EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 247 AM EDT TUE JUL 21 2015 VALID 12Z FRI JUL 24 2015 - 12Z TUE JUL 28 2015 ...FLOW PATTERN OVERVIEW AND MODEL/UNCERTAINTY ASSESSMENT LATEST GUIDANCE CONTINUES TO BE IN GOOD MEDIUM-LARGE SCALE AGREEMENT WITH THIS UNUSUAL EAST PACIFIC FLOW PATTERN AND THE PROGRESSION OF MAJOR SYNOPTIC-SCALE FEATURES ACROSS CANADA AND INTO AND ACROSS THE LOWER 48. USED A CONSENSUS BLEND OF THE WELL CLUSTERED 12Z GFS/ECMWF FOR DETAIL AND 12 UTC GEFS/NAEFS/ECENS MEANS FOR CONTINUITY FRI INTO SUN. OPTED FOR A LESS CERTAIN BLEND OF JUST THOSE ENSEMBLES LATER SUN INTO NEXT TUE AMID GROWING FORECAST SPREAD. THESE COMBINATIONS SEEMS TO OFFER A REASONABLE STARTING POINT ACROSS THE CONUS AND VICINITY THAT MAINTAINS GOOD WPC CONTINUITY. AN UPPER RIDGE CENTERED OVER TEXAS WILL CONTINUE TO MEANDER AROUND THE RED RIVER VALLEY BUT OTHERWISE REMAIN IN PLACE...FORCING TROUGHING TO LINGER TO ITS EAST ALONG THE EASTERN SEABOARD. A STRONGER UPPER LOW IS FORECAST TO CIRCULATE THROUGH BRITISH COLUMBIA WITH HEIGHT FALLS WELL THROUGH THE NW US UNDERNEATH AS PER A SHUFFLING OF THE PATTERN ACROSS ALASKA. ...SENSIBLE WEATHER HIGHLIGHTS... HEAVIER CONVECTIVE PRECIP FOCUS WILL LIE NEAR TWO MAIN FRONTAL BOUNDARIES...THE FIRST ASSOCIATED WITH A CANADIAN SHORTWAVE AND ITS TRAILING SURFACE FRONT ACROSS THE US NORTHERN TIER AND THE OTHER EXTENDING SEWD INTO THE SOUTHEAST WITH A RATHER FAR SOUTHWARD POLAR FRONT INTO SOUTHERN GA OR NORTHERN FL BY SUN/MON. SEVERE WEATHER IS POSSIBLE PER SPC THU INTO FRI AHEAD OF THE FRONT IN THE DAKOTAS/MN. WILL HAVE TO WATCH FLORIDA AND THE SE COAST IN GENERAL FOR HEAVY RAINFALL POTENTIAL WITH THE SURFACE FRONT IN PLACE POOLING ABOVE AVERAGE MOISTURE. SCHICHTEL