MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1134 AM EST SUN FEB 21 2016 VALID FEB 21/1200 UTC THRU FEB 25/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...SHORTWAVE CROSSING THE MIDWEST/OH VALLEY/MID-ATLANTIC BY MON... ...SURFACE LOW CROSSING THE OH VALLEY AND MID-ATLANTIC... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THERE IS GOOD AGREEMENT CONCERNING THE TRACK OF THE SHORTWAVE APPROACHING THE MIDWEST WHICH WILL BE TRACKING THROUGH THE OH VALLEY TONIGHT AND QUICKLY THROUGH THE MID-ATLANTIC EARLY ON MON. THIS WILL DRIVE A WEAK AREA OF LOW PRESSURE ACROSS THE OH VALLEY AND MID-ATLANTIC BEFORE GOING OFFSHORE. THERE ARE ONLY VERY MINOR TIMING/DEPTH DIFFERENCES AT THIS POINT WITH THE GUIDANCE AND SO A GENERAL MODEL COMPROMISE WILL BE PREFERRED AT THIS POINT. ...SHORTWAVE ENTERING THE PACIFIC NORTHWEST TODAY... ...AMPLIFYING TROUGH OVER THE FOUR CORNERS/SOUTHERN PLAINS MON/TUES... ...DEVELOPING SURFACE LOW OVER THE SOUTHERN PLAINS/GULF COAST STATES... PREFERENCE: BLEND OF THE 12Z GFS/00Z UKMET/00Z ECMWF CONFIDENCE: AVERAGE THE MODELS SHOW GOOD AGREEMENT IN DIGGING SHORTWAVE ENERGY SOUTHEAST DOWN THROUGH THE FOUR CORNERS REGION AND OUT ACROSS THE SOUTHERN PLAINS MON AND TUES. BY WED...A STRONG MID LEVEL TROUGH AND ASSOCIATED CLOSED LOW WILL LIFT NORTHEAST ALONG WITH A DEEPENING AREA OF SURFACE LOW PRESSURE FROM THE LOWER MS VALLEY INTO THE OH/TN VALLEYS. THERE ARE STILL SOME NOTABLE DIFFERENCES WITH DEPTH AND TIMING...ALTHOUGH THERE IS STRONGER MODEL CLUSTERING COMPARED TO THE 12Z MODEL CYCLE FROM YESTERDAY. THE 00Z CMC REMAINS A MUCH SLOWER OUTLIER WITH THE EVOLUTION OF THE HEIGHT FALLS ACROSS THE SOUTHERN PLAINS AND THE LOWER MS VALLEY AND HAS A SLOWER/WEAKER SURFACE LOW. THE 12Z NAM IS THE MOST PROGRESSIVE AND ALSO TENDS TO BE A BIT WEAK WITH ITS SURFACE LOW AT LEAST THROUGH TUES...BUT THEN FALLS IN LINE WITH THE GLOBAL MODEL CONSENSUS BY WED WHICH IS COMPROMISED OF A STRONGER CLUSTERING OF THE 12Z GFS/00Z ECMWF AND 00Z UKMET. HOWEVER...IT IS NOTED THAT THE 00Z ECMWF WAS MAY BE A LITTLE TOO FAR NORTH WITH ITS LOW TRACK THROUGH EASTERN TX AND SOUTHERN AR...AND ESPECIALLY SINCE THE LATEST GEFS MEAN AND ECENS MEAN WERE A LITTLE FARTHER SOUTH AND CLOSER TO A CONSENSUS HERE OF THE GFS AND UKMET. FARTHER DOWNSTREAM...THE ECMWF HAS MUCH BETTER AGREEMENT WITH THE ENSEMBLE MEANS ALONG WITH THE GFS AND UKMET. BASED ON THE LATEST TRENDS AND CLUSTERING...WILL PREFER A BLEND OF THE 12Z GFS/00Z UKMET AND 00Z ECMWF. ...DEVELOPING SURFACE WAVE NEAR THE MID-ATLANTIC COAST BY TUES... PREFERENCE: BLEND OF THE 12Z GFS/00Z UKMET/00Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS SHOW A COASTAL LOW DEVELOPING JUST OFF THE MID-ATLANTIC COAST ON TUES IN RESPONSE TO SOME LEAD SHORTWAVE ENERGY SHEARING DOWNSTREAM IN SOUTHWESTERLY FLOW AHEAD OF THE LARGER SCALE HEIGHT FALLS OVER THE SOUTHERN PLAINS. THE 12Z NAM REMAINS A BIT STRONGER WITH THIS LEAD SHORTWAVE ENERGY AND AS A RESULT SUGGESTS A STRONGER WAVE ALONG THE MID-ATLANTIC COAST WHERE THERE WILL ALREADY BE A FRONTAL ZONE SITUATED. THE 00Z CMC APPEARS TO BE KEEPING THE LOW CENTER A BIT TOO FAR EAST. THE 12Z GFS/00Z UKMET AND 00Z ECMWF SPLIT THE DIFFERENCE...BUT AS THEY HAVE SUPPORT FROM THE ENSEMBLE MEANS. THUS...WILL PREFER A CONSENSUS OF THESE SOLUTIONS. ...SHORTWAVE DIGGING SOUTHEAST INTO THE UPPER MIDWEST ON TUES... ...WEAK SURFACE LOW CROSSING THE NORTHERN PLAINS AND UPPER MIDWEST... PREFERENCE: NON-CMC CONSENSUS CONFIDENCE: AVERAGE THE MODELS INDICATE A NORTHERN STREAM SHORTWAVE AMPLIFYING DOWN ACROSS THE UPPER MIDWEST BY TUES WHICH WILL DRIVE SURFACE LOW PRESSURE ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST BEFORE HEADING ACROSS LAKE SUPERIOR. THE 00Z CMC IS THE WEAKEST AND MOST PROGRESSIVE SOLUTION WITH THIS SYSTEM. SUFFICIENT AGREEMENT EXISTS WITH THE REMAINING MODELS FOR A NON-CMC CONSENSUS TO BE PREFERRED. ...SHORTWAVE DIGGING SOUTHEAST INTO THE NORTHERN PLAINS BY WED... PREFERENCE: 12Z GFS CONFIDENCE: AVERAGE THE MODELS SHOW ANOTHER SHORTWAVE DIGGING SOUTHEAST FROM SOUTHWEST CANADA AND INTO THE NORTHERN PLAINS BY WED WHICH WILL BE ACCOMPANIED BY A COLD FRONT. THE 00Z CMC AND TO AN EXTENT THE 00Z UKMET ARE MORE PROGRESSIVE THAN THE 12Z NAM AND 12Z GFS. THE 00Z ECMWF IS THE SLOWEST SOLUTION. THE LATEST GEFS MEAN AND ECENS MEAN TEND TO FAVOR THE GFS OVERALL WHICH SUGGESTS THE ECMWF IS A BIT TOO SLOW...AND SO WILL LEAN TOWARD THE GFS WITH THIS SYSTEM. ...SHORTWAVE TROUGH CROSSING THE WEST COAST ON WED... PREFERENCE: NON-UKMET CONSENSUS CONFIDENCE: AVERAGE AN EASTERN PACIFIC SHORTWAVE TROUGH WILL APPROACH AND CROSS THE WEST COAST ON WED AND WEAKEN CONSIDERABLY AS IT ENCOUNTERS A MEAN LAYER RIDGE THAT WILL INITIALLY BE FOCUSED ALONG THE WEST COAST. THE 00Z UKMET IS A STRONGER OUTLIER SOLUTION AS THE SYSTEM MOVES INLAND. THE REMAINING GUIDANCE IS RELATIVELY WELL CLUSTERED TOGETHER WITH THEIR TIMING AND DEPTH OF THE SYSTEM...AND SO A NON-UKMET CONSENSUS WILL BE PREFERRED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON