EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1100 AM EST SAT NOV 26 2016 VALID 12Z TUE NOV 29 2016 - 12Z SAT DEC 03 2016 ...MUCH NEEDED RAIN IN THE FORECAST FOR THE EASTERN U.S. NEXT WEEK... ...OVERVIEW... THE MEDIUM-RANGE PERIOD WILL FEATURE THE FORMATION OF A LARGE-SCALE LOW PRESSURE SYSTEM OVER THE NORTHERN PLAINS AND UPPER MIDWEST WITH AN ASSOCIATED STRONG COLD FRONT SWEEPING ACROSS THE EASTERN U.S. BY THE LATTER HALF OF NEXT WEEK...AN ANOMALOUS UPPER LOW IS FORECAST TO DROP SOUTHEASTWARD FROM THE EASTERN PACIFIC INTO THE VICINITY OF DESERT SOUTHWEST INTO NORTHERN MEXICO. ...MODEL PREFERENCES... MODEL GUIDANCE IS TRENDING TOWARD A SLOWER AND MORE WRAPPED-UP CYCLONE TO BE CENTERED OVER THE UPPER MIDWEST BY DAY 3 TUESDAY. THE GFS SOLUTIONS CONTINUE TO BE ON THE FAST SIDE AS MORE ENERGY IS SENT DOWNSTREAM INTO THE NORTHEASTERN U.S. AND SOUTHEASTERN CANADA. THIS BEHAVIOR SEEMS TO BE A CONSEQUENCE OF A TYPICAL BIAS IN THE MODEL. THUS...THE DECISION WAS TO USE MAINLY A BLEND OF THE 00Z AND YESTERDAY'S 12Z ECMWF SOLUTIONS WITH A SMALL PERCENTAGE OF THE 06Z GFS THROUGH DAY 5 THURSDAY. BEYOND DAY 5...AS THE EASTERN U.S. LOW MOVES OUT OF NEW ENGLAND...THE GEFS MEAN APPEARS USABLE. THEREFORE...THE DAY 6 AND 7 PRESSURE FIELDS WERE A BLEND OF THE LATEST TWO RUNS OF THE ECMWF...THE 00Z EC MEAN...AS WELL AS THE 00Z NAEFS ENSEMBLE MEAN. THIS BLEND YIELDS A DEEPER AND BETTER-DEFINED UPPER LOW IN THE DESERT SOUTHWEST THAN WHAT IS SHOWN IN THE 06 GEFS MEAN. ...WEATHER HIGHLIGHTS/THREATS... LARGE-SCALE LOW PRESSURE SYSTEM CENTERED IN THE UPPER MIDWEST WILL PROMOTE WINTRY PRECIPITATION IN THE NORTHERN PLAINS AND NORTHERN NEW ENGLAND THROUGH THURSDAY. CONFIDENCE IS ABOVE AVERAGE IN THE EXPECTATION FOR ONE OR MORE AREAS OF HEAVY RAIN ALONG/AHEAD OF A WAVY FRONT MAKING ITS WAY ACROSS THE EAST. CURRENT INDICATIONS ARE FOR ONE RELATIVE MAXIMUM TO BE CENTERED NEAR THE MID-LWR MS VLY EARLY IN THE PERIOD. THIS AREA OF ENHANCED RNFL HAS TENDED TO BE MORE STABLE IN THE GUIDANCE THAN THE SECOND RELATIVE MAXIMUM FCST TO EXTEND FROM THE LWR MS VLY-SRN APLCHNS INTO THE MID ATLC/NORTHEAST. CONSULT SPC OUTLOOKS FOR LATEST INFO REGARDING STRONG TO SEVERE CONVECTION POTENTIAL. CURRENT OUTLOOK SHOWS AN AREA OF INTEREST FROM ERN TX INTO SWRN MS. MOST WINTRY PCPN SHOULD BE CONFINED TO THE NORTHERN TIER OF THE COUNTRY. SOME AREAS MAY SEE A PERIOD OF STRONG WINDS. OUT WEST...EXPECT THE MAJORITY OF PCPN TO FOCUS FROM THE PAC NW INTO THE NRN-CNTRL ROCKIES. THERE MAY BE SOME LOCALIZED ENHANCEMENT BUT IN GENERAL TOTALS SHOULD BE MODERATE. VERY LATE NEXT WEEK THERE COULD BE SOME DEVELOPMENT/EXPANSION OF PRECIPITATION OVER PARTS OF THE GREAT BASIN/SOUTHWEST/FOUR CORNERS DEPENDING ON EVOLUTION OF ENERGY ALOFT. BY NEXT SATURDAY...THE RAIN SHIELD SHOULD BE EXPANDING INTO MUCH OF TEXAS. COMBINATION OF EVOLUTION ALOFT AND HIGH PRESSURE BUILDING INTO THE INTERIOR WEST/GREAT BASIN MAY PROMOTE SEPARATE SANTA ANA WIND EPISODES LATE MONDAY INTO TUESDAY...AND THEN AGAIN FROM THURSDAY INTO NEXT SATURDAY AS "INSIDE SLIDER" SHORTWAVES ALOFT MOVE BY THE SIERRA NEVADA...ENCOURAGING FOEHN WINDS OFF THE TRANSVERSE RANGES OF SOUTHERN CA. THE WARM SECTOR AHEAD OF THE ADVANCING PLAINS FRONT WILL CONTAIN A BROAD AREA OF TEMPS 10-20F ABOVE NORMAL. FORECAST LOW TEMPERATURES MAY EXCEED PLUS 20F ANOMALIES AT SOME LOCATIONS. MOST OF THE WEST WILL SEE BELOW NORMAL TEMPS THROUGH THE PERIOD. ASIDE FROM LOCALIZED COLDER POCKETS... ANOMALIES SHOULD BE MODERATE MON-WED. COVERAGE OF MINUS 10F OR GREATER COLD ANOMALIES MAY INCREASE OVER CNTRL-SRN PORTIONS OF THE WEST LATE IN THE WEEK AS DEEPER TROUGHING ALOFT SETTLES OVER THE REGION. KONG/ROTH