EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1229 AM EDT SAT MAY 17 2014 VALID 12Z TUE MAY 20 2014 - 12Z SAT MAY 24 2014 WEST... UPSTREAM AMPLIFICATION ON THE CENTRAL PACIFIC RESULTS RESULTS IN A TROUGH AMPLIFYING AS IT COMES ACROSS CENTRAL AND SOUTHERN CA WITH A 500 MB HPA CLOSED LOW FORMING BY TUE MORNING 20 MAY AND THEN DRIFTING EAST SOUTHEAST ACROSS THE NV/CA/AZ BORDER REGION TO AZ/NM AT THE END OF NEXT WEEK. NEAR THE CORE OF THE DEVELOPING LOW...A CORE OF COLD AIR WILL KEEP DAILY HIGH TEMPS SEVERAL DEGREES BELOW NORMAL...INCLUDING IN THE HOT AND PARCHED CALIFORNIA. THE DEPARTURE OF THE TROUGH AT THE END OF NEXT WEEK ALLOWS CALIFORNIA TEMPERATURE TO REBOUND...WITH THE COLD AIR MOVING INLAND TO THE SOUTHERN ROCKIES AND ADJACENT HIGH PLAINS. LATE SEASON RAINS AND MOUNTAIN SNOWS OCCUR IN THE GREAT BASIN IN CONJUNCTION WITH THE UPPER LOW AND 700 MB CONVERGENCE NEAR THE FRONTAL ZONE. BY NEXT WEEKEND...A PRONOUNCED TAP OF MOISTURE SHOULD AID DEVELOPMENT OF SHOWERS OUT OF THE SOUTHERN ROCKIES ONTO THE HIGH PLAINS OF NORTHWEST TEXAS AND WESTERN OKLAHOMA... WHICH ARE LABELED AS EXCEPTIONAL DROUGHT IN THE LATEST DROUGHT MONITOR. THE MODELS/ENSEMBLE MEANS SHOWED GOOD AGREEMENT THROUGH ABOUT DAY 6 WITH THE UPPER TROUGH/500 MB LOW EVOLUTION...WITH THE GFS/GFS ENSEMBLE MEAN SHOWING SLIGHTLY FASTER FORWARD PROGRESSION OF THE UPPER TROUGH TOWARDS THE SOUTHERN HIGH PLAINS DAY 7. GIVEN THE AMPLIFIED UPSTREAM RIDGE...PREFERRED THE SLOWER ECMWF/ECMWF ENSEMBLE MEAN SOLUTIONS INSTEAD. ELSEWHERE...THE PERSISTENT CLOSED LOW ON THE NORTH PACIFIC WEST OF BRITISH COLUMBIA/SOUTH OF ALASKA BUILDS ABOVE NORMAL HEIGHTS IN THE NORTHERN ROCKIES TO HIGH NORTHERN PLAINS LEADS TO AN EXTENDED PERIOD OF WARMER THAN NORMAL TEMPERATURES. EAST... THE MODELS/ENSEMBLES SHOW A 500 MB WAVE WITH DEVELOPING CLOSED LOW PROGRESSING ACROSS THE UPPER MS VALLEY TUE...GREAT LAKES WES/THU...NORTHEAST FRI...ND OFF THE NEW ENGLAND COAST SAT. THE WAVE/LOW ARE FOLLOWED BY COLDER TEMPERATURES IN THE UPPER MS VALLEY DAY 3-4...GREAT LAKES DAYS 5-6...AND NORTHEAST DAY 7. THE MODELS HAVE SLOWLY NUDGED TOWARDS BETTER CLUSTERING. THE 18Z GFS CYCLONE DEVELOPMENT IN THE ENGLAND COASTAL WATERS FRI 23 MAY WAS OFF MAINE IN THE 18Z RUN AND IS NOW OFF SOUTHERN ENGLAND IN THE 00Z RUN..SO IT IS TRENDING TOWARDS THE PRIOR ECMWF/CANADIAN FORECASTS AND 12Z ECMWF ENSEMBLE MEAN AND 18Z GEFS MEAN. CONSEQUENTLY...THE 18Z GFS IS GIVEN LESS WEIGHTING IN THIS TIME FRAME. THE MODELS/ENSEMBLES ARE IN BETTER THAN AVERAGE AGREEMENT A MID LEVEL ANTICYCLONE DEVELOPS OVER THE LOWER MS VALLEY AND THEN DRIFTS SOUTHEAST TO THE GULF COAST/GULF OF MEXICO. THIS LEADS TO DEVELOPING WARMER THAN NORMAL TEMPS ACROSS THE LOWER MS VALLEY TO THE SOUTHEAST AND THEN FINALLY FL. PETERSEN