EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 259 AM EDT FRI OCT 30 2015 VALID 12Z MON NOV 02 2015 - 12Z FRI NOV 06 2015 ...ACTIVE WRN US/ROCKIES FLOW MAY LEAD TO MORE S-CENTRAL US RAINS... ...GUIDANCE/PREDICTABILITY ASSESSMENT... THE WPC MEDIUM RANGE PRODUCT SUITE HAS BEEN PRIMARILY DERIVED FROM A BLEND OF WELL CLUSTERED GUIDANCE FROM THE 18 UTC GFS AND 12 UTC ECMWF/ECMWF ENSEMBLE MEAN. THE 18 UTC GFS AND LATEST 00 UTC GFS ARE BOTH NOW NOW OVERALL MUCH MORE IN STEP WITH THE 12 UTC ECMWF/ECMWF ENSEMBLE MEAN THAN THE 12 UTC GFS. HIGHEST WPC MANUAL WEIGHTING WAS ASSIGNED TO THE 12 UTC ECMWF ENSEMBLE MEAN TO MAINTAIN MAX WPC CONTINUITY...BUT ALSO OPTED FOR MINORITY WEIGHTING OF THE 18 UTC GFS AND 12 UTC ECMWF TO PROVIDE ENHANCED DETAIL CONSISTENT WITH A PATTERN WITH BELOW NORMAL FORECAST SPREAD AND UNCERTAINTY. THE GEFS/NAEFS MEANS ARE REASONABLY IN LINE TOO. ...PATTERN OVERVIEW AND SENSIBLE WEATHER THREATS... FRONTAL WAVE FOCUSING PCPN ACROSS THE SERN US/SRN MID-ATLANTIC SHOULD BE QUICK TO EXIT MON AS SUPPORTING SHORTWAVE TROUGH ENERGY ALOFT SHEARS OFFSHORE. POOLING MOISTURE MAY FUEL SOME HEAVIER CONVECTIVE DOWNPOURS INTO MON PRIOR TO SYSTEM EJECTION. UPSTREAM...SIGNIFICANT MID-LATITUDE FLOW AMPLIFICATION IS EXPECTED TO OCCUR NEXT WEEK FROM THE PACIFIC INTO THE LOWER 48 NEXT WEEK HIGHLIGHTED AT MID-UPPER LEVELS BY A QUICKLY AMPLIFYING AND COOLING/UNSETTLING WRN/SWRN US TROUGH AND BUILDING/WARMING E-CENTRAL US/SERN US RIDGE. THE TROUGH/LOW IS NOW QUITE AMPLIFIED AND SLOW MOVING IN LATEST GUIDANCE AND AS SUCH OFFERS A THREAT OF WIDESPREAD PCPN...ESPECIALLY FROM THE SIERRA AND SW US/S-CENTRAL GREAT BASIN NEWD TO THE N-CENTRAL ROCKIES. THIS INCLUDES POTENTIAL FOR SOME HEAVIER TERRAIN ENHANCED SNOWS. ENERGY GRADUALLY WORKING TO THE S-CENTRAL US THEN SETS THE STAGE FOR ANOTHER POTENTIAL ROUND OF HEAVY RAINS LATER NEXT WEEK AS GULF MOISTURE RETURN FEEDS INTO/OVERTOP A SLOW MOVING DRAPED FRONTAL ZONE. THIS ALL OCCURS UNDERNEATH IMPULSE LADEN AND MORE PROGRESSIVE CANADIAN AND N-CENTRAL TO NERN US NRN STREAM FLOW THAT OFFERS MORE LIMITED PCPN SWATHS AND MODEST LOW LEVEL COLD AIR INTRUSION INTO THE LOWER 48. IMPULSE ENERGIES LIFTING OUT FROM THE WRN US MEAN TROUGH MAY LEAD TO SOME ORGANIZED OVERRIDING SNOWS EXTENDING OUT INTO THE NRN PLAINS. SCHICHTEL