MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1157 AM EST WED MAR 01 2017 VALID MAR 01/1200 UTC THRU MAR 05/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS MODEL EVALUATION INCLUDING PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...BROAD LONGWAVE TROUGH MOVING INTO THE PLAINS TUES/WED... ...ASSOCIATED SURFACE LOW(S) ACROSS THE GREAT LAKES/NORTHEAST WED INTO THU... ...TRAILING COLD FRONT IN THE MS RIVER VALLEY WED AND INTO THE MID-ATLANTIC/SOUTHEAST BY LATE WED/EARLY THU... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-CMC BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE A COMPLEX PATTERN CONTINUES TO EVOLVE OVER THE EASTERN THIRD OF THE COUNTRY...WITH MULTIPLE SHORTWAVE FEATURES EMBEDDED WITHIN A BROAD LONGWAVE TROUGH THAT WILL PUSH FROM THE MID/UPPER MISSISSIPPI RIVER VALLEY INTO THE NORTHEAST BY TONIGHT. SURFACE LOW PRESSURE LIFTS ACROSS THE EASTERN GREAT LAKES INTO NORTHERN NEW ENGLAND AND ATLANTIC CANADA BY THURSDAY MORNING. THE ASSOCIATED SURFACE COLD FRONT...DRAPED SSW INTO THE OHIO VALLEY AND WESTERN GULF COAST...WILL PUSH EAST ACROSS THE EASTERN SEABOARD AND SOUTHEAST THIS AFTERNOON AND TONIGHT...AND ACROSS THE COASTAL SOUTHEAST TONIGHT BEFORE PUSHING OFFSHORE BY THURSDAY MORNING. OVERALL...MODELS ARE IN GOOD AGREEMENT WITH THE EVOLUTION OF THIS SYSTEM WED/THU. THE 12Z GFS REMAINS SLIGHTLY FASTER WITH THE EJECTING SHORTWAVE THROUGH THURSDAY THAN EITHER THE 12Z NAM OR 00Z ECMWF...BUT BOTH MODELS CATCH UP TO THE GFS BY FRIDAY MORNING. HOWEVER...RESULTANT FORECAST IMPACTS ARE MINIMAL. THE 00Z GEM REMAINS A STRONG/DEEP OUTLIER RELATIVE TO THE MODEL CONSENSUS WITH THE BASE OF THE TROUGH OVER THE OH VALLEY AND MID ATLANTIC BY THURSDAY. IT IS NOTABLE THAT THE 06Z NAEFS ABRUPTLY ADJUSTED BACK FLATTER AND MORE PROGRESSIVE...TOWARD THE REST OF MODEL GUIDANCE. THIS A HOPEFUL TREND THAT THE 12Z CMC WILL FOLLOW SUIT AND CLICK INTO LINE WITH THE REST OF GUIDANCE FOR THE END OF THE PERIOD. FOR THE TIME BEING...WILL CONTINUE THE PREFERENCE OF A NON-GEM BLEND. ...WEAK DISTURBANCE DROPPING ACROSS THE NORTHERN PLAINS TONIGHT...TOWARDS THE OHIO VALLEY/MID-ATLANTIC THU/FRI... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/UKMET AND 0Z ECMWF BLEND CONFIDENCE: AVERAGE LATEST WV/IR SAT IMAGERY SHOWING THE FIRST IN A SERIES OF WEAK DISTURBANCES DROPPING ACROSS THE DAKOTAS. GOOD MODEL AGREEMENT THAT A SECOND...STRONGER SHORTWAVE AND WEAK SURFACE WAVE/CLIPPER LOW WILL DIVE SOUTHEAST FROM THE CANADIAN PRAIRIES AND ACROSS THE NORTHERN PLAINS TONIGHT/EARLY THU...QUICKLY TRAVERSING INTO THE OHIO VALLEY LATER THU...TO A POSITION OFF THE MID-ATLANTIC COAST BY FRIDAY AFTERNOON. MODEL DIFFERENCES CONTINUE AT THIS TIME WITH RESPECT TO HOW STRONG THIS WAVE IS...AND AT WHAT LATITUDE IT TRACKS ACROSS. THE 12Z GFS HAS TRENDED SLIGHTLY FASTER WITH THE UPPER SYSTEM AND WEAKER WITH THE SURFACE REFLECTION...BUT REMAINS ON THE STRONG/DEEP SIDE OF THE GUIDANCE ENVELOPE W/THIS FEATURE. THE 12Z NAM...AND ITS 12Z PARALLEL RUN...HAVE TRENDED A BIT FASTER ALONG WITH THE GFS...AND MASS FIELDS DO PRESENT SIMILARLY. HOWEVER...THE 12Z NAM IS NOW A STRONG OUTLIER WITH THE SURFACE WAVE...DEPICTING THE SFC WAVE CLOSING OFF AFTER 00Z/SAT. THE 00Z ECMWF HAS TRENDED DEEPER WITH SUCCESSIVE RUNS TOWARD THE GFS SOLUTION...BUT REMAIN CONTINUE TO DEPICT A WEAKER WAVE AT THE SURFACE. THE NEW 12Z UKMET HAS TRENDED TOWARD THE GFS' FASTER/WEAKER SOLUTION FROM 12Z. OVERALL...MODELS ARE TRENDING TOWARD A CONSENSUS WITH PREFERRED LATITUDE ACROSS THE NORTHERN MID-ATLANTIC THROUGH SATURDAY MORNING...WITH MOST MEMBERS STILL FAVORING A FASTER EVOLUTION AND A WEAKER OPEN SURFACE WAVE. THE 12Z UKMET...WHICH TRENDED WEAKER/FASTER WITH ITS SOLUTION...NOW JIVES WELL WITH THE NEW 12Z/GFS AND OLD 00Z ECMWF. PENDING THE ARRIVAL OF THE REMAINDER OF THE 12Z SUITE...WILL FOLLOW THIS BLEND AT AVERAGE CONFIDENCE. ...BROAD UPPER LOW IN GULF OF ALASKA... ...EMBEDDED SHORTWAVES CARVING OUT UPPER TROUGH ACROSS THE PAC NW FRI/FRI NIGHT... ...ONSHORE FLOW ACROSS THE PAC NW EARLY IN THE PERIOD W/ STRONG COLD FRONT DROPPING ACROSS PAC NW/NORTHERN GREAT BASIN FRI/FRI NIGHT... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/UKMET AND 0Z ECMWF BLEND CONFIDENCE: AVERAGE THE BROAD UPPER LOW OVER THE GULF OF AK WILL PUSH EAST THROUGH THE PERIOD...WITH SHORTWAVE ENERGY ON THE SOUTHERN PERIPHERY OF THE LOW MOVING TOWARD THE PACIFIC NORTHWEST. MODELS ARE IN PRETTY GOOD AGREEMENT THROUGH FRIDAY NIGHT...WITH MODEL SPREAD INCREASING A BIT BY EARLY SAT. MODEL DIFFERENCES ARE STILL NOT VERY SIGNIFICANT BY DAY 3...HOWEVER DO NOTE SOME TIMING DIFFERENCES WITH THE LEAD STRONGER SHORTWAVE. THE 12Z GFS HAS TRENDED AGAIN TOWARD THE SLOWER 00Z ECMWF/12Z UKMET CAMP. A BLEND OF THESE THREE SOLUTIONS WILL BE USED ONCE AGAIN AND CLUSTERS WELL WITH THE RESPECTIVE ENSEMBLE MEANS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... MONTEFUSCO