textproduct: Seattle/Tacoma

SYNOPSIS

A warm front has introduced a very mild air mass to Western Washington with near record high temperatures expected today. A cold front will stall offshore into Thursday with mainly dry conditions for interior areas and light rain at times near the coast. A series of frontal systems will bring a return of widespread rain and occasionally windy conditions Friday into early next week.

SHORT TERM /TODAY THROUGH FRIDAY/

Rain has ended for most areas except for a few showers near the coast early this morning. Temperatures are extraordinarily mild across the region in the wake of a warm front that lifted north across Western Washington late yesterday. Windy conditions will continue along the coast and across the north interior, but are expected to ease late today. A cold front will stall offshore today into Thursday. Areas of light rain will occasionally skirt the coast and Olympic Peninsula ahead of this boundary, but the remainder of the area is expected to be largely dry with high temperatures, especially today, threatening some daily records.

A fairly deep upper trough moving across the Gulf of Alaska will push an occluded front onshore into the region during the day on Friday. Fortunately, this system looks like it will be vertically stacked upon arrival...thereby losing a lot of its punch before coming ashore. Nonetheless, it will bring another round of rain along with breezy to locally windy conditions. It will also churn up some pretty large surf during its offshore journey with seas of 20+ feet reaching coastal areas again by Friday night.

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

A trailing upper trough is expected to quickly swing onshore Friday night. Another potent front approaches the region on Saturday night. Though this system is also vertically stacked, the path of the surface low gives it better wind potential, especially for the coast, along with a fairly deep moisture feed. And, as such, WPC has placed a large swath of the Olympic Peninsula under marginal risk in their Excessive Rainfall Outlook for 12Z Saturday to 12Z Sunday. Plenty of post-frontal showers are expected to spread onshore into Sunday keeping things fairly soggy. There's still decent model agreement with a brief break for Monday, but the key word is brief. Another wet and potentially windy front arrives in the Tuesday time frame. It might have started slow, but November as we know it is well and truly here now.

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AVIATION

Southwest flow aloft continues into tonight with a stalled frontal boundary over the offshore waters. Areas of MVFR in light rain will continue through the morning for coastal areas while VFR is expected for the interior under varying amounts of mid and high level cloud cover. Gusty southerly surface winds along the coast and across the north interior are expected to ease later today. With lighter surface winds expected tonight, there is an increased risk of areas of IFR low clouds forming west of Puget Sound, across the Southwest Interior, and far south Puget Sound on Thursday morning.

KSEA...VFR with varying amounts of high and mid level clouds today. Surface winds south to southeasterly 7 to 10 knots easing to 6 knots or less tonight.

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MARINE

Strong winds will continue to persist across the coastal waters through much of the day today as a cold front remains stalled offshore. This front will weaken as it slowly drifts onshore this evening, allowing winds to slowly ease this evening into early Thursday morning. Gale Warnings for the coastal waters and East Strait of Juan de Fuca, and Northern Inland Waters, and Small Craft Advisories for Admiralty Inlet will continue through evening as well. Seas 13 to 15 ft this morning may creep slightly upward towards 16 to 18 ft, but generally remaining in the 14 to 16 ft range through tonight. Seas will ease to around 11 to 13 ft on Thursday.

A pair of strong low pressure systems will move across the coastal waters late Thursday night into Friday, with the second moving through Saturday night into Sunday. Winds will begin to increase across the area waters on Thursday. Gales will begin as early as Thursday afternoon, through winds look to peak overnight into early Friday morning. Guidance continues to indicate 50-70% chances for storm force gusts over the outer coastal waters, but confidence has decreased for the inner coastal waters with high-end gales the more likely scenario there. Winds will ease Friday night before increasing again Saturday with a secondary peak Saturday evening. Gale force winds again are very likely across the coastal waters, with 40-50% chances for storm force gusts over the outer coastal waters.

Seas once again will build over the coastal waters on Friday. With the low center tracking closer towards our area, that will send the largest waves farther south towards Oregon. That being said, very large seas are expected, with ensemble guidance continuing to show very high confidence (>90%) in seas above 20 ft by Friday evening, with a 25-35% chance of seas above 25 ft through Saturday morning. Dominant periods will be very long, in the 16-18 s range. Seas look to briefly ease Saturday morning below 20 ft before another system will send another round of large, long period waves on Sunday with high (70-80%) confidence in seas above 20 ft with a 15-30% chance of seas exceeding 25 ft through early Monday.

With these systems, slight shifts in the low tracks will determine where the strongest wave generation/dynamic fetch regions will be. While it is looking more likely that the largest waves will be aimed towards Oregon and California from the Friday/Saturday system, the Sunday/Monday system favors a more northward track with the largest waves aimed towards the Washington coast. There is a 5-10% chance of waves exceeding 30 ft at the peak wave height Sunday night.

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HYDROLOGY

Steady rain throughout Tuesday across the Olympic basin contributed to a rapid rise on the Skokomish River near Potlatch with the river reaching moderate flood stage late yesterday evening. The river is expected to slowly recede later this morning, but additional rainfall over the upcoming weekend will bring renewed potential for flooding.

River flooding is not expected on the other rivers in the area in the next 7 days at this time.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory until 7 PM PST this evening for Grays Harbor County Coast-Island County-Lowlands of Western Skagit and Northwestern Snohomish Counties-Lowlands of Western Whatcom County-Northern Washington Coast-San Juan County.

Coastal Flood Advisory from 5 AM to 11 AM PST this morning for Lowlands of Western Whatcom County-San Juan County.

Coastal Flood Watch from Friday morning through Friday afternoon for San Juan County.

High Surf Advisory until 4 PM PST this afternoon for Grays Harbor County Coast-Northern Washington Coast.

PZ...Small Craft Advisory until 10 AM PST Thursday for Grays Harbor Bar-West Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Warning until 7 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-East Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland Waters Including The San Juan Islands.

Small Craft Advisory until 7 PM PST this evening for Admiralty Inlet.

Small Craft Advisory from 7 PM this evening to 10 AM PST Thursday 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.