EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 300 AM EDT SUN APR 08 2018 VALID 12Z WED APR 11 2018 - 12Z SUN APR 15 2018 ...WRN U.S. ACTIVE/WET FLOW LEADS TO A MAJOR NRN ROCKIES TO N-CENTRAL US SNOWSTORM THREAT... AMPLE ERN PACIFIC TROUGH ENERGY/HEIGHT FALLS IS SLATED TO BREACH THE WEST COAST TO SUPPORT ANOTHER ROUND OF WIDESPREAD AND TERRAIN ENHANCED PRECIPITATION FROM THE NORTHWEST AND N-CENTRAL CA INLAND TO THE N-CENTRAL GREAT BASIN/ROCKIES WED-THU IN A PATTERN WITH COOLING TEMPERATURES. MODELS AND ENSEMBLES CONTINUE TO SHOW A STRONG SIGNAL AND GOOD CLUSTERING IN THE DEVELOPMENT OF A SIGNIFICANT SPRING SNOWSTORM FROM THE NRN ROCKIES/PLAINS TO THE UPPER MIDWEST/GREAT LAKES AS DEEP CYCLOGENESIS OCCURS TO THE LEE OF THE ROCKIES WITH ADVENT OF EJECTING WRN US TROUGH ENERGY/HEIGHT FALLS. DEEPENING MOISTURE RETURN FROM THE GULF OF MEXICO WILL INCREASING LIFT INLAND AND WRAP INTO THE SYSTEM TO ENHANCE COMMAHEAD AND LEAD WARM AIR ADVECTION SNOWS OVER COOLED AIR. AS THE AMPLIFIED AND COOLING MID-UPPER LEVEL TROUGH AND ASSOCIATED SURFACE SYSTEMS PROGRESS FROM THE WRN TO CENTRAL US...THE LEAD FLOW PATTERN WILL SPREAD ANOMALOUSLY WARM TEMPS FROM THE S-CENTRAL INTERMOUNTAIN WEST/ROCKIES/PLAINS WED-THU TO THE E-CENTRAL/ERN U.S. FRI INTO THE WEEKEND. THIS WILL ALSO SET THE STAGE FOR A PATTERN FAVORABLE FOR CONVECTIVE RAINFALL DEVELOPMENT OVER THE EAST-CENTRAL US INCLUDING SOME SEVERE THREAT BEING FOLLOWED BY SPC. THIS ALL OCCURS SOUTH OF A NRN STREAM FRONTAL DRAPE DRIVEN SOUTHEASTWARD BY A LEADING LOW TRACK TRACK ALONG THE U.S. CANADIAN BORDER WED-FRI. A MODERATE SWATH OF PRECIPITATION WILL ACCOMPANY THE LOW INCLUDING SNOW INTO THE NRN U.S. TIER. THE STRENGTH OF THE POST-FRONTAL CANADIAN HIGH IN MOST GUIDANCE SUGGESTS FRONTAL DAMMING MAY LINGER INTO SATURDAY ACROSS THE MID-ATLANTIC...AS CUSTOMARY WHEN A MAJOR SPRING LOW LIFTS FROM THE PLAINS INTO THE UPPER MIDWEST. THE MODELS DO NOT SEEM TO HAVE A CONSISTENT HANDLE OF THIS POTENTIAL AS DEPICTED ON WPC PROGS. SCHICHTEL