Prognostic Meteorological Discussion
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FXUS02 KWBC 251536
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1135 AM EDT MON JUL 25 2016

VALID 12Z THU JUL 28 2016 - 12Z MON AUG 01 2016

...OVERVIEW...
594 DM RIDGE REMAINS A FIXTURE IN THE GREAT BASIN THROUGH DAY 5
--- AND A SERIES OF `EFFECTIVE FRONTS` SPREAD ACROSS THE LOWER 48
--- EAST OF THE DIVIDE. A STRONG SHORTWAVE ORIGINATING IN THE GULF
OF ALASKA IS EXPECTED TO MIGRATE ACROSS BRITISH COLUMBIA AND
ALBERTA DAYS 6-7 AND SPREAD ITS COLD FRONT ACROSS THE PACIFIC
NORTHWEST AND NORTHERN ROCKIES.

...MODEL PREFERENCES/UNCERTAINTY ASSESSMENT...
AS EARLY AS DAY 4...LOWER HEIGHTS IN THE EAST (582DM CONTOUR AND
TROUGH AXIS INVOF 95W) GIVE UP FEW DETAILS---WITH THE 25/00Z
DETERMINISTIC GFS MUCH FASTER WITH PRECIPITATION REACHING THE
DELMARVA (29/00Z-29/12Z) VERSUS THE ECMWF.

THIS `582 DM TROUGH AXIS` BECOMES THE NEW `EFFECTIVE FRONT` AND
THE 25/00Z GFS/ECMWF LOOKED A LITTLE BETTER ACROSS THE UPPER HALF
OF THE MS VALLEY AND LOWER HALF OF THE OHIO VALLEY FOR DAYS 5-6.
BUT HERE AGAIN...MODEL QPF PLACEMENT AND TIMING ALONG THIS
`EFFECTIVE FRONT` IS LESS THAN STELLAR.

THOUGH A 50/30/20 BLEND OF THE 25/00Z ECENS/NAEFS/GEFS MEANS
SEEMED THE BETTER APPROACH --- DID WANT TO MAINTAIN SOME
CONTINUITY AND UTILIZED SOME DETERMINISTIC GFS/ECMWF THROUGH
MID-POINT DAY 4 (29/12Z).

...SENSIBLE WEATHER HIGHLIGHTS...
CONTINUED WARMTH ACROSS THE WEST BENEATH THIS MASSIVE RIDGE ---
AND HIGH-BASED CONVECTION FOR THE DESERT SOUTHWEST AND GREAT
BASIN...AHEAD OF THE GULF OF ALASKA SOUTHWEST CANADA TROUGH.

EAST OF THE CONTINENTAL DIVIDE...THE `EFFECTIVE FRONTS` WILL BE
THE FOCUS FOR CONVECTIVE ACTIVITY --- WITH THE LARGER
PRECIPITATION TOTALS CONCENTRATED ACROSS THE OHIO
VALLEY...SOUTHERN NEW ENGLAND...AND LOWER HALF OF THE MISSISSIPPI
VALLEY.

VOJTESAK

$$





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