EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 157 AM EDT THU JUL 27 2017 VALID 12Z SUN JUL 30 2017 - 12Z THU AUG 03 2017 ...PATTERN OVERVIEW... FLOW WILL BECOME QUITE AMPLIFIED OVER THE LOWER 48 LATE THIS WEEKEND AND THROUGH THE MIDDLE OF NEXT WEEK AS UPPER RIDGING BUILDS IN OVER THE WEST AND A DOWNSTREAM TROUGH SETS UP ACROSS THE EASTERN HALF OF THE NATION. AT THE SURFACE, THE TAIL END OF A FRONTAL BOUNDARY PUSHING OFF THE EASTERN SEABOARD THIS WEEKEND WILL BE SLOW TO DISSIPATE WHILE IT STALLS AND LINGERS ACROSS NORTHERN FLORIDA AND THE CENTRAL GULF COAST FOR MUCH OF NEXT WEEK. FARTHER NORTH, WEAK SHORTWAVES STREAKING THROUGH SOUTHERN CANADA COULD HELP PRESS A SERIES OF COLD FRONTS FROM THE UPPER MIDWEST TO THE NORTHEAST THROUGHOUT THE MEDIUM RANGE PERIOD. ...GUIDANCE EVALUATION/PREFERENCES... DETERMINISTIC AND ENSEMBLE GUIDANCE REMAINED IN VERY GOOD AGREEMENT WITH THE LARGE SCALE SYNOPTIC PATTERN SETTING UP OVER THE CONUS NEXT WEEK, ESPECIALLY WITH THE EXPANDING HIGH PRESSURE IN THE WEST, WHERE MODELS APPEAR LOCKED INTO A CLOSED 500MB HIGH CENTERING OVER THE CENTRAL GREAT BASIN BY 12Z THURSDAY AUG 03. THERE REMAINS SOME UNCERTAINTY AND SPREAD WITH THE DETAILS OF WEAK SHORTWAVE IMPULSES WHILE THEY ROUND THE NORTHERN PERIPHERY OF THE WESTERN U.S. RIDGE AND TRACK EASTWARD ACROSS SOUTHERN CANADA OR SOUTHEASTWARD THROUGH THE HIGH PLAINS. SINCE THE MAJORITY OF 12Z/18Z DETERMINISTIC GUIDANCE FELL WITHIN THE 12Z ENSEMBLE SPREAD, THE WPC DAY 3-7 FORECAST USED A GENERAL BLEND OF DETERMINISTIC GUIDANCE, ENSEMBLE MEANS, AND CONTINUITY IN ORDER TO SMOOTH OUT SOME OF THESE SMALLER SCALE DETAIL DIFFERENCES. ...WEATHER HIGHLIGHTS... LOCATIONS ACROSS THE SOUTHERN/CENTRAL ROCKIES AND ADJACENT HIGH PLAINS SHOULD SEE A HEIGHTENED RISK FOR HEAVY RAINFALL NEXT WEEK AS IMPULSES OF ENERGY DROPPING SOUTH/SOUTHEASTWARD AROUND A BUILDING WESTERN U.S. RIDGE INTERACT WITH AN AXIS OF HIGHLY ANOMALOUS MOISTURE ACROSS THE REGION. HOWEVER, THERE REMAINS A FAIR AMOUNT OF DISCREPANCY AMONG DETERMINISTIC GUIDANCE WITH THE EXACT LOCATION AND MAXIMUM AMOUNT OF RAINFALL, EVEN WHEN COMPARING 48-HOUR FORECAST PRECIPITATION TOTALS. ELSEWHERE, PERSISTENT MONSOONAL MOISTURE SHOULD KEEP LOCALLY HEAVY RAINFALL A THREAT ACROSS THE FOUR CORNERS REGION, WHILE A FRONTAL BOUNDARY LINGERING FROM FLORIDA TO THE CENTRAL GULF COAST SHOULD PROVIDE A FOCUS FOR MULTIPLE DAYS OF CONVECTION AND HEAVY RAINFALL. A MEAN EASTERN U.S. TROUGH SHOULD KEEP TEMPERATURES BELOW NORMAL FROM THE PLAINS TO THE EAST COAST THIS WEEKEND AND INTO MUCH OF NEXT WEEK, WHILE AN EXPANDING RIDGE IN THE WEST SHOULD BRING CONSECUTIVE DAYS OF ABOVE NORMAL TEMPERATURES TO LOCATIONS FROM THE WEST COAST TO THE ROCKIES. AN EXCEPTION TO THE HEAT IN THE WEST WILL BE ACROSS THE FOUR CORNERS REGION, WHERE MONSOONAL CONVECTION SHOULD KEEP DAYTIME TEMPERATURES CLOSER TO, OR EVEN BELOW, SUMMERTIME AVERAGES. GERHARDT