562  
FXUS10 KWNH 301644  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1243 PM EDT TUE JUN 30 2020  
 
VALID JUN 30/1200 UTC THRU JUL 04/0000 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
CLOSED LOW ANCHORED OVER NEW ENGLAND...TRANSITIONING OFF  
MID-ATLANTIC BY FRIDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND DAY 1/2; NON-UKMET BLEND DAY 3  
CONFIDENCE: ABOVE AVERAGE  
 
MODEL GUIDANCE IS IN EXCELLENT AGREEMENT THROUGH DAY 2 WITH THE  
EVOLUTION OF THE CLOSED LOW THAT HAS BEEN ANCHORED OVER NEW  
ENGLAND. BY 48-60 HOURS, TROUGHING FROM THE NORTH DIPS DOWN WHICH  
WEAKENS THE CLOSED LOW AND GRADUALLY PUSHES IT EASTWARD OFF THE  
COAST. A PORTION OF THAT DROPS SOUTHEASTWARD WITH A BROAD BUT WEAK  
TROUGH BY DAY 3. HERE, THE UKMET IS SLOWER AND DISPLACED WESTWARD  
OF THE MODEL CONSENSUS. THEREFORE, A GENERAL MODEL BLEND IS  
PREFERRED FOR DAYS 1/2 AND A NON-UKMET BLEND FOR DAY 3.  
 
DEEP UPPER TROUGH/CLOSED LOW ACROSS THE INTERMOUNTAIN WEST  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-CMC BLEND  
CONFIDENCE: AVERAGE  
 
UPPER LEVEL LOW OVER THE INTERMOUNTAIN WEST IS EXPECTED TO LIFT  
NORTHEAST/NORTH TOWARD THE NORTHERN ROCKIES WHILE ANOTHER  
SHORTWAVE TROUGH DROPS SOUTHWARD OVER THE PACIFIC NW. THE PHASING  
OF THIS ENERGY WILL KEEP THE CLOSE LOW IN PLACE THROUGH MUCH OF  
THE PERIOD WITH SOME TENDENCY TO LIFT FURTHER NORTH INTO THE  
CANADIAN ROCKIES LATE IN THE DAY 2 PERIOD AND INTO DAY 3. ANOTHER  
COMPACT SHORTWAVE TROUGH THEN SWINGS ONSHORE THE PACIFIC NW COAST  
TO FINISH THE FORECAST PERIOD. IN THE LARGE SCALE SENSE, THERE IS  
RELATIVELY GOOD MODEL AGREEMENT BUT WITH INDIVIDUAL LOBES OF  
VORTICITY ROTATING THROUGH THE FLOW, SOME TIMING AND STRENGTH  
DIFFERENCES CREEP UP. THE CMC REMAINS A BIT OF AN OUTLIER,  
ESPECIALLY BY DAY 3, AS IT'S TOO FAST AND TOO DEEP WITH THE  
SHORTWAVE MOVING ONSHORE WASHINGTON STATE. OTHERWISE, GUIDANCE IS  
IN GOOD SHAPE TO GO WITH A BLEND OF THE OTHER DETERMINISTIC  
GUIDANCE.  
 
MCV CROSSING THE MIDDLE AND UPPER MS VALLEY TUESDAY/WEDNESDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 00Z GFS/CMC/UKMET  
CONFIDENCE: BELOW AVERAGE  
 
A CONVECTIVELY ENHANCED MCV ONGOING ACROSS THE MID-MS RIVER  
VALLEY, STUCK BETWEEN THE DOMINANT CLOSED LOW FLOWS ON EITHER  
SIDE, WILL GRADUALLY DRIFT EASTWARD/SOUTHEASTWARD OVER THE NEXT  
COUPLE OF DAYS. BY DAY 2, WITH BUILDING HEIGHTS THROUGH THE  
CENTRAL US, THE BULK OF THIS ENERGY IS PUSHED EASTWARD AND  
GRADUALLY DROPS TOWARD THE GULF STATES REGION (SEE SECTION BELOW).  
MODEL GUIDANCE HAS IMPROVED SUCH THAT A GENERAL MODEL BLEND CAN BE  
USED FOR THIS AREA NOW.  
 
MID-LEVEL CLOSED LOW OVER THE GULF COAST BY FRIDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND-  
CONFIDENCE: ABOVE AVERAGE  
 
MID-LEVEL TROUGHING AND A DEVELOPING CLOSED LOW OVER THE GULF  
COAST STATES IS EXPECTED BY THE END OF THE WEEK, WITH WEAK  
SHORTWAVE ENERGY DROPPING FROM THE MID-SOUTH. THERE IS DECENT  
AGREEMENT WITH THE AVAILABLE DETERMINISTIC GUIDANCE, THE ONLY  
EXCEPTION BEING THE 12Z NAM IS SPATIALLY DISPLACED FURTHER NORTH  
FROM THE OTHER GUIDANCE, BUT IT ISN'T MUCH. SENSIBLE WEATHER  
DIFFERENCES ARE LIKELY TO BE DRIVEN FROM MORE MESOSCALE PROCESSES,  
SO A GENERAL MODEL BLEND IS PREFERRED FROM A MASS FIELD  
PERSPECTIVE.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
TAYLOR  
 

 
 
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