EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1156 AM EDT MON SEP 08 2014 VALID 12Z THU SEP 11 2014 - 12Z MON SEP 15 2014 ...MUCH BELOW AVERAGE TEMPERATURES ALONG/EAST OF THE ROCKIES THU-SAT... ...EARLY SEASON UPSLOPE SNOWFALL EXPECTED FOR PARTS OF MONTANA/WYOMING... ...PATTERN OVERVIEW... THE COMBINATION OF BUILDING UPPER RIDGING OVER THE NE PAC AND W CANADA... THANKS IN PART TO THE EXTRATROPICAL TRANSITION OF TROPICAL STORM FENGSHEN IN THE W PAC... AS WELL AS OVER SE CANADA WILL SUPPORT DEEP TROUGHING OVER THE CENTRAL CONUS LATE THIS WEEK IN A PATTERN THAT IS MUCH MORE REMINISCENT OF WINTER RATHER THAN OF SUMMER'S WANING DAYS. THOUGH THE INITIAL TROUGH SHOULD LIFT THROUGH THE GREAT LAKES AND NORTHEAST INTO SE CANADA THIS WEEKEND... ENSEMBLES STILL SUPPORT THE LONGWAVE RIDGE/TROUGH PATTERN TO REMAIN MOSTLY IN PLACE ALONG 120W/95W... RESPECTIVELY. ...GUIDANCE/UNCERTAINTY ASSESSMENT... LONGWAVE PREDICTABILITY REMAINS BETTER THAN AVERAGE IN THE AMPLIFIED PATTERN. THE LEAD FRONT IN THE EAST SHOWS THE MOST RELATIVE SPREAD WITH THE 00Z-06Z GFS/GEFS MEAN QUICKER TO CARRY THE MID-LEVEL SHORTWAVE OR CLOSED LOW THROUGH THE NORTHERN GREAT LAKES COMPARED TO THE SLOWER ECMWF/CANADIAN/UKMET AND ECENS MEAN. WITH RIDGING BUILDING OFF OF SE CANADA... PREFER THE SLOWER CONSENSUS LED BY THE ECMWF. THE GEFS MEMBERS SEEM TO BE OUT OF STEP WITH THE 00Z-06Z RUNS CONSIDERING THE BETTER AGREEMENT BETWEEN THE TWO ENSEMBLE SYSTEMS IN EARLIER CYCLES. THEREAFTER... AS THE TROUGH EXITS TO THE NORTHEAST... LEAVING BEHIND A SLOWLY MOVING SURFACE FRONTAL BOUNDARY ALONG OR JUST OFFSHORE THE EAST COAST... PREFERRED TO TREND BACK TO THE ECMWF ENSEMBLE MEAN BY LATE IN THE WEEKEND INTO MON/D7. THE DETERMINISTIC RUNS FEATURE TOO MUCH INCONSISTENCY ESPECIALLY WITH ENERGY THAT HAS ORIGINS IN THE ARCTIC... WHICH ARE SELDOM TO BE TRUSTED. ...SENSIBLE WEATHER HIGHLIGHTS... STRONG SURFACE FRONT AND TRAILING HIGH PRESSURE /1036MB OR SO/ WILL SUPPORT UPSLOPE FLOW IN MT/WY/CO. WITH TEMPERATURES EXPECTED TO BE 20-35F BELOW AVERAGE... SNOW IS LIKELY ESPECIALLY IN HIGHER TERRAIN BEHIND THE FRONT LATER THIS WEEK. FARTHER EAST... PRECEDING WARM TEMPERATURES WILL BE REPLACED BY MODIFIED COOLING POST-FROPA. PRECIPITATION WILL ACCOMPANY THE FRONTAL PASSAGE BUT WITH LIGHT/MODEST AMOUNTS. BY THE WEEKEND... THE QUESTION REMAINS HOW CLOSE TO THE COAST THE FRONT WILL REMAIN WHICH WILL ULTIMATELY DETERMINE THE AMOUNT/LOCATION OF ADDITIONAL/OVERRUNNING PRECIPITATION. ECMWF ENSEMBLES SUGGEST THE MAIN AXIS TO REMAIN JUST OFFSHORE BUT THE POTENTIAL EXISTS FOR A CLOSER POSITION... AND MUCH HEAVIER RAIN ALONG THE I-95 CORRIDOR. FRACASSO