EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 241 AM EDT SUN APR 10 2016 VALID 12Z WED APR 13 2016 - 12Z SUN APR 17 2016 ...OVERVIEW AND GUIDANCE/UNCERTAINTY ASSESSMENT... THE PATTERN ACROSS THE LOWER 48 WILL LIKELY TAKE ON AN INCREASINGLY BLOCKY APPEARANCE WITH TIME. WHILE THERE ARE SOME ONGOING ADJUSTMENTS ON SPECIFICS THERE IS HIGH CONFIDENCE IN A DEEP TROUGH/PSBL EMBEDDED CLOSED LOW SETTLING INTO THE WEST/ROCKIES WHILE RIDGING AMPLIFIES OVER THE E-CNTRL STATES. THE FCST IMMEDIATELY DOWNSTREAM FROM AND TO THE S OF THIS RIDGE IS MORE OF A QUESTION MARK WITH VARIOUS POSSIBILITIES FOR NRN STREAM ENERGY THAT MAY DROP DOWN ALONG THE EAST COAST AND MEANINGFUL DIFFS WITH A MID LVL SYSTEM DRIFTING AWAY FROM THE SRN PLAINS. FOR ABOUT THE FIRST HALF OF THE PERIOD A BLEND INCORPORATING THE 18Z GFS/GEFS MEAN AND 12Z ECMWF/ECMWF MEAN... GRADUALLY DECREASING OPERATIONAL MODEL WEIGHTING WITH TIME... PROVIDES A REASONABLE STARTING POINT. SOME ERN PAC/WRN CONUS DETAILS HAVE CHANGED A BIT FROM PAST RUNS BUT THERE IS BETTER OVERALL AGREEMENT THAN SEEN PREVIOUSLY. GFS/ECMWF/CMC RUNS SEEM TO BE STRENGTHENING THE SIGNAL FOR UPR LOW FORMATION OVER OR JUST OFFSHORE THE EAST COAST BY LATE THU-FRI. THE FAVORED BLEND BEGINS HEDGING TOWARD THIS SCENARIO BY PULLING BACK THE UPR TROUGH/OFFSHORE WAVY SFC FRONT SOMEWHAT. AMONG NEW 00Z GUIDANCE THUS FAR THE GFS/GEFS MEAN ARE NOW ON THE WRN SIDE OF THE ENVELOPE. IT MAY TAKE SOME TIME FOR THIS PART OF THE FCST TO GET RESOLVED GIVEN SENSITIVITY TO SMALLER SCALE ASPECTS OF UPSTREAM SRN CANADA FLOW. FINALLY THE 00Z GFS STRAYS TO THE WEAK/PROGRESSIVE SIDE OF THE SPREAD WITH THE SRN TIER FEATURE. BY DAYS 6-7 SAT-SUN THE FCST STARTS WITH A COMPROMISE AMONG THE 18Z GEFS/12Z NAEFS/12Z ECMWF MEANS. BY LATE IN THE PERIOD INDIVIDUAL SOLNS BECOME INCREASINGLY DIVERSE WITH THE POSN OF AN EMBEDDED UPR LOW... RANGING FROM NM IN THE 12Z ECMWF TO THE NRN HIGH PLAINS IN THE 12Z GFS. THERE ARE ALSO SOME TIMING DIFFS WITH THE ECMWF MEAN RUNNING A LITTLE AHEAD OF THE OTHER MEANS AT LEAST WITH THE LEADING HGT FALLS. ECMWF-BASED GUIDANCE AS A WHOLE HAS ADJUSTED SLOWER VS PRIOR COUPLE OF RUNS AND A COMPROMISE WITH THE SLOWER GEFS/NAEFS MEANS SEEMS REASONABLE IN LIGHT OF INCREASING BLOCKINESS OF THE OVERALL PATTERN. THE RESULTING EAST COAST/WRN ATLC UPR TROUGH MAY ULTIMATELY BE SLOWER/MORE SEPARATED THAN WHAT THE MEANS SHOW BASED ON 00Z RUNS HOLDING ONTO THE IDEA OF A CLOSED LOW. ...SENSIBLE WEATHER HIGHLIGHTS/THREATS... THE VIGOROUS UPR TROUGH-EMBEDDED CLOSED LOW HEADING INTO/THROUGH THE WEST WILL BRING AREAS OF ENHANCED RAIN AND HIGH ELEV SNOW TO APPROX THE NRN 2/3 OF THE WEST AND THEN BY NEXT WEEKEND INCREASE COVERAGE/INTENSITY OF RNFL OVER THE PLAINS. INPUT OF GULF MSTR AND GRADUAL SLOWING TREND OF THE OVERALL PATTERN MAY LEAD TO SOME TRAINING OF HVY RNFL OVER PORTIONS OF THE PLAINS LOCATIONS SAT-SUN. STRONG CONVECTION MAY ALSO BE PSBL. CONSULT SPC OUTLOOKS FOR LATEST INFO REGARDING SEVERE THREATS. TO THE N OF A WAVY FRONT SINKING INTO THE GULF... MID LVL ENERGY DRIFTING OUT OF THE SRN PLAINS MAY SUPPORT AN AREA OF LOCALLY HVY RNFL FROM SRN TX EWD ALONG THE GULF COAST. LESSER AMTS OF MSTR MAY ALSO EXTEND FARTHER NWD TO SOME DEGREE. SPECIFICS OF THE PCPN FCST ALONG THE EAST COAST WILL DEPEND ON EXACT EVOLUTION OF UPR TROUGH/CLOSED LOW ENERGY. CURRENT ARRAY OF GUIDANCE RANGES FROM A MOSTLY DRY SCENARIO TO SOME LOCATIONS SEEING MULTIPLE DAYS OF UNSETTLED WEATHER. SYSTEM MOVING ACROSS THE WEST WILL BRING A PERIOD OF BELOW NORMAL TEMPS TO THAT REGION. RISING HGTS IN ITS WAKE WILL LEAD TO A WARMING TREND FROM THE WEST COAST INTO INTERMTN WEST NEXT WEEKEND. AT THE SAME TIME WARMTH WILL SPREAD EWD FROM THE PLAINS WITH GREATEST ANOMALIES OF PLUS 10-25F ACROSS THE NRN TIER. EXPECT GREATEST ANOMALIES FOR MAX TEMPS AROUND WED-THU WHILE SUCH ANOMALIES FOR MIN TEMPS MAY EXTEND INTO THE WEEKEND. RAUSCH