EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 241 AM EDT SAT MAR 25 2017 VALID 12Z TUE MAR 28 2017 - 12Z SAT APR 01 2017 ...OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES... THE PRIMARY FOCUS OF THE FCST CONTINUES TO BE ON THE SERIES OF FAIRLY VIGOROUS SYSTEMS AMPLIFYING INTO AND EJECTING FROM A W-CNTRL U.S. MEAN TROUGH, WHILE DETAILS OF NRN STREAM FLOW ACROSS THE NRN TIER STATES/SRN CANADA WILL ALSO REQUIRE MONITORING. THERE ARE PERSISTENT DIFFS WITH A SYSTEM CROSSING THE NORTHEAST EARLY-MID WEEK BUT THE MOST CONTENTIOUS PART OF THE FCST IS IN THE LATTER HALF OF THE PERIOD WHEN SOLNS DIVERGE FOR SHRTWV ENERGY HEADING INTO THE WEST BY THU WITH DOWNSTREAM EFFECTS ON AN UPR LOW TRACKING OUT OF THE FOUR CORNERS REGION INTO THE PLAINS TUE-THU. THE FIRST FEATURE OF INTEREST IS AN AREA OF DIFFUSE LOW PRESSURE HEADING TOWARD THE NORTHEAST AS OF EARLY TUE, WITH UPR SUPPORT PROVIDED BY A COMBINATION OF ENERGY EJECTING FROM THE WEST IN THE SHORT RANGE AS WELL AS UPR TROUGH ENERGY CROSSING ERN CANADA. THIS SYSTEM WILL LIKELY CONSOLIDATE TOWARD THE CANADIAN MARITIMES AS THE ERN CANADIAN TROUGH CLOSES OFF AN UPR LOW. FOR MULTIPLE RUNS GFS-BASED GUIDANCE HAS TENDED TO BE SOMEWHAT SLOWER THAN THE ECMWF AND MOST OTHER SOLNS TO VARYING DEGREES. LACK OF CONVERGENCE OVER THE PAST DAY SEEMS TO FAVOR AN INTERMEDIATE SOLN LEANING SLIGHTLY MORE IN THE ECMWF DIRECTION REFLECTING AVG TIMING OF GUIDANCE AS A WHOLE. THE NEW 00Z GUIDANCE THUS FAR MAINTAINS THE AFOREMENTIONED TIMING SPREAD. THE SYSTEM NEAR THE FOUR CORNERS REGION AS OF EARLY TUE SHOWS DECENT CLUSTERING INTO WED, WITH MOST GUIDANCE SHOWING A SOMEWHAT FASTER TREND OVER THE PAST 24-36 HRS. BEYOND WED THE PATH AND TIMING OF THIS SYSTEM DIVERGE IN RESPONSE TO INCREASING SPREAD IN THE HANDLING OF INCOMING PACIFIC ENERGY LATE IN THE WEEK. THE ECMWF/CMC AND THEIR MEANS REPRESENT THE MOST STABLE CLUSTERING AT THE MOMENT, RAPIDLY AMPLIFYING THE WRN TROUGH WITH A CLOSED LOW, OR AT LEAST A HINT OF ONE IN THE CASE OF THE CMC MEAN, REACHING THE FOUR CORNERS/SRN ROCKIES BY NEXT SAT. AT THE SAME TIME THE LEADING PLAINS SYSTEM WOULD PROGRESS NEWD IN A FASHION CONSISTENT WITH THE ESTABLISHED MEAN PATTERN. HOWEVER INDIVIDUAL MODEL RUNS HAVE DIFFERED FOR THE TRACK OF BOTH THE LATE WEEK WRN CLOSED LOW AND SYSTEM TRACKING OUT OF THE PLAINS. THE 18Z GFS DIFFERED THE MOST FROM MOST OTHER SOLNS IN PULLING OFF AN UPR LOW OFFSHORE CA WHILE BRINGING MOST REMAINING TROUGH ENERGY INTO THE PLAINS/MS VLY, RESULTING IN A SLOW/SWD EVOLUTION OF THE LEADING PLAINS SYSTEM. THE 12Z GFS WAS CLOSER TO THE MAJORITY CLUSTER. THE NEW 00Z GFS HAS RETURNED CLOSER THOUGH NOT YET TO REMAINING GUIDANCE OVER THE WEST WHILE PSBLY BEING TOO EAGER TO SHEAR THE PLAINS SYSTEM AND OVER-AMPLIFY NRN STREAM SHRTWV ENERGY APPROACHING THE EAST. USING SOME INPUT FROM YDAY'S 12Z AND 00Z ECMWF RUNS ALONG WITH THE ECMWF MEAN/CMC/12Z GFS YIELDED A GOOD INTERMEDIATE SOLN ALOFT WITH A DEEPER WRN CLOSED LOW THAN THE MEANS AND A TRACK CLOSEST TO THE ECMWF MEAN THAT HAS HAD THE MOST STABLE TRACK OVER THE PAST DAY. FOR THE PLAINS SYSTEM EJECTING INTO THE NORTHEAST IN THE SAME LATE WEEK TIME FRAME, THIS BLEND HELPED TO KEEP SYSTEM TIMING BTWN THE POTENTIALLY FAST 12Z ECMWF AND SLOWER/SWD 12Z GFS. THIS BLEND WAS USED FOR DAYS 5-7 THU-SAT. SOME 18Z GFS WAS INCLUDED WITH THE OTHER SOLNS WHEN BETTER CONSENSUS EXISTED DAYS 3-4 TUE-WED. ...SENSIBLE WEATHER HIGHLIGHTS/POTENTIAL HAZARDS... SYSTEM TRACKING OUT OF THE FOUR CORNERS REGION TUE ONWARD, AND BY LATE IN THE PERIOD PSBL EMERGENCE OF THE NEXT AMPLIFYING WRN SYSTEM, SHOULD PROMOTE SIGNIFICANT EPISODES OF CONVECTION OVER AND EWD FROM THE SRN AND PERHAPS CNTRL PLAINS. POTENTIAL FOR REPEAT ACTIVITY WILL LIKELY LEAD TO HIGHEST RNFL TOTALS AND EXCESSIVE/FLASH FLOOD CONCERNS OVER THE PLAINS. ALSO SPC IS MONITORING THE THREAT FOR SEVERE ACTIVITY FROM THE SRN PLAINS EXTENDING AT LEAST AS FAR EWD AS THE LOWER MS VLY WITH THE FIRST SYSTEM. MEANWHILE AS THE SYSTEMS TRACK OVER THE WRN STATES EXPECT SOME AREAS OF LOCALLY ENHANCED RAIN AND HIGHER ELEV SNOW. CURRENT INDICATIONS ARE THAT HIGHEST 5-DAY TOTALS SHOULD EXTEND FROM THE PAC NW INTO THE NRN-CNTRL ROCKIES AND PERHAPS AS FAR S AS THE SRN ROCKIES. SOME POTENTIAL EXISTS FOR ENHANCED ACTIVITY OVER THE INTERIOR WEST TO EXTEND TO THE SW OF THIS AXIS. FAIRLY SIGNIFICANT MODEL/ENSEMBLE SPREAD BY LATE WEEK/WEEKEND LOWERS CONFIDENCE IN PRECIP DETAILS OVER THE WEST BY THAT TIME FRAME. PARTS OF THE EAST WILL SEE LGT-MDT PRECIP EARLY IN THE PERIOD WITH WINTRY WEATHER LIKELY CONFINED TO NRN NEW ENGLAND. MSTR FROM THE NEXT PLAINS SYSTEM SHOULD HEAD INTO/ACROSS THE EAST BY THU-SAT WITH SOME AREAS OF HEAVIER RAIN PSBL AND WINTRY PRECIP TYPES AGAIN CONFINED TO VERY NRN LATITUDES. EXPECT LOCATIONS OVER THE SOUTH/SOUTHEAST AS WELL AS THE NRN PLAINS TO SEE ABOVE NORMAL HIGHS ON THE MOST CONSISTENT BASIS DURING THE PERIOD WITH SOME PLUS 10-20F ANOMALIES. THERE SHOULD BE GREATER COVERAGE OF ANOMALOUSLY WARM MIN TEMPS E OF THE ROCKIES IN ASSOC WITH CLOUDS/PRECIP AND MULTIPLE DAYS OF LOW LVL FLOW FROM THE GULF AHEAD OF THE EMERGING WRN U.S./PLAINS SYSTEM. TEMPS OVER THE WEST WILL VARY WITH SYSTEM PROGRESSION. RAUSCH