MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 126 AM EST FRI DEC 18 2015 VALID DEC 18/0000 UTC THRU DEC 21/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION INCLUDING THE UKMET/CANADIAN/ECMWF AND PREFERENCES SHORTWAVE TROUGH MOVING FROM THE WEST COAST TO THE MIDWEST THIS WEEKEND... PREFERENCE: 1/3 EACH NAM/GFS/ECMWF...MORE NAM WITH THE SOUTHERN STREAM THAN THE NORTHERN STREAM CONFIDENCE: AVERAGE ALL MODELS AGREE IN ALLOWING THE TROUGH TO SPLIT...WITH THE NAM MOVING PROGRESSIVELY TOWARD THE FAST SIDE OF THE GUIDANCE WITH THE NORTHERN STREAM...AND THUS LESS PROBABLE WITH THE LOW AND FRONTAL TIMING ACROSS THE UPPER MIDWEST...BUT IS WELL ALIGNED WITH THE SLOWER/STRONGER GFS/ECMWF WITHIN THE SOUTHERN STREAM. SHORTWAVE TROUGH NEARING THE PACIFIC NORTHWEST BY 12Z MONDAY... PREFERENCE: 1/3 EACH NAM/GFS/ECMWF CONFIDENCE: AVERAGE THE NEW ECMWF IS FASTER AND MORE AMPLIFIED THAN ITS PREVIOUS RUN AND IS NOW SIMILAR TO THE NAM/GFS. RECOMMEND AN EQUAL BLEND OF EACH TO ADDRESS SMALLER SCALE ISSUES. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... JAMES