MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 158 AM EST FRI MAR 10 2017 VALID MAR 10/0000 UTC THRU MAR 13/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 00Z MODEL EVALUATION ALONG WITH FINAL PREFERENCES/FORECAST CONFIDENCE... ...AMPLIFIED FLOW CROSSING THE MID-ATLANTIC REGION BY 10/1200Z... ...SURFACE WAVE LIFTING AWAY FROM THE DELMARVA PENINSULA... FINAL PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE WATER VAPOR IMAGERY AND MID-LEVEL HEIGHT FIELDS SHOW BROAD CYCLONIC FLOW ACROSS MUCH OF EASTERN NORTH AMERICA WITH FLOW GRADUALLY AMPLIFYING ACROSS THE MIDDLE MS VALLEY. WARM ADVECTION IN ADVANCE OF THIS SYSTEM CONTINUES TO SPREAD LIGHT/MODERATE MIXED PRECIPITATION TYPES ACROSS THE OH VALLEY/CENTRAL APPALACHIANS WITH DEEPER CONVECTION TO THE SOUTH ACROSS THE TN VALLEY/MID-SOUTH. THE MID-LEVEL HEIGHT FALLS CROSS THE MID-ATLANTIC FRIDAY MORNING WHICH SPAWNS A WAVE OFF THE DELMARVA PENINSULA. WITH THE 00Z UKMET MOVING CLOSER TO THE MODEL CONSENSUS...A COMPROMISE OF SOLUTIONS SEEMS REASONABLE AT THIS POINT. ...SLOW-MOVING MYRIAD OF MESOSCALE VORTICES TRACKING FROM MX TOWARD/ALONG THE GULF COAST... ...POTENTIAL SURFACE LOW IN THE GULF OF MX/SOUTHEASTERN U.S... FINAL PREFERENCE: BLEND OF THE 00Z GFS/GEFS MEAN WITH THE 00Z ECMWF/12Z ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: BELOW AVERAGE A RATHER EXPANSIVE AREA OF UNSETTLED WEATHER ACROSS CENTRAL/EASTERN MX WILL GRADUALLY SHIFT ITS FOCUS TOWARD THE NORTH AND EAST THE NEXT DAY OR SO. CURRENT SATELLITE IMAGERY/LIGHTNING DATA INDICATE A FAIRLY ACTIVE NIGHT ACROSS MX WHICH IS SOMEWHAT DISORGANIZED IN NATURE. ALL OF THIS ACTIVITY AND THE ASSOCIATED MID-LEVEL VORTICES MAY INDUCE A WAVE OF LOW PRESSURE ACROSS THE WESTERN GULF OF MX. HOWEVER...THIS ASPECT OF THE FORECAST REMAINS NEBULOUS AT BEST AS THE GUIDANCE CONTINUES TO SUGGEST SEVERAL DIFFERENT POSSIBILITIES. ENSEMBLE SCATTER LOW PLOTS THE PAST COUPLE OF DAYS HAVE SHOWN A DECREASING NUMBER OF MEMBERS SUPPORTING WAVE DEVELOPMENT BY 12/1200Z ACROSS THE NORTHWESTERN/NORTH-CENTRAL GULF OF MX. THE OTHER SCENARIO NOTED WAS THE NUMBER OF GEFS MEMBERS WHICH HAD BEEN SHOWING A SURFACE LOW OFF THE SOUTHEASTERN U.S. COAST BY THE SAME TIME. THE 12Z CYCLE SHOWS A MUCH LOWER NUMBER OF GEFS MEMBERS THAN PREVIOUS MODEL RUNS. THUS...CONFIDENCE IN ANY OF THESE SCENARIOS HAS DIMINISHED WHICH LOWERS CONFIDENCE IN THIS FORECAST. OVERALL...EACH PARTICULAR CAMP HAS SOME DETERMINISTIC MODEL SUPPORT WITH THE FARTHER EAST SCENARIO FAVORED BY THE 00Z NAM/GFS WHILE THE SLOWER FORECAST FEATURES THE 00Z ECMWF/CMC/UKMET. A BLENDED APPROACH CONTINUES TO BE THE BEST PATH HERE ALTHOUGH WILL UTILIZE SOME ENSEMBLE MEANS GIVEN THE 00Z GUIDANCE HAS NOT REALLY RESOLVED THE SITUATION JUST YET. ...ADDITIONAL AMPLIFICATION OF THE MID-LATITUDE FLOW ACROSS THE EASTERN U.S. BY SUNDAY... FINAL PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF FORECAST CONFIDENCE: AVERAGE WHILE A POSSIBLE SURFACE LOW INHABITS THE GULF OF MEXICO/GULF COAST REGION TOWARD THE END OF THE WEEKEND...THE MID-LATITUDE FLOW BEGINS TO RE-AMPLIFY AS A SERIES OF SHORTWAVES DIG THROUGH THE MS RIVER VALLEY AND INTO THE EASTERN U.S. REGARDLESS OF SOLUTION...AMPLIFIED FLOW ACROSS THE EASTERN U.S. WILL FAVOR BELOW AVERAGE TEMPERATURES GIVEN THE PERSISTENT COLD ADVECTION REGIME. ONE OF THE BIGGER CHANGES IN THE GUIDANCE WAS THE 00Z ECMWF BECOMING SLOWER/MORE AMPLIFIED WITH ONE PARTICULAR SHORTWAVE CROSSING THE SOUTHERN U.S. THIS WEEKEND. COMPARING THIS TO ENSEMBLE SPAGHETTI PLOTS...IT IS A BIT MORE EXTREME THAN MOST OF THE CONTOURS. THIS MORE PRONOUNCED WAVE ALSO RAISES SOME OF THE QPF AMOUNTS ACROSS THE CENTRAL U.S. PREFER TO STICK CLOSER TO THE PREVIOUS PREFERENCE AND KEEP THE 12Z ECMWF IN THE BLEND. ...INITIAL SHORTWAVE ENERGY PUSHING INTO COASTAL WA BY SATURDAY AFTERNOON... ...EVENTUAL MID-LEVEL HEIGHT FALLS CROSSING THE CENTER OF THE COUNTRY/ATTENDANT SURFACE WAVE... FINAL PREFERENCE: BLEND OF THE 00Z NAM/ECMWF WITH THE 00Z GEFS/12Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE SHORTWAVE ENERGY CROSSING THE PACIFIC NORTHWEST ON SATURDAY WILL GRADUALLY TURN MORE SOUTHEASTWARD IN ADVANCE OF A BUILDING UPPER RIDGE ACROSS THE WESTERN U.S. THIS PARTICULAR FEATURE AS WELL AS A NORTHERN STREAM TROUGH WILL SET THE STAGES FOR SURFACE WAVE DEVELOPMENT OVER THE MIDDLE MS VALLEY BY 13/1200Z. THE 00Z UKMET HAS MADE A SIGNIFICANT SHIFT TO THE SOUTH WHICH BRINGS IT MUCH CLOSER TO THE CONSENSUS SEEN IN ENSEMBLE LOW PLOTS. FOR A 96-HOUR FORECAST....THERE IS NOT TOO MUCH SPREAD IN THE MEMBERS WITH THE BEST CLUSTER OVER NORTHERN MO INTO IA ON MONDAY MORNING. THE 00Z GFS SHIFTED SOUTHWARD AWAY FROM ITS ENSEMBLE MEAN SO WILL NOT UTILIZE IT IN THE PREFERENCE HERE. THE 00Z NAM/ECMWF AS WELL AS THE SOME OF THE ENSEMBLE MEANS...00Z GEFS/12Z ECMWF...WOULD BE A GOOD STARTING POINT HERE. OF NOTE...THE 21Z SREF MEAN IS WELL EAST OF THIS CONSENSUS AND IS NOT RECOMMENDED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER