MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 204 AM EST THU FEB 11 2016 VALID FEB 11/0000 UTC THRU FEB 14/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z GUIDANCE EVALUATION INCLUDING FINAL MODEL PREFERENCE AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ QUICK MOVING S/WV MOVING FROM THE NRN HI PLAINS TO OFF THE CAROLINA COAST THUR/FRI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: MODEL BLEND CONFIDENCE: ABOVE AVERAGE GUIDANCE IS FAIRLY WELL CLUSTERED HERE WITH VERY CHANNELED S/WV ENERGY THRU THE PLAINS EARLY DAY 1..SUPPORTING NARROW BAND OF WAA PCPN..MAINLY LIGHT SNOW THRU PARTS OF THE DAKOTAS INTO THE MO VALLEY WHERE ENERGY WILL QUICKLY TRANSITION TOWARD DVLPG COASTAL DVLPMENT NEAR THE S/NC COAST WITH LOW DEEPENING AS IT RACES QUICKLY TO THE NE FRI NIGHT. AN OPERATIONAL MODEL BLEND SHOULD HANDLE THIS SYSTEM WELL. WEAK LOW ALONG ARCTIC COLD FRONT AFFECTING THE ERN LAKES INTO NEW ENGLAND FRI/SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: MODEL BLEND CONFIDENCE: ABOVE AVERAGE VORT MAX SOUTH OF DEEP ARCTIC VORTEX IS EXPECTED TO SLIDE EWD THRU THE CNTL/ERN GT LAKES INDUCING WEAK LOW ALONG ASSOCD REINFORCING ARCTIC COLD FRONT THAT WILL PUSH TOWARD NRN NEW ENGLAND FRI NIGHT/SAT. THIS SYSTEM WILL HAVE LIMITED MSTR TO WORK WITH AND MODELS SUGGEST AND OVERALL WEAKENING AS THE SYSTEM MOVED TOWARD NEW ENGLAND. HOWEVER...BY SAT...MODELS ALL SUGGEST THAT THE LOW LEVEL RESPONSE FROM UPR VORT LIFTING TOWARD ERN NEW ENGLAND WILL INDUCE INCREASING SURFACE TROFINESS AND MSTR CONNECTION WITH STGR OFFSHORE LOW (NORLUN TROF) TO SUPPORT INCREASING PCPN AMOUNTS INVOF TROF AXIS OVER ERN MAINE. THERE IS A STRONG INDICATION IN MOST OF THE 12Z AND 00Z GUIDANCE FOR THIS TO OCCUR AND IS SUPPORTED BY THE 18Z GEFS MEAN AS WELL. THE OVERALL MODEL SPREAD WAS RELATIVELY MINOR EVEN AT THIS TIME RANGE SUGGESTING A GENL MODEL BLEND/ENSEMBLE MEAN WOULD BE WELL SUITED. SERIES OF SYSTEMS AFFECTING THE NW THUR INTO SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: EC/GEFS MEANS CONFIDENCE: SLIGHTLY BELOW AVERAGE RATHER COMPLEX CIRC WAS NOTED OFF THE WEST COAST WED EVENING WITH A SERIES OF S/WVS ROTATING ABOUT A MEAN UPR LOW NEAR 47N/155W. MODELS BRING A LEAD S/WV AND ASSOCD FRONT TOWARD THE NW COAST THUR NIGHT/FRI. THE NAM AND GFS HAD BEEN SLIGHTLY ON THE FASTER END OF GUIDANCE WITH THIS FEATURE...THOUGH THE GFS HAS TRENDED EVER SO SLIGHTLY SLOWER DURING THE DAY 1 PD AND CLOSER TOWARD THE SLOWER MODEL CONSENSUS. THIS LEAD ENERGY AND FRONT ARE EXPECTED TO WEAKEN RAPIDLY ENEWD INTO SW CANADA FRI NIGHT WHILE TRAILING ENERGY...MORE TIED TOWARD INITIAL UPR LOW PUSHES TOWARD THE WA COAST FRI NIGHT..THEN WEAKENS RAPIDLY INLAND THROUGH THE NRN INTERMOUNTAIN REGION. BY DAY 3...SAT NIGHT INTO SUN MRNG...STG ZONAL FLOW PATRN SETS UP NORTH OF STG UPR RIDGING DVLPG OFF THE CALIFORNIA COAST WITH QUICK S/WV ENERGY MOVING TOWARD THE B.C. COAST HELPING TO INITIATE WHICH COULD BE A MULTI-DAY RAIN EVENT FOR THE PAC NW..SOME OF WHICH WILL BE HEAVY RAINS. TIMING DIFFERENCES BEGIN TO SHOW UP BY DAY 2 WITH THE 12Z EC BEING A LITTLE QUICKER/FLATTER WITH THE 2ND S/WV MOVING INTO WA STATE LATE FRI NIGHT. EVEN WITH THE TIMING DIFFERENCES THE 12Z EC AND 18Z GEFS MEANS MATCHED UP QUITE WELL BY 12Z SUN AND APPEAR TO BE A GOOD MIDDLE GROUND APCH AT THIS TIME...THOUGH WITH ONLY AVERAGE CONFIDENCE. SYSTEM IMPACTING THE NRN PLAINS SAT/SAT NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/NAM/GEFS MEAN CONFIDENCE: AVERAGE SOME AMPLITUDE/TIMING DIFFERENCES BEGIN TO SHOW UP SAT WITH REMAINS OF ERN PAC UPR LOW THAT QUICKLY DAMPENS OUT INTO THE PAC NW SAT MRNG BEFORE DIGGING SEWD ACRS THE NRN ROCKIES INTO THE PLAINS SAT NIGHT. THE 12Z EC APPEARS TO BE ON THE SOMEWHAT FASTER/FLATTER END OF GUIDANCE AND IS NORTH OF MOST OF ITS ENSEMBLE GUIDANCE...WHILE THE 00Z RUN IS MARGINALLY MORE AMPLIFIED..BUT STILL ON THE FASTER SIDE OF THE GUIDANCE. CONSIDERING HOW AMPLIFIED THE DOWNSTREAM UPR TROF IS...THERE APPEARS ROOM FOR THE UPR FLOW TO BUCKLE ACRS THE PLAINS. THE 12Z UKMET WAS THE MOST AMPLIFIED AND SLOWER WITH THE TROF THROUGH THE ROCKIES AND WHILE IT HAD SUPPORT FROM A FEW EC MEMBERS...THOUGHT A BLEND OF GFS/NAM/GEFS MEAN APPEARED TO BE A GOOD COMPROMISE AT THIS TIME. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... SULLIVAN