EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1146 AM EDT MON AUG 01 2016 VALID 12Z THU AUG 04 2016 - 12Z MON AUG 08 2016 ...OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES... LATEST RUNS OF OPERATIONAL MODELS AND ENSEMBLE MEANS MAINTAIN SIMILAR IDEAS FOR THE LARGE SCALE PATTERN THROUGH THE PERIOD... WITH PRIMARY UNCERTAINTIES INVOLVING MEDIUM TO SMALLER SCALE DETAILS THAT TEND TO HAVE FAIRLY LOW PREDICTABILITY. THUS A MODEL/ENSEMBLE MEAN CONSENSUS CONTINUES TO WORK WELL FOR DEPICTING THE MOST LIKELY FCST SCENARIO. PRIMARY EMPHASIS IS ON THE 06Z GFS/00Z ECMWF VERSUS THEIR MEANS EARLY IN THE PERIOD WITH A GRADUAL TRANSITION TOWARD 60 PCT ENSEMBLE MEAN WEIGHTING BY DAYS 6-7 SUN-MON. EXPECT MEAN TROUGHING TO PERSIST NEAR THE WEST COAST THROUGH THE PERIOD. THE MOST PROMINENT FEATURE WITHIN THE TROUGH WILL BE A WRN CANADA COMPACT CLOSED LOW WHICH TAKES UNTIL DAY 7 MON TO START SHOWING SOME TIMING SPREAD IN RESPONSE TO APPROACHING NERN PAC FLOW. THUS FAR TRENDS/CONTINUITY AMONG THE VARIOUS SOURCES OF GUIDANCE RECOMMEND INTERMEDIATE TIMING BTWN THE FASTER 00Z ECMWF/ECMWF MEAN AND OTHER SOLNS. FARTHER SWD A TRACKABLE IMPULSE SHOULD REACH NRN CA IN THE FIRST HALF OF THE PERIOD AND CONTINUE NEWD THEREAFTER. BY MID-LATE PERIOD IT REMAINS TO BE SEEN IF THAT EJECTING SHRTWV IS AS AMPLIFIED AS FCST BY THE 06Z GFS OVER THE NRN HIGH PLAINS BY DAY 6 SUN... OR IF A COUPLE TRAILING BUNDLES OF ENERGY BECOME AS STRONG/AMPLIFIED AS FCST BY THE 00Z ECMWF. THE PREFERRED BLEND DOWNPLAYS THESE LOWER CONFIDENCE DETAILS. FARTHER EWD THE PROGRESSION OF A VIGOROUS SYSTEM INITIALLY NEAR THE CANADIAN BORDER COMBINED WITH UPSTREAM FLOW WILL ULTIMATELY CARVE OUT A MEAN TROUGH OVER ERN CANADA AND NERN U.S.. THE CONSENSUS BLEND RESOLVES MODEST TIMING/AMPLITUDE DIFFS THAT ARE GENERALLY WITHIN TYPICAL ERROR RANGES FOR THE TIME FRAME OF INTEREST. MEAN RIDGING SHOULD BE MOST PERSISTENT FROM THE SRN HALF OF THE PLAINS/MS VLY INTO THE SOUTHEAST/FLORIDA. THIS RIDGE IS FCST TO SUPPORT A FAIRLY LOW LATITUDE TRACK FOR A STRONG TROPICAL WAVE THAT THE NATIONAL HURRICANE CENTER IS MONITORING OVER THE CENTRAL CARIBBEAN SEA. YDAY A NUMBER OF GEFS ENSEMBLE MEMBERS HAD INDICATED A HIGHER POTENTIAL FOR THE SFC SYSTEM AND ACCOMPANYING MSTR TO AFFECT SRN TEXAS. SINCE THEN GEFS MEMBERS HAVE TRENDED MORE SUPPRESSED THOUGH THE POSSIBILITY REMAINS FOR SOME MSTR TO AFFECT SRN TEXAS. ...WEATHER HIGHLIGHTS/THREATS... COLD FRONT PROGRESSING INTO THE EAST FROM THE NRN PLAINS WILL PROVIDE ONE FOCUS FOR CONVECTION DURING THE PERIOD. LATEST SPC OUTLOOK INDICATES SEVERE POTENTIAL OVER PARTS OF THE UPR MS VLY/NWRN GRTLKS DAY 3 THU. SOME CONVECTION MAY BE ON THE STRONG SIDE ON FOLLOWING DAYS BUT WITH LESS CONFIDENCE IN SPECIFICS. MONSOONAL MSTR AND MID LVL ENERGY SHOULD PROMOTE LOCALLY HVY RNFL OVER THE FOUR CORNERS STATES ESPECIALLY IN THE THU-FRI TIME FRAME. THEN EXPECT THIS MSTR/ENERGY TO CONTINUE NEWD/EWD AROUND THE MEAN RIDGE TO THE S/SE AND BRING A THREAT FOR HVY RNFL TO THE N-CNTRL PLAINS AND MID-UPR MS VLY FRI NIGHT ONWARD. TRAILING PART OF THE NRN PLAINS TO EAST COAST FRONT SHOULD STALL OVER THE CNTRL PLAINS AND MAY PROVIDE AN ADDED FOCUS FOR THIS CONVECTION. MEANWHILE ANTICIPATE DIURNALLY ENHANCED RNFL FROM THE LWR MS VLY/CNTRL GULF COAST TO THE SERN COAST/FLORIDA. GIVEN A MEAN PATTERN FAIRLY TYPICAL FOR AUGUST... TEMPS AT MOST LOCATIONS WILL LIKELY BE WITHIN 10F OF NORMAL THROUGH THE PERIOD. BEST CHANCE FOR SLIGHTLY HIGHER ANOMALIES WILL BE FOR WARM MINS AHEAD OF THE NRN PLAINS TO EAST COAST FRONT. RAUSCH