EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 232 AM EDT MON MAR 23 2015 VALID 12Z THU MAR 26 2015 - 12Z MON MAR 30 2015 ...OVERVIEW... THERE IS LITTLE CHANGE IN THE EXPECTATION OF THE ESTABLISHMENT AND THEN MAINTENANCE OF AN AMPLIFIED WRN RIDGE/ERN TROUGH MEAN PATTERN. CLUSTERING IS DECENT AT LEAST IN A BROAD SENSE ON THE FEATURES OF INTEREST. INITIAL TROUGHING AMPLIFYING INTO THE EAST SHOULD BE KICKED EWD BY SUN-MON AS UPSTREAM ENERGY DROPS INTO THE MEAN TROUGH POSN AT THAT TIME. MEANWHILE ERN PAC TROUGH SEPARATION MAY LEAVE BEHIND A BUNDLE OF ENERGY THAT COULD APPROACH/REACH THE WEST COAST. AS IS TYPICALLY THE CASE THERE IS SOME SPREAD AND RUN TO RUN VARIABILITY AMONG LATEST GUIDANCE FOR THE FINER DETAILS. ...GUIDANCE EVALUATION... FOR THE INITIAL AMPLIFYING TROUGH PROGRESSING FROM THE CNTRL INTO ERN CONUS... AMONG 12Z AND LATER RUNS SOME CHANGES IN SMALLER SCALE DETAILS LATE IN THE SHORT RANGE LEAD TO A SLOWER WAVE REACHING THE LWR GRTLKS AS OF 12Z THU. AS A RESULT THE TRAILING FRONT AND ASSOC PCPN AT THE START OF THE MEDIUM RANGE TIME FRAME ARE SOMEWHAT SLOWER THAN SOME PREVIOUS CYCLES. AFTER THIS WAVE LIFTS AWAY THERE IS STILL A CONSISTENT THEME OF ADDITIONAL WAVINESS ALONG THE FRONT NEAR AND JUST OFFSHORE THE EAST COAST FRI ONWARD. PERHAPS NOT SURPRISING GIVEN THE AMPLITUDE OF THE EVOLVING PATTERN... THE GUIDANCE AVG HAS TRENDED A LITTLE SLOWER WITH THE OVERALL FRONT IN THE PAST DAY. THE MOST COMMON SCENARIO SEEN IN 12Z/18Z SOLNS AND 00Z RUNS THUS FAR IS FOR THE BEST DEFINED WAVE TO TRACK FROM THE SOUTHEAST/CAROLINAS LATE FRI E THEN NE INTO THE ATLC. THIS IDEA COMPARES FAVORABLY TO THE ADMITTEDLY DIVERSE ENSEMBLE SPREAD WHILE FARTHER NWWD WAVINESS IN CMC RUNS HAS TENDED TO BE ON THE NWRN EDGE OF THE ENVELOPE. A COMPROMISE AMONG LATEST MODEL AND ENSEMBLE SOLNS LOOKS REASONABLE FOR CAPTURING UPDATED ADJUSTMENTS AND ACCOUNTING FOR REMAINING SPREAD. THE CRITICAL ASPECT OF THE UPSTREAM FCST IS WITH THE EXPECTED SEPARATION OF FLOW WITHIN THE ERN PAC TROUGH AROUND FRI. NRN ENERGY SHOULD ROUND THE WRN NOAM RIDGE AND DROP INTO THE DOWNSTREAM MEAN TROUGH WHILE LATEST MODEL RUNS ARE SHOWING A MORE PRONOUNCED SIGNAL THAT THE REMAINING SRN ENERGY MAY FORM A COMPACT CLOSED LOW THAT TRACKS TOWARD AND PSBLY INLAND FROM THE WEST COAST. GUIDANCE CAN SOMETIMES HAVE DIFFICULTY IN RESOLVING SPECIFICS OF HOW FLOW SEPARATES. MOST GUIDANCE HAS BEEN REASONABLY CONSISTENT IN SUGGESTING THAT THE NRN ENERGY SHOULD SUPPORT A SYSTEM THAT BRUSHES THE UPR GRTLKS/NEW ENGLAND. OPERATIONAL MODELS HAVE TENDED TO BE RATHER STRONG WITH THE SFC LOW BUT THE 00Z GFS HAS A MORE SHEARED DEPICTION OF ENERGY ALOFT AND THUS ONLY A MERE FRONT THAT IS MORE SIMILAR TO THE ENSEMBLE MEANS. THIS ADJUSTMENT SEEMS TO SUPPORT PRIOR THINKING OF LEANING MORE TOWARD THE ENSEMBLE MEANS WHILE AWAITING BETTER AGREEMENT FOR STRENGTH/TRACK OF THE SFC SYSTEM. THE CONCENTRATED APPEARANCE OF REMAINING ERN PAC ENERGY TRACKING TOWARD CA FIRST SHOWED UP IN THE 00Z/22 ECMWF RUN. THE 12Z ECMWF MAINTAINED THAT IDEA WITH 00Z MODEL RUNS THUS FAR DISPLAYING SIMILAR IDEAS ASIDE FROM MOST BEING SOMEWHAT WEAKER THAN ECMWF RUNS. HAVING MORE ENERGY COME INTO THE WEST IS A FAIRLY NEW TREND IN THE MEANS AND IT REMAINS TO BE SEEN HOW STRONG THE ENERGY WILL BE GIVEN THE STRENGTH OF THE DOWNSTREAM RIDGE. THUS FOR NOW PREFER A SOLN WEAKER THAN THE MODELS BY THE LATTER PART OF THE PERIOD. FOR DAYS 3-5 THU-SAT AN EVEN WEIGHTING OF THE 18Z GFS/12Z ECMWF AND 12Z ECMWF/12Z NAEFS/18Z GEFS MEANS REFLECTS THE MOST COMMON IDEAS OF LATEST GUIDANCE WHILE DAYS 6-7 SUN-MON USE A SLIGHTLY ENHANCED BLEND OF THE ENSEMBLE MEANS EXCLUSIVELY. ...SENSIBLE WEATHER HIGHLIGHTS... WAVY COLD FRONT CROSSING THE EAST EARLY IN THE PERIOD SHOULD INITIALLY BE ACCOMPANIED BY SOME BANDS OF ENHANCED RNFL... MOST LIKELY FROM THE OH VLY NEWD AND A LITTLE LATER OVER THE FL PENINSULA. SNOW ON THU SHOULD BE CONFINED TO THE UPR MS VLY/UPR GRTLKS BUT EXPECT WINTRY PCPN POTENTIAL TO SHIFT SEWD WITH TIME AS COLDER AIR MOVES INTO THE EAST. LATEST GUIDANCE SUGGESTS THERE COULD BE A LITTLE ADDED FOCUS FRI-SAT FROM OH VLY INTO THE SRN HALF OF THE APLCHNS/SRN MID ATLC. UPSTREAM SYSTEM DROPPING SEWD FROM CANADA SHOULD SPREAD AN AREA OF SNOW N/RAIN S FROM THE NERN TIER ACROSS THE NERN QUADRANT OF THE LOWER 48. ANY WRN CONUS PCPN SHOULD BE MOSTLY ON THE LGT SIDE... INCLUDING ACTIVITY OVER/NEAR THE NRN-CNTRL ROCKIES THU-FRI AND WITH ANY MSTR THAT COULD REACH THE WEST LATE IN THE PERIOD. CONFIDENCE IN THE LATTER IS MODERATE AT BEST GIVEN DEPENDENCE ON A COMPACT UPR LOW THAT IS TYPICALLY CHALLENGING TO FCST. THE AMPLIFIED MEAN PATTERN ALOFT WILL LEAD TO A CONTRAST IN TEMPS. EAST COAST WARMTH ON THU WILL BE FOLLOWED BY A BROAD AREA OF HIGHS 10-20F BELOW NORMAL OVER THE ERN HALF OF THE CONUS FRI-SAT WITH SOME MODERATION THEREAFTER. ON THE OTHER HAND A MAJORITY OF THE WRN CONUS SHOULD SEE MULTIPLE DAYS WITH HIGHS 10-25F ABOVE NORMAL WITH SOME LOCATIONS PSBLY REACHING DAILY RECORD VALUES. SOME OF THE WARM AIR OVER THE WEST SHOULD EXTEND INTO PARTS OF THE NRN-CNTRL PLAINS BY SAT. RAUSCH