294  
FXUS02 KWBC 270719  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
218 AM EST TUE FEB 27 2018  
 
VALID 12Z FRI MAR 02 2018 - 12Z TUE MAR 06 2018  
 
...WIDESPREAD SNOWFALL EXPECTED ACROSS THE WESTERN U.S. LATE WEEK  
AND THIS WEEKEND WITH LOCATIONS ALONG THE SIERRA NEVADA EXPECTED  
TO MEASURE THE GREATEST TOTALS...  
 
...DEVELOPING COASTAL STORM BRINGS THREAT OF STRONG WINDS/MARITIME  
CONCERNS...COASTAL FLOODING AND ACCUMULATING ICE/SNOW TO PORTIONS  
OF THE NORTHEAST INTO FRIDAY...  
 
   
..PATTERN OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
GUIDANCE AMPLIFIES AN E-CENTRAL PACIFIC RIDGE INTO ALASKA WHICH  
SUPPORTS DOWNSTREAM DIGGING OF ENERGY INTO A DEEP WEST COAST  
TROUGH OVER THE NEXT COUPLE OF DAYS. THIS WILL MOST LIKELY FEATURE  
AN EMBEDDED CLOSED LOW JUST OFF THE PACIFIC NORTHWEST COAST INTO  
FRI. ENERGY PUSHES INTO/THROUGH THE UPSTREAM RIDGE THIS WEEKEND  
LENDING INLAND PROGRESSION OF THE LEAD WEST COAST MEAN TROUGH AND  
EVENTUAL CENTRAL TO EAST-CENTRAL US CYCLO/FRONTAL GENESIS.  
 
MEANWHILE DOWNSTREAM...A CLOSED LOW IS EXPECTED TO TRACK OFFSHORE  
THE NRN MID ATLANTIC/NEW ENGLAND...LEADING TO A DEEP COASTAL LOW.  
THIS SYSTEM FEEDS INTO A DEVELOPING ANOMALOUSLY STRONG/BLOCKY  
PATTERN CONSISTING OF AN UPPER RIDGE THAT RETROGRADES WEST OF SRN  
GREENLAND.  
 
THE WPC MEDIUM RANGE PRODUCT SUITE TOOK ADVANTAGE OF BETTER THAN  
NORMAL CLUSTERING FRI INTO SUN TO UTILIZE A LATEST GFS/ECMWF MODEL  
BLEND THAT IS ALSO CONSISTENT WITH ENSEMBLE MEANS AND WPC  
CONTINUITY. SWITCHED TO A BLEND OF THE QUITE COMPATIBLE GEFS/ECMWF  
ENSEMBLE MEANS LATER SUN-NEXT TUE IN A PERIOD A SLOWLY INCREASING  
FORECAST SPREAD.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
A POTENT COASTAL STORM WILL EMERGE OFF THE NERN U.S. INTO FRI.  
ENHANCED PRECIP WRAPBACKS ACROSS THE NRN MID-ATLANTIC AND SRN NEW  
ENGLAND...WITH SOME SNOW/ICE THREAT IN COOLED FLOW AS THE LOW  
INTENSIFIES. THIS SYSTEM WILL BRING STRONG WINDS/MARITIME CONCERNS  
AND STRONG ONSHORE FLOW NORTH OF THE SURFACE LOW TRACK OFFERS SOME  
COASTAL NEW ENGLAND FLOODING THREAT.  
 
AN UPPER TROUGH SETS ALONG THE WEST COAST WITH AN EMBEDDED CLOSED  
LOW NEARING THE PACIFIC NW FRI. A WEEKEND INLAND PROGRESSION OF  
THE TROUGH/HEIGHT FALLS WILL BRING A CONSIDERABLE AREA OF ACTIVE  
WEATHER TO THE WRN STATES. BEST POTENTIAL FOR PERIODS OF HEAVY  
RAIN/HIGHER ELEVATION SNOW SHOULD EXTEND FROM COASTAL/CASCADE  
AREAS OF THE PACIFIC NW INTO NWRN CA AND THE SIERRA NEVADA  
RANGE...WITH BEST SNOW POTENTIAL FOR THE SIERRA NEVADA RANGE.  
ENHANCED PRECIP ALBEIT WITH LESSER TOTALS WILL BE POSSIBLE FOR THE  
REST OF THE CA COAST INLAND TO THE NRN/CENTRAL ROCKIES.  
PROGRESSION OF UPPER TROUGHING WILL LEAD TO DECREASING SNOW  
LEVELS. PRECIPITATION INCREASINGLY DEVELOPS FOR THE CENTRAL TO  
EAST-CENTRAL US AHEAD OF THE UPPER TROUGH SUN-NEXT TUE IN A  
PATTERN WITH MODERATE SYSTEM GENESIS AND GRADUAL GULF MOISTURE  
RETURN FOCUSING OVER THE LOWER MS/TN VALLEYS AND CENTRAL GULF  
COAST STATES. AN EMERGING THREAT MAY ALSO DEVELOP EARLY NEXT WEEK  
FARTHER NORTH WITH POTENTIAL CLOSED LOW/SNOWSTORM DEVELOPMENT  
SHOWN IN A SUBSET OF GUIDANCE NEAR THE UPPER MIDWEST/VICINITY.  
 
SCHICHTEL  
 

 
 
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