EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1209 PM EDT MON JUN 08 2015 VALID 12Z THU JUN 11 2015 - 12Z MON JUN 15 2015 *** OVERVIEW *** A BROAD TROUGH OVER THE NORTHEAST/SOUTHEAST CANADA WILL PROGRESS EAST ON THURSDAY BEFORE UPSTREAM ENERGY PHASING OVER THE GREAT LAKES REGION SWINGS ANOTHER TROUGH THROUGH THE NORTHEAST THIS WEEKEND. OUT WEST...VIGOROUS MID-LEVEL ENERGY DIGGING DOWN FROM CANADA WILL LOWER HEIGHTS FROM THE NORTHWEST TO THE NORTHERN PLAINS WHILE THE CORE OF THE ENERGY CROSSES BRITISH COLUMBIA AND MOVES TOWARDS CENTRAL CANADA. LATER IN THE PERIOD...A RIDGE AMPLIFYING OVER ALASKA SHOULD ENCOURAGE DOWNSTREAM TROUGHING OVER THE NORTHWEST/SOUTHWEST CANADA BY EARLY NEXT WEEK. ACROSS THE SOUTHERN TIER OF THE NATION...AN ELONGATED TROUGH INITIALLY IN PLACE OVER THE SOUTHWEST WILL GRADUALLY WEAKEN WHILE LIFTING NORTHEAST OVER AN UPPER RIDGE BUILDING IN OVER THE SOUTHEAST THIS WEEKEND AND EARLY NEXT WEEK. *** MODEL GUIDANCE PREFERENCES *** THE LARGEST SPREAD IN MODEL GUIDANCE APPEARS TO BE WITH THE VIGOROUS MID-LEVEL ENERGY DIGGING DOWN FROM THE GULF OF ALASKA THIS WEEKEND. DETERMINISTIC RUNS...AND EVEN ENSEMBLE MEANS...ARE STILL SHOWING QUITE A BIT OF SPREAD WITH THE EVOLUTION OF THE UPPER TROUGH/CLOSED LOW MOVING THROUGH CANADA AND WITH THE ASSOCIATED COLD FRONT PRESSING THROUGH THE NORTHWESTERN CORNER OF THE NATION. IN THE EAST...ONE CONCERN WILL BE THE UNCERTAINTY WITH A SURFACE LOW DEVELOPING ALONG A FRONTAL BOUNDARY STRETCHED FROM THE MIDDLE MISSISSIPPI VALLEY TO THE NORTHERN MID-ATLANTIC STATES. MODELS ARE STILL SHOWING LARGE RUN-TO-RUN DIFFERENCES WITH THE DEPTH/TRACK OF THE LOW WHILE IT MOVES FROM THE CENTRAL U.S. TO THE EASTERN SEABOARD THIS WEEKEND. LATER IN THE FORECAST PERIOD...THE PRIMARY CONCERN WILL BE WITH JUST HOW FAR WEST AN UPPER RIDGE BUILDS IN OVER THE SOUTHEAST. GIVEN THE LARGE AMOUNT OF SPREAD AND UNCERTAINTY IN THE GUIDANCE...THE WPC FORECAST WAS BASED ON A MULTI-MODEL BLEND FOR DAYS 3-7. THIS RESULTED IN MINIMAL CHANGES TO CONTINUITY. *** SENSIBLE WEATHER HIGHLIGHTS *** ABOVE NORMAL TEMPERATURES WILL BE PREVALENT IN THE INTERIOR PACIFIC NORTHWEST UNTIL THE END OF THE PERIOD AS LOWER HEIGHTS INVADE THE REGION. THE SOUTHWEST TO THE CENTRAL U.S. SHOULD SEE BELOW AVERAGE TEMPERATURES WITH THE FRONTAL BOUNDARY STRETCHED FROM KANSAS TO THE NORTHEAST/NORTHERN MID-ATLANTIC STATES. TEMPERATURES IN THE NORTHEAST SHOULD BE NEAR TO ABOVE AVERAGE...DEPENDING ON THE STRENGTH OF THE DEVELOPING SURFACE WAVE AND RESULTANT WIND DIRECTION. THERE IS STILL A STRONG PRECIP SIGNAL FOR THE CENTRAL/HIGH PLAINS TO THE UPPER MIDWEST AND GREAT LAKES...NORTH OF THE SURFACE FRONT...AND AN ADVANCING MOISTURE POOL IN THE GULF MAY AID IN MODEST RAINS FOR THE NW/N GULF COAST THIS WEEKEND. GERHARDT