EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1200 PM EDT THU MAY 12 2016 VALID 12Z SUN MAY 15 2016 - 12Z THU MAY 19 2016 ...GUIDANCE/UNCERTAINTY ASSESSMENT... THE 00 UTC GEFS/NAEFS/ECMWF ENSEMBLE MEANS SEEM REASONABLY COMPATABLE THROUGH MEDIUM RANGE TIME SCALES DESPITE A RELATIVELY COMPLEX FLOW PATTERN. IN ADDITION...THE 00 UTC GFS/ECMWF OFFER SOME SIMILAR THEMES WITH MOST INDIVIDUAL EMBEDDED SYSTEMS. THIS IS MAINLY EVIDENT IN THE 3-5 DAY TIMEFRAME VALID SUN INTO TUE. MODEST WEIGHTING OF THESE DETERMINISTIC MODELS IN A COMPOSITE BLEND ALONG WITH SMOOTHED ENSEMBLE MEANS INSERTS SOME ENHANCED SMALLER SCALE DETAIL AS CONSISTENT WITH PREDICTABILITY/WPC CONTINUITY. ...WEATHER PATTERN HIGHLIGHTS/THREATS... A COOLING/UNSETTLING AND DEEP MID-UPPER LEVEL LOW/TROUGH LIFTING OUT OF THE GREAT LAKES/NERN US INTO THE CANADIAN MARITIMES SUN/MON LAYS DOWN A WAVY TRAILING DRAPING FRONT DOWN ACROSS THE US SRN TIER THAT WILL LINGER AS A PCPN FOCUS. MEANWHILE UPSTREAM...A COOLING/UNSETTLING MID-UPPER LEVEL TROUGH PASSES OVER THE WEST SUN-TUE ALONG WITH SOME MODEST WIDESPREAD PCPN POTENTIAL. ENERGY ASSOCIATED WITH THIS FEATURE AND LESS PREDICTABLE EJECTING LEAD IMPULSES ARE EXPECTED TO ACT UPON THE MOISTURE POOLING LEAD DRAPED FRONT AND INDUCE CYCLOGENESIS AND AN INCREASINGLY FAVORABLE LEAD THETAE ADVECTION. THE DETAILS ARE OPEN FOR DISCUSSION...BUT THE NET EFFECT SEEMS TO SUPPORT AN EXPANDING S-CENTRAL TO E-CENTRAL US HEAVY PCPN EPISODE MON-NEXT THU. UPSTREAM KICKER TROUGH ENERGY THAT OFFERS ABOVE AVERAGE TRACKABILITY ACROSS THE NRN PACIFIC SUBSEQUENTLY IS THEN SLATED TO BRING ADDITIONAL PCPN INTO THE NWRN US BY TUE AND THEN WORK SEWD OVER THE WEST THROUGH MIDWEEK AND MAY REACH THE PLAINS IN ABOUT A WEEK. EXPECT A WRN US PCPN SWATH ASSOCIATED WITH THIS SYSTEM WILL BE TERRAIN ENHANCED AND INCLUDE SOME HIGH ELEVATION SNOW POTENTIAL. SCHICHTEL