582  
FXUS10 KWNH 301843  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
243 PM EDT MON MAR 30 2020  
 
VALID MAR 30/1200 UTC THRU APR 3/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
CLOSED LOW OVER NORTHEAST U.S. AND OFFSHORE SURFACE LOW EARLY THIS  
WEEK  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: HIGH  
 
A BROAD UPPER LEVEL LOW OVER NEW ENGLAND, WITH SHORTWAVE ENERGY  
PIVOTING AROUND IT, WILL CONTINUE TO SUPPORT OFFSHORE SURFACE LOW  
DEVELOPMENT WITH A SECONDARY COLD FRONT EXITING THE EAST COAST  
LATER TODAY. THERE IS ENOUGH MODEL AGREEMENT HERE TO MERIT A  
DETERMINISTIC MULTI-MODEL BLEND. NO CHANGES TO THE MODEL  
PREFERENCE AFTER THE ARRIVAL OF THE 12Z NON-NCEP GUIDANCE.  
 
CENTRAL PLAINS SHORTWAVE AND SOUTHERN U.S. SURFACE LOW  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z GFS/12Z ECMWF  
CONFIDENCE: MODERATE-HIGH  
 
A STRONG SOUTHERN STREAM SHORTWAVE EXITING THE ROCKIES AND  
EMERGING OVER THE CENTRAL PLAINS WILL SUSTAIN A WELL DEVELOPED  
SURFACE LOW ACROSS THE SOUTHERN TIER STATES THROUGH TUESDAY  
EVENING. THE LOW THEN EMERGES OVER THE WESTERN ATLANTIC AND THEN  
TRACKS TO A POSITION JUST NORTH OF BERMUDA BY WEDNESDAY EVENING.  
THERE IS GOOD OVERALL SYNOPTIC SCALE AGREEMENT AS THE SYSTEM  
TRACKS EASTWARD ACROSS THE GULF COAST REGION. THE 00Z UKMET IS  
FARTHER SOUTH WITH THE OFFSHORE TRACK, AND THE 00Z CMC BECOMES A  
SLOWER SOLUTION. BOTH THE GFS AND ECMWF HAVE GOOD ENSEMBLE  
SUPPORT, AND THUS A BLEND OF THESE TWO MODELS IS GOOD. THE 12Z  
UKMET TRENDED CLOSER TO THE MODEL CONSENSUS WHILE THE 12Z CMC IS  
STILL SLIGHTLY SLOWER.  
 
BROAD UPPER LEVEL GYRE OVER NORTHWEST WITH NORTHERN TIER COLD FRONT  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z ECMWF/12Z GFS/00Z EC MEAN  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
 
AN UPPER LEVEL LOW INITIALLY NEAR THE BRITISH COLUMBIA COAST WILL  
GRADUALLY REFORM OVER ALBERTA AND REMAIN NEARLY ANCHORED IN PLACE  
FOR THE NEXT FEW DAYS, WITH A COUPLE OF SHORTWAVES PIVOTING AROUND  
IT. THIS WILL SUPPORT A SURFACE LOW JUST NORTH OF THE CANADIAN  
BORDER, AND A SECOND LOW OVER THE DAKOTAS. OVERALL DETERMINISTIC  
TRENDS SINCE YESTERDAY SHOW GREATER DEFINITION WITH THESE  
SHORTWAVES TRACKING ACROSS THE NORTHWEST. THE ENSEMBLE MEANS SHOW  
RELATIVELY GOOD AGREEMENT WITH THESE FEATURES, WITH THE NAM  
SLIGHTLY FASTER TO BRING MID-LEVEL HEIGHT FALLS TO THE REGION, AND  
THE 00Z UKMET NOT QUITE AS AMPLIFIED AS THE OTHER MODELS WITH THE  
500MB PATTERN. THE 12Z UKMET TRENDED MORE AMPLIFIED OVER NORTH  
DAKOTA BY WEDNESDAY EVENING WITH THE SHORTWAVE TROUGH, AND THE GFS  
IS NOW AMONG THE DEEPER SOLUTIONS BY THE END OF THE FORECAST  
PERIOD ACROSS SOUTHERN CANADA.  
 
SOUTHWEST SHORTWAVE AND HIGH PLAINS CYCLOGENESIS MIDWEEK  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z ECMWF/12Z CMC/00Z EC MEAN  
CONFIDENCE: MODERATE  
 
A BROAD SOUTHERN STREAM TROUGH PIVOTING EASTWARD AROUND THE UPPER  
LEVEL GYRE OVER SOUTHWEST CANADA WILL CROSS THE SOUTHERN ROCKIES  
AND SUPPORT LEE SURFACE CYCLOGENESIS OVER EASTERN COLORADO, WITH A  
FRONTAL BOUNDARY EXTENDING WESTWARD ACROSS THE INTERMOUNTAIN WEST.  
THE MAIN MODEL DIFFERENCES NOTED HERE IS THE FASTER GFS AND A  
NORTHWARD DISPLACEMENT OF THE 6Z GEFS MEAN WITH THE SURFACE LOW  
OVER THE WESTERN HIGH PLAINS. THE 12Z GEFS MEAN TRENDED CLOSER TO  
THE OTHER DETERMINISTIC GUIDANCE WITH RESPECT TO THE SURFACE LOW.  
 
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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