MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1219 AM EST FRI NOV 25 2016 VALID NOV 25/0000 UTC THRU NOV 28/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 00Z NAM/GFS ALONG WITH PRELIMINARY PREFERENCES/FORECAST CONFIDENCE... ...MULTITUDE OF IMPULSES TRACKING FROM THE CENTER OF THE COUNTRY TOWARD THE NORTHEASTERN U.S... ...AREA OF SURFACE CYCLOGENESIS TAKING SHAPE OVER THE WESTERN ATLANTIC... PRELIMINARY PREFERENCE: A NON-12Z CMC MODEL COMPROMISE FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE WATER VAPOR IMAGERY TONIGHT SHOWED A MODEST BAND OF HEIGHT FALLS MOVING THROUGH THE MIDDLE MS VALLEY/UPPER GREAT LAKES REGION. THIS HAS SPREAD A DISORGANIZED BAND OF LIGHT PRECIPITATION TO THE REGION ALTHOUGH MOISTURE CONTENT IS SOMEWHAT LIMITED. THE LEAD IMPULSE SHOULD CONTINUE TO ACCELERATE TOWARD THE LOWER GREAT LAKES INTO FRIDAY MORNING WHILE TRAILING SHORTWAVE ENERGY SWEEPS IN BEHIND. THIS ENTIRE SYSTEM SHOULD GRADUALLY STRENGTHEN AND ATTAIN A NEGATIVE TILT ACROSS THE NORTHEASTERN U.S. AT A FIRST GLANCE...THE 12Z CMC REMAINS TOO QUICK ALOFT ACCOMPANIED BY A SURFACE LOW FARTHER NORTH AND CLOSER TO THE MAINE COAST. BASED ON AN EVALUATION OF THE RECENT ENSEMBLE LOW PLOTS...THERE HAS BEEN A MOVE AWAY FROM THE COAST WITH MANY OF THE MEMBERS FARTHER EAST THAN PREVIOUSLY...PARTICULARLY THE ECMWF CAMP. GIVEN MOST SOLUTIONS ARE CLOSE TO ONE ANOTHER...WILL PLAN ON STAYING AWAY FROM THE 12Z CMC AND FAVOR THE REMAINING MODELS. ...COMPACT SHORTWAVE CROSSING THE WA COAST DURING THE NEXT FEW HOURS... PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: HIGH AHEAD OF A SHORTWAVE MOVING TOWARD THE WA COAST...STRONG MOISTURE TRANSPORT AIMING AT THE COASTAL RANGES CONTINUES TO SUPPORT MODERATE TO LOCALLY HEAVY PRECIPITATION. THIS SYSTEM QUICKLY MOVES INTO SOUTHERN BRITISH COLUMBIA AND THUS NO LONGER IMPACTS THE CONUS. GIVEN STRONG AGREEMENT EARLY ON...A GENERAL MODEL COMPROMISE IS WARRANTED. ...STRONG SYSTEM MOVING THROUGH THE DESERT SOUTHWEST BY SATURDAY EVENING... ...EVENTUAL CLOSED LOW/DEEP SURFACE CYCLONE ACROSS THE NORTHERN PLAINS... PRELIMINARY PREFERENCE: LEAD WAVE MOVING TOWARD THE OR/CA BORDER: BLEND OF THE 12Z ECMWF/UKMET...THEREAFTER: BLEND OF THE 18Z GEFS/12Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: INITIALLY AVERAGE...THEN BECOMING BELOW AVERAGE ALONG THE SOUTHWESTERN FLANK OF LOWER HEIGHTS ACROSS THE EASTERN PACIFIC...A SHARPENING BAND OF HEIGHT FALLS WILL TAKE AIM ON SOUTHERN/CENTRAL CA DURING THE NEXT 36 TO 48 HOURS. COMPARING THE LAST FOUR ENSEMBLE SPAGHETTI PLOTS...THE BIG SHIFT IN THE MODELS OCCURRED ROUGHLY 36 HOURS WITH MORE STABILITY IN THE RECENT CYCLES. CONSIDERING THE FORECAST BEGINNING AT 26/0000Z...THERE IS CONSIDERABLE VARIABILITY IN THE INITIAL LOW TRACK ROUGHLY ALONG 40N LATITUDE. THE 00Z GFS SHIFTED TOWARD THE NORTHEAST WHICH HAS ONLY 2 OF ITS 20 GEFS MEMBERS SUPPORTING ITS CYCLONE TRACK. THE STRONGER ENSEMBLE CLUSTERING IS TO THE SOUTH WITH THE 12Z ECMWF/UKMET AND PERHAPS THE 21Z SREF MEAN FOLLOWING THIS IDEA. LATER ON...THE IMPRESSIVE SHORTWAVE ACCELERATES THROUGH SOUTHERN/CENTRAL CA BY 27/0000Z WITH THE ONLY MODEL LAGGING THE CONSENSUS BEING THE 21Z SREF MEAN WHICH IS SLOWER. CONSIDERABLE DIFFERENCES EMERGE LATER IN THE PERIOD AS THE SYSTEM MOVES THROUGH THE FOUR CORNERS REGION AND EVENTUALLY SITUATES ITSELF OVER THE CENTRAL U.S. BY SUNDAY NIGHT/MONDAY MORNING. MODELS REMAIN SCATTERED ABOUT WITH THE GFS/ECMWF SUITES STILL REMAINING SEPARATED. ENSEMBLE LOW PLOTS SHOW THE PAST THREE RUNS HAVE PLACED THE GEFS MEMBERS NORTH OF THE ECMWF SOLUTIONS. HONESTLY NOT SURE WHICH DIRECTION TO GO SO WILL TAKE A SPLIT RIGHT DOWN THE MIDDLE HERE. ...TRAILING BAND OF MID-LEVEL HEIGHT FALLS DIVING THROUGH THE CENTRAL GREAT BASIN ON SUNDAY... PRELIMINARY PREFERENCE: BLEND OF THE 18Z GEFS/12Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE AS THE FIRST SHORTWAVE MIGRATES THROUGH THE DESERT SOUTHWEST...ANOTHER BATCH OF ENERGY DIVES DOWN FROM THE NORTHEASTERN PACIFIC. BY SUNDAY MORNING...THIS SYSTEM IS EXPECTED TO BE IN THE VICINITY OF NORTHERN CA AND INTO THE CENTRAL GREAT BASIN. THE 00Z NAM DEPICTS A MORE PRONOUNCED CLOSED LOW MOVING DOWN THE SIERRA. LIKE YESTERDAY...THERE REMAINS A DISTINCT SEPARATION IN THE SOLUTIONS WITH THE 12Z ECMWF BEING EAST OF THE 00Z GFS. FURTHER...THE 12Z ECMWF HAS SUPPORT FROM THE 12Z CMC WHILE THE 00Z GFS HAS THE 12Z UKMET GENERALLY ON ITS SIDE. FEEL COMPELLED TO JUST SPLIT THE DIFFERENCE LIKE THE SYSTEM FARTHER DOWNSTREAM. ...SHORTWAVE WITHIN NORTHWESTERLY FLOW TRACKING INTO THE PACIFIC NORTHWEST LATE IN THE PERIOD... PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE LATE IN THE FORECAST PERIOD...MODELS INDICATE A PROGRESSIVE SHORTWAVE WILL DESCEND THE NORTHEASTERN SIDE OF A STRONG UPPER RIDGE. SOLUTIONS ARE REASONABLY CLOSE TO ONE ANOTHER ACROSS THE STATE OF WA ON MONDAY MORNING WHICH SUPPORTS A GENERAL MODEL COMPROMISE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER