677  
FXUS10 KWNH 071707  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
107 PM EDT FRI AUG 07 2020  
 
VALID AUG 07/1200 UTC THRU AUG 11/0000 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z NAM/GFS EVALUATION INCLUDING PREFERENCES AND FORECAST  
CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
OVERALL WEATHER PATTERN ACROSS THE CONTINENTAL U.S.  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND, WEIGHTED TOWARD THE 12Z NAM/12Z  
GFS/00Z ECMWF  
CONFIDENCE: AVERAGE  
 
THE OVERALL PATTERN ACROSS THE LOWER 48 WILL FEATURE A BROAD UPPER  
RIDGE CENTERED OVER THE SOUTHERN PLAINS INTO NORTHWESTERN MEXICO.  
THE MAIN DRIVER OF SYNOPTIC SCALE FRONTS/LOWS WILL BE WITH THE JET  
STREAM FOCUSED NEAR THE U.S./CANADIAN BORDER.  
 
AN INITIAL QUASI-STATIONARY FRONT WILL REMAIN DRAPED FROM THE  
MID-ATLANTIC TO THE LOWER MISSISSIPPI VALLEY. ALOFT, A WEAKENING  
UPPER LEVEL TROUGH OVER THE EASTERN 1/3 OF THE NATION TODAY WILL  
QUICKLY TRACK INTO THE WESTERN ATLANTIC THROUGH SATURDAY. THE  
MODELS ARE FAIRLY SIMILAR WITH THIS SCENARIO.  
 
ACROSS THE NORTH-CENTRAL U.S., A COLD FRONT WILL MOVE THROUGH THE  
DAKOTAS BY SATURDAY MORNING, STALL OVER SOUTH DAKOTA AND MINNESOTA  
LATE SATURDAY AND LIFT NORTH AS A WARM FRONT INTO SUNDAY MORNING.  
THIS BOUNDARY WILL BE INFLUENCED BY SHORTWAVES MOVING ABOUT A  
LONGWAVE TROUGH/CLOSED LOW MOVING ACROSS CENTRAL CANADA. THE  
MODELS SHOW GENERALLY GOOD AGREEMENT WITH THIS FEATURE, WITH ONLY  
MINOR TIMING/AMPLITUDE DIFFERENCES. THE GREATER DIFFERENCES ARE  
NOTED TO BE WITH CONVECTIVELY DRIVEN MID-LEVEL VORTICITY MAXIMA  
AND MESOSCALE BOUNDARIES FROM HEAVY RAINFALL. THERE IS NO CLEAR  
ANSWER AS TO WHICH MODEL OR CLUSTER OF MODELS WILL VERIFY BEST,  
BUT THERE HAVE BEEN TRENDS IN THE GUIDANCE OVER THE PAST 24-36  
HOURS FOR MORE DEFINITION TO THESE FEATURES NEAR THE 12Z NAM, 12Z  
GFS AND 00Z ECMWF...WITH THE 00Z UKMET/CMC LESS DEFINED IN THE  
MID-LEVELS.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
THIS PRODUCT WILL TERMINATE AUGUST 15, 2020:  
WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERMINATION.  
PDF  
 
OTTO  
 

 
 
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