EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 859 PM EST FRI FEB 10 2017 VALID 12Z TUE FEB 14 2017 - 12Z SAT FEB 18 2017 PATTERN OVERVIEW/MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ A PERSISTENT CENTRAL TO EASTERN PACIFIC TROUGH IS EXPECTED, WITH DOWNSTREAM HIGH AMPLITUDE RIDGING ACROSS WESTERN NORTH AMERICA THAT SHIFTS SLOWLY EAST WITH TIME. THIS FAVORS A DOWNSTREAM TROUGH OVER THE GREAT LAKES AND NORTHEAST. DIFFERENCES REMAIN FOR THE SYSTEM MOVING ACROSS THE SOUTHERN TIER OF THE COUNTRY, THOUGH THEY APPEAR SMALLER THAN PREVIOUS DAYS. THE FLOW PATTERN FAVORS A SLOWER MOTION TO THIS SYSTEM AS NO KICKER SHORTWAVES APPEAR TO BE PRESENT TO EJECT THE LOW QUICKLY AWAY FROM THE SOUTHWEST. LARGE ISSUES CONTINUE ACROSS ATLANTIC CANADA AND NEW ENGLAND, WITH THE 12Z ECMWF ADVERTISING AN ALL-TIME RECORD-BREAKING LOW PRESSURE AREA FOR BOSTON WHICH IS NOT SEEN ON THE OTHER GUIDANCE IN 6-7 DAYS. WE USED A CONSENSUS OF THE 12Z NAEFS MEAN, 12Z ECMWF/12Z ECMWF ENSEMBLE MEAN, 12Z UKMET, 12Z CANADIAN, AND 18Z GFS FOR PRESSURES, WIND GRIDS, AND 500 HPA HEIGHTS INTO THURSDAY. THEREAFTER, USED INCREASING PERCENTAGES OF THE 12Z ECMWF AND 12Z NAEFS MEANS TO DEAL WITH DETAIL ISSUES ACROSS THE WEST AND NEW ENGLAND, WHICH KEPT REASONABLE CONTINUITY. THE TEMPERATURES, PRECIPITATION CHANCES, CLOUDS, DEW POINTS, AND WEATHER GRIDS USED A LARGER PERCENTAGE OF ENSEMBLE MEAN SOLUTIONS TO DEAL WITH THE GREATER UNCERTAINTY IN THOSE FIELDS. THE PLAN FOR THE DAYS 4-7 QPF IS TO START WITH A SOLUTION RESEMBLING A COMPROMISE OF THE 18Z GFS/12Z ECMWF WHICH IS WEIGHTED A LITTLE MORE GFS-HEAVY IN NEW ENGLAND. IF THE 00Z GFS APPEARS REASONABLE, ITS IDEAS WILL BE INCORPORATED INTO THE PRECIPITATION FORECAST. WEATHER HIGHLIGHTS/THREATS ~~~~~~~~~~~~~~~~~~~~~~~~~~ THE EJECTING UPPER LOW ACROSS THE SOUTHERN TIER OF THE COUNTRY WILL GENERATE ENHANCED AREAS OF RAIN, POTENTIALLY HEAVY, FROM TX EASTWARD ALONG THE GULF COAST. WITH THE DOWNSTREAM FRONT MOVING SLOWLY THROUGH FL, A SHOWERY PERIOD IS EXPECTED. THE NEXT PACIFIC CYCLONE OFF THE COAST THURSDAY AND POSSIBLY ONSHORE FRIDAY SHOULD GET CLOSE ENOUGH TO PRODUCE WIDESPREAD PRECIPITATION FROM NORTHERN CA NORTH ACROSS OR AND WA, EVENTUALLY EXTENDING INLAND INTO THE NORTHERN ROCKIES AND TERRAIN IN AND NEAR THE GREAT BASIN. WITH ONE SNOWSTORM EJECTING AWAY FROM NEW ENGLAND MONDAY, IT IS UNCLEAR IN THE POTENTIAL OF A SECOND SNOW STORM FOR THE REGION THURSDAY INTO NEXT SATURDAY. FOR NOW, KEPT PRECIPITATION AMOUNTS CONSERVATIVE IN THIS AREA, WHICH CAN BE INCREASED IN THE DAYS AHEAD IF THE CURRENT CLOUDY FORECAST SITUATION CLEARS UP. THE NORTHERN PLAINS AND UPPER MS VALLEY SEE ABOVE NORMAL TEMPERATURES AS THE DEEP LAYER RIDGE OUT WEST WITH ABOVE NORMAL MID-LEVEL HEIGHTS STARTS DRIFTING EAST INTO THE HIGH PLAINS. ABOVE NORMAL TEMPERATURES ACROSS A WIDE PORTION OF THE ROCKIES/GREAT BASIN/SOUTHWEST US. LATE IN THE PERIOD, COOLING IS EXPECTED NEAR THE WEST COAST AS THE FRONTAL ZONE MARCHES THROUGH THE INTERMOUNTAIN WEST AND MID-LEVEL HEIGHTS FALL BELOW AVERAGE. DESPITE THE EXPECTED TROUGHING ACROSS THE NORTHEAST AND SOMEWHAT BELOW NORMAL 500 HPA HEIGHTS THROUGH THE PERIOD, TEMPERATURES SHOULD BE ROUGHLY NEAR SEASONAL NORMS FOR MUCH OF THE EAST, WITH A SHORT BOUT OF BELOW NORMAL TEMPERATURES FROM THE MID-SOUTH INTO THE SOUTHEAST THURSDAY INTO FRIDAY. ROTH/PETERSEN