textproduct: Seattle/Tacoma

SYNOPSIS

A strong frontal system will bring gusty winds and additional rainfall to western Washington tonight and Friday. A warm front will boost temperatures as it moves northwards into the area Saturday. A follow-up cold front Saturday night into Sunday will bring another round of rain and gusty winds. The weather pattern remains active into at least the first half of next week.

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/

Current satellite imagery shows typical autumn cloudy skies over W WA in advance of the incoming frontal system. Radar is starting to clearly show the leading edge of this system over the outer coastal waters.

A weak shortwave ridge will hold that system at bay briefly, keeping conditions dry for much of W WA this afternoon and into the early evening before rain moves in tonight. Gusty winds will accompany the incoming front with particular concern for higher wind speeds along the coast and the NW Interior /including the islands as well as portions of western Whatcom and Skagit counties/...where speeds could get as high as 20-30 mph with gusts to 50 mph. Models have remained consistent with these speeds and as such, inherited Wind Advisory for the aforementioned areas remains on track. As this system mainly impacts the area through the day Friday, this is when the bulk of the rainfall is expected with amounts ranging one-half to three-quarters of an inch on the high end...mainly expected over the higher terrain and along the coast...to one tenth to one quarter of an inch most remaining lowland locations. Snow levels will rise throughout the event, starting the day off at around 5000-6000 ft and lifting to around 9000 in the afternoon. As such, not much of a concern for high elevation snowfall at this time.

The front pushes out of the area very late Friday night, allowing for another weak, short-lived shortwave ridge to enter the area. This feature will not be terribly effective at dispelling clouds nor lingering post-frontal showers, but does provide a relative lull in activity for much of Saturday before the next frontal system comes knocking on the coastline come Saturday night. Another round of strong winds will accompany this front as it moves through during the overnight hours, with wind impacts being felt over much of the CWA. While the more wind prone locations along the coast, the islands and the NW interior will likely see headline conditions, it is entirely possible that other locations along the Sound may see speeds high enough to qualify. It is a little too far out to make decisions on headlines just yet, but situation is being monitored.

Even though the short term will be active, temperatures are expected to remain mild with daytime highs still a few degrees above seasonal normals. Saturday will actually see a boost in temperatures with daytime highs that day getting into the 60s for most lowland locations. Overnight clouds will keep lows from sinking too much, mostly ranging from the mid 40s to around 50 for the entire short term period.

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LONG TERM /SUNDAY THROUGH THURSDAY/

Winds ease quickly Sunday with most breezy conditions wrapping up by mid-morning. Frontal passage throughout the day will drag its feet a bit, but a follow-up shortwave ridge should begin to impact the area Sunday night into Monday. This break in the action continues until Monday afternoon, when the next frontal system will begin to enter the area. By this point, snow levels will have fallen to around 4000- 5000 ft, but are quick to rebound late Monday to above 6000 ft. The frontal passage late Monday will extend into Tuesday with another potential break possible Wednesday as upper level ridging builds over the Rockies. Models fall into disagreement here as the westward extent of the ridge is a point of contention. The operational deterministic models show the split well, with the ECMWF keeping the ridge east enough where rain could get at least as far east as the Olympic Peninsula while the GFS shows the ridge west enough to keep any systems off the coast. Ensembles show a wide array of solutions, however the mean does trend slightly drier...leaning more toward the ECMWF and perhaps even dragging precip slightly further east. The NBM falls in line with this latter thinking and is a good starting point for the forecast this far out. Neither daytime highs nor overnight lows stray too much from the temperature pattern established during the short term.

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AVIATION

VFR today into most of Friday. Ceilings will gradually deteriorate Friday afternoon into the late evening as a frontal system pushes through the area, trending towards MVFR. There is a slight chance (10- 20%) for IFR. Rain will start moving in along the coast around 06Z and fill into the interior terminals after 10Z. Additionally, gusty winds will develop tonight into Friday. The strongest winds will be along the coast and north of PAE. Sustained wind speeds of 15-25 kt with gusts toward 30-40 kt are possible. Winds will also be breezy along the southern interior and north Puget Sound with gusts toward 20-30 kt.

KSEA...VFR today through Friday afternoon with mid to high clouds. A frontal system will bring rain activity early in the morning. Ceilings will deteriorate after Friday 03Z towards MVFR. SE winds around 5-7 kt. Winds look to become breezy Friday evening after 03Z with gusts toward 15 kt possible.

MARINE

An active weather patter across area waters will continue into next week as a series of frontal systems cross the region. These frontal systems will bring both the combination of seas and winds. The next frontal system will impact the waters tonight into Friday, bringing elevated seas around 14-20 ft and gale force winds across the coastal waters and portions of the interior waters. Additionally, there is a slight chance (15-20%) for storm force winds at times for the coastal waters, East Strait, and Northern Inland Waters. A stronger system will arrive this weekend for elevated seas and possible widespread gale force winds. Models are hinting at a 30-40% chance for storm force gusts over the coastal waters and Strait on Saturday afternoon and a 20% chance for for Admiralty Inlet, Northern Inland Waters, and Puget Sound. Additionally, models continue to be consistent with the chances for seas above 20 feet by early Sunday morning. Brief high pressure will build over the waters Sunday night into early Monday. Multiple systems will move over the waters next week, with the continued potential for additional headlines.

A period of strong afternoon ebbs are expected for Grays Harbor Bar starting Friday, which could coincide with with a rough to severe bar at times.

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HYDROLOGY

River flooding is not expected through the next seven days. However, a series of increasingly wet weather systems will bring rain (and high mountain snow) to the region, especially from Friday onward. While current forecasts are not expected to cause flooding, this will begin to saturate soils and raise base flows that could bring a concern with subsequent storms systems into next week.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory from 4 AM to 4 PM PST Friday for Island County- Lowlands of Western Skagit and Northwestern Snohomish Counties-Lowlands of Western Whatcom County-San Juan County.

Wind Advisory from 1 AM to 1 PM PST Friday for Northern Washington Coast.

Wind Advisory from 7 AM to 4 PM PST Friday for Grays Harbor County Coast.

PZ...Small Craft Advisory until 7 AM PST Saturday for Grays Harbor Bar.

Gale Warning until 2 PM PST Friday for West Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Warning from 10 PM this evening to 2 PM PST Friday for East Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Warning from 2 AM to 2 PM PST Friday for Northern Inland Waters Including The San Juan Islands.

Small Craft Advisory until 4 PM PST Friday for Admiralty Inlet.

Small Craft Advisory until 10 PM PST this evening for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.

Gale Warning from 10 PM this evening to 4 PM PST Friday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.