727
FXUS02 KWBC 291825
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
224 PM EDT SUN JUN 29 2008
VALID 12Z WED JUL 02 2008 - 12Z SUN JUL 06 2008
A PAIR OF POSITIVE ANOMALIES BETWEEN 70-75 DEGREES NORTH OVER
NORTHWEST CANADA AND GREENLAND FAVOR TWO PERSISTENT VORTICES...ONE
IN THE NORTHEAST PACIFIC AND ANOTHER CENTERED OVER QUEBEC. IN
BETWEEN...A MEAN RIDGE WILL PERSIST FROM THE SWRN U.S. TO THE NRN
ROCKIES AND INTERIOR WESTERN CANADA...THOUGH DUE TO THE AMPLIFIED
NATURE OF THE RIDGE IN WESTERN CANADA ENERGY SHOULD UNDERCUT THIS
SYSTEM MOVING NEAR THE WESTERN US/CANADIAN BORDER MID TO LATE
PERIOD. INDEED...THE 00Z GFS/ECMWF INDICATE THIS IDEA ON FRIDAY
AS SOME ERN PAC SHRTWV ENERGY PUSHES EWD ACROSS THE PAC NW. THE
12Z GUIDANCE PRODUCED NO NEW SURPRISES. IN THE MIDWEST...THE 06Z
GFS CLOSED OFF A CYCLONE NEAR MISSOURI. A CHECK OF THE 00Z
NCEP/CANADIAN/ECMWF ENSEMBLE MEMBERS SHOW THERE IS SUPPORT FROM 1
OF THE 90 MEMBERS FOR THE 06Z GFS CLOSED CYCLONE...NOT ENOUGH TO
GO WITH ITS SOLUTION. THE EXPECTED BREAKDOWN OF THE RIDGE ALONG
THE WESTERN US/CANADIAN BORDER ALSO ARGUES AGAINST THIS IDEA. THE
00Z GFS AND ECMWF ARE GENERALLY SIMILAR AND HAVE SUPPORT FROM
TELECONNECTIONS...SO USED A BLEND OF THEIR PRESSURES THROUGH THE
PERIOD WHICH LED TO GOOD CONTINUITY.
A BULK OF THE PRECIPITATION THIS PERIOD IS EXPECTED TO LIE ON AN
AXIS FROM THE CENTRAL PLAINS THROUGH THE MID-MISSISSIPPI VALLEY
AND TENNESSEE VALLEYS INTO THE MID-ATLANTIC STATES ALONG A
QUASI-STATIONARY FRONTAL ZONE. LOCAL AMOUNTS OF 5-10 INCHES ARE
POSSIBLE HERE. FLORIDA SHOULD RECEIVE THE BULK OF THEIR
PRECIPITATION EARLY IN THE PERIOD AS A WEAK FRONT DROPS INTO THE
PANHANDLE BEFORE MID-LEVEL RIDGING STABILIZES THE ATMOSPHERE
LIMITING THE RAINFALL POTENTIAL.
ROTH/HEDGE
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