MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 250 PM EDT SAT JUL 25 2015 VALID JUL 25/1200 UTC THRU JUL 29/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/CMC AND ECMWF ...INITIAL UPPER TROUGH/FRONT CROSSING THE GREAT LAKES REGION... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS ARE IN GOOD AGREEMENT IN TAKING THE CURRENT UPPER TROUGH OVER ONTARIO AND THE GREAT LAKES REGION OFF TO THE EAST OVER THE NEXT COUPLE OF DAYS AND CLIPPING NORTHERN NEW ENGLAND. THIS WILL ALLOW A WEAKENING COLD FRONT TO CROSS THE LOWER LAKES REGION AND PORTIONS OF THE INTERIOR NORTHEAST. THE MODELS ARE IN GOOD AGREEMENT WITH THE LARGER SCALE MASS FIELD DETAILS AND SO A GENERAL MODEL COMPROMISE WILL BE PREFERRED. ...SHORTWAVE IMPULSE CROSSING THE NORTHERN PLAINS/UPPER MIDWEST... PREFERENCE: NON-NAM CONSENSUS CONFIDENCE: ABOVE AVERAGE A SHORTWAVE IMPULSE CURRENTLY EJECTING EAST ACROSS THE DAKOTAS WILL ADVANCE DOWNSTREAM ACROSS THE UPPER MIDWEST BY EARLY SUN AND THEN SHEAR OUT WHILE DROPPING EAST-SOUTHEAST THROUGH THE GREAT LAKES REGION. THE 12Z NAM IS A STRONGER OUTLIER SOLUTION...WITH REMAINING MODELS WELL CLUSTERED AROUND A MORE SHEARED/WEAKER SYSTEM THAT CROSSES THE UPPER MIDWEST. A NON-NAM CONSENSUS WILL BE PREFERRED. ...UPPER LOW/TROUGH DIGGING INTO WESTERN BRITISH COLUMBIA... ...TROUGH RELOADING IN THE WEST LATER TODAY AND SUN... ...CYCLOGENESIS OVER THE NORTHERN HIGH PLAINS... PREFERENCE: BLEND OF 12Z GFS AND 12Z ECMWF CONFIDENCE: AVERAGE AN UPPER LOW AND ASSOCIATED TROUGH DIGGING SOUTHEAST DOWN ACROSS BRITISH COLUMBIA WILL DROP DOWN ACROSS THE NORTHWEST U.S. THROUGH MON BEFORE THEN EJECTING EAST OUT ACROSS THE NORTHERN PLAINS ON TUES. MEANWHILE...LEE-SIDE CYCLOGENESIS OVER THE NORTHERN HIGH PLAINS WILL OCCUR BY EARLY MON...WITH THE GUIDANCE AGREEING ON THE DEVELOPMENT OF LOW PRESSURE OVER SOUTHEAST MT. THIS LOW WILL EJECT NORTHEAST AND BECOME OCCLUDED OVER SOUTHERN CANADA WITH TRIPLE POINT LOW PRESSURE DEVELOPING OVER THE DAKOTAS BY MON NIGHT. THE 12Z UKMET OVERALL REMAINS A BIT MORE PROGRESSIVE AND DEEPER THAN THE MULTI-MODEL CONSENSUS WITH THE SYSTEM ONCE IT REACHES THE HIGH PLAINS. THE 12Z NAM AND 12Z CMC ARE BOTH OVERALL TOO SLOW IT APPEARS...AND THE NAM ALSO APPEARS TOO STRONG ALOFT BY TUES OVER THE NORTHERN HIGH PLAINS. THE 12Z GFS AND 12Z ECMWF SPLIT THE DIFFERENCE AND CLUSTER WELL WITH TIMING AND DEPTH...ALTHOUGH THE ECMWF DOES BECOME A LITTLE MORE PROGRESSIVE BY TUES AND HAS A SOLUTION A LITTLE CLOSER TO THE UKMET. A BLEND OF THE GFS AND ECMWF WILL REMAIN THE PREFERENCE FOR THE TIME BEING AND THIS HAS GOOD ENSEMBLE SUPPORT FROM THE GEFS MEAN AND ECENS MEAN. ...MID LEVEL TROUGH IMPACTING THE SOUTHEAST/FL PENINSULA... PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF CONFIDENCE: AVERAGE THE MODELS INDICATE THE DEVELOPMENT OF A SW/NE ORIENTED MID LEVEL TROUGH AXIS THIS WEEKEND EXTENDING FROM THE EASTERN GULF OF MEXICO TO THE SOUTHWEST ATLANTIC BASIN WITH A FRONTAL ZONE THAT WILL BE DRAPED ACROSS THE SAME AREA. THE NUMERICAL GUIDANCE STILL INDICATES THAT THERE WILL BE DEVELOPMENT OF MULTIPLE WAVES OF LOW PRESSURE ALONG THE FRONT THROUGH SUN AND MON WHICH WILL BE IMPACTING THE FL PENINSULA. THE 12Z NAM OVERALL APPEARS A TAD TOO DEEP ALOFT WITH THE ENERGY. THE 12Z CMC BECOMES AN OUTLIER SOLUTION WITH ITS DEEPENING LOW CENTER OFF THE SOUTHEAST COAST MON AND TUES. ALL OF THE MODELS DEVELOP AN AREA OF LOW PRESSURE ALONG OR JUST OFFSHORE THE WEST COAST OF THE FL PENINSULA TONIGHT AND SUN...AND LINGER LOW PRESSURE OVER THE FAR EASTERN GULF OF MEXICO JUST WEST OF TAMPA THROUGH MON BEFORE THIS LOW THEN LIFTS NORTH AND WEAKENS. THE 12Z UKMET HOWEVER SUGGESTS A DEEPER LOW THAT MOVES INTO THE FL PANHANDLE. THE CONSENSUS IS FOR A SOMEWHAT WEAKER EVOLUTION FOR THE TIME BEING. THE 12Z GFS AND 12Z ECMWF REMAIN BETTER CLUSTERED AND MORE CONSISTENT AND THUS A BLEND OF THESE SOLUTIONS WILL BE PREFERRED. ...UPPER TROUGH REDEVELOPING OFF THE EAST COAST MON AND TUES... PREFERENCE: BLEND OF THE 12Z GFS/12Z UKMET AND 12Z ECMWF CONFIDENCE: AVERAGE THE MODELS IN GENERAL FAVOR THE IDEA OF A TROUGH DEVELOPING ALOFT OFF THE EAST COAST BY TUES. THE 12Z NAM AND 12Z CMC ARE STRONG OUTLIERS WITH THE HEIGHT FALLS. THE 12Z UKMET/12Z ECMWF AND 12Z GFS ARE ALL WEAKER AND HAVE THE SUPPORT OF THE LATEST GEFS MEAN AND ECENS MEAN...AND SO A BLEND OF THE WEAKER SOLUTIONS WILL BE PREFERRED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON