EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1159 AM EDT SUN JUL 24 2016 VALID 12Z WED JUL 27 2016 - 12Z SUN JUL 31 2016 ...OVERVIEW AND GUIDANCE/UNCERTAINTY ASSESSMENT... MODELS REMAIN IN GOOD AGREEMENT WITH THE LARGE SCALE EVOLUTION OF FLOW OVER THE LOWER 48 LATER THIS WEEK AND THROUGH THE WEEKEND. RIDGING IN THE WESTERN U.S. SHOULD STAY CENTERED OVER THE GREAT BASIN...WITH THE NEXT APPROACHING UPPER TROUGH POTENTIALLY LOWERING HEIGHTS OVER THE PACIFIC NORTHWEST AND WEST COAST BY SATURDAY. EAST OF THE DIVIDE...ANOMALOUS RIDGING OVER THE MID-ATLANTIC STATES SHOULD GRADUALLY SUPPRESS INTO THE SOUTHEAST WHILE AN UPSTREAM TROUGH SETS UP OVER THE MIDDLE/UPPER MISSISSIPPI VALLEY AND GREAT LAKES. THE WPC DAY 3-7 FORECAST WAS LARGELY BASED OFF ENSEMBLE MEAN GUIDANCE...DUE TO BOTH THE LOW PREDICTABILITY WITH SMALLER SCALE SHORTWAVE ENERGY RIPPLING THROUGH THE MEAN FLOW AS WELL AS WITH THE INCREASING AMOUNT OF ENSEMBLE SPREAD THAT DEVELOPS WITH THE TIMING AND AMPLITUDE OF THE NEXT UPPER TROUGH PROGRESSING INTO THE NORTHWEST THIS UPCOMING WEEKEND. ...WEATHER HIGHLIGHTS/THREATS... THE PATTERN SHOULD GENERALLY FAVOR AREAS OF ORGANIZED CONVECTION FROM THE NORTHERN PLAINS INTO THE NORTHERN MID-ATLANTIC STATES...BUT THE EXACT DETAILS OF WHERE AND HOW MUCH RAIN WILL FALL ARE DIFFICULT TO RESOLVE IN THE MEDIUM RANGE PERIOD. THE COMBINATION OF MONSOONAL MOISTURE AND IMPULSES ALOFT WILL CONTRIBUTE TO DIURNAL CONVECTION OVER THE SOUTHWEST AND ROCKIES...WHILE FLORIDA AND LOCATIONS FROM THE CENTRAL GULF COAST TO THE TENNESSEE VALLEY SHOULD SEE PERIODS OF SHOWERS AND THUNDERSTORMS AS WELL. THE WESTERN U.S. HEAT WILL EXPAND INTO THE NORTHWEST LATER THIS WEEK...BUT THEN THE REGION SHOULD SEE A NOTICEABLE COOLING TREND BY THE WEEKEND AS HEIGHTS LOWER WITH THE ARRIVAL OF THE NEXT UPPER TROUGH. MUCH OF THE EAST COAST WILL SEE ABOVE NORMAL TEMPS MID-LATE WEEK BEFORE TEMPERATURES TREND CLOSER TO NORMAL ACROSS THE NORTHERN HALF OF THE EASTERN U.S.. HOWEVER...PARTS OF THE SRN MID ATLC/SOUTHEAST MAY REMAIN 5-10F ABOVE NORMAL THROUGH THE WEEKEND. NRN INTO CNTRL PLAINS LOCATIONS SHOULD SEE A PERIOD OF BELOW NORMAL HIGHS WITH A WARMING TREND BY NEXT WEEKEND. GERHARDT