MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1239 PM EDT SAT JUN 18 2016 VALID JUN 18/1200 UTC THRU JUN 22/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS AND PRELIMINARY MODEL PREFERENCES ...SURFACE FRONT ACROSS THE NORTHERN PLAINS/UPPER MIDWEST THROUGH TODAY... PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE MODELS ARE SIMILAR IN THEIR DEPICTIONS OF THIS FEATURE. A GENERAL MODEL COMPROMISE IS RECOMMENDED. ...UPPER-LEVEL LOW OVER THE PACIFIC NORTHWEST THROUGH SAT... ...ENERGY/SURFACE LOW EJECTING ACROSS THE NORTHERN PLAINS ON SUN... ...ATTENDANT COLD FRONT ADVANCING TOWARD THE GREAT LAKES ON MON... PRELIMINARY PREFERENCE: GFS/00Z UKMET BLEND CONFIDENCE: AVERAGE MODELS ARE IN GOOD AGREEMENT THROUGH THIS EVENING AS THE UPPER LOW BEGINS TO MOVE EAST INTO THE NORTHWESTERN U.S. AFTER THIS TIME, SPREAD BEGINS TO INCREASE AS THE LOW OPENS UP INTO A SHORTWAVE AND BEGINS TO MOVE MORE QUICKLY EAST TOWARD THE NORTHERN PLAINS. THE NAM APPEARS TO BE TOO SLOW WITH THE EASTWARD PROGRESSION OF THIS WAVE BY 12Z SUN. THE GFS DEPICTS A TIMING RELATIVELY CLOSE TO THE 06Z GEFS MEAN AND 00Z ECMWF ENSEMBLE MEAN, WHICH IS A BIT SLOWER AND MORE AMPLIFIED RELATIVE TO THE 00Z DETERMINISTIC ECMWF. THESE DIFFERENCES MANIFEST AT THE SURFACE AS WELL, WITH THE GFS AND 00Z UKMET SHOWING A SLIGHTLY SLOWER PROGRESSION OF THE COLD FRONT INTO THE UPPER MIDWEST RELATIVE TO THE 00Z ECMWF. THE GFS AND THE 00Z UKMET APPEAR TO BE THE TWO SOLUTIONS MOST CLOSELY SURROUNDING THE ENSEMBLE CONSENSUS. ...LARGER SCALE TROUGH DIGGING TOWARD THE GREAT LAKES ON TUES... PRELIMINARY PREFERENCE: GFS/00Z ECMWF BLEND CONFIDENCE: AVERAGE BU TUESDAY AS LARGER SCALE TROUGH WILL DIG SOUTH OF THE HUDSON BAY ACROSS ONTARIO TOWARD THE GREAT LAKES. THE GFS IS INITIALLY A LITTLE MORE AMPLIFIED RELATIVE TO THE NAM AND 00Z ECMWF WITH THE LEADING SHORTWAVE EMBEDDED IN THIS TROUGH, BUT LOOKS CLOSER TO THE 00Z ECMWF AS TIME GOES ON. WHILE THERE IS A RANGE OF SPREAD AS THE DEEP UPPER LOW EVOLVES OVER HUDSON BAY, THE GFS AND 00Z ECMWF APPEAR TO CLUSTER BEST AROUND THE ENSEMBLE MEANS. ...UPPER-LEVEL LOW OFF THE WEST COAST BY SUN/MON... ...TROUGH MOVING INTO THE PACIFIC NORTHWEST MON NIGHT/TUES... PRELIMINARY PREFERENCE: GFS/00Z ECMWF CONFIDENCE: BELOW AVERAGE A VORTICITY MAX LEFT BEHIND WHEN THE INITIAL UPPER LOW LIFTS EAST WILL INTERACT WITH A SHORTWAVE MOVING SOUTH FROM THE GULF OF ALASKA TO FORM A BROAD UPPER-LEVEL LOW WITH TWO CENTERS OFF THE WEST COAST ON SUNDAY INTO MONDAY. THE NORTHERN CENTER WILL EVENTUALLY OPEN INTO A SHORTWAVE AND MOVE INTO THE PACIFIC NORTHWEST ON TUESDAY. THE GFS AND 00Z UKMET ARE INITIALLY THE SOLUTIONS MOST CLOSELY CLUSTERED WITH THE 06Z GEFS AND 00Z ECMWF ENSEMBLE MEANS. AS THE LOW BEGINS TO OPEN INTO A SHORTWAVE, HOWEVER, THE GFS AND 00Z UKMET ARE MUCH QUICKER TO MOVE THE SYSTEM INTO THE PACIFIC NORTHWEST, WHILE BOTH ENSEMBLE MEANS DEPICT A SLOWER PROGRESSION (SLOWER THAN ANY OF THE DETERMINISTIC SOLUTIONS). A PRELIMINARY GLANCE AT THE 12Z UKMET AS IT IS COMING IN SHOWS THAT IT HAS NOT BACKED OFF OF SHOWING A FASTER SOLUTION THAN THE ENSEMBLE MEANS, AND HAS EVEN SPED THE WAVE UP A LITTLE MORE RELATIVE TO ITS PREVIOUS RUN BY 12Z TUESDAY. GIVEN THE APPARENT ENSEMBLE AGREEMENT ON A SLOWER EASTWARD PROGRESSION OF THE SHORTWAVE, BUT EVIDENT TRENDS TOWARD A FASTER SOLUTION, WILL LEAN TOWARD THE SLOW SIDE OF THE DETERMINISTIC GUIDANCE AND RECOMMEND A BLEND OF THE GFS AND 00Z ECMWF. ...LOW DEVELOPING OFF THE EAST COAST BY SUN... PRELIMINARY PREFERENCE: NAM/00Z ECMWF/00Z UKMET CONFIDENCE: AVERAGE AN UPPER-LEVEL LOW IS FORECAST TO DEVELOP FROM AN UPPER TROUGH BETWEEN THE U.S. EAST COAST AND BERMUDA ON SUNDAY, WHICH WILL THEN MOVE WESTWARD/NORTHWESTWARD TOWARD THE COAST BEFORE OPENING AGAIN INTO A SHORTWAVE AND QUICKLY MOVING NORTHEASTWARD BY TUESDAY AS IT INTERACTS WITH THE TROUGH DEEPENING SOUTH OF HUDSON BAY. MODELS HAVE COME INTO BETTER AGREEMENT RELATIVE TO YESTERDAY WITH RESPECT TO THE TRACK OF THIS CLOSED LOW AND ITS ASSOCIATED SURFACE LOW, WITH MOST DETERMINISTIC SOLUTIONS NOW CLUSTERED AROUND THE ENSEMBLE MEANS. THE SOLUTIONS ALIGNING MOST CLOSELY WITH THE CONSENSUS OF THE 00Z ECMWF ENS MEAN/06Z GEFS MEAN ARE THE 00Z ECMWF/00Z UKMET AND THE NAM. THE GFS SEEMS TO BE A LITTLE TOO FAR WITH THE SURFACE LOW AND IS A BIT SLOWER TO MOVE IT NORTH AFTER INTERACTING WITH THE LARGE SCALE TROUGH. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RYAN