textproduct: Seattle/Tacoma

SYNOPSIS

Showers remain possible over western Washington into Saturday as low pressure moves through the area. Winds and seas will also slowly ease during this time. Overnight lows this weekend may fall enough for localized frost and freeze potential. The next front to impact the area expected late Tuesday into Wednesday for more rain and breezy winds.

SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/

Current radar showing two main bands of precipitation this evening: the first along the Whatcom/Skagit county border and another stretching over the southern half of Snohomish county down into portions of northern King. This second one mainly due to a lingering convergence zone. Latest satellite shows low clouds favoring most of the CWA east of the Sound , although there is also another patch from the northern coast stretching eastward to the Olympics.

Current weather is in line with inherited forecast and as such, no need for any evening updates. For additional forecast details, please refer to the Previous Discussion section below. 18

From Previous Discussion...Rain has mostly ended across western Washington with the exception of a post-frontal convergence zone centered over Seattle and extending east into the Cascades. This feature will slowly shift south and eastward and weaken this evening as the winds slowly ease. Winds across the area remain in the 10-20 mph range with gusts between 20-35 mph. Winds are peaking now and will slowly ease this evening. High temperatures today in the upper 50s to low 60s will cool into the upper 30s to mid 40s.

Another weak low pressure system will move across the area on Saturday, keeping chances for scattered showers in the forecast through tomorrow afternoon. High temperatures remain seasonably cool, into the mid to upper 50s. Skies look to clear out Saturday evening. As the low moves south, offshore flow will begin to pick up Saturday evening with breezy northeasterly winds from western Whatcom county and through the San Juans with gusts up to around 25 mph. Elsewhere, across southwestern Washington, clear skies and mostly light winds Saturday night will promote efficient cooling, with lows reaching from the mid 40s in the metro area to mid 30s in the sheltered valley locations. Our first frost advisory for the season has been issued for portions of the SW WA Cascades and the middle Chehalis river valley. The upper reaches near Olympia and Chehalis could potentially get fog, so there is greater uncertainty there. The winds would be the limiting factor for the foothills and valleys farther north into King and Snohomish counties, but trends will have to be monitored for expansion of the frost advisory.

Sunday looks to be drier and sunnier as high pressure builds back in over the area. Breezy north/northeasterly winds look to continue with gusts up to 20 mph, especially over the waters. Highs in the upper 50s to low 60s. Cool conditions continue Sunday night with the potential for more frost.

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LONG TERM /MONDAY THROUGH FRIDAY/

Ensembles continue to highlight drier but cooler conditions into Monday. Morning lows Monday will likely reflect the previous couple of nights, in the mid to upper 30s for most areas. Could see potentially another round of frost and freeze potential, particularly in the Cascade valley and southwest interior locations. Otherwise, Monday will be mostly dry with high temperatures in the low 60s. A weak system looks to cross over the area Tuesday into Wednesday for a round of light rain. Beyond the middle of the week, there is uncertainty in the pattern but generally, guidance indicates that a return to high pressure and mild conditions is favored.

Mazurkiewicz

AVIATION

Post-frontal onshore flow tonight with westerly flow over western WA. Showers are mainly within the convergence zone over Snohomish and King counties this evening. However, we will see increasing shower activity overnight and into Saturday as an upper low moves overhead. Most of this activity will be over the Cascades. Ceilings will be a mixed bag with VFR and MVFR in showers. Drier weather Saturday night as the upper low shifts to the E/SE. 33

KSEA...Showers in the vicinity due to the convergence zone through 06z tonight. Surface winds veering from E to SE to S, then becoming N again (to 10 kt) by 18-21z Sat. 33

MARINE

Strong onshore flow continues this evening behind a frontal passage that occurred early this morning. Small Craft Advisories remain in effect most of the interior waters except Puget Sound, and the Central/Eastern Strait of Juan de Fuca where Gale Warnings remain in effect. Winds through the interior waters are peaking now and will ease below thresholds this evening.

Over the coastal waters, Small Craft Advisories continue through mid- day Saturday. Winds will slowly ease overnight into Saturday morning, but seas look to remain above 10 feet through mid-day Saturday. Seas will remain choppy and locally-wind driven with the dominant period being in the 8-10 second range.

A weak low pressure system will move through on Saturday, behind which winds will turn offshore Saturday evening. Winds will briefly be enhanced slightly in the Northern Inland Waters near the San Juans and off the coast in the central and southern coastal waters zones, with potential for wind gusts to approach Small Craft criteria overnight into early Sunday morning.

Winds ease next week as high pressure builds back in from well offshore. The next low pressure system look to move across the area Tuesday night into Wednesday, but there remains some uncertainty in timing as this is later than previously forecast.

After Saturday, seas look to remain in the 5-8 ft range Sunday through the first part of next week.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...Frost Advisory from midnight Saturday night to 8 AM PDT Sunday for Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Thurston and Lewis Counties-Middle Chehalis River Valley.

PZ...Small Craft Advisory until 5 AM PDT Saturday for Grays Harbor Bar.

Gale Warning until 11 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory until 11 PM PDT this evening for Northern Inland Waters Including The San Juan Islands.

Small Craft Advisory until 8 AM PDT Saturday for Coastal Waters From Cape Flattery To James Island Out 10 Nm- Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.

Small Craft Advisory until 2 PM PDT Saturday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm.