EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1125 AM EDT SUN MAY 31 2015 VALID 12Z WED JUN 03 2015 - 12Z SUN JUN 07 2015 ...PATTERN OVERVIEW AND GUIDANCE/UNCERTAINTY ASSESSMENT... IT REMAINS EVIDENT THAT GUIDANCE CONTINUES TO DEPICT REASONABLE AGREEMENT WITH OVERALL MEAN FLOW ALOFT BUT MEANINGFUL DETAIL DIFFS PERSIST...WHILE SOME TREND REVERSALS ARE NOTED OVER PAST DAY OR SO OVER THE ERN/SERN US. CONSENSUS TRENDS OVER THE WEST DURING THE PAST COUPLE DAYS HAVE BEEN TOWARD A DEEPER LATE WEEK/WEEKEND TROUGH ALOFT WITH INCREASING POTENTIAL FOR AN EMBEDDED UPR LOW TO CLOSE OFF WITHIN THE SRN HALF OF THE TROUGH. ECMWF/ECMWF MEAN RUNS DEPICTED THIS IDEA SOMEWHAT EARLIER THAN GFS/GEFS SOLNS. THE 00/06Z GFS RUNS HAVE TRENDED SOMEWHAT CLOSER TO THE MAJORITY CLUSTER OVER THE WEST. AN ISSUE INTRODUCED BY RECENT GFS RUNS IS THE POSSIBILITY THAT MID-LVL ENERGY/MSTR FROM ERN PAC TROPICAL CYCLONE ANDRES COULD BE CAPTURED BY THE EVOLVING TROUGH. CURRENTLY THE FULL RANGE OF GUIDANCE SUGGESTS THIS TO BE AN UNLIKELY SCENARIO AS REMAINING SOLNS TRACK ANDRES FAR ENOUGH WWD LEADING INTO THE MEDR PERIOD THAT THE DEEPENING WRN TROUGH DOES NOT CAPTURE ANDRES. CONSULT NHC PRODUCTS FOR THE LATEST INFO REGARDING ANDRES WHICH IS CURRENTLY A HURCN. DETERMINING HOW ONE OR MORE SHRTWVS CONTAINED WITHIN A MORE SHALLOW INITIAL WRN TROUGH AS OF DAY 3 WED WILL AFFECT THE DOWNSTREAM SFC PATTERN REMAINS PROBLEMATIC. IMPULSES ALOFT ARE STILL QUITE SMALL IN SCALE AND THEREFORE HAVE LOW PREDICTABILITY...PLUS THIS ENERGY WILL BE PASSING TROUGH A WRN-SRN CANADA MEAN RIDGE AND HEADING INTO AN AREA OF CONFLUENT FLOW BEHIND AN ERN CANADA MEAN TROUGH. LATEST GUIDANCE AND WPC PROGS DOWNPLAY SURFACE WAVE DEVELOPMENT. TO THE E OF A SRN PLAINS/NRN MEXICO RIDGE ALOFT THAT SHOULD BRING DRIER CONDS TO THE SRN PLAINS...THE CONSENSUS TREND HAS REVERSED WITH RESPECT TO ENERGY FCST TO SETTLE OVER THE SERN QUADRANT OF THE LOWER 48. NOW THERE IS RENEWED SUPPORT FOR A SLOWER/MORE CLOSED UPR FEATURE ALBEIT NOT QUITE AS FAR SWWD AS SEEN IN PAST GFS/GEFS RUNS. SATL IMAGERY SUGGESTS THE BEST DEFINED ENERGY IS CURRENTLY WITHIN THE SRN HALF OF THE TROUGH SO A SEPARATED SOLN SEEMS REASONABLE AS SHOWN IS THE FORECASTER ADJUSTED WPC ENSEMBLE MEAN BLEND. AHEAD OF THIS UPR SYSTEM...GFS/GEFS AND CMC RUNS HAVE BEEN MOST ENTHUSIASTIC ABOUT PSBL SFC DEVELOPMENT WITHIN MOIST FLOW EXTENDING NNEWD FROM THE WRN CARIBBEAN. PROGRESSIVE FLOW ALOFT IS NOT VERY SUPPORTIVE. WEAKER DEPICTION IN THE PAST COUPLE ECMWF RUNS AND MINIMAL REFLECTIONS IN THE ECMWF/CMC ENSEMBLE MEANS RECOMMEND A WEAKER SFC SYSTEM AS WELL. BASED ON THE CONSIDERATIONS FOR FEATURES OF INTEREST AND UNCERTAINTY...WPC MEDIUM RANGE SURFACE FRONTS/PRESSURES AND 500 MB PROGS WERE PRIMARILY BASED FROM A BLEND OF 70 PCT 00 UTC NAEFS (GEFS/CMC) ENSEMBLE MEAN AND 30 PCT 00 UTC ECMWF ENSEMBLE MEAN. THIS MAINTAIN GOOD WPC CONTINUITY OVERALL AS NOTED. ...SENSIBLE WEATHER HIGHLIGHTS/THREATS... AREAS FROM THE NRN-CNTRL HIGH PLAINS INTO THE UPR MS VLY AS WELL AS THE OVER THE SERN THIRD OF THE CONUS SHOULD SEE THE GREATEST POTENTIAL FOR LOCALLY HVY TO EXCESSIVE RNFL DURING THE PERIOD. ONE OR MORE EPISODES OF CONVECTION OVER THE NRN TIER WILL DEPEND ON DIFFICULT TO RESOLVE SHRTWV DETAILS SO SHORTER RANGE FCSTS WILL NEED TO BE MONITORED AS THESE ISSUES BECOME BETTER REFINED. CONSULT SPC OUTLOOKS REGARDING PSBL SEVERE THREATS ACROSS THE NRN TIER. AS NOTED EARLIER THE GFS IDEA OF PULLING MSTR/MID LVL ENERGY FROM EPAC HURCN ANDRES INTO PARTS OF THE WEST IS CURRENTLY A MINORITY SOLN. HOWEVER...THE AMPLITUDE OF THE WRN/SWRN US MID-UPPER LEVEL TROUGH MAY OFFER SOME UNSEASONAL SCATTERED SHOWER SUPPORT. MEANWHILE THE RECENT WWD/MORE CLOSED ADJUSTMENT WITH SRN TIER ENERGY VERSUS YESTERDAY EXPANDS COVERAGE OF ENHANCED RNFL OVER THE SOUTHEAST AND PSBLY AS FAR NWWD AS THE TN VLY. MOIST FLOW ALOFT EXTENDING NNEWD FROM THE WRN CARIBBEAN SHOULD SUPPORT LOCALLY HVY RNFL NEAR SRN FL. RAUSCH/SCHICHTEL