MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1224 PM EDT SUN APR 3 2016 VALID APR 3/1200 UTC THRU APR 7/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ THE 12Z INITIALIZED WITH SLIGHTLY LOWER PW VALUES OVER SOUTH FLORIDA COMPARED TO RAOB SOUNDINGS, AND SLIGHTLY WARM AT 850MB OVER EASTERN WISCONSIN. OTHERWISE, MODEL INITIALIZATION ERRORS APPEAR NEGLIGIBLE. ***PACIFIC TROUGH MOVING FROM THE WEST INTO THE PLAINS BY TUESDAY*** PREFERENCE: 12Z GFS/6Z GEFS MEAN/00Z CMC BLEND CONFIDENCE: NEAR AVERAGE IN THE OFFSHORE WATERS OF THE PACIFIC, A PRONOUNCED UPPER TROUGH WILL CONTINUE MIGRATING EASTWARD WHILE REACHING THE PACIFIC NORTHWEST COAST BY LATE SUNDAY NIGHT. IT IS FORECAST TO CROSS OVER THE NORTHERN ROCKIES ON MONDAY AND SHOULD HOLD INTACT AS IT EMERGES OVER THE NORTHERN PLAINS. A WELL-DEFINED SURFACE LOW IS ALSO FORECAST AHEAD OF THE TROUGH AXIS OVER THE NORTH-CENTRAL U.S. BY TUESDAY. SMALL TIMING AND DEPTH ISSUES ALOFT ARE TRANSLATING INTO ISSUES AT THE SURFACE WITH RESPECT TO THE SURFACE LOW PLACEMENT BY WEDNESDAY MORNING. THE ECMWF AND ITS MEAN ARE ON THE NORTHERN SIDE WITH THE SURFACE LOW THAT TRACKS ACROSS THE NORTHERN PLAINS. THE UKMET IS MORE AMPLIFIED WITH THE MID-UPPER LEVEL TROUGH THAN THE MODEL CONSENSUS. THERE IS GOOD AGREEMENT WITH THE TRAILING COLD FRONT CROSSING THE SOUTHERN PLAINS BY THE END OF THE FORECAST PERIOD WITH ONLY MINOR TIMING DIFFERENCES. ***ALBERTA CLIPPER SYSTEM TRACKING FROM THE DAKOTAS TO THE NORTHEAST U.S.*** PREFERENCE: 12Z NAM/00Z ECMWF/00Z EC MEAN BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE A SHORTWAVE DISTURBANCE LOCATED OVER THE UPPER MIDWEST SUNDAY AFTERNOON IS FORECAST TO TRAVEL EASTWARD AND AROUND THE LARGE SCALE UPPER LEVEL TROUGH, WITH A TRACK NOT TOO DIFFERENT FROM THE SYSTEM CURRENTLY EXITING THE NORTHEAST U.S. THE MID-LEVEL FEATURES SUGGEST A SHORTWAVE THAT IS NOT AS INTENSE AS THE FIRST ONE, WITH A SURFACE LOW REFLECTION CHARACTERISTIC OF AN ALBERTA CLIPPER THAT IS RATHER PROGRESSIVE AND WILL USHER IN ANOTHER ROUND OF COLD WEATHER. WITH RESPECT TO THE SURFACE LOW TRACK, THE 00Z UKMET IS THE NORTHERN MOST SOLUTION, BUT NOT SIGNIFICANTLY. AT 500MB, THE 00Z CMC IS AMONG THE BROADER SOLUTIONS WITH THE TROUGH AXIS. THE 12Z GFS IS SLIGHTLY FASTER THAN ITS 6Z GEFS MEAN. THE 00Z ECMWF AND ITS MEAN ARE IN BETTER AGREEMENT AND ARE CLOSE TO THE MODEL CONSENSUS. ***UPPER TROUGH AND SURFACE LOW DEPARTING NEW ENGLAND SUNDAY EVENING*** PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE PRONOUNCED SHORTWAVE TROUGH AND ITS ACCOMPANYING SURFACE LOW DEVELOPMENT NEAR THE NEW ENGLAND COAST IS EXPECTED TO CONTINUE LIFTING TO THE NORTHEAST AND EXIT THE REGION BY MONDAY MORNING. THE GUIDANCE IS IN GOOD AGREEMENT HERE, SO WE PREFER A GENERAL MODEL COMPROMISE TO DEAL WITH ANY LINGERING DETAIL ISSUES. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... HAMRICK