EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1058 AM EST THU FEB 26 2015 VALID 12Z SUN MAR 01 2015 - 12Z THU MAR 05 2015 ...OVERVIEW... PATTERN SHIFT IS IN THE OFFING---WITH THE TEMPORARY BREAKDOWN OF RIDGING ACROSS THE NORTHEAST PACIFIC. AND WITH SUBSTANTIAL BUILDING OF A BROAD UPPER-LEVEL RIDGE OFF THE US SOUTHEAST COAST. THE ACTIVE WEATHER SHIFTS TO THE SOUTHWEST/SOUTHERN GREAT BASIN...FOUR CORNERS...PLAINS AND MID-MISSISSIPPI/OHIO VALLEYS. ...UNCERTAINTY ASSESSMENT... THE 26/00Z ECENS...GEFS AND NAEFS GENERALLY HAVE THE FLOW PATTERN IN ORDER THROUGH THE MEDIUM RANGE---AND COULD EASILY MAINTAIN CONTINUITY WITH THE PREVIOUS SURFACE/500MB WPC GRAPHICS. WHAT UNCERTAINTY REMAINS: THE 26/00Z DETERMINISTIC GFS/ECMWF SEEM TO HAVE NARROWED THE POSSIBILITIES DOWN SOMEWHAT OVER THE PLAINS---WITH RESPECT TO THE MIGRATORY TRACK OF MULTIPLE MID-LEVEL WAVES---BETWEEN THE 3/00Z AND 4/12Z TIME FRAME. A MULTI-WAVE SCENARIO ALLOWS FOR THE DISTINCT SEPARATION BETWEEN NORTHERN AND SOUTHERN STREAM ENTITIES---A THEME THAT HAS BEEN COMMONPLACE THIS WINTER SEASON (EAST OF THE DIVIDE). THIS SHOULD GENERATE A CLEAR DISTINCTION BETWEEN AN ARCTIC BOUNDARY ---AND A MODIFIED CANADIAN BOUNDARY THAT IS INFUSED WITH A 'MILDER' SOUTHERN STREAM AIRMASS. DURING THE DAY 6-7 PERIOD...THERE REMAINS CONSIDERABLE SPREAD ACROSS THE PACIFIC NORTHWEST. THE 26/00Z DETERMINISTIC CANADIAN/ECMWF INDICATING LOWER-AMPLITUDE SHORTWAVE TROUGHS SKIRTING SOUTHEASTWARD ALONG THE WEST COAST OF BRITISH COLUMBIA---WHILE THE GFS INDICATES A SIZABLE MID-LEVEL RIDGE CONFIGURATION OVER WESTERN CANADA---LIMITING THE NUMBER OF POSSIBLE SHORTWAVES MIGRATING INTO THE INTERMOUNTAIN WEST'S UPPER-LEVEL TROUGH. ...MODEL PREFERENCES... WILL USE A BLEND OF THE 26/00Z ECENS/GEFS ENSEMBLES AND THE DETERMINISTIC RUNS FOR DAYS 3-5. THIS WILL REASONABLY DEPICT THE PRESENCE OF AN ACTIVE UPPER-LEVEL TROUGH IN THE WEST...AND POTENTIAL FOR A SERIES OF ORGANIZED SURFACE WAVES WITH A STORM TRACK THAT MIGRATES BETWEEN SOUTHWEST KANSAS AND LAKE ERIE (DAY 5 AND 6). PERSONALLY...LIKED THE ECMWF SOLUTION FOR DAYS 5-6---TO ADD SOME SMALLER-SCALE DETAILS. BUT DO ADMIT---THE DAY 5-7 FORECAST AND THE UPPER-LEVEL TROUGH IN THE WEST HAS POTENTIAL FOR SHORTWAVE DEVELOPMENT---AND COULD OFFER 'SURPRISES' DOWN THE ROAD---IN THE SOUTHERN STREAM. ...SENSIBLE WEATHER HIGHLIGHTS... A WETTER PERIOD FOR THE INTERMOUNTAIN WEST...WEST COAST AND FOOTHILLS OF THE ROCKIES AS MULTIPLE SHORTWAVES MIGRATE THROUGH THE BASE OF THE UPPER-LEVEL TROUGH---BEGINNING ALONG THE CENTRAL OREGON COAST AND ARCING COUNTER-CLOCKWISE THROUGH THE MID-COLORADO RIVER BASIN AND FOUR CORNERS REGION A MIGRATORY CYCLONE---PROJECTED TO TRACK FOR THE SOUTH CENTRAL HIGH PLAINS TO THE EASTERN LAKES---SHOULD PROVIDED A WINTER WEATHER SCENARIO FOR THE LOWER MISSOURI-MID MISSISSIPPI VALLEYS AND CENTRAL MIDWEST---ALONG WITH A WET PATTERN FOR THE SOUTHEAST AND MID-ATLANTIC REGION...AHEAD OF THIS CYCLONE'S COLD FRONT. VOJTESAK