EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1153 AM EDT MON JUN 26 2017 VALID 12Z THU JUN 29 2017 - 12Z MON JUL 03 2017 ***PATTERN OVERVIEW AND MODEL PREFERENCES*** MODEL GUIDANCE THIS MORNING ARE IN OVERALL GOOD AGREEMENT WITH THE GENERAL SYNOPTIC PATTERN THROUGH NEXT MONDAY. A BROAD UPPER TROUGH LIFTING OUT OF NEW ENGLAND ON DAY 3/THU WILL BE REPLACED BY A ZONAL FLOW WITH A SHORTWAVE TROUGH MOVING INTO THE GREAT LAKES AS THE NEXT SIGNIFICANT TROUGH DIGS DOWN THE NORTHERN ROCKIES/HIGH PLAINS AND MIGRATES INTO THE NORTHEAST BY NEXT MONDAY. THE DEPTH AND TIMING OF THE UPPER AIR AND THE ASSOCIATED SURFACE FEATURES SHOWN BY VARIOUS MODELS APPEAR PRETTY GOOD. THE 00Z UKMET HAS AN ANOMALOUSLY DEEP LOW MOVING INTO THE GREAT LAKES ON DAY 5/SATURDAY. THIS SCENARIO IS TAKEN OUT OF CONSIDERATION. BY DAYS 6 AND 7...THE GFS IS MORE ENTHUSIASTIC WITH THE FORMATION OF A LOW PRESSURE SYSTEM OVER THE CENTRAL HIGH PLAINS. THE ECMWF SHOWS ONLY A VERY MODEST DEVELOPMENT WITH THIS FEATURE. A BLEND OF THE 00Z EC MEAN WITH THE 06Z GEFS WAS USED TO ACCOUNT FOR THIS FEATURE. ALSO NOTED WAS THAT THE 06Z GFS AGREES BETTER WITH THE 00Z ECMWF/EC MEAN THAN THE 00Z GFS SOLUTIONS. THUS...THE WPC MEDIUM-RANGE GRID FIELDS WERE DERIVED USING A 50-50 BLEND OF THE 06Z GFS WITH THE 00Z ECMWF BEGINNING ON DAY 3/THU...GRADUALLY TRENDING TOWARD A 50-50 BLEND OF THE 00Z EC MEAN AND THE 06Z GEFS BY DAY 7/MONDAY. ***SENSIBLE WEATHER*** AS THE UPPER TROUGH LIFTS OUT OF THE NORTHEAST AND A ZONAL FLOW GETS ESTABLISHED ACROSS THE NORTHERN TIER...A COLD FRONT WILL BECOME NEARLY STATIONARY FROM THE GREAT LAKES DOWN ACROSS THE MIDWEST INTO THE NORTHERN PLAINS AS THE BERMUDA HIGH HOLDS STRONG AND EXTENDS WESTWARD INTO THE DEEP SOUTH. THIS WILL LIKELY FOCUS SHOWERS AND THUNDERSTORMS AHEAD OF THE STATIONARY FRONT AND LEAD TO THE POSSIBILITY OF HEAVY RAIN ACROSS THE MIDWEST CONTINUING INTO FRIDAY AND TOWARDS THE OHIO AND TENNESSEE VALLEYS ON SATURDAY. BY DAY 6/SUNDAY AND DAY 7/MONDAY...SHOWERS AND THUNDERSTORMS SHOULD BECOME MORE SCATTERED IN NATURE ACROSS THE EASTERN HALF OF THE COUNTRY...ALTHOUGH THUNDERSTORM CHANCES COULD INCREASE ON MONDAY OVER THE CENTRAL PLAINS AHEAD OF THE DEVELOPING LOW. THE NORTHERN PLAINS SHOULD GRADUALLY DRY OUT WHILE TEMPERATURES REMAIN BELOW NORMAL. IN THE WESTERN U.S...THE HEAT SHOULD REMAIN TAME WITH MAINLY DRY CONDITIONS AND TEMPERATURES SLIGHTLY ABOVE NORMAL. KONG