MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1132 PM EST WED NOV 18 2015 VALID NOV 19/0000 UTC THRU NOV 22/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...WEAKENING CLOSED LOW EXITING THE UPPER GREAT LAKES... ...DEEP PHASED CYCLONE MOVING ACROSS ONTARIO... ...COLD FRONT PUSHING THROUGH THE EAST THURS AND FRI... ...SURFACE WAVE IMPACTING SOUTHERN NEW ENGLAND ON FRI PREFERENCE: GENERAL MODEL COMPROMISE...THROUGH 48 HOURS BLEND OF THE 00Z GFS/12Z UKMET AND 12Z ECMWF...AFTER 48 HOURS CONFIDENCE: ABOVE AVERAGE...BECOMING AVERAGE AFTER 48 HOURS THE LATEST MODELS ARE IN EXCELLENT AGREEMENT WITH THE DETAILS OF THE EXITING MID LEVEL CLOSED LOW OVER THE UPPER GREAT LAKES REGION AND THE DEEP PHASED CYCLONE THAT EVOLVES OVER ONTARIO BEFORE THEN LIFTING UP OVER HUDSON BAY BY SAT. THE GUIDANCE ALSO SHOWS GOOD AGREEMENT WITH THE TIMING OF THE COLD FRONT MOVING THROUGH THE EASTERN U.S. AND ALSO WITH THE FRONTAL WAVE THAT IMPACTS SOUTHERN NEW ENGLAND ON FRI. DIFFERENCES THOUGH BEGIN BY SAT WITH THE DETAILS OF HOW THIS WAVE PUSHES EAST OF NEW ENGLAND. STRONGER MODEL CLUSTERING FAVORS A CONSENSUS OF THE 00Z GFS/12Z UKMET AND 12Z ECMWF...WITH THE 00Z NAM AND 12Z CMC PROBABLY A TAD TOO STRONG WITH THEIR LOW CENTERS. SO...WILL PREFER A GENERAL MODEL COMPROMISE THROUGH 48 HOURS...AND THEN A CONSENSUS OF THE 00Z GFS/12Z UKMET AND 12Z ECMWF THEREAFTER. ...SURFACE LOW APPROACHING THE PACIFIC NORTHWEST... ...ENERGY TRAVERSING THE INTERMOUNTAIN WEST THROUGH THURS... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE GUIDANCE SHOWS GOOD AGREEMENT WITH THE DETAILS OF THE SURFACE LOW MOVING INTO WESTERN ORE EARLY THURS AND THEN THROUGH THE INTERMOUNTAIN REGION BY LATE THURS. WILL PREFER A GENERAL MODEL COMPROMISE ACROSS THIS REGION AS A RESULT. ...DEEPENING SURFACE LOW/UPPER TROUGH OVER THE PLAINS/MIDWEST/GREAT LAKES... PREFERENCE: BLEND OF THE 00Z GFS AND 12Z ECMWF CONFIDENCE: AVERAGE THE LOW CENTER MOVING THROUGH THE INTERMOUNTAIN WEST ON THURS WILL BE REDEVELOPING AND DEEPENING OUT ACROSS THE CENTRAL HIGH PLAINS BY EARLY FRI AS ROBUST NORTHERN STREAM SHORTWAVE ENERGY DIVES SOUTHEAST ACROSS THE NORTHERN AND CENTRAL ROCKIES. THIS WILL LEAD TO AN AMPLIFYING UPPER TROUGH ACROSS THE PLAINS AND MIDWEST FRI AND SAT WHICH WILL DRIVE SURFACE LOW PRESSURE EAST ACROSS THE CENTRAL PLAINS...MID MS VALLEY AND THEN NORTHEAST TOWARD THE LOWER GREAT LAKES REGION SAT NIGH AND SUN. THE 00Z GFS HAS TRENDED A BIT SLOWER AND DEEPER WITH THE STRENGTHENING LOW CENTER AND IS JUST A TAD FASTER THAN THE 12Z ECMWF SAT AND SUN AS IT EJECTS ACROSS THE MID MS VALLEY AND LOWER GREAT LAKES. BY SUN...THE 00Z GFS BECOMES THE MOST AMPLIFIED SOLUTION. THE 00Z NAM AND 12Z CMC ARE BOTH WEAK OUTLIERS AND WILL BE DISCOUNTED AND THE 12Z UKMET APPEARS TO BE TOO SLOW. STRONGER ENSEMBLE SUPPORT FAVORS A MORE AMPLIFIED SOLUTION...AND SINCE THE 00Z GFS TRENDED STRONGER...IT WILL NOT BE DISCOUNTED. HOWEVER...THERE IS SOME POTENTIAL FOR IT TO BE A BIT TOO AMPLIFIED ON SUN. THUS...WILL TEMPER IT BY RECOMMENDING A BLEND OF THE 00Z GFS AND 12Z ECMWF. ...WARM FRONT EJECTING OUT INTO THE NORTHERN HIGH PLAINS ON SUN... PREFERENCE: 12Z ECMWF CONFIDENCE: AVERAGE THE MODELS SHOW A VERY DEEP LOW CENTER MOVING THROUGH CENTRAL CANADA BY EARLY SUN...AND THIS WILL ALLOW A WARM FRONT TO BEGIN IMPACTING THE NORTHERN HIGH PLAINS. THE MASS FIELD SPREAD WITH THE LOW CENTER IS RATHER MINIMAL...BUT THE 12Z ECMWF SEEMS TO BE RESOLVING THE SURFACE PRESSURE FIELDS INVOLVING THE HIGH PLAINS AND ADJACENT TERRAIN A BIT BETTER. THUS...WILL PREFER THE 12Z ECMWF WITH THIS SYSTEM FOR NOW. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON