EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 238 AM EDT FRI AUG 26 2016 VALID 12Z MON AUG 29 2016 - 12Z FRI SEP 02 2016 ...OVERVIEW... THE ULTIMATE STRENGTH AND TRACK OF PSBL TROPICAL DEVELOPMENT THAT MAY REACH THE GULF OF MEXICO FROM NEAR THE ERN BAHAMAS CONTINUES TO BE THE GREATEST UNCERTAINTY OF THE FCST. CONSULT THE NATIONAL HURRICANE CENTER'S TROPICAL WEATHER OUTLOOK FOR LATEST INFO REGARDING PSBL DEVELOPMENT. AS FOR LARGER SCALE EVOLUTION MOST GUIDANCE DEPICTS AN ADJUSTMENT IN UPR RIDGE EMPHASIS FROM THE MID ATLC TO THE CNTRL U.S. AS A MEAN TROUGH AMPLIFIES NEAR THE WEST COAST AND A BROADER/FLATTER MEAN TROUGH SETTLES NEAR THE EAST COAST. DIFFS PRIMARILY INVOLVE AMPLITUDE/LONGITUDE OF THE WEST COAST TROUGH AND MEDIUM TO SMALLER SCALE DETAILS WITHIN THE EVOLVING ERN TROUGH. ...GUIDANCE/UNCERTAINTY ASSESSMENT... THE FEATURE THAT MAY TRACK INTO THE GULF OF MEXICO HAS GREATER THAN AVG FCST UNCERTAINTY DUE TO DIFFS IN STEERING DEPENDING ON EXACTLY HOW STRONG THE FEATURE BECOMES AND PSBL DEPENDENCE ON EXACT DETAILS OF HOW THE MID ATLC RIDGE ALOFT GIVES WAY TO THE RIDGE OVER THE CNTRL U.S.. MODEL AND ENSEMBLE SPREAD REMAINS QUITE WIDE RANGING FROM WEAK/SUPPRESSED SOLNS ACROSS THE SRN GULF TO ALONG THE WEST COAST OF THE FLORIDA PENINSULA. SOME NEW 00Z SOLNS DIFFER FROM THEIR 12Z RUNS. ONGOING GUIDANCE SPREAD FAVORS MAINTAINING CONTINUITY NEAR YDAYS FCST WITH A TRACK OVER THE E-CNTRL GULF. ELSEWHERE ASIDE FROM A MODEL/ENSEMBLE MEAN CONSENSUS FCST ON DAY 3 MON... LATEST GEFS/ECMWF MEANS BEST REFLECT THE LARGE SCALE AGREEMENT FOR THE TROUGHS NEAR THE WEST COAST AND APPROACHING THE EAST COAST WHILE DOWNPLAYING LOWER CONFIDENCE DETAIL UNCERTAINTIES. AT SOME FCST HRS THE 12Z/18Z GEFS MEANS ALIGN THE WEST COAST TROUGH A LITTLE WWD OF MOST OTHER SOLNS SO THE GEFS MEAN WAS GIVEN SOMEWHAT LESS WEIGHT THAN THE ECMWF MEAN. THERE ARE INDICATIONS FROM SOME GUIDANCE THAT AN EMBEDDED UPR LOW MAY EXIST WITHIN THE TROUGH AND HAVE AN ORIGIN FROM N-CNTRL CANADA AND SRN-SERN ALASKA COAST. THE NEW 00Z GFS/CMC RUNS ARE QUITE SIMILAR BY DAY 7 FRI AND HAVE A TROUGH AXIS NEAR THE MEANS. ...WEATHER HIGHLIGHTS/THREATS... CURRENTLY THE ERN HALF OF THE GULF COAST APPEARS TO HAVE THE BEST POTENTIAL FOR SOME LOCALLY HVY RNFL IN ASSOC WITH THE FEATURE THAT MAY TRACK INTO THE GULF OF MEXICO FROM NEAR THE ERN BAHAMAS. COLD FRONT PUSHING E/SE FROM THE NRN PLAINS THROUGH THE EAST COAST MAY BE ACCOMPANIED BY SCT CONVECTION. TRAILING PART OF THIS FRONT WILL LIKELY BECOME STNRY OVER THE NRN PLAINS AND BE A CONTRIBUTOR... ALONG WITH SHRTWV ENERGY ALOFT... TO ONE OR MORE EPISODES OF NRN TIER CONVECTION. THE UPR TROUGH AMPLIFYING NEAR THE WEST COAST ALONG WITH WHAT REMAINS OF AN ERN PAC UPR LOW REACHING THE WRN STATES BY TUE-WED MAY GENERATE SOME RNFL ALONG THE PAC NW COAST AND PSBLY INLAND. IMPULSES ALOFT AND ADEQUATE MSTR COULD ALSO SUPPORT ACTIVITY OVER PORTIONS OF THE ROCKIES. FOR THE OVERALL 5-DAY PERIOD EXPECT ABOVE NORMAL TEMPS FROM THE GRTBASIN/NRN ROCKIES THROUGH THE NRN PLAINS AND INTO THE EAST. THE AMPLIFYING UPR TROUGH NEAR THE WEST COAST WILL TEND TO KEEP HIGHS BELOW NORMAL OVER THAT REGION. RAUSCH