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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0700Z Oct 28, 2014)
 
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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
300 AM EDT TUE OCT 28 2014

VALID 12Z FRI OCT 31 2014 - 12Z TUE NOV 04 2014

...OVERVIEW...
ACTIVE PATTERN ACROSS THE LOWER 48 WILL FOCUS ON A SURFACE CYCLONE
IN THE NORTHEAST CORNER OF THE COUNTRY DURING THE FIRST HALF OF
THE FORECAST PERIOD...AND ACROSS THE PLAINS-GREAT LAKES REGION
DURING THE LATTER HALF OF THE PERIOD.

...UNCERTAINTY ASSESSMENT...
IN THE WEST...THE MAIN CHALLENGE CONTINUES TO BE TIED TO THE
NORTHEAST PACIFIC AND BEYOND THE DAY 5 PERIOD. ALTHOUGH THE
ESTABLISHMENT OF A VORTEX IN THE GULF OF ALASKA AROUND DAY 4-5 IS
NOT THE ISSUE...THE SEQUENCE AND INTENSITY OF INDIVIDUAL
NORTHEASTWARD-MOVING SHORTWAVES ARCING COUNTER-CLOCKWISE INTO THE
SOUTHWEST COAST OF BRITISH COLUMBIA STILL IS. PRIMARILY---FRONTAL
STRUCTURE ALONG THE OREGON AND WASHINGTON COASTS. THE UNCERTAINTY
LIES IN THE DETERMINISTIC JET-LEVEL WIND FORECASTS ON/AFTER 2/12Z
(MID-POINT DAY 5) ALONG 50N LATITUDE. AT THIS POINT...THE CURRENT
SET OF SURFACE GRAPHICS LOOK MORE LIKE THE 27/12Z DETERMINISTIC
ECMWF SOLUTION ON DAY 6-7...WITH A CONSIDERABLY WEAKER SEQUENCE OF
WARM/COLD FRONT  PROGRESSIONS INTO THE PACIFIC NORTHWEST---LIMITED
BY THE NORTHERN AND WESTERN FLANKS OF AN EXPANSIVE EAST CENTRAL
PACIFIC SURFACE RIDGE---RAPIDLY BUILDING INTO NORTH CENTRAL
CALIFORNIA/SOUTHERN OREGON AND SPREADING EASTWARD ACROSS THE GREAT
BASIN AND CENTRAL ROCKIES ON DAYS 5-6.

ACROSS THE CENTRAL STATES...THE MAIN CHALLENGE IS NOT NECESSARILY
WITH THE DEPTH OF THE SURFACE CYCLONE EJECTING OUT OF THE UPPER
THIRD OF THE MISSOURI RIVER BASIN ON DAY 5. THE 27/12Z
DETERMINISTIC GFS/ECMWF ARE REASONABLY CLOSE. BUT THE QUESTION
REMAINS...AS TO HOW INSTRUMENTAL WILL A SECONDARY SHORTWAVE AND
NOTABLE JET STREAK EJECTING OUT OF THE FOUR CORNER REGION (NM/TX
BORDER) ON SUNDAY BE? WITH RESPECT TO CONVECTIVE INITIATION ALONG
THE SOUTHERN END OF THE COLD FRONT. THE DETERMINISTIC 27/12Z
GFS/ECMWF BOTH 'PROG' A BROAD REGION OF DIFFLUENT JET-LEVEL FLOW
BETWEEN ABQ AND STL. AND MORE IMPORTANTLY...HOW FAR NORTH CAN THE
SURGE OF JET-LEVEL SOUTHWEST FLOW AHEAD OF THE FRONT IMPACT THE
SENSIBLE WEATHER---IN TERMS OF CLOUDINESS...WIND SPEED AND
PRECIPITATION ACROSS THE MID-MISSISSIPPI VALLEY...LOWER MISSOURI
VALLEY AND CENTRAL GREAT LAKES ON MONDAY (DAY 6)?

IN THE EAST...THE CHALLENGE WILL BE TO SORT THE DETAILS OF
SECONDARY SURFACE CYCLOGENESIS IN THE WESTERN ATLANTIC THIS
WEEKEND. WITH THE COLD FRONT HAVING PROGRESSED OFFSHORE OF THE
EAST COAST ON DAY 3...THE QUESTION IS WHERE THE CLOSED 500MB
CIRCULATION TRACKS ALONG AND EAST OF 70W LONGITUDE FOR THE
WEEKEND...AND WHICH PORTIONS OF THE NORTHEAST OBSERVE THE BEST
WRAP-AROUND PRECIPITATION WITH THE CYCLONE AS IT MOVES ACROSS
MAINE AND NEW BRUNSWICK.

...MODEL PREFERENCES...
FROM WEST TO EAST...THOUGHT THE 27/12Z GEFS/ECENS MEANS BLENDED AT
A 40/60 RATIO RESPECTIVELY CONTINUE TO DEPICT THE PATTERN AND THE
DETERMINISTIC GFS/ECMWF WERE DECENT PIECES OF GUIDANCE THROUGH DAY
4 WITH THE IMPORTANT SURFACE CYCLONES AFFECTING THE LOWER 48. FOR
DAY 5-7...THE ECENS MEANS MAINTAINS A SLIGHTLY MORE-AMPLIFIED
LONGWAVE TROUGH-RIDGE-TROUGH SEQUENCE ACROSS THE LOWER 48 VERSUS
THE GEFS. BUT THE KEY FEATURE OF THE PATTERN REMAINS IN
PLACE---THE PROGRESSIVE NATURE OF THE PATTERN ACROSS CENTRAL
CANADA.

...SENSIBLE WEATHER HIGHLIGHTS...
COLD AND LOCALLY DAMP FOR NEW ENGLAND AND THE EASTERN GREAT LAKES
IN ASSOCIATION WITH THE WRAP-AROUND PRECIPITATION AND SURFACE
CYCLOGENESIS DEVELOPING OFF THE SOUTHERN NEW ENGLAND COAST AND
TRACKING ACROSS ATLANTIC CANADA. A BRISK NORTHWEST FLOW AND STRONG
CELL OF CANADIAN HIGH PRESSURE BUILDING IN BEHIND THIS SYSTEM
SPREADS INTO THE THE SOUTHEAST AND GULF COAST.

STRONG PACIFIC JET ENERGY AND SURFACE CYCLOGENESIS EJECTING OUT OF
THE ROCKIES WILL GENERATE WINDY CONDITIONS DOWNSTREAM IN THE
PLAINS...WITH SCATTERED PRECIPITATION DEVELOPING ALONG THE
TRAILING COLD FRONT.

VOJTESAK