899  
FXUS02 KWBC 051601  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1100 AM EST MON MAR 05 2018  
 
VALID 12Z THU MAR 08 2018 - 12Z MON MAR 12 2018  
 
...PATTERN OVERVIEW/THREATS AND GUIDANCE/PREDICTABILITY  
ASSESSMENT...  
 
YET ANOTHER NOR'EASTER WILL PARALLEL THE NEW ENGLAND COAST THU AND  
DELIVER A SWATH OF SIGNIFICANT SNOW ACROSS AT LEAST THE INTERIOR  
NORTHEAST. LATEST GUIDANCE OFFERS GOOD CLUSTERING WITH THE  
NOR'EASTER OFF THE NEW ENGLAND COAST WITH A POSITION JUST EAST OF  
CAPE COD BY 12 UTC THU. THE MODELS ARE BEGINNING TO COME INTO  
BETTER FOCUS WITH THE UPPER LEVEL PATTERN OVER SOUTHEAST  
CANADA...SUGGESTING TWO SEPARATE UPPER LOWS EMBEDDED WITH A  
BROADER GYRE. PLEASE REFER TO SHORT RANGE PRODUCTS FROM THE WPC  
WINTER WEATHER DESK AND YOUR NWS FORECAST OFFICE FOR THIS SYSTEM.  
 
UPSTREAM...AN UPPER LOW AND SURFACE FRONT WILL PUSH INTO THE  
PACIFIC NORTHWEST THU AND THROUGH THE INTERIOR WEST AND ROCKIES  
FRI. PRECIPITATION MAKES A RETURN TO THE WEST COAST BY THE END OF  
THE WEEK. SHOWERS AND MOUNTAIN SNOW ARE EXPECTED FROM CENTRAL  
CALIFORNIA TO WASHINGTON STATE...WITH QPF EXPECTED TO THEN SPREAD  
ACROSS THE WEST TO THE ROCKIES. THE HEAVIEST SNOW IS LIKELY FOR  
THE NRN SIERRA AND THE CASCADES.  
 
THIS SYSTEM MAY REDEVELOP IN THE SRN PLAINS/LOWER MS VALLEY SAT  
AND THEN ORGANIZE OVER THE SOUTHEAST SUN UNDERNEATH UNCERTAIN NRN  
STREAM FLOW TO POTENTIALLY DEEPEN AS AN ERN US COASTAL WINTER  
STORM INTO MON. LATEST MODEL FORECASTS HAVE BEGUN TO CLUSTER  
BETTER OVER THE NERN PACIFIC AND INLAND OVER THE WEST. GUIDANCE  
STILL VARIES WITH DOWNSTREAM SYSTEM TIMING AND PHASING SPECIFICS  
INTO THE CENTRAL AND ERN US. BY THE END OF THE FORECAST PERIOD  
NEXT WEEKEND...A DEVELOPING LOW PRESSURE SYSTEM OVER THE CENTRAL  
PLAINS IS EXPECTED TO INCREASE MOISTURE RETURN FROM THE GULF OF  
MEXICO AND ENHANCE RAINFALL CHANCES FROM THE CENTRAL GULF COAST TO  
THE MIDWEST. THERE MAY BE SOME AREAS OF ENHANCED RAINFALL AND  
ORGANIZED THUNDERSTORM ACTIVITY ACROSS PORTIONS OF THE SOUTHEAST  
U.S. OVER THE WEEKEND.  
 
LATER HOWEVER...THERE IS A STRONG SIGNAL FOR PATTERN AMPLIFICATION  
UPSTREAM AND AT LEAST THE GENERAL PATH OF SYSTEM ENERGY OVER THE  
CENTRAL AND ERN STATES THAT WOULD SUPPORT A PATTERN WITH MUCH  
GREATER THAN NORMAL OPPORTUNITY FOR A COASTAL STORM THREAT THAT  
COULD SIGNIFICANTLY EFFECT THE ERN SEABOARD AND MARITIME INTERESTS.  
 
OVERALL...THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED  
FROM A COMPOSITE BLEND OF REASONABLY COMPATABLE GUIDANCE FROM THE  
LATEST GFS/ECMWF AND GEFS/ECMWF ENSEMBLE MEANS.  
 
SCHICHTEL  
 

 
 
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