MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1205 AM EDT SUN JUN 22 2014 VALID JUN 22/0000 UTC THRU JUN 25/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION AND PRELIMINARY MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE MODEL FORECASTS. PACIFIC NORTHWEST ~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE GUIDANCE CONTINUES TO SHOW REASONABLY GOOD AGREEMENT WITH THIS NEGATIVELY TILTED SHORTWAVE AND SURFACE LOW MOVING TOWARDS THE WESTERN US/CANADIAN BORDER MONDAY NIGHT/TUESDAY MORNING. THE 00Z NAM IS SOMEWHAT WEAKER THAN THE SLIGHTLY MORE AMPLIFIED 12Z EC WITH THE UPR TROF OVER SW CANADA BY 12Z WED BUT SENSIBLE WEATHER IMPACTS ARE NOT APPRECIABLY AFFECTED. A GENERAL MODEL COMPROMISE IS ADVISED WITH ABOVE AVERAGE CONFIDENCE CONSIDERING THE MINIMAL SPREAD IN THE GUIDANCE. CENTRAL U.S. INTO THE GT LAKES/NE U.S. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-UKMET..NON-NAM BLEND CONFIDENCE: LOW PATRN OVER THE LOWER 48 STATES WILL BE DOMINATED BY QUASI ZONAL FLOW..WHILE INTERACTION OF SLOWLY PROGRESSIVE TROF AXIS OVER SCNTL CANADA WITH EMBDD WEAK IMPULSES IN WESTERLY FLOW FROM THE ROCKIES ACRS THE CNTL PLAINS WILL LEAD TO WEAK FRONTAL WAVE DVLPMENT LATE SUN/SUN NIGHT OVER THE CNTL PLAINS/MO VALLEY REGION. THAT LOW IS EXPECTED TO LIFT NEWD INTO THE GT LAKES BY TUES MRNG WHERE IT WILL RESPONSE MORE TOWARD THE NRN STREAM ENERGY AND STRENGTHEN ACRS ERN CANADA ON TUES ALLOWING A SWD PUSH OF COOLER HIGH PRESSURE INTO THE NRN PLAINS/GT LAKES REGION BY WED MRNG. THE NAM IS A LITTLE WEAKER TO EVOLVE THE LOW INTO THE WRN GT LAKES REGION BY MON EVENING BUT MANAGES TO COME INTO CLOSE AGREEMENT WITH CONSENSUS BY TUE MRNG OVER THE NCNTL LAKES..WITH THE EXCEPTION OF THE 12Z UKMET WHICH WAS A CONSIDERABLY FASTER SOLN. OTHERWISE...THE MORE IMPORTANT MODEL DIFFERENCES ARE WITH QPF PARTICULARLY OVER THE CNTL PLAINS WITH GLOBAL MODELS LIKELY NOT RESOLVING THE SMALL SCALE WEAK IMPULSES AND MODEL GENERATED MCV'S IN WLY FLOW VERY WELL. CASE IN POINT IS DVLPG MCS OVER ERN SD WHICH IS NOT WELL HANDLED BY THE 00Z NAM AND WHICH MAY SPIN UP AN MCV THAT THE 00Z NAM DOES NOT HAVE. INCREASING TROUGHING ACROSS THE SOUTH/GULF COAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM COMPROMISE CONFIDENCE: AVERAGE AS TROUGHING MOVES THROUGH THE UPPER AND MID MISSISSIPPI VALLEYS INTO THE GREAT LAKES, RIDGING ACROSS THE WESTERN GULF OF MEXICO BECOMES REPLACED WITH UPPER LEVEL TROUGHING AS WEAK SHEAR AXIS DRIFTS SEWD FROM WRN TX. THE 00Z NAM REMAINS A BIT MORE AMPLIFIED WITH THE UPR TROF OVER S TX/ERN MEX BY WED MRNG WITH A SLIGHTLY STGR RETURN FLOW SURGE OF HIER PWS INDICATED OVER THE WRN GULF AT THAT TIME. WHILE OVERALL DIFFERENCES ARE MINOR...SUGGEST LEANING AWAY FROM THE SLIGHTLY MORE AMPLIFIED NAM AT THIS TIME. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... SULLIVAN