MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1220 AM EDT FRI JUL 29 2016 VALID JUL 29/0000 UTC THRU AUG 01/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION INCLUDING PREFERENCE AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TUTT ENERGY LIFTING INTO MID-ATLANTIC/NEW ENGLAND FRI INTO SAT WITH SURFACE LOW DEVELOPING IN VA PIEDMONT AND MOVING ALONG NORTHEAST COAST THROUGH SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-CMC BLEND CONFIDENCE: ABOVE AVERAGE SYNOPTIC SPREAD REMAINS FAIRLY SMALL WITH RESPECT TO THE REMAINING SHORTWAVE ENERGY OF THE OLD TUTT TRANSLATING ACROSS THE MID-ATLANTIC INTO NEW ENGLAND BY FRI EVENING. SOME SPREAD REMAINS WITH RESPECT TO THE SURFACE LOW ALONG THE FRONTAL BOUNDARY BUT GIVEN IT IS GENERALLY WEAK...THIS WOULD BE EXPECTED GIVEN THE FIELD'S RESPONSE TO MESOSCALE CONVECTION...PLEASE REFER TO WPC QPFPFD FOR ADDITIONAL DETAILS ON THE QPF/QPF AXIS. THE 12Z CMC IS THE ONLY SIGNIFICANT OUTLIER BEING FAST (ATYPICAL OF THE CMC) AND DEEP (TYPICAL) MAINLY AT THE SURFACE; ESPECIALLY COMPARED TO GEFS/ECENS MEANS. A NON-CMC BLEND IS PREFERRED AT ABOVE AVERAGE CONFIDENCE. MULTIPLE WEAK SHORTWAVES OVERTOPPING SW RIDGE TO CARVE OUT A BROAD/WEAK TROF ACROSS LOWER MISSOURI RIVER VALLEY FRI AND INTO THE SOUTHERN GREAT LAKES/OH RIVER VALLEY BY SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/NAM AND 12Z ECMWF BLEND CONFIDENCE: AVERAGE BROAD TROUGHING EXISTS AND WILL CONTINUE TO DEVELOP ACROSS THE NORTHERN PLAINS INTO THE MS RIVER VALLEY IN THE WAKE OF THE EXITING CLOSED LOW IN CANADA/TUTT CELL LIFTING NORTHEAST THROUGH NEW ENGLAND. THIS PATTERN SUPPORTS NUMEROUS CONVECTIVELY INDUCED UPSCALE GROWTH SCENARIOS...SOME WITH ADDITIVE EFFECTS...AS WAVES DROP SOUTHEAST AROUND THE PERIPHERY OF THE SOUTHWESTERN U.S. RIDGE. THE 12Z CMC AND UKMET BOTH SUPPORT THIS ADDITIVE EFFECT ACROSS THE LOWER OHIO VALLEY INTO LOWER GREAT LAKES BY SAT; THE UKMET LESSER SO. CONTRARY TO THIS THE 12Z ECMWF AND 00Z NAM/GFS CONTINUE TO BE ALIGNED QUITE WELL WITH THE TIMING OF THE ENSEMBLE. THOUGH VARIATION IN QPF CAN BE QUITE SUBSTANTIAL...PLEASE REFER TO QPFPFD FOR ADDITIONAL DETAILS. OTHERWISE WILL CONTINUE TO SUPPORT A 00Z GFS/NAM AND 12Z ECMWF BLEND AS MOST PROBABLE OUTCOME AT THIS TIME. LEAD SHORTWAVE TROF CLOSING OFF WHILE CROSSING SW CANADA BY SAT INTO MON SECOND CLOSED LOW APPROACHING THE PAC NORTHWEST BY MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~ PREFERENCE: NON-CMC BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE A DEVOLVING CLOSED LOW IN THE GULF OF ALASKA IS ELONGATING WITH NUMEROUS INTERNAL SHORTWAVES NOTED. AS THE OVERALL PATTERN SUPPORTS SOUTHEASTWARD TRACKING OF THE ENERGY...THE MODELS ARE IN GENERAL AGREEMENT WITH THE EVENTUAL INTERACTION OF SHORTER WAVE FEATURES CONSOLIDATING INTO TWO MORE CONCENTRIC CLOSED LOW(S) ACROSS WESTERN CANADA AND THE GULF OF ALASKA OVER THE WEEKEND INTO MON. THE LEAD WAVE HAS STRONGER MODEL AGREEMENT BUT THERE REMAINS SOME SPREAD PARTICULARLY WITH THE OVERALL STRENGTH. THE 00Z NAM (ALONG WITH THE 12Z UKMET) HAS SHIFTED TO A MUCH DEEPER CONCENTRIC SOLUTION BUT ALSO A NORTHERN SOLUTION WITH THE CENTER/TRACK. THE GFS HAS BEEN VERY SOLID AND CONSISTENT OVER THE PAST DAY OR SO WITH THE EVOLUTION OF THIS LOW THOUGH ALSO ON THE WEAKER/SHALLOWER SIDE IS MORE CENTRAL TO THE OVERALL CLUSTER AND CONTINUES TO BE MOST FAVORED. THE ECMWF HAS BEEN LESS RELIABLE THOUGH APPEARS TO BE CONSOLIDATING ON A SOLUTION...THOUGH THE 12Z RUN (SUPPORTED BY THE 12Z ECENS MEAN) REMAINS THE SOUTHERN-MOST ON THE TRACK OF THE LOW. THE 12Z CMC IS MOST OF AN OUTLIER AS IT REMAINS QUITE ELONGATED/ECCENTRIC COMPARED TO THE OTHER CONCENTRIC DETERMINISTIC MODELS. OVERALL WILL CONTINUE TO FAVOR A NON-CMC BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. THE UPSTREAM SECOND CLOSED LOW APPROACHES VANCOUVER ISLAND/NW WASHINGTON BY THE END OF THE FORECAST PERIOD... MODELS ARE MUCH TIGHTER PACKED ON THE EVOLUTION EXCEPT THE CMC WHICH IS WEAKER/SLOWER. THE 12Z UKMET IS A BIT FAST...PER USUAL BUT NOT ENOUGH TO BREAK FROM THE NON-CMC BLEND FOR BOTH SYSTEMS. GALLINA www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...