EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1100 AM EST SAT MAR 05 2016 VALID 12Z TUE MAR 08 2016 - 12Z SAT MAR 12 2016 ...OVERVIEW... THERE IS LITTLE CHANGE IN THE GENERAL FCST REGARDING THE TWO PROMINENT AREAS OF VERY ACTIVE WEATHER/HEAVY PRECIP DURING THE PERIOD...FROM THE WEST COAST INLAND FROM A PERSISTENT ERN PAC MEAN TROUGH ALOFT AND FROM THE SRN PLAINS INTO THE LOWER-MID MS VALLEY/OH VALLEY AND CENTRAL GULF COAST STATES AS A PERSISTENT FEED OF MOISTURE FROM THE GULF OF MEXICO INTERACTS WITH A SLOW MOVING WAVY SURFACE FRONT. ...GUIDANCE EVALUATION/PREFERENCES... THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A 50-50 BLEND OF THE REASONABLY COMPATABLE 00 UTC ECMWF/ECMWF ENSEMBLE MEAN. THIS MAINTAINS GOOD WPC CONTINUITY BOTH FROM OVERNIGHT SHORT RANGE MODEL PREFERENCES AND DURING MEDIUM RANGE TIME SCALES. OF PARTICULAR NOTE THIS BLEND INCORPORATES SUFFICIENTLY LOW WEIGHT OF THE GFS TO LEAN AWAY FROM ITS FASTER SFC FRONT THAT CROSSES THE NERN QUARTER OF THE CONUS AND BEGINS TO PUSH SWD ALONG THE E COAST IN BACKDOOR FASHION. WHILE GUIDANCE HAS NOT BEEN UNANIMOUS ON TIMING AS SLOW AS RECENT ECMWF RUNS...THERE IS STILL A STRONG MAJORITY OF SOLNS THAT RECOMMEND LESS AMPLITUDE OF SUPPORTING ENERGY ALOFT THAN FCST BY THE GFS. MEANWHILE THIS BLEND REFLECTS A FAIRLY AGREEABLE EVOLUTION OF THE DEEP TROUGH/UPR LOW OVER MEXICO AND WAVY FRONTAL BNDRY TO THE E. BY THE SECOND HALF OF THE PERIOD THE MOST PRONOUNCED DIFFERENCE THAT ARISES IS WITH A MODERATELY AMPLIFIED SHRTWV THAT MAY EJECT FROM THE ERN PAC INTO/THROUGH THE WRN STATES. IF THIS SHRTWV EXISTS ITS AMPLITUDE/TIMING WILL HAVE A MEANINGFUL INFLUENCE ON THE ULTIMATE EJECTION OF THE MEXICO/SRN PLAINS FEATURE. THROUGH THE 18Z CYCLE GUIDANCE WAS SPLIT ON THE IDEA OF AN INCOMING WRN SHRTWV. ECMWF RUNS HAVE BEEN FAIRLY CONSISTENT WITH IT AND THE 12Z CMC DEPICTED IT AS WELL. AFTER BACKING OFF IN THE OLD 00Z CYCLE THE 12Z ECMWF MEAN RETURNED TO ITS SOLN FROM 24 HRS AGO. GFS/GEFS/CMC MEAN RUNS THROUGH 12Z-18Z GENERALLY SHOWED LITTLE ENERGY PROGRESSING WELL INLAND... BUT RECENT GFS PARALLEL RUNS HAVE LEANED MORE TOWARD THE ECMWF IDEA. BASED IN PART ON A TONED-DOWN VERSION OF ECMWF-BASED GUIDANCE APPEARING TO HAVE DONE BETTER IN FCSTG THE ARRIVAL OF HGT FALLS NOW IN THE SHORT RANGE PERIOD... PREFER TO USE A COMBINATION OF RECENT ECMWF RUNS/12Z ECMWF MEAN ALONG WITH SOME COMPONENT OF THE 18Z GEFS MEAN. AMONG 00Z RUNS THUS FAR THE GFS/CMC SHOW THIS SHRTWV BUT ARE FASTER THAN MOST OTHER SOLNS. FARTHER EWD THIS BLEND PROVIDES A REASONABLE INTERMEDIATE FCST FOR THE BACKDOOR FRONT ALONG THE EAST COAST. ...SENSIBLE WEATHER HIGHLIGHTS... OVER THE WEST...EXPECT THE BEST FOCUS FOR HEAVIEST RAIN/HIGH ELEVATION SNOWS TO BE FROM THE CENTRAL WEST COAST AND PAC NW INTO THE NRN ROCKIES DURING THE FIRST HALF OF THE PERIOD AND THEN MOST LIKELY SHIFTING SWD TO SOME DEGREE WITH CONSIDERABLE MOISTURE REACHING THE SIERRA NEVADA RANGE AND INTO THE SWRN US/GREAT BASIN. BEST POTENTIAL FOR HIGHEST 5-DAY PCPN TOTALS WILL BE ACROSS NRN CA/SWRN OR WITH VALUES OF 5-10 INCHES LIKELY OVER FAVORED TERRAIN. WPC PROGS PROVIDE GOOD CONTINUITY WITH THE MULTI-DAY HEAVY RAIN EVENT LIKELY TO EXTEND FROM PARTS OF THE SRN PLAINS THROUGH THE MID-LOWER MS VALLEY INTO THE OH VALLEY/LOWER GREAT LAKES REGION. PERSISTENT DEEP LAYER FLOW FROM THE GULF OF MEXICO AHEAD OF THE STRONG MEXICO/SRN PLAINS UPPER SYSTEM...AND PRESENCE OF A WAVY FRONT...WILL COMBINE TO GENERATE AREAS OF HEAVY RAIN. EXPECT SOME LOCATIONS OVER THE SERN PLAINS AND/OR MID-LOWER MS VALLEY TO SEE 5-DAY TOTALS AT LEAST IN THE 5-10 INCH RANGE. STRONG TO SEVERE CONVECTION IS ALSO POSSIBLE...SO PLEASE ALSO CONSULT SPC OUTLOOKS FOR MORE INFORMATION REGARDING UPDATED SEVERE THREATS. LIGHTER PCPN WILL ACCOMPANY A FRONT CROSSING THE NERN QUADRANT OF THE LOWER 48 AND ULTIMATELY SINK SWD ALONG THE EAST COAST. THIS FRONT WILL TRAIL BACK INTO THE SRN PLAINS/MS VLY SYSTEM AND WILL INCREASING BE A FOCUS FOR ENHANCED PCPN OVER TIME WITH THE GRADUAL APPROACH OF S-CENTRAL SYSTEM ENERGIES AND LEAD DEEPER MOISTURE. FOR TEMPS...THE ACTIVE PATTERN OVER THE WEST WILL KEEP TEMPS NEAR TO BELOW NORMAL ESPECIALLY OVER WA/OR/CA AND MORE VARIABLE INLAND. FOR THE MOST PART ABOVE TO MUCH ABOVE NORMAL READINGS SHOULD PREVAIL FROM THE HIGH PLAINS EWD. MIN TEMPS SHOULD BE ESPECIALLY ANOMALOUS WITH A BROAD AREA 10-30F ABOVE NORMAL...AND DAILY RECORD VALUES FOR WARM MINS AND SOME MAXES ARE PSBL FROM THE NRN PLAINS EWD/SEWD. ISOLD LOCATIONS OVER THE NORTHEAST/MID-ATLANTIC MAY SEE HIGHS APPROACH OR REACH DAILY RECORD VALUES TUE-THU AHEAD OF THE APPROACHING BACKDOOR COLD FRONT. SCHICHTEL