MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1229 AM EDT WED APR 19 2017 VALID APR 19/0000 UTC THRU APR 22/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... AN EVALUATION OF THE 00Z NAM/GFS GUIDANCE ALONG WITH INITIAL PREFERENCES AND FORECAST CONFIDENCE ...BROAD UPPER TROUGH FROM LOWER MS VALLEY INTO NORTHEAST MEXICO MOVING SLOWLY SOUTHEAST TODAY... PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE THE 00Z NAM AND GFS WERE CLOSE TO THE MODEL CONSENSUS WITH THIS FEATURE AS DRIFTS OUT INTO THE WESTERN AND CENTRAL GULF OF MEXICO TODAY AND TONIGHT...AND WERE CONSISTENT WITH THEIR PREVIOUS SOLUTIONS. THEREFORE...A GENERAL MODEL BLEND IS RECOMMENDED WITH ABOVE AVERAGE CONFIDENCE. ...SHORT WAVE OVER THE NORTHERN PLAINS AND TRAILING COLD FRONT CROSSING UPPER GREAT LAKES AND NEW ENGLAND TODAY/TONIGHT... PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE BOTH THE 00Z NAM AND GFS WERE CLOSE TO THE MODEL CONSENSUS WITH THIS FEATURE...AND REMAIN CLOSE AS THE SHORT WAVE CROSSES NORTHERN NEW ENGLAND EARLY THU. THERE IS CONTINUED MODEL CONSISTENCY WITH THIS FEATURE...SO A GENERAL MODEL BLEND IS RECOMMENDED WITH ABOVE AVERAGE CONFIDENCE. ...DEEPENING LONG WAVE TROUGH OVER THE NORTHERN PLAINS/UPPER GREAT LAKES THU TRACKING INTO NEW ENGLAND FRI... ...DEVELOPING SURFACE LOW AND FRONTAL BOUNDARY REACHING THE GREAT LAKES THU AND NEW ENGLAND FRI... PREFERENCE: NON-12Z UKMET BLEND CONFIDENCE: SLIGHTLY AVERAGE THE 00Z NAM AND 00Z GFS WERE CLOSE TO THE CONSENSUS TAKING A DEVELOPING LONG WAVE TROUGH ACROSS THE NORTHERN PLAINS AND UPPER MS VALLEY WED...AND FOLLOW THE GENERAL MODEL TREND TO CLOSE OFF THE MID LEVEL SYSTEM OVER THE UPPER GREAT LAKES THU NIGHT INTO FRI. THE 12Z UKMET CONTINUES TO BE SLOWER THAN THE STRONG MODEL CONSENSUS AS IT TAKES THE LONG WAVE TROUGH ACROSS QUEBEC AND NORTHERN NEW ENGLAND THU NIGHT INTO FRI. BECAUSE OF THIS...THE 12Z UKMET IS EXCLUDED FROM THE MODEL CONSENSUS...AND FORECAST CONFIDENCE IS SLIGHTLY ABOVE AVERAGE. ...LONG WAVE TROUGH MOVING INTO THE WEST THU/FRI...CLOSING OFF OVER THE CENTRAL PLAINS LATE FRI... PREFERENCE: BLEND OF 00Z NAM/00Z GFS/12Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 00Z NAM AND 00Z GFS ARE CLOSE TO THE MODEL CONSENSUS TAKING AN ELONGATING LONG WAVE TROUGH FROM THE PACIFIC NORTHWEST COAST TO THE ROCKIES THU INTO EARLY FRI. AFTER 22/00Z...BOTH SOLUTIONS ARE CONSISTENT WITH THE IDEA OF CLOSING OFF A MID LEVEL SYSTEM AT THE BASE OF THE TROUGH OVER THE CENTRAL PLAINS AND MID MS VALLEY. THE 00Z NAM MAY END UP A BIT FURTHER NORTH THAN THE CONSENSUS WITH THE PLACEMENT OF THE CLOSED SYSTEM AT 22/12Z...BUT IT IS CLOSE ENOUGH TO THE VERY GOOD MODEL CONSENSUS (ESPECIALLY FOR DAY 3 WITH A CLOSING MID LEVEL SYSTEM) TO INCLUDE IN THE RECOMMENDED BLEND. ...NEGATIVELY TILTED LONG WAVE TROUGH APPROACHING THE PACIFIC NORTHWEST LATE FRI NIGHT/EARLY SAT... PREFERENCE: NON-12Z UKMET BLEND CONFIDENCE: AVERAGE THE 00Z NAM AND 00Z GFS ARE CLOSE TO THE CONSENSUS WITH THE LONG WAVE TROUGH AS IT TAKES ON A NEGATIVE TILT APPROACH OR/NORTHERN CA NEAR 22/12Z. THE 00Z GFS IS A BIT DEEPER THAN THE CONSENSUS BY THAT TIME (AND DEEPER THAN THE 18Z GEFS MEAN)...BUT IT IS CLOSE TO THE 12Z GFS STRENGTH...AND WELL WITHIN THE MODEL ENVELOPE. THE 12Z UKMET IS FASTER AND NOT QUITE AS DEEP AS THE MODEL CONSENSUS...SO IT IS NOT INCLUDED IN THE PREFERENCE. WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/ WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/ HAYES