EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1111 AM EST FRI FEB 07 2014 VALID 12Z MON FEB 10 2014 - 12Z FRI FEB 14 2014 ...OVERVIEW... A LOW AMPLITUDE LONGWAVE TROUGH IS EXPECTED TO REMAIN OVER THE CENTRAL CONUS NEXT WEEK/MON-FRI...WITH THE MOST SIGNIFICANT AND IMPACTFUL WEATHER INCLUDING WET CONDITIONS ACROSS THE PACIFIC NORTHWEST...INITIALLY COLD BUT WARMING CONDITIONS ACROSS THE PLAINS/MIDWEST/GREAT LAKES...AND WET CONDITIONS ACROSS THE SOUTHEAST. THE COMPLEXITY OF THE OVERALL PATTERN THAT INCLUDES A RETROGRADING BLOCK OVER ALASKA...A HIGHLY-DETAILED AND DECAYING UPPER LOW OVER THE NORTHEAST PACIFIC...AND ITS POSSIBLE INTERACTION WITH SEPARATE NORTHERN STREAMS OVER NUNAVUT AND SIBERIA CREATE ABOVE AVERAGE UNCERTAINTY FOR DAYS 3/4...AND HIGH UNCERTAINTY FOR DAYS 6/7. RECENT VERIFICATION OF GLOBAL GUIDANCE CONFIRMS THE LOW CONFIDENCE LEVELS LATE IN THE PERIOD DUE TO SIMILARITIES OF THE VERIFIED PATTERN TO THE ANTICIPATED ONE. ...MODEL PREFERENCES AND SENSIBLE WEATHER HIGHLIGHTS... ACROSS THE PACIFIC NORTHWEST/N. CA/ N. ROCKIES...PREFER A SOLUTION CLOSEST TO THE GLOBAL ENSEMBLE MEANS THAT AVERAGES THE FASTER/STRONGER 00Z GFS WITH THE SLOWER 06Z GFS/00Z ECMWF. THE SOLUTION SPREAD IS UNUSUALLY HIGH FOR JUST A DAY 3/4 FORECAST...BUT IS CONSISTENT WITH THE UNCERTAINTY IN HOW THE UPPER CYCLONE OFFSHORE WILL ERODE. HEAVY LOWER ELEVATION RAINS AND HIGHER ELEVATION SNOWS SHOULD AFFECT THE REGION BY NEXT TUESDAY. AFTER A BRIEF RESPITE IN THE HIGHER PRECIPITATION RATES...ANOTHER SURGE OF HEAVY PRECIPITATION MAY RETURN TO THE REGION BY DAY 7/FRI...ALTHOUGH IT IS POSSIBLE THAT THIS SUBSEQUENT EVENT MAY INFLUENCE AREAS SLIGHTLY MORE TO THE NORTH. AGAIN...RELIED UPON THE GLOBAL ENSEMBLE MEANS TO ADDRESS THE SPREAD LARGELY REPRESENTED BY THE FASTER/STRONGER 00Z GFS ON ONE END WITH THE SLOWER 06Z GFS/00Z ECMWF ON THE OTHER. ACROSS THE CENTRAL AND EAST...USED AN AVERAGE OF THE GLOBAL ENSEMBLE MEANS AS A WHOLE BUT WITH CONSIDERABLE MANUAL ADJUSTMENTS LATER IN THE PERIOD THAT INDICATES LITTLE OR NO CONFIDENCE IN MODEL DETAILS. FOR DAY 3/MON...PREFER THE WEAKER 00Z ECMWF/00Z ECMWF ENSEMBLE MEAN WITH LOW PRESSURE NEAR THE NORTHEAST COAST VERSUS THE STRONGER AND SEEMINGLY UNLIKELY 06Z GEFS MEAN GIVEN PERSISTENT UPPER LEVEL CONFLUENCE ACROSS THE REGION. MAINLY LIGHT SNOWS ARE EXPECTED WITH THIS SYSTEM. MEANWHILE...RAIN WITH SOME MIXED PRECIPITATION WILL BEGIN TO DEVELOP ACROSS EAST TEXAS AND LOWER MS VALLEY AS THE NEXT SHORTWAVE TROUGH ENTERS THE REGION...BEFORE POSSIBLY EXPANDING ACROSS THE ENTIRE EAST COAST LATER IN THE PERIOD AS MULTIPLE SYSTEMS APPROACH FROM THE WEST AND POSSIBLY INTERACT WITH IT. BY DAY 6/THU...THE 00Z ECMWF LIES NEAR THE NORTHERN EDGE OF THE GUIDANCE WITH A SERIES OF LOWS DEEPENING NEAR THE MID-ATLANTIC COAST BEFORE MOVING TOWARD NOVA SCOTIA BY DAY 7/FRI. THE 06Z GFS DEVELOPS THE INITIAL LOW FARTHER SOUTH CLOSER TO THE GLOBAL ENSEMBLE MEANS BUT EVENTUALLY JOINS THE ECMWF OVER THE NORTHEAST/NEW ENGLAND. HOWEVER...THESE SOLUTIONS REQUIRES VERY COMPLICATED AND PERFECTLY-TIMED INTERACTIONS WITH MULTIPLE SYSTEMS...THAT WHILE PLAUSIBLE...CONTAIN SUCH LOW CONFIDENCE THAT WILL DOWNPLAY THEM SIGNIFICANTLY. INSTEAD...PREFER TO EMPHASIZE THE SOUTHERN STREAM THAT ALLOWS FOR LESS NORTHERN/SOUTHERN STREAM INTERACTION. IN TURN...THIS RESULTS IN A LESS IMPACTFUL NORTHERN STREAM SYSTEM CROSSING THE GREAT LAKES AND ALLOWS HIGH PRESSURE OVER NEW ENGLAND TO REMAIN MORE ANCHORED IN PLACE THAN DEPICTED BY CURRENT GUIDANCE THAT WOULD PREVENT THE SOUTHERN STREAM LOW FROM MOVING SO FAR NORTH. JAMES