textproduct: Seattle/Tacoma

SYNOPSIS

Showers will continue this morning, as well as breezy winds today as an upper level moves through to the south. Drier and warmer conditions will begin Thursday and continue through this weekend with a stronger ridge of high pressure building offshore.

SHORT TERM /TODAY THROUGH FRIDAY/

The general forecast remains on track as rain begins to fill in across much of the western Washington interior this morning. These showers are being driven by a broad and vertically- stacked low pressure system centered over southwest Oregon and moving inland. Increasing moisture from the southeast will move up and into western Washington later this morning for increased chances of some light rain, particularly across southwestern Washington and the Cascades. Additionally, with westerly surface flow, that will help to maintain convergence across the Puget Sound, with increased chances for continued cloudiness and showers there through much of the day. Winds will likely remain elevated throughout the day with a few gusts up to 20 to 30 mph as the system moves through. With snow levels above 5000 to 6000 ft, the vast majority of precipitation will fall as rain over the mountains.

Winds and rain begin to taper off overnight into early Thursday as the system departs to the east and upper level ridging develops over the northeast Pacific, putting western Washington under drier, northwesterly flow aloft. As a shortwave rides along the upper low over eastern Washington, there will still be some slight chances for showers for portions of the Cascades. However, the remainder of the area should remain mostly dry. Snow levels will lower to around 3000 to 4000 ft, so there may be some light mixed precip or flurries, but no significant accumulations are expected. Onshore flow will continue to prevail at the surface on Thursday with continued convergence over the Puget Sound, mostly in the way of increased clouds whereas most other places will see more sunshine Thursday. Higher confidence in more area-wide sunshine Friday as surface gradients turn offshore and a thermal trough begins to build along the coast. Winds will increase on Friday as north-south gradients temporarily increase with low pressure nudging northward from Oregon.

Clearer skies and lighter winds will allow for warming daytime highs--into the mid to upper 60s by Friday--and relatively cool overnight lows--in the upper 30s to to low 40s. With the system not far away, chances will linger for some light precipitation over the Cascades. High temperatures will return to near 60 Thursday, further increasing to the mid 60s on Friday.

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

Models show a fairly steady weather pattern continuing into the weekend and early next week with mostly dry conditions, highs in the low to mid 60s, and lows in the 40s. Winds remain mostly light though offshore flow will continue into the weekend, keeping relative humidity dry. Deterministic models are hinting at several weak shortwaves move across the area starting early next week, but the vast majority of ensemble members are keeping the area dry, with only slight chances for showers across portions of southwest Washington and the Cascades at this time.

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AVIATION

South to southeasterly flow aloft will turn east to north- northeasterly on Wednesday as a broad upper trough moves onshore over northern California and southwest Oregon. Ceilings (and periodic limitations in visibility in heavier rain) are generally MVFR to IFR, with areas of LIFR where more persistent rain has been present. Rain will continue to fall across the area this morning, departing after 18-21Z this morning. This will keep ceilings low through much of the morning and into the afternoon. Improvement to higher flight categories is not expected until after 22Z Wed - 03Z Thur as clouds start to clear out over northern portions of the area. In addition to the rain, weak convergence will continue to persist over the central Puget Sound (btwn BFI and PAE) at least through 21-23Z this afternoon before southwesterly winds win out. This is keeping locally lower cigs in the TAFs at the Seattle metro terminals.

Onshore flow, breezy at times, is keeping most terminals west/southwesterly, with the exception of PAE which remains northwest. Winds will turn to become more southwesterly and increase this afternoon with gusts 20 to 30 kt possible across the South Sound area.

KSEA...A weak PSCZ and steady rain has brought LIFR/IFR cigs to the terminal early this morning. Ceilings have been up and down but will likely remain primarily IFR or lower through at least 17-21Z, with slow improvement through the afternoon Ceilings will be slow to improve--if at all throughout the day with a window of VFR possible after 00z. However, low cigs are likely to return overnight Wednesday. SW wind 5 to 10 kt, increasing to 10 to 15 kt gusts up to 20 to 25 kt throughout the daytime hours.

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MARINE

Broad high pressure is remaining well offshore for an onshore flow pattern. The flow will turn more northerly over area waters Friday into Saturday with a broad surface ridge over the western Canadian provinces and lower pressure over the Pacific Northwest.

Small Craft Advisories remain in effect for the Central/East Strait of Juan de Fuca, coastal waters and Puget Sound for today. Seas will build and steepen over the coastal waters today up to 11 to 15 ft, as well as nearing rough bar criteria at Grays Harbor by tonight. Seas will then gradually subside later Thursday into the weekend.

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HYDROLOGY

No river flooding is expected in the next seven days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 8 AM PDT this morning for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory until 8 PM PDT this evening for Puget Sound and Hood Canal.

Small Craft Advisory from 11 AM this morning to 11 AM PDT 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.