137  
FXUS10 KWNH 031838  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
137 PM EST SAT MAR 03 2018  
 
VALID MAR 03/1200 UTC THRU MAR 07/0000 UTC  
 
12Z MODEL EVALUATION...ALONG WITH MODEL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..POWERFUL NOR'EASTER PULLING AWAY FROM THE EAST COAST
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS ARE IN VERY GOOD AGREEMENT IN TAKING THE STRONG  
NOR'EASTER AWAY FROM THE EAST COAST OVER THE NEXT 24 HOURS AND OUT  
OVER THE OPEN ATLANTIC OCEAN. A GENERAL MODEL BLEND WILL BE  
PREFERRED GIVEN THE MINIMAL MASS FIELD SPREAD.  
 
   
..DEEP CLOSED LOW IMPACTING THE WESTERN U.S. TODAY
 
   
..NEGATIVELY TILTED TROUGH APPROACHING THE PLAINS ON SUNDAY
 
   
..IMPACTING THE MIDWEST THROUGH MONDAY/TUESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z GFS/12Z UKMET/12Z ECMWF BLEND...THROUGH 60 HOURS  
12Z GFS/12Z ECMWF BLEND...AFTER 60 HOURS  
CONFIDENCE: ABOVE AVERAGE...BECOMING AVERAGE AFTER 60 HOURS  
 
A DEEP LAYER CLOSED LOW AND ASSOCIATED BROAD TROUGH IMPACTING THE  
WEST COAST WILL GRADUALLY BE CROSSING THE INTERMOUNTAIN REGION  
THROUGH SUNDAY. THE MODELS THEN INDICATE ENERGY LIFTING OUT OF THE  
BASE OF THE TROUGH BY SUNDAY NIGHT WHICH WILL ALLOW THE TROUGH TO  
TAKE ON A NEGATIVE TILT OUT ACROSS THE CENTRAL/NORTHERN PLAINS ON  
MONDAY. EXPECT A NEW MID/UPPER LEVEL LOW CENTER TO EVOLVE AS WELL  
AS THE SYSTEM AMPLIFIES. SURFACE LOW PRESSURE OVER THE GREAT BASIN  
THROUGH SUNDAY IS EXPECTED TO REORGANIZE OVER THE PLAINS ON MONDAY  
AND BEGIN LIFTING ACROSS THE UPPER MIDWEST BY MONDAY NIGHT. THE  
GUIDANCE IS GENERALLY IN GOOD AGREEMENT WITH THEIR TIMING AND  
DEPTH OF THE TROUGH EVOLUTION THROUGH MONDAY, AND THE SPREAD WITH  
THE SURFACE LOW DETAILS ACROSS THE PLAINS IS RATHER MINIMAL.  
HOWEVER, THE 12Z CMC DOES TEND TO TRACK ITS HEIGHT FALLS AND  
SURFACE LOW A BIT FARTHER SOUTH COMPARED TO THE OTHER MODELS.  
 
MORE SPREAD THOUGH OCCURS MONDAY NIGHT AND TUESDAY AS THIS SYSTEM  
ENCOUNTERS A VERY BLOCKY DOWNSTREAM PATTERN OVER EASTERN NORTH  
AMERICA. HOWEVER, WITH THE 12Z CYCLE OF GUIDANCE, THERE HAS BEEN  
SOME CONSOLIDATION OF THE SOLUTIONS AS THE 12Z UKMET AND MORE SO  
THE 12Z ECMWF HAVE TRENDED TOWARD THE 12Z GFS SOLUTION WHICH HAD A  
HEIGHT FALL EVOLUTION A TAD MORE SUPPRESSED OVER THE GREATER  
MIDWEST AND TOWARD THE OHIO VALLEY LATER IN THE PERIOD. THE 12Z  
NAM NOW SORT OF STICKS OUT AS A SOMEWHAT STRONGER OUTLIER ALOFT BY  
THE END OF THE PERIOD, AND ITS DOMINANT SURFACE LOW IS ALSO A BIT  
NORTH OF THE MODEL CONSENSUS. THE UKMET ALSO TENDS TO HAVE ITS  
SURFACE LOW A BIT FARTHER NORTH LIKE THE NAM, BUT ALOFT IT HAS  
TRENDED TOWARD THE GFS SOLUTION. BASED ON THE LATEST MODEL  
CLUSTERING AND TRENDS, WILL SUGGEST A GFS, UKMET AND ECMWF BLEND  
THROUGH MONDAY, AND THEN A STRAIGHT UP GFS AND ECMWF BLEND  
THEREAFTER WHICH IS SUPPORTED ALSO BY THE LATEST GEFS MEAN.  
 
   
..TROUGH DIGGING SOUTHEAST ACROSS THE NORTHEAST ON MONDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF  
CONFIDENCE: AVERAGE  
 
THE MODELS TAKE A PORTION OF THE TROUGH/CLOSED LOW JUST SOUTHWEST  
OF HUDSON BAY AND SLOWLY SHIFT IT SOUTHEAST ACROSS QUEBEC ON  
SUNDAY AND THEN IN MORE OF SHEARED FASHION DOWN ACROSS THE  
NORTHEAST ON MONDAY AS THE SYSTEM ENCOUNTERS A BLOCKING HIGH THAT  
IS SETTLING SOUTHWEST FROM SOUTHERN GREENLAND. THE GUIDANCE  
COMPARED TO YESTERDAY HAS TRENDED TOWARD MORE ENERGY DROPPING  
SOUTHEAST ACROSS THE NORTHEAST WITH A BETTER DEFINED CLOSED LOW  
FEATURE. THIS ENERGY THEN QUICKLY GOES SOUTHEAST AND OFFSHORE BY  
MONDAY. THE 12Z NAM AND 12Z CMC BECOME A LITTLE SLOWER THAN THE  
12Z GFS AND 12Z ECMWF, BUT THE 12Z UKMET TRENDED A BIT MORE  
PROGRESSIVE AND IS NOW CLOSER TO THE FASTER GFS/ECMWF CAMP. THE  
LATEST GEFS MEAN AND ECENS MEAN FAVOR THE FASTER SOLUTIONS AND  
THUS WILL CONTINUE TO SUPPORT A BLEND OF THE GFS AND ECMWF  
SOLUTIONS.  
 
   
..SHORTWAVE TROUGH OVER THE NORTHERN HIGH PLAINS TUESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE GUIDANCE DROPS ANOTHER SHORTWAVE TROUGH DOWN ACROSS THE  
NORTHERN HIGH PLAINS BY TUESDAY. THERE IS SOME VERY MINOR DEPTH  
DIFFERENCES BY LATE TUESDAY OVER MONTANA WITH THE HEIGHT FALLS,  
BUT WILL A GENERAL MODEL BLEND SHOULD SUFFICE FOR THE TIME BEING.  
 
 
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