358  
FXUS10 KWNH 030426  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1225 AM EDT FRI JUL 3 2020  
 
VALID JUL 3/0000 UTC THRU JUL 6/1200 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z INITIAL MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST  
CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
TROUGH OVER THE NORTHEAST U.S.  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z GFS/12Z ECMWF BLEND  
CONFIDENCE: MODERATE  
 
THE UPPER LOW THAT IS DEPARTING THE NORTHEAST U.S. FRIDAY MORNING  
WILL BE FOLLOWED BY ANOTHER ROUND OF HEIGHT FALLS BY SUNDAY ACROSS  
NEW ENGLAND, AS A SHORTWAVE ROTATES AROUND A BROAD UPPER LEVEL  
TROUGH OVER EASTERN CANADA. AT THE SURFACE WILL BE A WEAK  
BACK-DOOR COLD FRONT THAT SINKS SOUTH ALONG THE EAST COAST, AND A  
SECOND COLD FRONT CROSSING NEW ENGLAND BY MONDAY MORNING. THE  
MODELS ARE IN DECENT AGREEMENT ON THE TIMING OF THE FIRST FRONT.  
FOR THE NEXT TROUGH OVER THE NORTHEAST, THE NAM IS A BIT MORE  
AMPLIFIED BY SUNDAY MORNING, WITH THE CMC ALSO ON THE STRONGER  
SIDE OF THE GUIDANCE. THE 12Z UKMET IS INDICATING A SLOWER  
PASSAGE OF THE TROUGH AXIS, WITH A STRONGER RIDGE AXIS ACROSS THE  
GREAT LAKES AND ONTARIO. A BLEND OF THE GFS/ECMWF SHOULD WORK  
WELL AS A STARTING POINT.  
 
TROUGH OVER THE GULF COAST REGION  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z GFS/NAM/12Z ECMWF  
CONFIDENCE: LIMITED-MODERATE  
 
ALONG THE GULF COAST, A BROAD TROUGH WILL DEVELOP BENEATH THE  
RIDGE EXPANDING FROM THE PLAINS TO THE OHIO VALLEY ON FRIDAY.  
THIS TROUGH WILL THEN BE AMPLIFIED BY MID-LEVEL IMPULSES ROTATING  
ATOP THE RIDGE AND ACROSS THE GULF COAST. WHILE DISCREPANCIES  
EXIST IN THE TIMING, INTENSITY, AND PLACEMENT OF THESE SMALLER  
SCALE SHORTWAVES/MCVS, THE END RESULT IS A BROAD AND MODEST TROUGH  
THAT BECOMES ANCHORED ALONG THE GULF COAST AND TOWARDS THE  
SOUTHEAST U.S. THE MODELS GENERALLY AGREE THAT THE TROUGH WILL  
PERSIST THROUGH THE WEEKEND BUT UNLIKELY TO CLOSE OFF. THE UKMET  
IS WEAKER WITH THIS FEATURE OWING TO A STRONGER CENTRAL U.S. RIDGE  
COMPARED TO THE OTHER GUIDANCE. HOWEVER, IS SHOULD BE NOTED THAT  
CONFIDENCE DROPS BY SUNDAY DUE TO INTERACTIONS WITH THE SMALLER  
SCALE SHORTWAVES, AND POSSIBLE SURFACE LOW DEVELOPMENT BENEATH  
THIS TROUGH.  
 
DEEP UPPER TROUGH/CLOSED LOW ACROSS THE PACIFIC NORTHWEST AND  
WESTERN CANADA  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z CMC/ECMWF/EC MEAN  
CONFIDENCE: MODERATE  
 
A LARGE CLOSED LOW PIVOTING ACROSS THE PACIFIC NORTHWEST AND INTO  
WESTERN CANADA WILL REMAIN NEARLY IN PLACE AS SEVERAL VORT  
IMPULSES ROTATE CYCLONICALLY AROUND EACH OTHER TO REINFORCE THE  
TROUGH. THROUGH SATURDAY MORNING, THE GUIDANCE IS IN VERY GOOD  
AGREEMENT WITH THE POSITION AND AMPLITUDE OF THIS FEATURE. BY  
SATURDAY AFTERNOON, THE UKMET IS QUICKER TO LIFT OUT THE TROUGH  
ACROSS THE PACIFIC NORTHWEST, AND THE NAM/GFS ARE STRONGER WITH  
THIS TROUGH ACROSS BRITISH COLUMBIA AND ALBERTA ON SUNDAY. THE  
NEXT DISTURBANCE DROPS SOUTHEAST ALONG THE COAST BY MONDAY  
MORNING, AND THE NAM IS A STRONGER SOLUTION WITH THAT SHORTWAVE  
AND A BIT MORE PROGRESSIVE.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
HAMRICK  
 

 
 
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