Prognostic Meteorological Discussion
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000
FXUS02 KWBC 261545
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1144 AM EDT SUN APR 26 2015

VALID 12Z WED APR 29 2015 - 12Z SUN MAY 03 2015

...PATTERN OVERVIEW AND GUIDANCE/UNCERTAINTY ASSESSMENT...

THE MAJORITY OF GUIDANCE SUGGESTS THAT IN THE MEAN A RIDGE SHOULD
BUILD INTO THE CENTRAL AND EVENTUALLY EAST-CENTRAL CONUS WHILE A
TROUGH SETTLES INLAND FROM THE WEST COAST AND AN ERN TROUGH TRACKS
GRADUALLY OFFSHORE. MODELS AND ENSEMBLES ARE STILL HAVING SOME
DIFFICULTY IN RESOLVING IMPORTANT ERN TROUGH DETAILS AFFECTING WRN
ATLANTIC COASTAL LOW EVOLUTION AND INDIVIDUAL SHORTWAVES PASSING
THROUGH THE WEST COAST TROUGH. HOWEVER...THE 06 UTC GFS/GEFS MEAN
AND 00 UTC ECMWF/ECMWF ENSEMBLE MEAN HAVE CONSIDERABLY CONVERGED
UPON A MORE COMMON SOLUTION DAYS 4/7 OVER NOAM. THIS BOLSTERS
FORECAST CONFIDENCE SOME DESPITE THE LARGE RECENT AND SOME SMALLER
LINGERING GUIDANCE VARIANCE ISSUES.

THE WPC MEDIUM RANGE PRODUCT SUITE HAS ACCORDINGLY BEEN PRIMARILY
DERIVED FROM A BLEND OF THE REASONABLY COMPATABLE/CLUSTERED 06 UTC
GFS/GEFS MEAN AND 00 UTC ECMWF/ECMWF ENSEMBLE MEAN...LEANING SOME
GREATER WEIGHTING ON THE DETERMINISTIC ECMWF TO ADD SYSTEM
DETAIL/DEPTH.

...SENSIBLE WEATHER HIGHLIGHTS...

COMPLEX STREAM INTERACTION WITH MID-UPPER LEVEL MEAN TROUGH
DEVELOPMENTS OVER THE ERN THIRD OF THE NATION MAY SUPPORT AN
UNSETTLING LEAD SERN US TO ERN US COASTAL LOW WITH A DEVELOPING
ASSOCIATED WRAP-BACK AND LEAD/TRAILING FRONTAL PCPN SWATH ACROSS
THE REGION WED-FRI.

MEANWHILE UPSTREAM...A SERIES OF IMPUSLES ALOFT AND ASSOCIATED
SURFACE FRONTAL SYSTEMS ARE SLATED TO WORK TO THE NWRN US AND
PROGRESS EASTWARD ACROSS THE US NRN TIER OVER THE UPCOMING WEEK TO
SPREAD GENERALLY MODEST LEAD PCPN AND SOME COOLING IN THE WAKE OF
SYSTEM PASSAGE.

SCHICHTEL

$$




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