806  
FXUS10 KWNH 260514  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
113 AM EDT THU MAR 26 2020  
 
VALID MAR 26/0000 UTC THRU MAR 29/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..SURFACE LOW CROSSING THE MID ATLANTIC STATES THU NIGHT/FRI
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z NAM, 00Z GFS, 12Z ECMWF BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
A WEAK SURFACE TO 850 MB LOW IS FORECAST TO CROSS THE MISSISSIPPI  
RIVER VALLEY LATER TODAY AND NEAR THE NORTHERN MID-ATLANTIC COAST  
FRIDAY MORNING. THE ENSEMBLE MEANS DO NOT SUPPORT THE SLOWER 12Z  
UKMET/CMC AND LATITUDE DIFFERENCES REMAIN AMONG THE REMAINING 00Z  
NAM, 00Z GFS AND 12Z ECMWF. FOR NOW, A MIDDLE GROUND BETWEEN THE  
NAM/GFS/ECMWF IS PREFERRED, OR MORE SIMILAR TO THE 00Z NAM.  
 
...MID-LEVEL TROUGH TRACKING FROM THE WEST COAST TO THE CENTRAL  
PLAINS THROUGH SUN MORNING...  
...SURFACE LOW MOVING FROM EASTERN CO INTO THE MID/UPPER MS  
VALLEY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z GFS, 12Z ECMWF AND 12Z UKMET BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
TRENDS IN THE ECMWF ENSEMBLES HAVE BEEN SLOWER WITH THE MID-LEVEL  
TROUGH AS IT CROSSES THE ROCKIES INTO THE GREAT PLAINS, BUT THE  
GEFS HAS SPED UP SINCE PREVIOUS RUNS. THE LATEST GUIDANCE SHOWS  
THE 00Z NAM WITH AN OPEN WAVE INTO THE CENTRAL U.S. WHICH IS AN  
OUTLIER CONSIDERING THE REMAINING DETERMINISTIC AND ENSEMBLE  
GUIDANCE. THE 12Z CMC IS REASONABLE WITH TIMING BUT WEAKER THAN  
THE REMAINING AVAILABLE GUIDANCE. THE MIDDLE GROUND IS CURRENTLY  
BEST SUPPORTED BY THE 00Z GFS (SLOWER THAN 18Z GEFS MEAN), AND THE  
SIMILAR 12Z ECMWF/UKMET. THE 00Z GFS IS STRONGEST WITH THE LOW TO  
MID-LEVEL LOW EARLY SATURDAY, BUT THE 12Z ECMWF/UKMET BECOME  
STRONGEST BY SUNDAY MORNING COMPARED TO THE GFS. THE 00Z GFS IS  
ALSO SLIGHTLY FASTER THAN THE AGREEABLE 12Z ECMWF/UKMET BUT THE  
TRIO (GFS/ECMWF/UKMET) ARE WELL WITHIN THE MIDDLE OF THE LATEST  
ENSEMBLE SPREAD.  
 
...SHORTWAVE AND SURFACE COLD FRONT APPROACHING PACIFIC NORTHWEST  
SAT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z GFS, 12Z ECMWF AND 12Z UKMET BLEND  
CONFIDENCE: AVERAGE  
 
TIMING AND STRENGTH DIFFERENCES EXIST WITH A SHORTWAVE AND RELATED  
COLD COLD FRONT NEARING THE PACIFIC NORTHWEST THIS WEEKEND. THE  
00Z NAM IS FASTER THAN THE ENSEMBLE MEANS AND THE 12Z CMC IS  
WEAKEST. THE 00Z GFS, 12Z ECMWF AND 12Z UKMET ARE REASONABLE IN  
THE MIDDLE OF THE DIFFERENCES SEEN IN TIMING AND AMPLITUDE AND IN  
DECENT AGREEMENT WITH THE ENSEMBLE MEANS.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
OTTO  
 

 
 
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