EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 137 AM EDT FRI MAY 05 2017 VALID 12Z MON MAY 08 2017 - 12Z FRI MAY 12 2017 ...PATTERN OVERVIEW AND GUIDANCE EVALUATION... THE TRANSITION FROM WINTER TO SUMMER INCLUDES THE SPINNING DOWN OF THE JET STREAM, WHICH OFTEN LEADS TO CLOSED OFF FEATURES OVER THE NORTHERN HEMISPHERE. NEXT WEEK IS NO EXCEPTION. A STUBBORN CLOSED LOW IS FORECAST TO LINGER/WOBBLE OVER/NEAR THE NORTHEAST WHILE ANOTHER SLOWLY EXITS THE SOUTHWEST INTO THE SOUTHERN PLAINS. YET ANOTHER CLOSED LOW IS FORECAST TO DIP CLOSE TO THE PACIFIC NORTHWEST LATER NEXT WEEK. THE MODELS/ENSEMBLES AGREE ON THE SYNOPTIC EBB AND FLOW BUT DIFFER IN A FEW AREAS. A BLEND OF THE GUIDANCE SERVES WELL AS A STARTING POINT FOR MON-THU BEFORE BIGGER DIFFERENCES EMERGE. BIGGER AREAS OF CONTENTION LIE IN THE EAST WITH THE N-S POSITION OF THE SFC FRONTAL BOUNDARY ON THE BACK SIDE OF THE UPPER LOW AND IN THE SOUTHERN PLAINS BY NEXT THU/FRI WITH THE EXIT SPEED OF THE UPPER LOW OUT OF THE FOUR CORNERS REGION. HERE, THE GFS REMAINS QUICKER THAN THE ECMWF/CANADIAN, AND PUT MORE WEIGHT IN THESE SLOWER SOLUTIONS (ALONG WITH THE ECMWF ENSEMBLE MEAN). IN BETWEEN, THE SHAPE OF THE UPPER RIDGE AND CLOSED HIGH WILL INFLUENCE HOW THE NORTHEASTERN UPPER LOW EVOLVES AND DANCES WITH OTHER MID-LEVEL VORTICITY. ...WEATHER HIGHLIGHTS... IN THE WEST, THE SLOWLY FILLING CLOSED UPPER LOW WILL SEND EMBEDDED SHORTWAVES INTO THE ROCKIES WHICH WILL SUPPORT LOCALLY MODEST RAIN AND HIGHER ELEVATION SNOW (ESPECIALLY NEAR/ALONG THE TRACK OF THE UPPER LOW). THIS WILL EXPAND EASTWARD INTO THE PLAINS LATER IN THE WEEK, AIDED BY GULF OF MEXICO MOISTURE INFLUX. SEVERE CONVECTION MAY BE POSSIBLE -- SEE THE LATEST SPC OUTLOOKS. TEMPERATURES WILL BE NEAR/BELOW AVERAGE UNDER THE LOWER HEIGHTS BUT ABOVE AVERAGE NEAR THE RIDGE AXIS, ESPECIALLY INTO WESTERN MONTANA WED-FRI. IN THE EAST, UPPER LOW WILL ENSURE RATHER CLOUDY AND SHOWERY WEATHER FOR MUCH OF THE PERIOD WITH COOLER THAN AVERAGE TEMPERATURES. 'SELF-DESTRUCTIVE SUNSHINE' SUPPORTS WIDESPREAD AFTERNOON SHOWERS, MODULATED BY THE WOBBLING OF THE UPPER LOW AND ORBITING VORTICITY WANDERLINGS. SNOW IS POSSIBLE IN THE HIGHEST ELEVATIONS (MON/TUE IN THE ADIRONDACKS, GREEN/WHITE MOUNTAINS, AND MAHOOSUCS) AND NEAR THE COLD CORE OF THE UPPER LOW THOUGH SURFACE TEMPERATURES WILL BE ABOVE FREEZING AT LEAST DURING THE DAY. FRACASSO