MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 254 AM EDT THU APR 27 2017 VALID APR 27/0000 UTC THRU APR 30/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH FINAL MODEL PREFERENCES/CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...CYCLONE EXITING THE MID-ATLANTIC/SOUTHERN NEW ENGLAND... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE THE MODELS ARE IN VERY GOOD AGREEMENT WITH THE EXIT OF THIS SYSTEM AWAY FROM THE MID-ATLANTIC AND SOUTHERN NEW ENGLAND THROUGH THURS. A GENERAL MODEL BLEND WILL AGAIN BE PREFERRED. ...LARGE UPPER TROUGH/FRONTAL SYSTEM CROSSING THE GREAT LAKES/UPPER MS VALLEY THROUGH THURS... ...SURFACE FRONT REACHING THE MID-ATLANTIC/NORTHEAST BY FRI NIGHT... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-00Z NAM CONSENSUS CONFIDENCE: ABOVE AVERAGE THE 00Z NAM AGAIN IS A TAD SLOWER THAN THE MODEL CONSENSUS WITH THE UPPER TROUGH LIFTING NORTHEAST ACROSS THE UPPER MS VALLEY/GREAT LAKES THROUGH THURS. REGARDING THE FRONTAL TIMING THERE IS MINIMAL SPREAD...SO OVERALL AT THIS POINT...WILL LEAN TOWARD A NON-NAM CONSENSUS. ...UPPER LOW OVER SOUTHERN ALBERTA MOVING SLOWLY EAST ACROSS SASKATCHEWAN BY SAT... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-00Z NAM CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS ARE IN GOOD AGREEMENT WITH THIS SYSTEM UNTIL SAT WHEN THE 00Z CMC/ECMWF SOLUTIONS BEGIN TO LAG THE PROGRESSION OF THE 00Z NAM/GFS/UKMET SOLUTIONS BY JUST A LITTLE. THE SYSTEM WILL BE WEAKENING BY SAT WHICH ALL OF THE GUIDANCE AGREES ON...HOWEVER THE NAM TENDS TO HANG ON TO A SOMEWHAT STRONGER SOLUTION FOR LONGER AND GRADUALLY BECOMES MORE OF AN OUTLIER. WILL PREFER A NON-NAM CONSENSUS AT THIS POINT. ...AMPLIFYING TROUGH OVER THE INTERMOUNTAIN WEST THURS/FRI... ...CLOSED LOW EVOLUTION INTO THE CENTRAL/SOUTHERN PLAINS BY SAT... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF CONFIDENCE: AVERAGE MULTIPLE SHORTWAVES EMBEDDED IN A STRONG NORTHWESTERLY JET ACROSS THE CENTRAL GREAT BASIN WILL DEEPEN A LARGE UPPER TROUGH OVER THE INTERMOUNTAIN WEST AND PLAINS THURS NIGHT AND FRI...WITH A STRONG CLOSED MID LEVEL LOW CENTER EJECTING OUT INTO THE CENTRAL/SOUTHERN PLAINS REGION THROUGH SAT. THIS WILL DRIVE SURFACE LOW PRESSURE FROM THE SOUTHERN HIGH PLAINS ACROSS THE RED RIVER VALLEY FRI NIGHT AND SAT...AND NORTHEAST INTO THE MID MS VALLEY BY SUN AS A TRAILING COLD FRONT SWEEPS ACROSS THE SOUTHERN PLAINS AND LOWER MS VALLEY. THE MODELS SHOW GENERALLY GOOD MASS FIELD AGREEMENT THROUGH EARLY SAT AS THE AMPLIFYING UPPER TROUGH CLOSES OFF OVER THE FOUR CORNERS REGION...ALTHOUGH IT WAS NOTICED THAT THE 00Z ECMWF AGAIN LOOKS A TAD TOO WEAK IN THE 700/500 MB LAYER. IT WAS ALSO SEEN THAT THE 00Z UKMET WAS LIKELY A LITTLE TOO FAR NORTH WITH ITS LOW CENTER OVER WEST TX AND THE DOWNSTREAM WARM FRONT EXTENDING INTO THE MID MS VALLEY. BY LATER SAT AND SUN...THE 00Z UKMET TAKES ITS MID LEVEL LOW CENTER A BIT NORTH OF THE MODEL CONSENSUS WHICH DRIVES ITS SURFACE WAVE FARTHER NORTH. THE 00Z GFS AND 00Z ECMWF TEND TO CLUSTER TOGETHER THE BEST WITH THE MID LEVEL LOW CENTER...THE SURFACE LOW EVOLUTION AND THEIR RESPECTIVE TRAILING FRONTS...ALTHOUGH THE 00Z ECMWF DID SLOW DOWN JUST A TAD FROM ITS PREVIOUS RUN. OVERALL...THE 00Z CMC REMAINS AS THE SLOWEST SOLUTION...AND THE 00Z NAM IS THE DEEPEST SOLUTION. THE LATEST GEFS MEAN AND ECENS MEAN BOTH STILL SUPPORT THE DETERMINISTIC GFS/ECMWF CLUSTER..AND SO A BLEND OF THE GFS/ECMWF WILL BE PREFERRED. ...PACIFIC FRONTAL SYSTEM REACHING BRITISH COLUMBIA/PACIFIC NORTHWEST SAT... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z ECMWF CONFIDENCE: AVERAGE THE GUIDANCE ALL SUGGESTS AN UPPER TROUGH ADVANCING INTO THE PACIFIC NORTHWEST BY SAT AND THEN CLIPPING THE NORTHERN ROCKIES BY SUN. THE 00Z NAM AND 00Z CMC ARE THE SLOWEST SOLUTIONS...WITH THE 00Z UKMET THE FASTEST AND ALSO GENERALLY THE DEEPEST. THE 00Z GFS AND 00Z ECMWF SPLIT THE DIFFERENCE WITH TIMING...BUT THE 00Z GFS IS ALSO OVERALL THE WEAKEST SOLUTION. THE 00Z ECMWF TENDS TO REFLECT A REASONABLE SOLUTION FOR NOW WITH DEPTH AND TIMING OF THE ENERGY. WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/ WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/ ORRISON