MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1208 AM EDT SUN MAR 22 2015 VALID MAR 22/0000 UTC THRU MAR 25/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...SHORTWAVE GRADUALLY SHEARING ACROSS THE GREAT LAKES/NORTHEAST... PREFERENCE: BLEND OF THE 00Z GFS AND 12Z ECMWF CONFIDENCE: AVERAGE THE MODELS ARE IN GOOD AGREEMENT TAKING THE SHORTWAVE OVER THE PACIFIC NORTHWEST DOWNSTREAM ACROSS FAR SOUTHERN CANADA THROUGH SUN AND THEN GRADUALLY SHEARING SOUTHEAST THROUGH THE GREAT LAKES AND NORTHEAST MON AND TUES. THE 00Z NAM TENDS TO LAG THE MULTI-MODEL CONSENSUS A LITTLE BIT AS THE ENERGY REACHES THE GREAT LAKES REGION. THEREAFTER...THE 12Z GEM BECOMES THE SLOWEST MODEL. THE STRONGER MODEL AGREEMENT RESIDES WITH THE 00Z GFS AND 12Z ECMWF...SO A BLEND OF THESE SOLUTIONS WILL BE PREFERRED. ...UPPER TROUGH PROGRESSING ACROSS THE SOUTHERN PLAINS/GULF COAST STATES... PREFERENCE: NON-NAM CONSENSUS CONFIDENCE: ABOVE AVERAGE THE MODELS TAKE THE TROUGH OVER THE SOUTHERN PLAINS EAST ACROSS THE GULF COAST STATES AND SOUTHEAST THROUGH MON. THERE IS VERY GOOD MASS FIELD AGREEMENT NOW WITH THIS SYSTEM AMONG THE MODELS...WITH THE MODEST EXCEPTION BEING WITH THE 00Z NAM. THE 00Z NAM IS A LITTLE STRONGER THAN THE MULTI-MODEL CONSENSUS...AND SO A NON-NAM CONSENSUS WILL BE PREFERRED. ...DEEPENING SURFACE LOW APPROACHING REACHING NOVA SCOTIA EARLY SUN... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE ANY REMAINING DIFFERENCES IN THE SHORT RANGE PERIOD WITH THIS SYSTEM ARE SMALL ENOUGH TO RECOMMEND A GENERAL MODEL COMPROMISE. ...CLOSED LOW DROPPING SOUTH FROM HUDSON BAY THIS WEEKEND... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS ARE IN GOOD AGREEMENT WITH MASS FIELD DETAILS OF THIS SYSTEM. ...UPPER TROUGH ADVANCING INTO THE WESTERN U.S. BY MON... ...ENERGY EJECTING OUT INTO THE PLAINS/MIDWEST ON TUES... PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF AND 12Z ECENS MEAN CONFIDENCE: BELOW AVERAGE A PROGRESSIVE SHORTWAVE CROSSING INTO WESTERN U.S ON MON IS EXPECTED TO GRADUALLY AMPLIFY OUT ACROSS THE CENTRAL/NORTHERN PLAINS AND THE MIDWEST THROUGH TUES. THIS WILL DRIVE A SIGNIFICANT AREA OF LOW PRESSURE IN THE LEE OF THE ROCKIES WITH TWO DISTINCT CENTERS. ONE WILL BE OVER THE DAKOTAS BY TUES...WITH THE OTHER MOST LIKELY OVER KS. THE LOWS ARE ANTICIPATED TO CONSOLIDATE INTO ONE CENTER TUES NIGHT OVER THE MIDWEST AND APPROACH THE GREAT LAKES ON WED. THE 00Z NAM AND 12Z UKMET BOTH ARE MORE CONCENTRATED WITH HEIGHT FALLS DIGGING INTO THE MIDWEST BY THE END OF THE PERIOD. THE 12Z GEM/12Z ECMWF AND 00Z GFS ARE A TAD SLOWER AND HANG MORE ENERGY BACK OVER THE UPPER MIDWEST...WITH THE 12Z GEM BY FAR THE DEEPEST SOLUTION. THE STRONGER MODEL CLUSTERING AT THIS POINT WOULD TEND TO FAVOR A COMPROMISE BETWEEN THE 00Z GFS/12Z ECMWF AND 12Z ECENS MEAN. THE LATEST GEFS MEAN MAY BE A BIT TOO SLOW WITH THE SURFACE LOW EVOLUTION AND THE SREF MEAN APPEARS DISPLACE WAY TOO FAR NORTH. CONFIDENCE IS LIMITED...BUT A CONSENSUS OF THE GFS/ECMWF AND ECENS MEAN WILL BE PREFERRED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON