWATH OF ORGANIZED SNOWS ON THE NRN PERIPHERY OF THE EXPANDING PCPN SHIELD WITH A MIX OF PCPN TYPES OR CHANGEOVER ZONE JUST S. WPC WEATHER/PRECIPIATION TYPE GRIDS/GRAPHICS OFFER OUR BEST ESTIMATE AT THIS TIME BASED FROM LATEST GUIDANCE PREFERENCES. LOCATIONS WITHIN THE BROAD PCPN AREA MAY SEE LOCALLY HEAVY AMOUNTS. PASSAGE OF THIS SYSTEM SHOULD SUPPORT A PERIOD OF LAKE EFFECT SNOW. DRY CONDS ACROSS THE NW QUARTER OF THE COUNTRY WILL TREND WETTER SUN-WED AS ERN PAC ENERGY SLIPS THROUGH THE LONGER TERM MEAN RIDGE ALOFT...ESPECIALLY OVER FAVORED TERRAIN...BUT AT LEAST THE LATEST SLEW OF MODELS HAVE TRENDED BACK TOWARD A MUCH LESS DIGGY LOOK. SCHICHTEL