MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1208 AM EDT TUE JUL 07 2015 VALID JUL 07/0000 UTC THRU JUL 10/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...SHORTWAVE TROUGH CLIPPING THE GREAT LAKES/NORTHERN NEW ENGLAND... ...SURFACE WAVE DEVELOPING ALONG THE ATTENDANT FRONT OVER THE OH VALLEY... PREFERENCE: NON-NAM CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS TAKE THE SOUTHERN PORTION OF A NORTHERN STREAM SHORTWAVE TROUGH ACROSS THE GREAT LAKES AND NORTHERN NEW ENGLAND THROUGH TUES AND WED. AN ASSOCIATED COLD FRONT WILL CROSS THESE AREAS AS WELL...BUT THE TAIL END OF THE FRONT SHOULD STALL OUT OVER THE OH VALLEY AS A WAVE OF LOW PRESSURE DEVELOPS AND MOVES EAST ALONG IT. THIS WAVE WILL EXIT THE MID-ATLANTIC REGION ON THURS. THE 00Z NAM GRADUALLY BECOMES A TAD SLOW WITH THE SHORTWAVE TROUGH EVOLUTION AS IT REACHES NORTHERN NEW ENGLAND...WITH THE REMAINING MODELS WELL CLUSTERED. AT THE SURFACE...THERE IS REASONABLY GOOD AGREEMENT WITH THE SURFACE LOW EVOLUTION...ALTHOUGH THE 00Z NAM BECOMES A BIT DEEPER THAN THE MULTI-MODEL CONSENSUS AS THE WAVE MOVES OFFSHORE ON THURS. A NON-NAM CONSENSUS WILL BE PREFERRED. ...SHORTWAVE TROUGH SHEARING ACROSS THE CENTRAL APPALACHIANS/MID-ATLANTIC THROUGH TUES... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW VERY GOOD AGREEMENT HERE AT THIS POINT...AND SO A GENERAL MODEL COMPROMISE WILL BE PREFERRED AS THIS SYSTEM SHEARS OUT THROUGH TUES. ...SHORTWAVE CROSSING THE SOUTHWEST AND CENTRAL/SOUTHERN PLAINS... ...DEVELOPING SURFACE LOW LIFTING THROUGH THE MID MS/OH VALLEYS... PREFERENCE: BLEND OF THE 00Z GFS AND 12Z ECMWF CONFIDENCE: AVERAGE A MID LEVEL SHORTWAVE EMBEDDED WITHIN THE SOUTHWEST FLOW AHEAD OF THE APPROACHING WEST COAST UPPER LOW IS FORECAST TO ADVANCE EAST OUT INTO THE CENTRAL AND SOUTHERN HIGH PLAINS TUES AND WED AND AMPLIFY SOMEWHAT. THIS WILL ALSO DEVELOP AND AREA OF LOW PRESSURE NORTH OF THE RED RIVER VALLEY THAT WILL ADVANCE NORTHEAST TOWARD THE MIDWEST BY WED AND THEN SHEAR EASTWARD ACROSS THE OH VALLEY ON THURS. THE 00Z NAM IS THE STRONGEST SOLUTION OVERALL SURFACE AND ALOFT. THE 12Z CMC WAS SEEN AS BEING PERHAPS A TAD SLOW WITH THE SURFACE WAVE EVOLUTION. THE STRONGER MODEL CLUSTERING FAVORS A BLEND OF THE 00Z GFS AND 12Z ECMWF...AND THAT WILL BE THE PREFERENCE. ...EASTERN PACIFIC UPPER LOW HOVERING WEST OF CALIFORNIA... PREFERENCE: GENERAL MODEL COMPROMISE...THROUGH 72 HOURS BLEND OF THE 00Z GFS AND 12Z ECMWF...AFTER 72 HOURS CONFERENCE: ABOVE AVERAGE ALL OF THE LATEST DETERMINISTIC GUIDANCE TAKES AN UPPER LOW OVER THE EASTERN PACIFIC CURRENTLY CENTERED NEAR 357 130W SLOWLY EASTWARD INTO CALIFORNIA LATE WED AND THURS. THE UPPER LOW IS THEN EXPECTED TO OPEN UP INTO A LARGER SCALE UPPER TROUGH THAT WILL MOVE INTO THE INTERMOUNTAIN WEST BY FRI IN RESPONSE TO ADDITIONAL UPSTREAM HEIGHT FALLS APPROACHING THE WEST COAST. THERE IS VERY GOOD MASS FIELD AGREEMENT THROUGH ABOUT 72 HOURS...BUT THEREAFTER THE 12Z CMC BECOMES A BIT MORE PROGRESSIVE WITH THE UPPER TROUGH. THE 12Z UKMET BECOMES A LITTLE SLOWER. THE 00Z GFS/00Z NAM AND 12Z ECMWF ARE CLUSTERED IN BETTER AGREEMENT IN BETWEEN THE UKMET/CMC SOLUTIONS BY THE END OF THE PERIOD. A GENERAL MODEL COMPROMISE WOULD SUFFICE THROUGH ABOUT 72 HOURS AND THEN A BLEND OF THE GFS/NAM AND ECMWF THEREAFTER. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON