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