Snoqualmie, WA 98065 Weather

Synopsis

Weakening upper level low off the north coast will elongate and continue to weaken through Saturday. What is left of the low will move inland Saturday night. Upper level ridge building over the area Sunday. The ridge will move east Monday allowing a warm front to nick the north coast. Another ridge will build Tuesday into Wednesday. The ridge will move to the east Thursday with a splitting front moving into Western Washington.

Short term

Upper level low drifting southwest today. Flow aloft over Western Washington already southerly this morning. As the low moves southwest difluent flow aloft developing this afternoon. This combined with a little daytime heating to increase the instability over the area will produce more widespread shower activity this afternoon especially over the interior. Increasing shower activity in the afternoon will knock a couple of degrees off the high temperatures with lower 50s common across the area. The forecast high of 51 degrees for Seattle would be the coldest day since another 51 degree day back on May 15th.

Upper level low elongating and weakening tonight and Saturday but will still be off the coast by late Saturday afternoon. Jet stream moving inland over Northern California. Shower activity drying up quickly this evening. Shower chances becoming confined to the coast after midnight and to the coastal waters Saturday morning. Varying amounts of middle and high level clouds moving through the area. Lows in the 30s and lower 40s. If there is enough clearing chance for lows in the upper 20s in the Lower Chehalis Valley and Southwest Interior. A Freeze Watch for these areas has been upgraded to a Freeze Warning. Highs Saturday in the lower to mid 50s.

Upper level low weakening to an upper level trough and moving inland Saturday night. Nothing left with this feature by this point. Light surface gradients early Sunday morning with patchy fog developing in the fog prone locations like the Southwest Interior. Lows in the 30s and lower 40s.

Light onshore gradients Sunday morning for areas of morning low clouds and fog. Upper level ridge building into the area during the day making for a sunny afternoon. Highs in the lower to mid 50s. Felton

Long term

Extended models in pretty good agreement with the upper level ridge over the area Sunday night moving east Monday. This will allow a warm front to nick the north coast later Monday into Monday night. Another upper level ridge building Tuesday remaining over Western Washington Wednesday but the ridge axis will be east of the area. Splitting front reaching Western Washington Thursday for a chance of rain. Highs in the mid 50s with some upper 50s Wednesday. Lows in the 30s and lower 40s. Felton

Aviation

Another round of steadier rain is rotating through the region this morning, bringing fairly widespread rain which is lowering ceilings and restricting visibility. Expect widespread MVFR conditions through the afternoon as this move through, with local pockets of IFR under heavier showers. As the day progresses, a winds become predominantly east or southeasterly. Showers begin to decrease as the low continues to lose strength over the area. With light winds and some clearing overnight, expect to see fog and low stratus development from around the Seattle metro area southward through KOLM and KCLS. Moderate confidence for the development of IFR conditions 11-17z in these areas, with improvement into the late morning Saturday as the air mass begins to dry out at the low levels.

KSEA: MVFR conditions are expected in steadier rain this afternoon. Northerly winds will become east/southeast through the day, with rain tapering late afternoon or evening. This should bring a gradual clearing trend, but this will result in IFR fog/low stratus Saturday morning at the terminal.

Marine

Weak surface low pressure over the coastal waters will remain in place into Saturday before dissipating as high pressure builds across the interior of Western Washington early in the coming week. East or southeast winds across the coastal waters and near the west entrance to the strait will occasionally reach 15 to 20 knots over the next couple of days until the offshore low finally dissipates. Otherwise, winds into early next week look to remain rather light across area waters.

Coastal seas generally 4 to 6 feet today and into the weekend. They are expected to build back to around 10 feet Monday as another larger swell train reaches the waters.

27/18

Watches, warnings and advisories

WA: Freeze Warning from midnight tonight to 9 AM PDT Saturday for Lowlands of Lewis and Southern Thurston Counties-Middle Chehalis River Valley.

PZ: None.