MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1232 AM EST SAT MAR 01 2014 VALID MAR 01/0000 UTC THRU MAR 04/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET AND GEM GLOBAL ...STRONG SYSTEM IN THE SOUTHWEST TONIGHT...SHEARING TOWARD THE EAST COAST SUN/MON... ...SURFACE LOW DEVELOPING ALONG THE ARCTIC FRONT OVER THE TN/OH VALLEYS/MID-ATLANTIC... PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE THE 00Z NAM IS A BIT STRONGER THAN THE GLOBAL MODEL CONSENSUS WITH THE STRONG DEEP LYR LOW CENTER OFFSHORE CA THAT WILL BE MOVING INLAND ACROSS CNTRL/SRN CA OVERNIGHT AND THROUGH SAT. THE ENERGY AGAIN IS EXPECTED TO QUICKLY MOVE INTO THE FOUR CORNERS REGION BY SUN WHILE SHEARING OUT...AND THE ENERGY WILL SHEAR DOWNSTREAM INTO THE LWR MS/TN VLYS BY MON WHILE INTERACTING WITH THE SRN PORTION OF AN ARCTIC FRONTAL ZONE THAT WILL BE DRAPED FROM THE LWR MS VLY NEWD INTO THE MID-ATLANTIC REGION. ASIDE FROM THE NAM BEING A LITTLE STRONGER WITH THE INITIAL SURGE OF HEIGHT FALLS INTO CA...THERE IS NOT SPREAD ALOFT DOWNSTREAM AT LEAST UNTIL THE SHEARING ENERGY REACHES THE LWR MS/TN VLYS AND MID-ATLANTIC LATE SUN THROUGH MON....WHEN THE NAM BEGINS BECOMES A BIT MORE PROGRESSIVE WITH THE ENERGY ENTERING A DEVELOPING MID/UPR LVL CONFLUENCE ZONE OVER THE MID-ATLANTIC AND NEW ENGLAND. THE 00Z GFS/00Z UKMET/00Z GEM GLOBAL AND THE 12Z ECMWF ARE CLUSTERED TOGETHER RATHER WELL IN BEING A LITTLE LESS SHEARED AND SLOWER. AT THE SFC...THE MODELS ARE SUGGESTING THAT THE SHEARING ENERGY WILL FOSTER AT LEAST TWO SFC WAVES OF LOW PRESSURE ALONG AN ARCTIC FRONTAL ZONE...WITH ONE ON SUN DEVELOPING MOST LIKELY IN THE LEE OF THE APPALACHIANS OVER THE CNTRL MID-ATLANTIC BEFORE EXITING NEWD OFFSHORE NEW ENGLAND BY EARLY MON. THE 00Z NAM IS A STRONG OUTLIER NOW WITH THE FIRST WAVE...AS THE 00Z UKMET/00Z GEM GLOBAL SOLNS ARE SEEN TRENDING NOW A LITTLE FLATTER AND MORE SUPPRESSED TWD THE ALREADY MORE SUPPRESSED 00Z GFS AND 12Z ECMWF. ALL OF THE MODELS SUGGEST THE ARCTIC FRONTAL ZONE SETTLING FARTHER SOUTH ACROSS THE MID-ATLANTIC AND TN VLY IN THE WAKE OF THE INITIAL WAVE...SETTING THE STAGE FOR A SECOND WAVE AS THE CORE OF WHAT IS LEFT OF THE UPSTREAM SHORTWAVE ENERGY AIMS FOR THE EAST COAST. THE 00Z NAM/00Z GFS/00Z GEM GLOBAL AND 12Z ECMWF ARE MORE SUPPRESSED WITH THE SECOND WAVE THAT EJECTS OUT OF THE TN VLY SUN NIGHT...WITH THE 00Z UKMET AGAIN FARTHEST NORTH. ALL OF THE MODELS TAKE THIS SECOND WAVE MORE BODILY EASTWARD AND RAPIDLY ACROSS THE SRN MID-ATLANTIC MON WITH THE FRONTAL ZONE CONTINUING FARTHER SOUTH AS HIGH PRESSURE NOSES ACROSS THE NORTHEAST. THE LATEST GEFS MEAN/ECENS MEAN SOLNS STRONGLY SUPPORT THE DETERMINISTIC GFS/ECMWF CLUSTER WITH THE UPSTREAM SHEARING ENERGY AND SUBSEQUENT DOWNSTREAM WAVE ACTIVITY/FRONTAL ZONE PLACEMENTS. GIVEN OVERALL TRENDS OF THE GEM GLOBAL AND UKMET AND THE BROADER ENSEMBLE SUPPORT...MINUS THE SREF MEAN...WILL PREFER A GFS/ECMWF BLEND ATTM...WITH STILL SLIGHTLY LIMITED CONFIDENCE GIVEN SOME OF THE SPREAD IN THE WAVE ACTIVITY. ...SHORTWAVE SWINGING THROUGH THE GREAT LAKES/NORTHERN NEW ENGLAND THIS WEEKEND... ...ARCTIC FRONT CROSSING THE MIDWEST AND DRAPING SOUTH ACROSS THE OHIO VALLEY AND MID-ATLANTIC SUN AND MON... PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF CONFIDENCE: AVERAGE THE 00Z NAM IS WEAKER/SLOWER AND MORE SHEARED WITH SHORTWAVE CLIPPING THE NRN GREAT LAKES SAT NIGHT...WHICH RESULTS IN THE CORRESPONDING SFC LOW BEING WEAKER/SLOWER AS WELL. THE 00Z GEM GLOBAL/00Z UKMET SOLNS HAVE TRENDED AWAY FROM THE NAM...AND SUPPORT THE 00Z GFS/12Z ECMWF CLUSTER WHICH IS A BIT MORE PROGRESSIVE YET LESS SHEARED WITH THE ENERGY. THIS GFS/ECMWF LED CLUSTER HAS STRONG SUPPORT FROM THE LATEST GEFS MEAN/ECENS MEAN SOLNS WITH THIS ENERGY AND SUGGESTING A MORE PROGRESSIVE SHORTWAVE/SFC LOW TRACK INTO SERN CANADA. THIS ALLOWS FOR AN ARCTIC COLD FRONT TO ADVANCE SOUTHEASTWARD A LITTLE QUICKER DOWN THROUGH THE MIDWEST/OH VLY THROUGH SAT...AND ACROSS NEW ENGLAND AND TWD THE MID-ATLANTIC ON SUN...AS SOMEWHAT STRONGER MID/UPR LVL CONFLUENCE SETS UP OVER THE NORTHEAST IN THE WAKE OF DEPARTING LOW PRESSURE. ONLY THE NAM IS SEEN BEING SLOWER TO BUILD THAT SAME CONFLUENCE ZONE DUE TO THEIR SLOWER SHORTWAVE TIMING INTO SERN CANADA...AND IS THUS A BIT SLOWER TO SEND THE ARCTIC FRONT SOUTHWARD. WILL STILL PREFER A GFS/ECMWF BLEND ATTM WITH CONFIDENCE INCREASING TO AVERAGE. ...UPPER LOW OVER WESTERN CANADA SUN THROUGH TUES... PREFERENCE: NON-NAM CONSENSUS CONFIDENCE: AVERAGE BY MON...THE 00Z NAM IS THE ONLY DETERMINISTIC MODEL AGAIN TO FOCUS THE EVOLVING UPPER LOW OVER SOUTHWESTERN CANADA FARTHER WEST...JUST OFF OR ON TOP OF THE BRITISH COLUMBIA COAST. THERE REMAINS BETTER CLUSTERING AMONG THE NON-NAM SOLUTIONS...WHICH CONTINUES INTO TUES. A NON-NAM CONSENSUS WILL BE PREFERRED ATTM. ...SHORTWAVE CURRENTLY OVER THE SRN PLAINS...REACHING THE SOUTHEAST BY SAT MORNING... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW SUFFICIENTLY GOOD ENOUGH AGREEMENT WITH THIS SYSTEM TO PREFER A GENERAL MODEL COMPROMISE. www.wpc.ncep.noaa.gov/html/model2.shtml... ORRISON