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    Light northeast flow aloft over Western Washington will
    gradually shift to southeasterly today as an upper level ridge
    centered over the northern British Columbia coast moves into the
    interior this afternoon. The air mass is generally dry and stable
    except for low level marine moisture extending locally inland
    through the Chehalis Gap. Daytime heating will destabilize the
    atmosphere somewhat near the Cascade crest for a chance of an
    afternoon shower or thunderstorm as mid level moisture creeps
    westward around a broad trough over the Northern Rockies.
    VFR conditions can be expected across the region today with the
    exception of some IFR ceilings in stratus along the coast and areas
    of the interior from Puget Sound westward this morning.
    KSEA...Onshore gradients have weakened over the past few hours, but
    an area of stratus over the Kitsap Peninsula has been gradually
    expanding eastward to near Vashon Island as of 0930Z. Upcoming TAF
    for Sea-Tac will probably include at least a tempo IFR ceiling
    through 16Z but expecting fairly rapid clearing with a shallow
    marine layer. VFR expected thereafter. South-southwest wind 5 to 10
    knots through the morning, becoming northwesterly 4 to 8 knots
    around 00Z as a very weak northerly gradient tries to develop.   27