textproduct: Seattle/Tacoma

SYNOPSIS

Broad low pressure over the Pacific Northwest will keep chances for showers and isolated thunderstorms in the forecast through Sunday. Drier and warmer conditions expected for the beginning of next week. A weak system will brush the area Thursday.

SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/

Low pressure will remain the dominant feature over the Pacific Northwest through this weekend. Satellite imagery shows the low center just off the coast of central Oregon and will likely remain there as it slowly weakens through the weekend. Low is stacked vertically, and the upper level low supporting it will also slowly fill in through the weekend. Scattered showers are slowly dissipating this evening after an active convective stretch the last few hours across portions of Puget Sound. Drier conditions are expected tonight into Saturday morning before the return of additional shower and thunderstorm potential. The best chances for thunderstorms remain across the Cascade and Olympic Mountains, as well as portions of the Cascade foothills on Saturday afternoon and evening. Some activity may drift again into the lowlands late afternoon with more southeast flow aloft. Going into Sunday, chances for showers become more confined to the higher terrain and a marginal (15% or less) chance for isolated thunderstorms.

Skies generally remain partly to mostly cloudy, with high temperatures in the mid 60s to low 70s. Lows in the upper 40s to mid 50s.

LONG TERM /MONDAY THROUGH FRIDAY/

Models remain consistent on finally ejecting the upper level trough out to the east Sunday night into Monday. Following, that will leave western Washington generally in dry, split to northwesterly flow as ridging tries to develop while an upper level low develops off the coast of California. This will allow for more sunny and drier conditions across the area for the start of next week, with temperatures expected to rise into the mid to upper 70s, perhaps near 80 in some spots by Wednesday. The pattern gets more uncertain as the evolution depends on the interaction between a develop upper level trough coming down along the British Columbia coast and the remnants of Hurricane Marie getting pulled up and east towards the west coast. Temperatures look to trend cooler, back towards the low 70s, and chance for rain will start to return to the forecast late Thursday and into Friday.

JD/62

AVIATION

Variable flow aloft continues as an upper level low moves slowly over western Washington. VFR conditions likely continuing throughout the rest of the evening. The thunderstorm threat has subsided here as lingering showers wane. N/NE winds generally around 4 to 8 knots into Saturday morning. Low clouds may develop around lower prone terminals briefly early Saturday morning, but chances remain low (20%) of any impact to conditions (MVFR/IFR).

KSEA...VFR conditions this evening with some mid to high level clouds around. Winds variable, turning to N/NE at times and remaining generally light (3 to 6 kts) tonight. Winds will maintain more of a north direction by Saturday morning, with conditions remaining VFR.

41

MARINE

No significant marine conditions expected on the whole, with winds and seas largely remaining short of any advisory criteria. The thunderstorm threat has come to an end this evening as benign conditions have rebounded. Otherwise, northerly winds develop 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 will generally hold around 4 to 5 ft over the coastal waters, with a mostly short period component this weekend and into the start of next week.

SEW WATCHES/WARNINGS/ADVISORIES

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