MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 241 AM EDT SAT OCT 17 2015 VALID OCT 17/0000 UTC THRU OCT 20/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/CMC AND ECMWF ...SOUTHWEST U.S. UPPER LEVEL LOW/TROUGH SHIFTING EAST THROUGH SUN... PREFERENCE: NON-UKMET CONSENSUS CONFIDENCE: ABOVE AVERAGE A WELL DEVELOPED UPPER LEVEL LOW CURRENTLY OVER CENTRAL CALIFORNIA WILL BE OPENING UP INTO A TROUGH AXIS AND WILL ADVANCE EAST INTO THE FOUR CORNERS REGION THROUGH SUN. THE 00Z UKMET CONTINUES TO BE JUST A TAD FASTER TO WEAKEN THE SYSTEM...WITH THE REMAINING MODELS WELL CLUSTERED WITH A SLIGHTLY MORE GRADUAL DAMPENING OUT OF THE ENERGY. WILL PREFER A NON-UKMET CONSENSUS YET AGAIN. ...UPPER TROUGH/CLOSED LOW DIGGING INTO THE INTERMOUNTAIN WEST THROUGH EARLY NEXT WEEK... PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE ANOTHER PRONOUNCED UPPER LEVEL TROUGH IS PROGGED TO REACH THE WEST COAST THIS WEEKEND...WITH THE ENERGY DIGGING INLAND BY SAT NIGHT AND EARLY SUN. THE GUIDANCE AGREES VERY WELL IN TAKING ENERGY IN THE BASE OF THIS TROUGH AND AMPLIFYING INTO A CLOSED LOW AND SEPARATING AWAY FROM THE MAIN BELT OF THE WESTERLIES TO THE NORTH ON SUN. THE CLOSED LOW IS THEN FORECAST TO DIG SOUTHEAST AND INTO THE SOUTHWEST U.S. MON AND TUES. THE 00Z CMC IS A TAD STRONGER THAN THE GLOBAL MODEL CONSENSUS WITH THE CLOSED LOW...WITH THE 00Z UKMET GENERALLY THE WEAKEST ALTHOUGH IT HAS TRENDED A BIT STRONGER FROM ITS PREVIOUS RUN. THE 00Z NAM/00Z GFS AND 00Z ECMWF SHOW BETTER AGREEMENT...BUT THE 00Z NAM MAY OVERALL BE A TAD SLOW. WILL PREFER A BLEND OF THE 00Z GFS AND 00Z ECMWF AT THIS POINT...AND THESE SOLUTIONS ARE REASONABLY WELL SUPPORTED BY THE LATEST GEFS MEAN AND ECENS MEAN. ...SHORTWAVE TROUGH IMPACTING THE PACIFIC NORTHWEST/NORTHERN ROCKIES MON AND TUES... PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF CONFIDENCE: AVERAGE THE GUIDANCE SHOWS A SHORTWAVE TROUGH APPROACHING BRITISH COLUMBIA AND MOVING INTO THE PACIFIC NORTHWEST BY EARLY MON. THERE IS NOW GOOD AGREEMENT AMONG THE MODELS AS THE ENERGY TRAVERSES THE NORTHWEST THROUGH MON. HOWEVER...AS THE ENERGY REACHES THE NORTHERN ROCKIES BY MON NIGHT AND TUES...THE 00Z UKMET IS A LITTLE DEEPER AND MORE PROGRESSIVE THAN THE REMAINING MODELS. THE 00Z NAM/00Z GFS/00Z CMC AND 00Z ECMWF TEND TO SHOW BETTER AGREEMENT...ALTHOUGH THE 00Z NAM IS PERHAPS A LITTLE TOO SLOW. WILL PREFER TO MAINTAIN CONTINUITY AND PREFER AGAIN A BLEND OF THE 00Z GFS AND 00Z ECMWF. ...COLD FRONT CROSSING THE NORTHERN PLAINS AND UPPER MIDWEST BY MON AND TUES... PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF CONFIDENCE: AVERAGE THE MODELS AGREE VERY WELL IN BRINGING A COLD FRONT ACROSS THE NORTHERN PLAINS AND THROUGH THE UPPER MIDWEST MON AND TUES. THE 00Z NAM/00Z CMC AND TO A SLIGHT EXTENT THE 00Z UKMET ARE A LITTLE SLOWER THAN THE 00Z GFS AND 00Z ECMWF. WILL PREFER THE CLUSTERING OF THE SLIGHTLY MORE PROGRESSIVE SOLUTIONS...AND THUS PREFERRING A BLEND OF THE 00Z GFS AND 00Z ECMWF AT THIS POINT. THIS IS SUPPORTED BY THE LATEST GEFS MEAN AND ECENS MEAN. ...LOW PRESSURE TROUGH CROSSING NORTHERN NEW ENGLAND ON SAT... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS ARE NOW IN VERY GOOD AGREEMENT WITH THIS SHORTWAVE IMPULSE AND ASSOCIATED SURFACE TROUGH THAT CROSSES NORTHERN NEW ENGLAND EARLY ON SATURDAY. THEREFORE A GENERAL MODEL COMPROMISE CAN BE USED HERE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON