EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1204 PM EDT TUE OCT 28 2014 VALID 12Z FRI OCT 31 2014 - 12Z TUE NOV 04 2014 ...ERN US EARLY SEASON WINTER THREAT AND DEEP TROUGHING/PCPN INLAND TO THE WEST... THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM THE 00 UTC ECMWF ENSEMBLE MEAN. THIS SOLUTION OVERALL MIMICS BUT IS SLIGHTLY LESS DEVELOPED AND SLIGHTLY MORE PROGRESSIVE THAN THE 00 UTC ECMWF. EVEN SO...THE 00 UTC ECMWF ENSEMBLE MEAN STILL LIES WELL ON THE AMPLIFIED SIDE OF THE FULL ENVELOPE OF ALL MODEL AND ENSEMBLE GUIDANCE SYSTEMS. THIS FOLLOWS THE LASTEST GENERAL TREND TOWARD FLOW AMPLIFICATION FROM MOST GUIDANCE AND LEAD-IN NRN HEMISPHERIC WATER VAPOR LOOPS...BUT DOES LIMITS BY THE NATURE OF THE MEAN THE DEEPEST SMALLER SCALE SYSTEM ORGANIZATION/PHASING CONSIDERING AT LEAST AVERAGE FORECAST SPREAD AND UNCERTAINTY. THE WEATHER RELATED THREATS HIGHLIGHTED DURING THIS MEDIUM RANGE FORECAST PERIOD ARE PREDOMINANTLY ASSOCIATED WITH TWO MAIN DEVELOPING WEATHER FEATURES. EXPECT STRONG LEAD MID-UPPER LEVEL TROUGH AMPLIFICATION WILL OCCUR DOWNSTREAM OF AMPLIFYING CENTRAL NOAM RIDGE AS MID AND UPPER LATITUDE IMPULSE ENERGY DIGS SHARPLY SSEWD FRIDAY INTO THE WEEKEND...WITH DEVELOPING MODERATELY HEAVY PCPN FROM OFF THE GREAT LAKES THROUGH THE APPALACHIANS INTO THE MID-ATLANTIC AND NORTHEAST. THERE IS SOME THREAT OF CLOSING AN ANOMALOUSLY COLD LOW NEAR THE MID-ATLANTIC BUT REGARDLESS ACTS TO SOLIDIFY AN ASSOCIATED SURFACE LOW/FRONTAL THEN COASTAL SYSTEM WITH WRAPPING PCPN INTO THE MID-ATLANTIC/NORTHEAST WITH FREEZING TEMPS POTENTIAL ALSO TRAILING DOWN THROUGH THE SRN/SERN US. THERE IS A REAL RISK OF HEAVIER SNOWS ON THE BACKSIDE OF THIS SYSTEM OFF THE LAKES INTO ESPECIALLY THE APPALACHIANS AND POSSIBLY INTO THE MID-ATLANTIC AND PORTIONS/TERRAIN ACROSS THE NORTHEAST. MEANWHILE OUT WEST...GUIDANCE SEEMS TO BE MORE CLOSELY ALIGNING ON THE CONCEPT OF TRACKING AN AMPLIFIED AND COOLING/UNSETTLING/PCPN FOCUSING MID-UPPER LEVEL TROUGH AND ASSOCIATED SURFACE LOW/FRONTAL SYSTEM AND PCPN WELL DOWN THROUGH MUCH OF THE WEST COAST THIS WEEKEND...LIFTING MORE IN ERNEST THROUGH THE ROCKIES INTO THE PLAINS EARLY NEXT WEEK. THIS INCLUDES A THREAT FOR HEAVIER SNOWS DOWN THROUGH THE SIERRA AND NORTHEASTWARD TO THE NORTH-CENTRAL ROCKIES TERRAIN WITH SYSTEM APPROACH/PASSAGE. THIS THEN LEADS TO A ORGANIZED CONVECTIVE THREAT OVER THE CENTRAL US MON/TUE CONSIDERING DYNAMIC POTENTIAL AND ENHANCING RETURN FLOW WORKING FROM THE GULF. SCHICHTEL