076  
FXUS10 KWNH 261633  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1232 PM EDT SUN JUL 26 2020  
 
VALID JUL 26/1200 UTC THRU JUL 30/0000 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..MID-UPPER LEVEL TROUGHING OVER THE NORTHERN CONUS
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
NO CHANGES TO THE PREVIOUS THINKING. MID TO UPPER-LEVEL ENERGY  
OVER SOUTHERN CANADA IS EXPECTED TO CLOSE OFF BEFORE SETTLING OVER  
ONTARIO LATER IN THE PERIOD, WHILE THE LARGER SCALE TROUGH DEEPENS  
OVER THE GREAT LAKES REGION. AT THE SURFACE, A PRONOUNCED COLD  
FRONT IS FORECAST TO MARCH ACROSS THE NORTHERN TIER INTO THE GREAT  
LAKES WHILE UPSTREAM RIDGING BUILDS OVER THE CANADIAN ROCKIES. IN  
THE INCREASINGLY AMPLIFIED PATTERN, THE MODELS HAVE CONVERGED ON A  
SIMILAR IDEA AND SHOW VERY GOOD AGREEMENT THROUGH 84 HOURS WITH  
THE SYNOPTIC PATTERN.  
 
   
..MID-LEVEL ENERGY OVER CALIFORNIA/GREAT BASIN
 
   
..ENERGY ADVANCING SOUTHEAST ACROSS THE PLAINS BY WEDNESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND...THROUGH 72 HOURS  
NON-NAM BLEND...AFTER 72 HOURS  
CONFIDENCE: ABOVE AVERAGE  
 
A BROAD UPPER TROUGH AND EMBEDDED CLOSED LOW OVER CA WILL DRIFT  
EAST-NORTHEAST OVER THE NEXT COUPLE OF DAYS AND CROSS INTO THE  
GREAT BASIN AROUND THE NORTH SIDE OF THE SUBTROPICAL RIDGE OVER  
THE SOUTHWEST AND THE SOUTHERN PLAINS. THIS ENERGY THEN IS  
EXPECTED TO ACTUALLY AMPLIFY A BIT OVER PORTIONS OF THE NORTHERN  
ROCKIES BY WEDNESDAY AND THEN DIG SOUTHEAST OUT ACROSS THE PLAINS.  
THE MODELS OVERALL SHOW GOOD SYNOPTIC SCALE AGREEMENT THROUGH MOST  
OF THE PERIOD. HOWEVER, THE 12Z NAM DOES GENERALLY APPEAR TO BE A  
TAD TOO SLOW AND TOO FAR NORTH WITH ITS ENERGY OVER THE PLAINS ON  
WEDNESDAY. THE 12Z NAM AND 12Z GFS BOTH MAY ALSO BE A TAD TOO  
STRONG, BUT THERE IS ROOM FOR A SOMEWHAT STRONGER CLOSED MID-LEVEL  
LOW TO EVOLVE OVER THE CENTRAL PLAINS BY THE END OF THE PERIOD  
CONSIDERING THE NOTABLE STRENGTHENING OF THE SUBTROPICAL RIDGE  
OVER THE DESERT SOUTHWEST BY THE END OF THE PERIOD. A GENERAL  
MODEL BLEND WILL BE PREFERRED THROUGH 72 HOURS, WITH A NON-NAM  
BLEND THEREAFTER GIVEN SOME OF ITS ENERGY PLACEMENT CONCERNS.  
 
   
..SHORTWAVE TROUGHS APPROACHING CA/PACIFIC NORTHWEST
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-UKMET BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
A PAIR OF NEW SHORTWAVES TROUGH WILL BE APPROACHING THE WEST COAST  
OVER THE NEXT FEW DAYS, WITH ONE ARRIVING OVER THE PACIFIC  
NORTHWEST ON TUESDAY, AND ONE ARRIVING ACROSS CA ON WEDNESDAY.  
GENERALLY THE MODELS ARE IN GOOD AGREEMENT, WITH STRONG EXCEPTION  
TO THE 00Z UKMET WHICH IS MUCH TOO SLOW WITH THE ENERGY  
APPROACHING CA ON WEDNESDAY. THE UKMET OVERALL ENDS UP MORE OUT OF  
PHASE RELATIVE TO THE OTHER MODELS WITH THE ENERGY OVER THE  
PACIFIC NORTHWEST AND EVEN A RATHER STRONG CLOSED LOW THAT IS  
SITUATED SOUTH OF THE GULF OF AK AT THE END OF THE PERIOD. A  
NON-UKMET BLEND WILL AGAIN BE PREFERRED FOR THE TIME BEING.  
 
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  
 
ORRISON  
 

 
 
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