EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 300 AM EDT SAT APR 07 2018 VALID 12Z TUE APR 10 2018 - 12Z SAT APR 14 2018 ...WINTER WEATHER THREATS FROM THE MOUNTAIN WEST TO THE N-CENTRAL US AND FOR THE NORTHEAST... ...PATTERN HIGHLIGHTS/THREATS AND GUIDANCE EVALUATION/UNCERTAINTY ASSESSMENT... GUIDANCE OVER THE PAST FEW DAYS HAS TRENDED TOWARD THE SEEMINGLY REASONABLE IDEA THAT A SERIES OF LOW PRESSURE SYSTEMS WORKING TO THE ERN PACIFIC WILL LEAD TO MID-UPPER LEVEL FLOW AMPLIFICATION DOWNSTREAM OVER THE CONUS BY EARLY NEXT WEEK. THIS PATTERN WILL BE HIGHLIGHTED THEN BY A WARMING RIDGE OVER THE WRN US AND A COOLING TROUGH OVER THE E-CENTRAL US. SOME RECORD HIGH TEMPS ARE POSSIBLE OVER THE SOUTHWEST TUESDAY TO THURSDAY WITH STEADY SYSTEM PROGRESSION. IN THIS PATTERN...NRN STREAM FLOW DIGS SOUTHEASTWARD FROM CANADA TO COOL THE N-CENTRAL TO NERN US TIER. A WAVY FRONTAL DRAPE/CLIPPER LOW MAY SPREAD MODEST PCPN FROM THE N-CENTRAL US TO THE EAST COAST/NORTHEAST EARLY NEXT WEEK. UNDERNEATH...A WAVY SRN STREAM SYSTEM WILL SPREAD RAIN/CONVECTION ACROSS THE SRN/SERN US AND A MODERATE MID-ATLANTIC COASTAL LOW MAY DEVELOPMENT TUE WITH OFFSHORE TRACK AND DEEPENING TO THREATEN THE COOLED NORTHEAST WITH SPRING SNOWS BY MIDWEEK. MID-LATER NEXT WEEK...ERN PACIFIC SYSTEM ENERGY ORGANIZES AND A DYNAMIC/AMPLIFIED MID-UPPER LEVEL TROUGH IS EXPECTED TO BREACH THE WEST COAST AND SPREAD PCPN INLAND ACROSS THE NWRN US AND ESPECIALLY WITH HEIGHT FALLS FARTHER SOUTH INTO CA AND THE INTERMOUNTAIN WEST AS ENHANCED INTO THE COASTAL RANGES AND SIERRA AND INLAND RANGES TO THE ROCKIES. ENERGY/HEIGHT FALLS REACH THE PLAINS BY FRI AND THERE REMAINS A GOOD MODEL AND ENSEMBLE SIGNAL FOR STRONG N-CENTRAL US CYCLOGENESIS/FRONTOGENESIS. THIS SETS THE STAGE FOR ORGANIZED WRAP-AROUND PCPN AROUND THE DEVELOPING LOW INCLUDING THE THREAT FOR SOME HEAVIER SPRING SNOWS FROM THE COOLED N-CENTRAL ROCKIES/PLAINS NORTHEASTWARD ACROSS THE NRN PLAINS/UPPER MIDWEST. MEANWHILE...INCREASING RETURN MOISTURE FLOW WOULD ALSO SUPPORT AN INCREASINGLY CONVECTIVE LEAD COMPONENT ACROSS THE E-CENTRAL US IN THE WARM SECTOR AND INTO A LEAD FRONTAL BOUNDARY TO THE EAST OF THE LOW. THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A COMPOSITE BLEND OF THE GFS/ECMWF AND GEFS/ECMWF ENSEMBLE MEANS THAT ARE REASONABLY WELL CLUSTERED. SCHICHTEL