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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0619Z Apr 23, 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
219 AM EDT THU APR 23 2015

VALID 12Z SUN APR 26 2015 - 12Z THU APR 30 2015

...OVERVIEW...
A SERIES OF PACIFIC TROUGHS WILL MAKE THEIR WAY ACROSS THE LOWER
48 THIS FORECAST PERIOD---SETTING UP A WET FORECAST FOR THE
SOUTHERN ROCKIES...PLAINS AND SOUTHEAST.

...MODEL PREFERENCES/UNCERTAINTY ASSESSMENT...
THE 22/12Z ECENS-NAEFS-GEFS MEANS PROVIDED A VERY REASONABLE MASS
FIELD FORECAST BASELINE---AND THE DETERMINISTIC ECMWF...GFS AND
CANADIAN WERE BEGINNING TO ESTABLISH BETTER CONTINUITY OVER SOUTH
CENTRAL CANADA. THE GUIDANCE HAS RESOLVED THE STORM TRACK---TAKING
THE PACIFIC SYSTEM NORTHEASTWARD TOWARDS THE ARCTIC CIRCLE (ALONG
100W LONGITUDE) RATHER THAN SENDING IT EASTWARD INTO THE DAKOTAS
(DAY 3-4).

THE AMPLIFICATION OF LONGWAVE RIDGE ACROSS THE WEST COAST AND
NORTHERN ROCKIES BEHIND THAT SYSTEM---NOW GIVES THE 'NEW' PACIFIC
JET 'ROOM' TO DIG SOUTHEASTWARD ALONG THE CONTINENTAL DIVIDE AND
BEGIN THE PROCESS OF CARVING OUT THE BASE OF A 'NEW' TROUGH
AXIS---EAST OF THE MISSISSIPPI RIVER ALONG 30N LATITUDE FROM 90W
TO 80W LONGITUDE---BETWEEN TUESDAY AND THURSDAY OF NEXT WEEK.

EMBEDDED WITHIN THIS 'NEW' TROUGH---WILL BE AN ACTIVE FOUR CORNERS
CLOSED 500MB LOW. THE FORECAST CHALLENGE WILL BE THE MIGRATION OF
THIS SYSTEM ACROSS THE SOUTHERN PLAINS---AND ITS INTENSIFICATION
DOWNSTREAM ACROSS THE SOUTHEAST AND SOUTHERN MID-ATLANTIC
REGION...PRIOR TO ITS EXIT INTO THE WESTERN ATLANTIC OCEAN. A KEY
COMPONENT OF THE SYSTEM'S INTENSIFICATION WILL BE THE
INCORPORATION OF SOUTHEASTWARD-MOVING SHORTWAVE ENERGY AND AT WHAT
LATITUDE/LONGITUDE THIS NORTHERN STREAM ENERGY WILL 'PHASE' WITH
THE CUTOFF SYSTEM.

PRIOR TO ITS PHASING---A SERIES OF WEAKER FAST-MOVING SHORTWAVES
ARE ANTICIPATED TO EJECT EASTWARD ACROSS THE PIEDMONT AND
CONSOLIDATE IN THE WESTERN ATLANTIC WITH A STAGNANT CYCLONIC FLOW
INVOF THE CANADIAN MARITIMES.

...SENSIBLE WEATHER HIGHLIGHTS...
VERY WET 4-DAY PERIOD FOR THE SOUTHEAST QUARTER OF THE
NATION...INCLUDING FLORIDA. MOST RECENT MODEL QPF GUIDANCE CENTERS
THE HEAVIEST RAINFALL AMOUNTS ALONG THE BROAD BASE OF THE EASTERN
TROUGH---ALONG/SOUTH OF THE I-10 CORRIDOR FROM SOUTHWEST LOUISIANA
TO NORTHEAST FLORIDA INCLUDING A LARGE PORTION OF CENTRAL AND
SOUTH FLORIDA. A SECONDARY PRECIPITATION MAXIMA IS EXPECTED ALONG
A 'ARC' FROM SOUTHEAST COLORADO INTO SOUTH CENTRAL OKLAHOMA AND
EAST CENTRAL TEXAS.