textproduct: Seattle/Tacoma

SYNOPSIS

Low pressure will bring showers and thunderstorms to western Washington this weekend, with drier weather moving into next week. Offshore flow will lead to slightly warmer weather midweek. A front and trough will bring cooler weather and a chance of showers toward the end of the week.

SHORT TERM /TODAY THROUGH MONDAY/

An upper level low will spin over the Pac NW today with another round of afternoon/evening showers and thunderstorms over western Washington. Cells will initially form over the Cascades then drift west over the lowlands, similar to what was observed yesterday. Showers and thunderstorms will decrease toward sunset this evening. We will see a few sunbreaks in between showers with afternoon highs around 70. The coast will be cooler and in the 60s.

The upper low continues to wobble overhead on Sunday but showers will mostly stick over the mountains. The air mass remains slightly unstable for isolated mountain thunderstorms as well. With lighter/weaker steering flow, the storms will be slow-moving with the potential for higher precipitation totals (especially over the southern Cascades).

The upper low shifts farther east and inland on Monday with just isolated showers over the Cascades. Low level onshore flow will be stronger for morning clouds and late afternoon sunbreaks. 33

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Western WA lies in between weather systems next week with broad low pressure over western Canada and a cutoff low (associated with Hurricane Marie) well offshore along 135W. East/offshore flow will lead to slightly warmer weather in the mid to upper 70s both Wednesday and Thursday. Expect lows in the 50s. The Canadian low will bring troughing over the area by Friday for cooler weather and a chance of showers. 33

AVIATION

Variable flow aloft continues as an upper level low moves slowly over western Washington. Surface winds largely light and variable this early morning before favoring a north to northeasterly direction later this morning and into this evening. Light and variable winds expected to return tonight.

VFR conditions persist at most terminals, the exception being BLI and OLM as some low clouds/fog push conditions down to IFR/LIFR, but will return to VFR conditions by noon today. Scattered showers with isolated thunderstorms possible again today but probabilities do not favor TAF inclusion at this time.

KSEA...VFR conditions in place and expected to remain that way for the TAF period. Thunderstorms are possible in the Cascades this afternoon, and at this time do not have indication of going near the terminal and will leave it out of TAF inclusion. Winds light and variable this morning, turning more northerly by this afternoon before shifting northeasterly around 00Z. Speeds increasing to around 5-10 kts this afternoon.

18/Mazurkiewicz

MARINE

No significant marine conditions expected on the whole, with winds and seas largely remaining short of any advisory criteria. Scattered showers and isolated thunderstorms will be possible again today as the upper level low over the region has moved very little. Northerly winds expected over the waters this weekend into next week. A marginal westerly push through the Strait of Juan de Fuca around Monday looks to be the next potential period of advisory strength conditions. Seas mainly 3 to 5 feet this weekend and into the start of next week.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...None.