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 warm 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 moving through next week.

SHORT TERM /TODAY THROUGH SATURDAY/

Current satellite imagery shows typical autumn cloudy skies over W WA this morning. Radar shows that there are still some isolated showers out there, mainly over the Cascades although there are a couple of cells over the Olympic Peninsula. Lastly, what is very likely the leading edge of the system expected tonight is just starting to show up over the outer coastal waters.

A weak shortwave ridge will hold that system at bay briefly, keeping conditions dry for much of W WA today, but this feature shifts eastward fairly quickly...bringing activity to the coastline as early as this evening but more likely late tonight. Gusty winds will accompany the incoming front with particular concern for higher wind speeds along the coast and the North 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. This has warranted an inherited Wind Advisory for these areas and the headline looks to be on track, so no morning update or revision is expected at this time. 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.

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 /SATURDAY NIGHT THROUGH WEDNESDAY/

From Previous Discussion...Active weather continues through next week as the parade of storms impact the Pac NW. There's little break in the action and each storm brings the potential for gusty winds, additional lowland rain, and high elevation snow. A larger swell train may reach the coast Saturday night or Sunday with the potential for 20 ft seas affecting the coast. 33

AVIATION

A mix of conditions ranging from VFR to LIFR this morning. Ceilings should gradually improve by this afternoon, giving way to widespread VFR as mid and high level clouds associated with a warm front offshore begin to thicken across the region. Ceilings will fall to MVFR late tonight and early Friday across portions of the Olympic Peninsula and North Interior as precipitation associated with the warm front spreads onshore. Gusty east to southeasterly surface winds will develop late tonight into Friday across portions of the coast and North Interior with gusts towards 25-35 kt.

KSEA...Currently VFR at the terminal, but some low clouds still hanging around, so will opt to keep conditions lowered at MVFR for now. By 20Z, clouds should have lifted to VFR. SW winds this morning around 5-6 kt becoming SE this evening. Breezy SW winds developing Friday afternoon after 21Z.

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MARINE

From Previous Discussion...An active period of weather across area waters is expected into early next week as a series of frontal systems cross the region. Winds will increase across the coastal waters, strait entrances, and northern inland waters later tonight into Friday as a warm front approaches the coastal waters and stalls. This system will shift onshore and weaken Friday night as an associated surface low makes landfall near the south end of Haida Gwaii. A complex and much deeper area of low pressure will lift northeastward offshore on Saturday night pushing a vigorous frontal system into the area. If models maintain their current trends, this system will likely generate gales across all area waters along with coastal seas easily crossing the 20 foot threshold.

High pressure may briefly rebuild across the waters Sunday night into early Monday before another front arrives with the renewed potential for additional headlines.

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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 from 7 PM this evening to 7 AM PST Saturday for Grays Harbor Bar.

Gale Warning from 4 PM this afternoon to 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 from 4 PM this afternoon to 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.