textproduct: Seattle/Tacoma

SYNOPSIS

Dry northerly flow aloft continuing today. Combination of a weak system reaching the area and increasing low level flow producing cloudier and cooler weather Monday into Tuesday. Upper level ridge over Western Washington Wednesday and Thursday with weak trofiness Friday and Saturday.

SHORT TERM /TODAY THROUGH TUESDAY/

The latest forecast remains on track this morning with no updates. Sunny day today with dry northerly flow aloft. The fog and low clouds in Grays Harbor county will dissipate early this morning. Frost advisory remaining in effect for portions of the Central and Southern Puget Sound until 10 am. Highs in the lower to mid 60s.

Surface high pressure building offshore tonight increasing the low level onshore flow. Low clouds developing along the coast tonight spreading inland to the Puget Sound area early Monday morning. Lows in the upper 30s to mid 40s.

Weak upper level disturbance combined with the low level onshore flow keeping skies mostly cloudy Monday. Chance of drizzle/light showers along the coast with a chance of afternoon showers over the mountains. Highs cooling into the mid 50s to near 60.

Weak disturbance moving through Monday night with low level onshore flow into Tuesday morning. Chance of light showers continuing for the coast and mountains with mostly cloudy skies elsewhere. Lows in the mid 40s.

Low level onshore flow becoming light Tuesday. Upper level ridge offshore beginning to move towards Western Washington but not close enough to provide good subsidence to break up the marine layer. Under mostly cloudy skies highs remaining in the mid 50s to near 60.

Felton

LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/

Extended models in good agreement initially with the upper level ridge moving over Western Washington Wednesday for more sunshine and warmer temperatures. Highs in the 60s.

Ridge remaining over the area Wednesday night before shifting east Thursday. Low level flow turning offshore Wednesday night becoming light Thursday. Thursday the warmest day in the forecast period with highs in the 60s and lower 70s.

Operational runs of the ECMWF and GFS bring a weak trough over the area Friday into Saturday. Ensemble solutions not really getting on board with the operational run solutions. There is general agreement on cooler highs but the operational runs are around 5 degrees cooler than the ensemble means. Will stay with the mean solutions for now which cools highs mostly into the 60s both days with increasing cloud cover Saturday. Confidence not very high in the Friday and Saturday forecast.

AVIATION

An upper ridge will remain offshore, with troughing over the Intermountain West. North flow aloft continues with this pattern. Light to weak onshore flow into Monday morning. Predominantly clear skies with VFR for the interior sites through Sunday. There is a corridor of fog along US-12 and US-101 from Oakville to Hoquiam that is diminishing on satellite this morning. Onshore flow will then increase Sunday night into Monday for a more widespread low stratus push inland. North winds light this morning before increasing into the afternoon.

KSEA...Clear conditions expected today and tonight. North winds mainly 5 kt and below this morning. NW winds increase again around 20-21z. A 25-35% chance of MVFR cigs are forecast to develop early Monday morning.

41/HPR

MARINE

High pressure will remain over the coastal waters, with lower pressure inland. Onshore flow will persist into the new but of varying intensity. Guidance is hinting at westerly pushes down the Strait of Juan de Fuca Sunday evening and Monday evening, but the probability of gusts reaching small craft advisory thresholds is low at this time so the Central/Eastern Strait will be capped at 20 kt. A possible system end of the week producing breezy winds across more of the waters. Additionally, low clouds/fog Sunday morning along the Pacific Coast may reduce visibilities at times to mariners with another threat existing on Monday morning.

Seas this weekend hold around 4-6 ft, and increase to 6-8 ft Monday through next week.

41

HYDROLOGY

No river flooding is expected over the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Frost Advisory until 10 AM PDT this morning for City of Seattle-Lowlands of Lewis and Southern Thurston Counties- Lowlands of Pierce and Southern King Counties-Olympia and Southern Puget Sound-Southern Hood Canal.

PZ...None.