918  
FXUS10 KWNH 180435  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1234 AM EDT SAT JUL 18 2020  
 
VALID JUL 18/0000 UTC THRU JUL 21/1200 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z PRELIMINARY MODEL EVALUATION INCLUDING PREFERENCES AND  
FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..CONUS
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: AVERAGE  
 
NORTHERN TIER OF THE CONUS WILL REMAIN ACTIVE WITH FAST FLOW ATOP  
AN EXPANSIVE MID-LEVEL RIDGE COVERING MUCH OF THE LOWER 48. WITHIN  
THE FLOW ATOP THE RIDGE, THE PRIMARY CONCERN IS A MID-LEVEL  
SHORTWAVE DRIVING A COLD FRONT ACROSS THE COUNTRY FROM THE  
NORTHERN PLAINS THIS MORNING, TO OFF THE NEW ENGLAND COAST TUESDAY  
MORNING. ALONG THIS FRONT, A WAVE OF LOW PRESSURE IS ALSO LIKELY  
TO DEVELOP AND MOVE NORTHEAST THROUGH THE GREAT LAKES SUNDAY.  
 
GUIDANCE IS IN VERY GOOD AGREEMENT WITH THE PLACEMENT AND  
INTENSITY OF MOST FEATURE THROUGH THE FIRST 48-60 HOURS.  
THEREAFTER, SOME SPREAD BEGINS TO DEVELOP WITH A SHORTWAVE PROGGED  
TO DROP OUT OF THE NORTHERN ROCKIES MONDAY MORNING AND THEN BECOME  
CONVECTIVELY ENHANCED LATE MONDAY INTO THE CENTRAL PLAINS. AS THIS  
OCCURS, IT MAY ENHANCED THE LONGWAVE TROUGH AMPLITUDE AND BEGIN TO  
BREAK DOWN THE RIDGE. BY DAY 3, TIMING AND INTENSITY OF THESE  
SMALLER SCALE FEATURES, ESPECIALLY WHEN CONVECTIVELY ENHANCED, CAN  
BE TROUBLESOME. THE LARGE-SCALE FEATURES ARE GENERALLY WELL  
ALIGNED SO A GENERAL MODEL BLEND STILL SHOULD BE REASONABLE INTO  
D3. HOWEVER, BOTH THE NAM AND UKMET SUGGEST SOME TROPICAL MOISTURE  
WITH A WEAK MID-LEVEL WAVE COULD BE PULLED NORTHWARD TOWARDS THE  
GULF COAST ON D3, ASSOCIATED WITH SOME STRONGER TROUGHING INTO THE  
RIDGE. AT THIS POINT THESE ARE OUTLIERS SO SHOULD BE USED WITH  
CAUTION, BUT IT APPEARS THEIR SOLUTIONS ARE DUE HEAVILY TO THE  
EVOLUTION OF THIS AFOREMENTIONED SHORTWAVE, FOR WHICH LARGE-SCALE  
EVOLUTION REMAINS WELL ALIGNED. SO FOR NOW A GENERAL MODEL BLEND  
IS REASONABLE, BUT SOME LESSER WEIGHT ON THE NAM/UKMET MAY LEAD TO  
A MORE COMPROMISED SOLUTION, ESPECIALLY FOR THE CENTRAL PLAINS AND  
GULF COAST, BY TUESDAY.  
 
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  
 
WEISS  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page