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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0559Z Apr 22, 2015)
 
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EDT WED APR 22 2015

VALID 12Z SAT APR 25 2015 - 12Z WED APR 29 2015

...OVERVIEW...
CYCLONIC FLOW PREVAILS ACROSS SOUTHEAST CANADA AND SUPPORTS BELOW
NORMAL TEMPERATURES IN THE GREAT LAKES AND NORTHEAST THROUGH THIS
UPCOMING WEEKEND. SOME MODERATION IN TEMPERATURE IS ANTICIPATED
OVER THE GREAT LAKES HEADING INTO NEXT WEEK.

DEEP TROUGH WILL ANCHOR IN THE GULF OF ALASKA ON DAY 4...AND A
SERIES OF SOUTHWEST TO NORTHEAST MOVING SHORTWAVES---ARE EXPECTED
TO MIGRATE INTO THE PACIFIC NORTHWEST AND BRING RAINFALL TO THE
REGION NEXT WEEK.

ACTIVE JET STREAM AXIS SETUP FROM THE SOUTHERN HIGH PLAINS TO THE
DELMARVA WILL CARRY SEVERAL NOTEWORTHY PACIFIC SHORTWAVES AND
PRECIPITATION ACROSS THE SOUTHEAST QUARTER OF THE NATION THIS
MEDIUM RANGE PERIOD.

...MODEL PREFERENCES...
THE 21/12Z ECENS...NAEFS AND GEFS WERE VERY REASONABLE PIECES OF
GUIDANCE FOR THE MEDIUM RANGE---AND WERE USED IN A 40/30/30 RATIO
RESPECTIVELY FOR DAY 5-7. THOUGHT THE 21/12Z GFS MAINTAINS THE
BEST OVERALL CONTINUITY WITH THE PRIMARY SYNOPTIC-SCALE FEATURES
OF THIS WEATHER PATTERN---AND COULD BE USED WITHOUT REGRET HEADING
INTO DAY 5. IT (THE 21/12Z GFS) CLOSELY FIT THE THE ENSEMBLE
MEANS---FROM COAST TO COAST---INTO DAY 7. IT BEGINS TO GET A TAD
FASTER ALONG THE WEST COAST AFTER DAY 5---BUT WAS A REASONABLE
SOLUTION HEADING INTO DAY 7---ALONG THE EAST COAST. FOR THE FOURTH
RUN IN A ROW---THE ECMWF FAILS TO RESOLVE THE PATTERN ADEQUATELY
ACROSS SOUTHERN CANADA FROM WEST TO EAST COAST---AND REALLY COULD
NOT USE ITS GUIDANCE BEYOND 26/00Z.

...SENSIBLE WEATHER HIGHLIGHTS...
FORECAST IS ON TRACK ACROSS THE NORTHEAST QUARTER OF THE
NATION---CYCLONIC FLOW...BELOW NORMAL TEMPERATURES AND INSTABILITY
SHOWERS PREVAIL FOR THE FIRST HALF OF THE PERIOD. THE CYCLONIC
FLOW AND ITS SENSIBLE WEATHER...SHIFTS NORTHEASTWARD FOR DAYS
6-7---INTO THE CANADIAN MARITIMES AND NORTHERN NEW ENGLAND.

THE PACIFIC BECOMES THE SOURCE REGION FOR SENSIBLE WEATHER DURING
THE FORECAST PERIOD. EARLY IN THE PERIOD---ITS MID-LEVEL ENERGY
MIGRATES OUT OF THE COLORADO FRONT RANGE AND MOVES DOWNWIND ACROSS
THE MID-MISSISSIPPI VALLEY AND EXITS THE LOWER 48 BETWEEN THE
DELMARVA AND OUTER BANKS.

DURING THE LATTER HALF OF THE PERIOD---THE MID-LEVEL ENERGY ENTERS
THE WEST COAST INVOF WASHINGTON STATE AND MIGRATES
EAST-SOUTHEASTWARD INTO THE CENTRAL PLAINS AND SOUTHEAST QUARTER
OF THE NATION. THE ENERGY GRADUALLY CARVES OUT A TROUGH AXIS
BETWEEN 80W-90W LONGITUDE BY DAY 7. 

VOJTESAK