textproduct: Seattle/Tacoma

SYNOPSIS

Upper level ridge offshore extending into Northern British Columbia combined with large upper level low centered over the Canadian Prairies giving Western Washington northerly flow aloft through the weekend. The low will move east Monday. Weak system embedded in northwesterly flow aloft moving through Monday night/early Tuesday. Upper level ridge over the area Wednesday and Thursday.

SHORT TERM /TODAY THROUGH MONDAY/

Satellite imagery shows high clouds west of Puget Sound and mostly clear skies Puget Sound eastward. Temperatures at 3 am/10z were in the mid 30s to mid 40s.

Northerly flow aloft over Western Washington for the weekend. High clouds at times embedded in the flow aloft moving through the area. Not enough to prevent plenty of sunshine both days. Highs in the lower to mid 60s today and 60s Sunday. Could need another frost advisory portions of the Southwest Interior and South Puget Sound Sunday morning with lows in the mid 30s. For the remainder of the area lows near 40.

Flow aloft becoming northwesterly Monday with the large upper level low to the east moving east and the upper level ridge offshore retrograding a little. Weak shortwave embedded in the flow aloft reaching the area late in the day to increase cloud cover and create a chance of showers over the higher terrain. Increasing low level onshore flow Sunday night plus increasing clouds Monday cooling highs into the mid 50s to lower 60s. Lows in the lower to mid 40s. Felton

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Weak shortwave moving through Monday night for a chance of showers. Chance of showers continues in the higher terrain Tuesday with the air mass slightly unstable. For the lowlands, partly sunny skies. Highs mid 50s to lower 60s.

Upper level ridge moving over Western Washington Wednesday into Thursday for more sunshine and warmer temperatures. Model solutions very inconsistent Friday. A small number of ensemble solutions have cooler temperatures with a chance of showers as a trough moves through the area. A majority of the solutions keep the weather dry with above normal temperatures. Will stay with that idea for now but will not be surprised if the forecast for Friday changes in the next couple of forecast packages. Highs Wednesday through Friday in the 60s and lower 70s. Lows in the upper 30s to mid 40s.

AVIATION

North-northeast flow aloft throughout the period with a ridge offshore and a trough to the east. VFR skies today with mid to high level few-sct. A less than 10% chance of LIFR (fog) developing for KOLM and neighboring terminals in the Chehalis River Valley through 16z this morning. Breezy northerly surface winds this afternoon with gusts near 20 kt. VFR again tonight however, increasing onshore flow will bring low ceilings along the coast (KHQM).

KSEA...VFR expected through the TAF period. North winds 5-10 kt with gusts near 20 kt this afternoon. Winds become lighter after 00z.

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MARINE

High pressure will remain offshore with lower pressure inland. North flow will continue over the waters with this pattern, with the winds offshore at times. Increasing onshore flow will bring the potential for SCA winds for Central and Eastern Strait Sunday evening. Elsewhere, winds largely remain light, with the potential for a weak diurnal push through the strait again on Monday. Seas will remain in the 4-8 ft range.

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HYDROLOGY

No river flooding in the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES

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

PZ...None.