EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1206 PM EDT MON JUN 16 2014 VALID 12Z THU JUN 19 2014 - 12Z MON JUN 23 2014 ...GENERAL FLOW PATTERN... THE MEDIUM RANGE PERIOD WILL FEATURE A LARGE SCALE MEAN RIDGE OVER THE CENTRAL U.S./CANADA...WITH TWO CLOSED VORTICES ANCHORED ON EITHER SIDE...ONE SPINNING IN THE NORTHEAST PACIFIC AND A SECOND ROTATING OVER EASTERN CANADA. A COMPACT UPPER LOW INITIALLY OVER THE NORTHERN ROCKIES/PLAINS IS FORECAST TO GRADUALLY LIFT NORTHEASTWARD WITHIN THE LARGE SCALE RIDGE AND MEANDER OVER THE NORTH CENTRAL U.S. LATE THIS WEEK AND INTO THE WEEKEND. BY SUNDAY...THE CLOSED LOW SHOULD BEGIN TO OPEN UP AND PROGRESS DOWNSTREAM THROUGH THE GREAT LAKES/UPPER MID-WEST. MEANWHILE...THE CLOSED VORTICES ON EITHER SIDE OF THE LARGE SCALE RIDGE SHOULD KEEP GENERAL TROUGHING IN PLACE JUST ALONG EITHER COAST. ...MODEL DIFFERENCES/PREFERENCES... THE GREATEST MODEL CONCERNS OVER THE CONUS APPEAR TO BE WITH THE EVOLUTION OF THE COMPACT UPPER LOW MOVING THROUGH THE NORTHERN TIER. ALTHOUGH THE MAJORITY OF GUIDANCE IS CURRENTLY IN FAIRLY GOOD AGREEMENT WITH THIS FEATURE...THE MODEL CONSENSUS IS ONLY A RELATIVELY RECENT TREND. ALSO...THE ECMWF HAS YET TO LOCK IN ON A SOLUTION...WITH THE LATEST 00Z RUN COMING IN MUCH MORE PROGRESSIVE THAN YESTERDAY'S 12Z RUN. THE DAY 3-7 WPC FORECAST STARTED WITH A COMBINATION OF THE 00Z GFS/GEFS MEAN AND THEN TRANSITIONED TO A BLEND OF THE 00Z GEFS/ECMWF ENSEMBLE MEAN. THIS SEEMED TO BEST REPRESENT THE CURRENT MODEL CONSENSUS...EXCLUDING THE 00Z ECMWF...AND ACCOUNT FOR ANY SMALL SCALE DETAIL DIFFERENCES. ...SENSIBLE WEATHER HIGHLIGHTS... HEAVY RAINS AND THUNDERSTORMS WILL BE POSSIBLE WITH A DEEP SURFACE CYCLONE SLOWLY LIFTING THROUGH THE NORTHERN PLAINS AND TRAILING COLD FRONT PUSHING ACROSS THE MIDWEST/CENTRAL PLAINS LATE THIS WEEK. HEAVY RAINS WILL ALSO BE POSSIBLE FROM THE UPPER MID-WEST TO THE MID-ATLANTIC COAST LATE THIS WEEK AND INTO THE WEEKEND...WHERE AN EAST-WEST ORIENTED FRONTAL BOUNDARY STRETCHED THROUGH THE REGION WILL SERVE AS A FOCUS FOR CONVECTION WITHIN A WARM AND UNSTABLE AIRMASS IN PLACE. LATE IN THE PERIOD...AN INCREASE IN DEEP MOISTURE SHOULD SUPPORT INCREASED SHOWER AND THUNDERSTORM ACTIVITY OVER PARTS OF THE ROCKIES/HIGH PLAINS. RAUSCH