EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1100 AM EST TUE FEB 07 2017 VALID 12Z FRI FEB 10 2017 - 12Z TUE FEB 14 2017 ...PATTERN OVERVIEW/GUIDANCE EVALUATION/PREFERENCES... AS A SIGNIFICANT TROUGH LIFTS NORTHEARWARD OFF THE NORTHEAST COAST...HIGH PRESSURE AND COLD AIR IN THE WAKE OF THE SYSTEM WILL BE BRIEF AND TRANSIENT AS HIGH PRESSURE MOVES OFF THE EAST COAST ON DAY 3/FRIDAY. BEHIND THIS SYSTEM...NEARLY ZONAL FLOW NATIONWIDE WILL BEGIN TO BUCKLE AS A SERIES OF PACIFIC TROUGHS MOVES EASTWARD INTO THE WESTERN US. AS ONE TROUGH MOVES ONSHORE ACROSS THE WEST ON DAY 4/SATURDAY...A SEPARATE MORE NORTHERLY SYSTEM WILL MOVE ACROSS THE NORTHWEST. THE EVOLUTION OF THESE TWO TROUGHS FOLLOW VERY DIFFERENT PATHS OVER THE NEXT SEVERAL DAYS AS THE WESTERN TROUGH CONTINUES TO DROP SOUTHWARD INTO THE SOUTHWESTERN US AND CUT OFF WHILE THE NORTHERN SYSTEM REMAINS PROGRESSIVE AND MOVES EASTWARD ACROSS THE NORTHERN THIRD OF THE COUNTRY. BY DAY 5/SUNDAY...AS THE TROUGH BUILDS OVER THE SOUTHWEST AND THE OTHER SYSTEM MOVES EASTWARD...SIGNIFICANT UPPER RIDGING FOLLOWS IN THEIR WAKE OVER THE WEST COAST. MEANWHILE...RIDGING ALSO BUILDS NORTHWARD AHEAD OF THESE TWO SYSTEMS ACROSS EASTERN US ON DAY 5/SUNDAY. ON THE FINAL TWO DAYS OF THE FORECAST...THE SOUTHWESTERN TROUGH INITIALLY REMAINS OVER THE SOUTHWEST WHILE THE NORTHERN SYSTEM CONTINUES EASTWARD TOWARD THE GREAT LAKES AND NORTHEAST. COMBINED WITH THE RIDGE OVER THE NORTHWEST US...LARGE SCALE CONFLUNCE BECOMES PRONOUNCED OVER THE MIDDLE OF THE COUNTRY ON DAY 6/MONDAY AND MOVES EASTWARD AS THE NORTHERN TROUGH PROGRESSES TOWARD THE NEW ENGLAND COAST. WHILE AN UPPER RIDGE REMAINS SIGNIFICANT OVER THE SOUTHEAST US...THIS PATTERN FAVORS A STRONG CONFLUENT UPPER SIGNAL FROM THE CENTRAL US EASTWARD. ONLY ON DAY 7/TUESDAY DOES THE SOUTHWESTERN TROUGH APPEAR TO START MOVING SLIGHTLY MORE EASTWARD. IN GENERAL...THE OVERNIGHT ENSEMBLES CLEARLY DEPICT THIS EVOLUTION ESPECIALLY THROUGH DAY 5. THE OPERATIONAL 06Z GFS AND 00Z ECMWF MATCH IMPORTANT DETAILS SEEN IN THE ENSEMBLE MEANS WHILE THE 00Z OPERATIONAL UKMET APPEARED OUTH OF PHASE WITH SEVERAL SYSTEMS ESPECIALLY THE SOUTHWESTERN ONE RELATIVELY EARLY IN THE FORECAST AND WAS WEIGHTED VERY LITTLE IN THE FINAL SELECTION OF BLENDS. THE 00Z CANADIAN APPEARED RELATIVELY SIMILAR IN GENERAL DETAILS WITH RESPECT TO THE ENSEMBLES AND 06Z GFS/00Z ECMWF. WITH THE ENSEMBLES...THE ECMWF APPEARS LATE IN THE FORECAST ON DAYS 6 AND 7 TO HAVE A MORE SIGNIFICANT TROUGH AND POSSIBLE CYCLONIC DEVELOPMENT WITH THE NORTHERN SYSTEM WHILE THE GEFS ENSEMBLES SEEM FLATTER AND LESS AMPLIFIED. THEREFORE...A RATHER STRAIGHTFORWARD 60/40 BLEND OF THE OPERATIONAL RUNS/ENSEMBLE MEANS THROUGH DAY 5 INCLUDED THE 00Z ECMWF/06Z GFS/06Z GEFS/00Z NAEFS AND 00Z ECMWF ENSEMBLE MEANS. THAT RATIO WAS REVERSED IN THE FINAL TWO DAYS SINCE THERE IS AN INCREASE IN UNCERTAINTY AS THE ECMWF RUNS ALSO BEGAN TO SUGGEST A FEATURE MOVING EASTWARD THROUGH THE WESTERN RIDGE ACROSS SOUTHWESTERN CANADA ON DAY 6/MONDAY AND THEN MOVING EAST SOUTHEASTWARD ACROSS THE SOUTHERN CANADIAN PLAINS/NORTHERN PLAINS BY THE END OF THE FORECAST. THE MEDIUM RANGE PROGS ACCOUNT FOR THIS POTENTIAL FEATURE AS A COLD FRONT ENTERING MINNESOTA ON DAY 7. ...WEATHER HIGHLIGHTS/THREATS... THE COLDEST AIR DURING THE FORECAST PERIOD WILL START OFF IN NEW ENGLAND AT THE START OF DAY 3/FRIDAY BUT WILL QUICKLY MOVE EASTWARD AND MODIFY AS THE HIGH MOVES OFFSHORE. VERY MILD AIR WILL COVER MUCH OF THE MIDDLE OF THE NATION WITH TEMPERATURE ANOMALIES EXCEEDING 15 TO 25 DEGREES. AND EVEN THOUGH THERE IS A TROUGH AND ASSOCIATED COLD FRONT MOVING ACROSS THE WESTERN US ON FRIDAY...THE AIRMASS IS PACIFIC IN NATURE SO TEMPERATURES WILL REMAIN NEAR NORMAL ALONG THE WEST COAST BUT ABOVE NORMAL ACROSS THE INTERMOUNTAIN WEST. THE MILD TEMPERATURES WILL AGAIN BE FOCUSSED ACROSS THE CENTRAL TO SOUTHERN PLAINS AND THEN SPREAD EASTWARD INTO THE EAST ON DAY 4/SATURDAY. BY DAY 5/SUNDAY...TEMPERATURES WILL AVERAGE 15 TO 20 DEGREES ABOVE AVERAGE ACROSS MUCH OF THE EAST. WITH UPPER LEVEL CONFLUENCE PROMOTING THE DEVELOPMENT OF HIGH PRESSURE ACROSS THE WESTERN STATES...TEMPERATURES WILL BE BELOW NORMAL BUT NOT UNUSUALLY COLD ACROSS THE WEST...ESPECIALLY THE HIGHER ELEVATIONS. HOWEVER...THE COLDER AIR STILL REMAINS PACIFIC IN ORIGIN AND BY DAY 6/MONDAY AS COLDER AIR MOVES EASTWARD BEHIND A FRONT ASSOCIATED WITH THE NORTHERN TROUGH...TEMPERATURES BEHIND THE FRONT WILL BE COOLER BUT MAY STILL REMAIN ABOVE SEASONAL NORMS. BY DAY 7/TUESDAY...COOLER AIR WILL BE MOVING BACK ACROSS THE NORTHEAST WITH PERHAPS THE ONLY PARAT OF THE NATION WITH LEGITMATELY COLD TEMPERATURES. WITH PRECIPITATION A POSSIBILITY ACROSS THE SOUTHERN PLAINS ASSOCIATED WITH THE TROUGH OVER THE SOUTHWESTERN US...THIS AREA MAY ALSO BE ONE OF THE FEW OTHER AREAS TO EXPERIENCE BELOW NORMAL TEMPERATURES DUE TO PRECIP/CLOUD COVER LATER IN THE FORECAST PERIOD. MOSTLY LIGHT SNOW IS EXPECTED IN THE NORTHEAST ON LATE FRIDAY INTO SATURDAY AS THE HIGH MOVES OFFSHORE AND AND A WEAK DISTURBANCE/WARM AIR ADVECTION CROSSES THE GREAT LAKES. MORE HEAVY RAIN FOR THE PACIFIC COAST AND MOUNTAIN SNOW WILL ACCOMPANY THE DUAL TROUGHS CROSSING THE PACIFIC STATES ON FRIDAY INTO SATURDAY. AS THE NORTHERN TROUGH MOVES EASTWARD...THERE IS THE POTENTIAL FOR SHOWERS AND SNOW ALONG THE NORTHERN FRINGE OF THE PRECIPITATION FIELD ACROSS THE CENTRAL TO NORTHERN PLAINS/UPPER MISSISSIPPI VALLEY AS A SURFACE LOW MOVES EAST NORTHEASTWARD TOWARD THE GREAT LAKES. ANOMALOUS WARMTH WILL DOMINATE THE PICTURE WITH A LACK OF ARCTIC AIR ENTERING THE U.S. THE LARGEST DEPARTURES FROM CLIMATOLOGY ARE EXPECTED OVER THE CENTER OF THE COUNTRY WITH HIGHS LIKELY 20 TO 30 DEGREES ABOVE NORMAL OVER THE CENTRAL/SOUTHERN PLAINS. ON SATURDAY...HIGHS INTO THE UPPER 70S ARE LIKELY AS FAR NORTH AS SECTIONS OF KS WHILE 80S AND PERHAPS A FEW LOW 90S ARE POSSIBLE ACROSS THE LONE STAR STATE. OVERNIGHT LOWS SHOULD BE QUITE MILD OVER QUITE A FEW LOCATIONS OF THE COUNTRY LIKELY NEARING OR SURPASSING DAILY RECORDS FOR WARM MINIMUM TEMPERATURES. THE ONLY TRUE COOL SPOT WILL BE UNDERNEATH THE UPPER LOW ACROSS THE SOUTHWESTERN U.S. AND EXTENDING INTO THE FOUR CORNERS WITHIN REGIONS OF PRECIPITATION. SPEAKING OF WHICH...AFTER RAIN/SNOW EARLY IN THE PERIOD...CONDITIONS ALONG THE WEST COAST SHOULD BECOME MUCH DRIER GIVEN SUFFICIENT HEIGHT RISES. ALL OF THE EARLY ACTIVITY WILL TRANSLATE EASTWARD INTO THE FOUR CORNERS/SOUTHERN TO CENTRAL ROCKIES. ACROSS THE EASTERN HALF OF THE COUNTRY...LIGHT TO MODERATE RAINFALL SHOULD EXTEND ALONG THE ADVANCING COLD FRONT WITH THE ECMWF BEING MUCH WETTER GIVEN A MUCH MORE DEFINED SYSTEM. AS THIS SYSTEM DEEPENS FURTHER...A WINTRY PRECIPITATION THREAT IS LIKELY FROM THE GREAT LAKES INTO INTERIOR NEW ENGLAND BY LATE SUNDAY. AS THE FRONT MOVES SOUTHWARD ACROSS THE SOUTHERN PLAINS...THE SOUTHWESTERN TROUGH/SOUTHWESTERLY FLOW ALOFT AND GULF MOISTURE WILL LIKELY LEAD TO RAIN ACROSS THE SOUTHERN PLAINS LATE IN THE FORECAST. KOCIN