EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1155 AM EDT SUN JUN 07 2015 VALID 12Z WED JUN 10 2015 - 12Z SUN JUN 14 2015 ...SENSIBLE WEATHER HIGHLIGHTS/OVERVIEW AND MODEL GUIDANCE PREFERENCES... A BROAD AND WEAK UPPER TROUGH WILL DOMINATE THE FLOW OVER THE WESTERN UNITED STATES ON DAYS 3 TO 7/WEDNESDAY THRU SUNDAY ALLOWING A WEAK SURFACE FRONT/TROUGH TO FORM ALONG ITS EASTERN FLANK OVER THE CENTRAL AND SOUTHERN PLAINS. WEAK UPPER TROUGHING OVER THE SOUTHEAST ON WEDNESDAY WILL YIELD TO RISING HEIGHTS AND UPPER RIDGING THAT WILL ALSO BECOME A DOMINANT WEATHER FEATURE LATER IN THE FORECAST PERIOD. MUCH OF THE SHORTWAVE ACTION WILL OCCUR ALONG THE NORTHERN BORDER OF THE US WITH ONE SHORTWAVE TROUGH CROSSING FROM THE UPPER LAKES TO NORTH OF NEW ENGLAND ON WEDNESDAY AND THURSDAY/DAYS 3 AND 4. THIS SYSTEM WILL DRAG A COLD FRONT ACROSS MIDWEST AND THEN ACROSS THE NORTHEAST THROUGH DAY 5. THE COMBINATION OF THESE LARGER SCALE SYSTEMS WILL BE TO SET UP A SURFACE FRONTAL BOUNDARY EXTENDING FROM THE SOUTHERN PLAINS ACROSS THE UPPER MISSISSIPPI VALLEY INTO THE NORTHEAST...PUTTING A FOCUS OF SHOWER/THUNDERSTORM DEVELOPMENT. SOUTH AND EAST OF THIS FRONT...THE DEVELOPMENT OF THE SOUTHEAST RIDGE MEANS INCREASINGLY WARM AND HUMID CONDITIONS ARE LIKELY ACROSS THE LOWER TO MID MISSISSIPPI VALLEY/LOWER OHIO VALLEY/SOUTHEAST AND MIDDLE ATLANTIC STATES THROUGH DAY 5/FRIDAY. THIS IS ALSO THE PERIOD WHEN MOST OF THE OVERNIGHT OPERATIONAL MODELS RESEMBLE THE ENSEMBLE MEANS WITH SOME DIFFERENCES CROPPING UP ON DAY 5/FRIDAY...SUCH AS A MORE PROGRESSIVE SURFACE LOW OVER THE MIDWEST IN THE GFS. LATER IN THE FORECAST ON DAYS 6 TO 7/SATURDAY AND SUNDAY...THE ECMWF MEANS SHOW SLIGHTLY MORE TROUGHING OVER THE NORTHEAST US TO THE NORTH OF THE SOUTHEAST RIDGE THAN EITHER THE GEFS/NAEFS MEANS. HOWEVER...THE CORRESPONDING OPERATIONAL RUNS APPEAR ALMOST REVERSED WITH RESPECT TO THE ECMWF/GFS. OVER THE NORTHWEST...THE ENSEMBLE MEANS ARE INDICATING SIGNIFICANT TROUGHING POSSIBLY IN THE FORM OF TWO SEPARATE SHORTWAVES...WITH A COLD FRONT MOVING SOUTH AND EASTWARD ACROSS THE PACIFIC NORTHWEST TOWARDS MONTANA AND THE NORTHERN PLAINS. HAVE GONE MORE TOWARD THE 00Z ECMWF ENSEMBLE MEAN SOLUTION FOR THE LOCATION OF THE SURFACE FRONT IN THESE AREAS AND THE SURFACE LOW IN MANITOBA. MEANWHILE...THE STATIONARY FRONT OVER THE MIDDLE OF THE COUNTRY APPEARS TO REMAIN EAST OF THE BROAD TROUGH AXIS OVER THE SOUTHWEST AND WILL LIKELY CONTINUE TO FOCUS SOME SHOWERS AND THUNDERSHOWERS FROM THE PLAINS TOWARD THE UPPER MISSISSIPPI VALLEY/MIDWEST BY SUNDAY DAY 7. RELATIVELY COOLER/DRIER CONDITIONS WILL PREVAIL ACROSS NEW ENGLAND AND POSSIBLY ACROSS PORTIONS OF THE NORTHERN MID ATLANTIC STATES WHILE COOL CANADIAN/NORTH PACIFIC AIR MAKES ITS WAY ACROSS THE NORTHWEST INTO MONTANA AND POSSIBLY NORTH DAKOTA. ELEVATED THUNDERSTORMS ARE LIKELY OVER THE WEST OUT AHEAD OF THIS SYSTEM. KOCIN