688  
FXUS10 KWNH 241833  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
132 PM EST SAT FEB 24 2018  
 
VALID FEB 24/1200 UTC THRU FEB 28/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION...WITH LATEST MODEL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..STRONG UPPER TROUGH OVER THE HIGH PLAINS REGION TODAY
 
   
..CYCLOGENESIS OVER THE PLAINS AND LIFTING ACROSS THE MIDWEST
 
   
..TRAILING COLD FRONT SWEEPING THROUGH THE EASTERN U.S
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-NAM BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS TAKE A STRONG MID/UPPER LEVEL TROUGH ENTERING THE  
CENTRAL AND SOUTHERN HIGH PLAINS TODAY LIFT IT NORTHEAST ACROSS  
THE UPPER MIDWEST BY TONIGHT AS IT TAKES ON A NEGATIVE TILT WHICH  
WILL HELP DEEPEN SURFACE LOW PRESSURE THAT WILL CROSS THIS REGION.  
THE 12Z NAM ENDS UP AGAIN JUST A TAD STRONGER ALOFT THAN THE  
REMAINING GUIDANCE AS THE SYSTEM LIFTS NORTHEAST ACROSS THE UPPER  
MIDWEST AND UPPER GREAT LAKES TONIGHT AND THROUGH EARLY SUNDAY.  
MEANWHILE, A TRAILING COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL  
SWEEP EAST ACROSS THE EASTERN U.S. THROUGH SUNDAY AND THEN MOVE  
OFFSHORE SUNDAY NIGHT. MODEL SPREAD WITH THE FRONT IS RATHER  
MINIMAL AT THIS TIME, AND THE MODELS OVERALL ARE IN RATHER GOOD  
AGREEMENT WITH THE SECONDARY AREA OF LOW PRESSURE OFFSHORE NEW  
ENGLAND SUNDAY NIGHT AND EARLY MONDAY. BASED ON THE OVERALL  
CLUSTERING OF SOLUTIONS AND LATEST TRENDS, A NON-NAM BLEND WILL BE  
PREFERRED.  
 
   
..SHORTWAVE ARRIVING OVER THE PACIFIC NORTHWEST TODAY
 
   
..CROSSING THE FOUR CORNERS/HIGH PLAINS ON SUNDAY
 
   
..EJECTING EAST ACROSS THE MISSISSIPPI/OHIO VALLEYS ON MONDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND...THROUGH 48 HOURS  
BLEND OF THE 12Z GFS AND 12Z ECMWF...AFTER 48 HOURS  
CONFIDENCE: ABOVE AVERAGE  
 
THE NEXT IN A SERIES OF SHORTWAVES TO DROP SOUTHEAST DOWN ACROSS  
WESTERN NORTH AMERICA IS CURRENTLY ARRIVING ACROSS THE PACIFIC  
NORTHWEST AND WILL RAPIDLY DROP DOWN INTO THE FOUR CORNERS REGION  
ON SUNDAY BEFORE RAPIDLY EJECTING EAST TOWARD THE MID MISSISSIPPI  
VALLEY AND OHIO VALLEY ON MONDAY. THE ENERGY WILL THEN CROSS PARTS  
OF THE MID-ATLANTIC AND NORTHEAST BY MONDAY NIGHT. THE MODELS ARE  
IN GOOD AGREEMENT WITH THEIR MASS FIELD DETAILS OF THIS SYSTEM  
UNTIL MONDAY WHEN THE 12Z NAM, 12Z CMC AND 12Z UKMET BECOME JUST A  
TAD MORE PROGRESSIVE AND FLATTER THAN THE 12Z GFS AND 12Z ECMWF.  
THE LATEST GEFS MEAN AND ECENS MEAN BOTH FAVOR THE LATTER CAMP  
WHICH IS ALSO WELL CLUSTERED. WILL PREFER A GENERAL MODEL BLEND  
THROUGH 48 HOURS, AND THEN A GFS/ECMWF BLEND THEREAFTER.  
 
   
..SHORTWAVE ARRIVING OVER THE PACIFIC NORTHWEST ON SUNDAY
 
   
..CLOSED LOW EVOLUTION OVER THE SOUTHWEST BY MONDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE GUIDANCE BRINGS ANOTHER SHORTWAVE INTO THE PACIFIC NORTHWEST  
ON SUNDAY ALONG WITH A PROGRESSIVE COLD FRONT. THE GUIDANCE IS IN  
GOOD AGREEMENT WITH THE ARRIVAL OF THE SHORTWAVE ENERGY AND THE  
EVOLUTION OF THE HEIGHT FALLS DIGGING DOWN ACROSS CALIFORNIA AND  
THE GREAT BASIN ON MONDAY WHICH WILL LEAD TO A LARGER SCALE TROUGH  
EVOLUTION AIMING FOR THE SOUTHWEST. OVERALL, THERE HAS BEEN A  
SOMEWHAT STRONGER TREND IN THE GUIDANCE WITH THE IDEA OF A CLOSED  
MID/UPPER LEVEL LOW CENTER EVOLVING OVER THE SOUTHWEST BY TUESDAY.  
THE 12Z GUIDANCE HAS COME INTO BETTER AGREEMENT WITH PLACEMENT OF  
THIS CLOSED LOW OVER SOUTHERN CALIFORNIA BY TUESDAY AS THE LATEST  
UKMET AND ECMWF HAVE SHIFTED A LITTLE FARTHER EAST TO BE IN GOOD  
AGREEMENT WITH THE NAM, GFS AND CMC SOLUTIONS. GIVEN THE MODEL  
MASS FIELD AGREEMENT, A GENERAL MODEL BLEND WILL NOW BE PREFERRED.  
 
   
..SHORTWAVE ARRIVING OVER THE NORTHERN ROCKIES ON TUESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-CMC BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS BRING ANOTHER NORTHERN STREAM TROUGH DOWN FROM WESTERN  
CANADA AND ACROSS THE NORTHERN ROCKIES BY TUESDAY. THE 12Z CMC IS  
TAD SLOWER AND DEEPER THAN THE REMAINING MODELS WHICH ARE  
REASONABLY WELL CLUSTERED. WILL SUGGEST A NON-CMC BLEND AS A  
RESULT AT THIS TIME.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
ORRISON  
 

 
 
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