EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1200 PM EDT SAT JUL 19 2014 VALID 12Z TUE JUL 22 2014 - 12Z SAT JUL 26 2014 ...SYNOPSIS... DURING THE SEVEN DAY PERIOD RIDGING INTENSIFIES AND THEN PERSISTS IN TWO LOCATIONS...THE ALEUTIANS AND THE SOUTHWEST U.S. OUR VARIOUS TOOLS...THE MODELS ALONG WITH ARGUMENTS BASED ON WAVE SPACING...TELECONNECTIONS...AND PERSISTENCE...SUPPORT THE NOTION OF PRONOUNCED TROUGHING BETWEEN THE TWO RIDGE CENTERS AND DOWNSTREAM OVER EASTERN NORTH AMERICA. THE SHORTWAVE DETAILS AND DEPTH WITHIN THE TROUGHS OFFER MORE CHALLENGES...BUT WE HAVE MODERATE TO HIGH CONFIDENCE IN THE TIMING OF THE NEXT CYCLE OF PATTERN AMPLIFICATION. ...GUIDANCE EVALUATION/PREFERENCES... LARGE SCALE AGREEMENT AMONG THE ENSEMBLE MEANS IS GOOD THROUGH DAY 5... THURSDAY...OVER THE U.S. BY THAT TIME...HOWEVER...THE ECMWF ENSEMBLE MEAN DEVELOPS LOWER HEIGHTS THAN MOST GUIDANCE IN THE EASTERN U.S...WHILE THE OPERATIONAL ECMWF ACTUALLY REPRESENTS ONE OF THE MORE PROGRESSIVE AND LOWER AMPLITUDE SOLUTIONS FROM THE 00Z CYCLE. THE OPERATIONAL RUN DID APPEAR GENERALLY TOO FAST GIVEN A MULTI-CYCLE TREND TOWARD SLOWER PROGRESSION IN THE MAIN BELT OF WESTERLIES. THIS APPEARS IN THE ECMWF SOLUTION OVER THE EAST ON DAYS 3/4...AND OVER SOUTHERN CANADA BEGINNING DAY 5. THE LATTER WEATHER SYSTEM IS ONE THAT PREVIOUS ECMWF RUNS HAD SUGGESTED WOULD PINCH OFF AND BECOME SLOW MOVING. THAT SCENARIO NOW APPEARS LESS LIKELY AS THE 00Z RUN STRONGLY BROKE AWAY FROM THAT CONCEPT. THIS CAUSED US TO GO AHEAD AND PUSH THIS LATE-PERIOD SYSTEM ALONG MORE QUICKLY...INCLUDING ITS ASSOCIATED SURFACE FRONT IN THE EASTERN U.S. OVERALL...THE OPERATIONAL 06Z GFS WAS IN BETTER AGREEMENT WITH THE MEANS...BUT THAT MODEL CONTINUED TO MARK THE DEEP / SOUTHERLY EDGE OF THE SPREAD WITH RESPECT TO A CLOSED LOW APPROACHING WA/OR ON DAYS 3/4. THE GFS IS NOT TRULY AN OUTLIER...BUT GIVEN THERE IS LITTLE SPREAD IN THAT REGION IT DOES STAND OUT...AND THE CONSENSUS IS PREFERRED. THE WPC FORECAST WAS WEIGHTED INITIALLY TOWARD THE ECMWF OPERATIONAL AND ENSEMBLE...BUT THEN MOVED QUICKLY TOWARD A 70/30 PERCENT BLEND OF THE ECMWF ENSEMBLE MEAN WITH THE NAEFS MEAN. THIS WAS DONE IN AN ATTEMPT TO ACCEPT THE EC MEAN PLACEMENT OF THE TROUGHS...BUT ACKNOWLEDGE UNCERTAINTY AS TO THEIR DEPTH. ...SENSIBLE WEATHER HIGHLIGHTS... THE PACIFIC NORTHWEST SYSTEM ON DAYS 3/4...AT 1.5 STANDARD DEVIATIONS BELOW CLIMATOLOGY IN THE HEIGHT FIELD...AND WITH PRECIPITABLE WATER ABOVE 1 INCH...IS LIKELY TO PRODUCE INCREASED THUNDERSTORM COVERAGE AND INTENSITY. THIS MAY HAMPER ONGOING WILDFIRE FIGHTING EFFORTS GIVEN RECENT HOT WEATHER AND A NUMBER OF ONGOING FIRES. FARTHER EWD... EARLY IN THE PERIOD GUIDANCE CONTINUES TO HIGHLIGHT THE UPR MS VLY/GRTLKS AREA WITH THE BEST POTENTIAL FOR SOME LOCALLY HVY CONVECTION ALONG A WAVY FRONT THAT SHOULD THEN CONTINUE TOWARD THE EAST COAST. UNCERTAIN DETAILS SFC/ALOFT AFTER MIDWEEK LEAD TO REDUCED CONFIDENCE IN PINPOINTING ANY OTHER FAVORED AREAS FOR HEAVIER RNFL ALONG THE FRONT. HIGHEST ANOMALIES FOR TEMPS E OF THE ROCKIES SHOULD BE WITH MINS OVER/NEAR THE UPR MS VLY/GRTLKS TUE-WED WITH SOME PLUS 10-15F DEPARTURES PSBL. PORTIONS OF THE SOUTHEAST MAY SEE LOCALLY HVY DIURNAL CONVECTION WITH A STNRY FRONT OVER THE AREA DURING THE FIRST HALF OF THE PERIOD AND ONE OR MORE IMPULSES ALOFT PROVIDING SOME ADDED FOCUS. BY LATE IN THE PERIOD SERN CONUS ACTIVITY MAY DEPEND IN PART ON THE UNCERTAIN DETAILS OF THE AMPLIFYING ERN TROUGH ALOFT. BURKE/FRACASSO/RAUSCH