textproduct: Seattle/Tacoma

UPDATE

Stratus and fog will once again be the main forecast issue this evening and tonight, and latest satellite trends show this manifesting west to east. Precip over portions of Whatcom and Skagit counties has wrapped up according to latest radar. Inherited forecast remains on track and no need for an evening update.

SYNOPSIS

Strong high pressure remains the dominant weather feature throughout the rest of this week and into the weekend. Drier conditions remain in the forecast, as well as chances for widespread stratus and patchy fog over the next several days. Areas that clear will have a higher likelihood of fogging in.

SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/

A decaying weather system skirting to the north of the forecast area has had little perceptible impacts on the weather today, as stratus has blanketed the lowlands of Puget Sound. The stratus has been widespread throughout the lowlands today, with clearer skies in the mountains and adjacent foothills. Temperatures have been cooler than yesterday, which were above average for this time of year.

An increase in easterly flow, particularly through the Cascade gaps is in the forecast for tomorrow. Winds will increase beginning around midday out of the northeast in Puget Sound, and in the late afternoon in the Cascades, lasting into Friday morning. Easterly wind gusts are forecast to be between 15 and 25 mph, peaking Friday morning. Any fog and/or stratus that is present Thursday morning should erode fairly quickly as the dry easterly flow moves into Puget Sound.

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LONG TERM /SATURDAY THROUGH WEDNESDAY/

Clearer skies are forecast for the weekend as the high pressure moves a bit more directly over the state. The cluster analysis shows the ridge flattening out a bit by early next week, which at this point is more of a signal for more expansive fog coverage early next week as opposed to precipitation. The much extended forecast shows more of an indication of low pressure coming back, but it is far too uncertain to pin down at this point.

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AVIATION

An upper level ridge will remain the dominant influence over the region through the TAF period, with westerly flow aloft becoming more northerly tonight. A weak, decaying front at the surface will dissipate over the coastal waters this evening and will allow for some high cloud cover to stream in overhead. Latest satellite imagery showing stratus moving in over the western half of the CWA and pattern suggests tonight will be similar to what was experienced last night and early this morning.

That said, cigs currently a mixed bag with VFR, MVFR and IFR conditions present...the latter two being present over the majority of the CWA, while VFR conditions linger in, of all places, the south Sound. Widespread MVFR to IFR conditions late tonight into tomorrow as another round of low stratus will be possible overnight into Thursday morning, with latest guidance hinting at roughly a 30-45 percent chance of conditions lowering to IFR across the central Sound terminals and a 20-35 percent chance for terminals lowering to IFR along the coast. Models continue to show that clearing skies will kick in Thursday afternoon and evening.

Winds will remain light and variable between 3-6 kt through the much of the overnight period, before increasing to 7-12 kt from the north through the morning hours on Thursday.

KSEA...Conditions have rebounded to VFR for now, but the terminal seems to be bouncing back and forth between that and MVFR. Another round of low stratus will be possible at the terminal by Thursday morning, with probabilistic guidance indicating a 30-40 percent chance of conditions lowering back down to IFR early Thursday. Light and variable winds 3-6 kt will continue through the overnight period, before increasing to 7-12 kt Thursday morning (between 13- 16Z).

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MARINE

A weak frontal system will dissipate over the coastal waters this afternoon. A strong surface high over the northeastern Pacific will then strengthen and move into the interior of British Columbia on Thursday, while a thermal trough builds along the coast. Offshore flow will develop as a result and will bring gusty winds near the gaps in coastal terrain at times through the weekend. This will mainly impact the central and western Strait of Juan de Fuca waters and the coastal water zones from Cape Flattery to James Island and from Point Grenville to Cape Shoalwater (out to 60 NM).

Seas will hover between 10-12 ft today, with a Small Craft Advisories in effect for the coastal waters and the west Entrance of the Strait through tonight. Seas will gradually subside back towards 3-6 ft by Friday and persist at this range into early next week.

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HYDROLOGY

No river flooding is expected over the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 10 PM PST this evening for Grays Harbor Bar-West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 10 AM to 10 PM PST Thursday for Central U.S. Waters Strait Of Juan De Fuca-West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory until 1 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.