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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1558Z Feb 26, 2015)
 
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Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


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