EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1251 AM EST MON NOV 14 2016 VALID 12Z THU NOV 17 2016 - 12Z MON NOV 21 2016 ...WIDESPREAD SNOW POSSIBLE FOR THE NORTHERN ROCKIES INTO THE HIGH PLAINS LATER THIS WEEK... ...PATTERN OVERVIEW AND GUIDANCE PREFERENCES... A STRONG STORM SYSTEM WILL MOVE ACROSS THE CENTRAL/EASTERN STATES LATE THIS WEEK INTO THE WEEKEND, THOUGH MANY QUESTIONS REMAIN ON ITS DETAILS. UPPER PATTERN WILL REMAIN FAIRLY AMPLIFIED YET MOSTLY PROGRESSIVE. ENSEMBLES REMAIN IN GOOD AGREEMENT, BUT DIFFER MARKEDLY ON HOW QUICKLY THE WESTERN TROUGH EJECTS/DEEPENS AS IT LIFTS THROUGH THE PLAINS. THE 12Z ECMWF AND ITS ENSEMBLES WERE QUICKER BY NEARLY A DAY BY FRIDAY COMPARED TO THE SLOWER GEFS/CANADIAN MEMBERS. ECMWF ENSEMBLES HAVE BEEN A BIT MORE STEADY COMPARED TO THE GEFS ENSEMBLES, WHICH ONLY RECENTLY WERE SLOWER THAN PREVIOUS RUNS. THE DETERMINISTIC RUNS MIMICKED THEIR PARENT ENSEMBLES. THE 12Z UKMET/CANADIAN WERE SLOWER LIKE THE 12Z/18Z GFS. A MIDDLE GROUND SOLUTION WAS VERY CLOSE TO WPC CONTINUITY FROM DAY SHIFT (WHICH WAS ESSENTIALLY CONTINUITY FROM THE PREVIOUS NIGHT SHIFT) AND WAS DEEMED ACCEPTABLE AS A STARTING POINT. TOO MUCH RUN-TO-RUN WAVERING HAS OCCURRED THE PAST FEW DAYS IN BOTH THE GFS AND ECMWF TO GIVE WEIGHT TO ONE SOLUTION OVER THE OTHER. HOWEVER, IT DOES APPEAR THAT A ROBUST LOW WILL TRACK INTO THE GREAT LAKES SO AT LEAST THERE HAS BEEN SOME CONVERGENCE OF SOLUTIONS. TO THE EAST, AS THE SYSTEM NEARS THE COAST, ENSEMBLES CONTINUE TO ADVERTISE SOME NEGATIVE TILT TO THE UPPER TROUGH WHICH MAY SUPPORT A SFC LOW NEAR THE NY BIGHT THAT MAY ONLY SLOWLY LIFT NORTHEASTWARD NEXT MONDAY. THIS MAY BE COMPLICATED BY WHATEVER SYSTEM MAY BE LINGERING NEAR BERMUDA LATER THIS WEEKEND (NON-TROPICAL). THE WEST REMAINS UNDER THE INFLUENCE OF SW FLOW INTO THE PAC NW COAST AND NORTHERN CALIFORNIA, WITH THE POTENTIAL FOR A SOUTHWARD EXPANSION OF PRECIPITATION EARLY NEXT WEEK. MODELS HAVE NOT BEEN CONSISTENT ON HOW THE SFC FRONTAL STRUCTURE MAY EVOLVE OFF THE COAST, BUT ENSEMBLES SEEM TO FOCUS THE MOISTURE PLUME INTO NORTHERN CALIFORNIA (NEAR AND NORTH OF SAN FRANCISCO) BY NEXT MONDAY. ...WEATHER HIGHLIGHTS AND IMPACTS... THOUGH DETAILS REMAIN TO BE SORTED OUT, CONFIDENCE IS INCREASING IN A MODEST AND WIDESPREAD NORTHERN TIER SNOWFALL FROM WYOMING NORTHEASTWARD THROUGH THE DAKOTAS AND NORTHERN MINNESOTA AS THE SFC LOW HEADS TOWARD THE GREAT LAKES. ENSEMBLE RANGE IN AMOUNTS COVERS EVERYTHING FROM ZERO TO 20 INCHES ALONG THE CORRIDOR OF POTENTIALLY HEAVIEST SNOW -- SO IT IS IMPORTANT TO THINK PROBABILISTICALLY AT THIS TIME FRAME. ALONG/AHEAD OF THE COLD FRONT, RAIN WILL BREAK OUT INITIALLY OVER EASTERN KS/OK/TX ONCE SOME GULF MOISTURE GETS TAPPED AND THEN SPREAD INTO THE OH/TN VALLEY AND CENTRAL APPALACHIANS NEXT WEEKEND, AND FINALLY INTO THE NORTHEAST/MID-ATLANTIC. COLD AIR WRAPPING AROUND THE SFC LOW OVER THE RELATIVELY WARM GREAT LAKES SHOULD SUPPORT SOME LAKE-ENHANCED PRECIPITATION THIS WEEKEND INTO NEXT MONDAY. TEMPERATURES WELL ABOVE AVERAGE EAST OF THE FRONT WILL SLOWLY BE REPLACED BY NEAR TO BELOW AVERAGE TEMPERATURES (BY ABOUT 5-10 DEGREES F) THROUGH THE PERIOD. TEMPERATURES WILL WARM UP AGAIN IN THE WEST AND ROCKIES NEXT WEEKEND AS RIDGING MOVES IN. THE COLDEST AIR OF THE SEASON IS FORECAST TO OVERSPREAD THE NORTHERN TIER OF THE CENTRAL STATES, PERHAPS AIDED BY A FRESH SNOW. FRACASSO