EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 200 AM EST WED JAN 31 2018 VALID 12Z SAT FEB 03 2018 - 12Z WED FEB 07 2018 ...SUPERBOWL SUNDAY TO MONDAY COASTAL LOW THREAT FOR THE SRN/SERN U.S. AND ERN SEABOARD... ...OVERVIEW AND GUIDANCE PREFERENCES... MEDIUM RANGE FLOW ALOFT CONTINUES TO FEATURE RIDGING OFF THE WEST COAST AND BROAD CYCLONIC FLOW/TROUGHING DOWNSTREAM OVER MUCH OF THE REST OF THE LOWER 48. MODELS AND ENSEMBLES OFFER SIMILAR LARGER SCALE FLOW PATTERNS AND HAVE BECOME A BIT BETTER CLUSTERED WITH LESS PREDICTABLE SMALLER SCALE EMBEDDED FEATURES. THERE REMAINS VARIANCE WITH BOTH THE SPECIFICS OF COLD HIGH PRESSURE DIGGING INTO THE LOWER 48 AND THE DEVELOPMENT AND PCPN/WINTER THREAT OF FRONTAL WAVES ON THE LEADING EDGE OF THE COLD DOME. THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM THE 12 UTC GFS/ECMWF...THE 18 UTC GEFS MEAN AND THE 12 UTC ECMWF ENSEMBLE MEAN WHOSE COMPOSITE BLEND MAINTAINS MAX WPC CONTINUITY. HOWEVER...LEANED MORE WEIGHT ON THE COLDER SOLUTIONS OF THE NATIONAL BLEND OF MODELS...THE GFS/GEFS AND MOS IN AREAS DEEP IN THE INFLUENCE OF ARCTIC AIR VERSUS THE WARMER LOW LEVEL TEMPERATURES OF THE ECMWF/ECMWF ENSEMBLE MEAN. TEMPS FOR THE POTENTIAL WINTERY THREAT OVER THE SRN/SERN AND ERN US WOULD BE MORE DEPENDENT ON ANY ULTIMATE COASTL LOW TRACK AND THE 00 UTC GFS/ECMWF HAVE TRENDED SLIGHTLY INLAND OF PREVIOUS RUNS. ...WEATHER HIGHLIGHTS/THREATS... OVER THE NWRN US...IT REMAINS THE CASE THAT A SERIES OF PROGRESSIVE IMPULSES RUNNING OVER THE EAST PACIFIC/WEST COAST RIDGE WILL SUPPORT ADDITIONAL PERIODS OF MODEST PRECIPITATION. HOWEVER...EXPECT LOCALLY HEAVIER TERRAIN ENHANCED SNOWS ACROSS THE NWRN US AND ESPECIALLY THE NRN ROCKIES WITH ADDED NRN STREAM IMPULSES OF LESS CERTAIN TIMINGS. EXPECT ADDITIONAL POST-FRONTAL UPSLOPE SNOWS UP TO THE DIVIDE. UPSTREAM...THERE REMAINS A DECENT MODEL SIGNAL TO BRING ADDITIONAL MODEST ERN PACIFIC SYSTEM ENERGY/PCPN TO THE PACIFIC NW EARLY NEXT WEEK. A WEEKEND CLIPPER SYSTEM WILL SPREAD SNOWS ACROSS THE N-CENTRAL US...GREAT LAKES...THEN NORTHEAST. UNDERNEATH...RAINS WILL MEANWHILE INCREASE OVER THE GULF COAST BY SUNDAY WITH RETURN FLOW TO INCLUDE SOME LOCAL HEAVIER DOWNPOURS. WIDESPREAD MODERATE PCPN SHOULD EXPAND NEWD INTO EARLY NEXT WEEK INTO THE MID-SOUTH AND ACROSS THE ERN US. THIS WOULD OFFER AN INTERIOR WINTER WEATHER THREAT. A COLD HIGH SURGE IN THE WAKE OF THE CLIPPER HAS SOME TIMING/STRENGTH VARIANCE IN GUIDANCE BUT BEST CLUSTERING SUGGESTS A PATH FROM W-CENTRAL CANADA INTO THE N-CENTRAL US SATURDAY TO THEN SPREAD OVER THE REST OF THE CENTRAL AND ERN US SUNDAY INTO MONDAY. SCHICHTEL