271  
FXUS02 KWBC 011532  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1032 AM EST THU MAR 01 2018  
 
VALID 12Z SUN MAR 04 2018 - 12Z THU MAR 08 2018  
   
..ROBUST WINTER STORM FOR THE NORTH CENTRAL US EARLY NEXT WEEK
 
 
   
..OVERVIEW AND WEATHER HIGHLIGHTS/THREATS
 
 
A DYNAMIC SYSTEM WILL EXIT THE ROCKIES ON SUNDAY AND LIFT THROUGH  
THE PLAINS INTO THE MIDWEST NEXT MON/TUE. THIS WILL SPREAD SNOW TO  
THE NORTHWEST OF THE SURFACE LOW TRACK ACROSS THE DAKOTAS INTO  
MINNESOTA AND WISCONSIN, WITH THE POTENTIAL FOR BLIZZARD  
CONDITIONS. TEMPERATURES WILL BE WELL BELOW AVERAGE BEHIND THE  
FRONT BY ABOUT 10-20 DEGREES BUT ABOVE AVERAGE AHEAD OF THE FRONT  
FROM THE PLAINS TO THE OHIO VALLEY. RAIN AND EMBEDDED CONVECTION  
WILL EXPAND THROUGH THE LOWER MISSISSIPPI VALLEY LATE SUN THROUGH  
WITH THE POTENTIAL FOR LIGHT TO MODERATE AMOUNTS OF RAIN. COOLER  
THAN AVERAGE TEMPERATURES WILL EASE INTO THE EAST/SOUTHEAST BY  
NEXT WED/THU AS THE FRONT SINKS INTO THE GULF AND THROUGH FLORIDA.  
 
ANOTHER SWATH OF SNOW IS POSSIBLE THROUGH THE NORTHEAST AS A NEW  
LOW PRESSURE MOVES NORTHEASTWARD NEXT WED/THU JUST OFF THE COAST.  
TO THE WEST, AN UPPER LOW AND ASSOCIATED SURFACE FRONT WILL SLOWLY  
MOVE TOWARD THE OREGON COAST BUT ITS SPEED IS STILL IN QUESTION.  
AT LEAST SOME PRECIPITATION IS EXPECTED TO REACH THE COAST FROM  
NORTHERN CALIFORNIA NORTHWARD MIDWEEK.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
MODELS/ENSEMBLES START WITH VERY GOOD CLUSTERING AND A BLEND OF  
THE LATEST GUIDANCE SERVED WELL FOR SUNDAY. AFTER THEN, THE  
GUIDANCE DEPARTS FROM A GOOD CONSENSUS WITH THE HANDLING OF THE  
CENTRAL US SYSTEM AS THE ENSEMBLES SPLIT N-S WITH ITS TRACK. THIS  
WILL AFFECT THE LOCATION OF THE HEAVY SNOW AREA AND RAIN/SNOW  
LINE, BUT THE PROBABILITY OF MODERATE/HEAVY SNOW (SEVERAL INCHES)  
IS RATHER HIGH DESPITE LOW/MEDIUM CONFIDENCE IN PLACEMENT.  
MAINTAINED A MIDDLE GROUND SOLUTION ALONG THE LINE OF WPC  
CONTINUITY BEST REPRESENTED BY EITHER THE 00Z UKMET (OR ALSO THE  
00Z CANADIAN ENSEMBLE MEAN) OR A SPLIT BETWEEN THE 06Z GFS AND 00Z  
ECMWF. AS THE SYSTEM MOVES TO THE EAST COAST, USED A BLEND OF THE  
RECENT GFS/ECMWF AND CONTINUITY WITH THE ENSEMBLE MEANS WHICH  
TAKES A DEFINED SYSTEM NEAR THE 40N/70W BENCHMARK AND THEN OUT TO  
SEA. FOR THE WEST, ECMWF WAS CONSIDERED TOO FAR WEST WITH THE  
UPPER LOW AND PREFERRED THE SOLUTIONS THAT AT LEAST BROUGHT A  
PIECE OF THE TROUGH TO THE NORTHEAST, MOST  
LIKE THE 06Z GFS.  
 
FRACASSO  
 

 
 
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