MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1127 PM EST SAT JAN 03 2015 VALID JAN 04/0000 UTC THRU JAN 07/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION WITH PRELIMINARY MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO IMPACT THEIR SHORT RANGE FORECASTS. SHORTWAVE PIVOTING INTO THE GREAT LAKES EARLY WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-UKMET COMPROMISE CONFIDENCE: ABOVE AVERAGE THE 12Z UKMET IS SHARPER THAN THE REST OF THE GUIDANCE (AND SLIGHTLY FASTER WITH THIS SHORTWAVE'S TIMING). CONSIDERING THE BREADTH OF THE UPPER TROUGH, A LESS SHARP SOLUTION IS ADVISED. PREFER A COMPROMISE OF THE 00Z GFS/00Z NAM/12Z CANADIAN/12Z ECMWF WITH ABOVE AVERAGE CONFIDENCE. SYSTEM SWINGING THROUGH WESTERN CANADA & THE NORTHERN TIER OF THE COUNTRY THROUGH TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z ECMWF/00Z GFS COMPROMISE CONFIDENCE: AVERAGE THE GUIDANCE HAS TRENDED QUICKER WITH THIS SYSTEM OVER THEIR PAST DAY OF RUNS, PLACING GREATER MERIT ON THE 02/21Z SREF MEAN RUN SEEN THIS TIME YESTERDAY, WHICH LOOKS SIMILAR TO ITS CURRENT RUN. THE GUIDANCE SPREAD IS TYPICAL, WITH THE UKMET FLATTER/FASTER, THE GFS/NAM EQUALING THE UKMET'S TIMING BUT LYING FARTHER NORTH WITH THE SURFACE LOW, AND THE ECMWF/00Z GFS PARALLEL RUN ON THE SLOW SIDE OF THE GUIDANCE. CONSIDERING MODEL TRENDS, THE ECMWF IS LIKELY TOO SLOW. THIS SYSTEM IS MOVING AROUND THE PERIPHERY OF A BROAD UPPER TROUGH, WHICH COULD EASILY ALLOW FOR A MORE PROGRESSIVE SYSTEM. PREFER A COMPROMISE OF THE 12Z ECMWF AND 00Z GFS WITH AVERAGE CONFIDENCE FOR NOW UNTIL THE GUIDANCE SETTLES DOWN. LOW PRESSURE MOVING ACROSS THE GREAT LAKES/NORTHEAST/SOUTHEAST CANADA SAT-SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: HIGH THE GUIDANCE IS IN GOOD AGREEMENT WITH THIS SYSTEM. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH