textproduct: Seattle/Tacoma

SYNOPSIS

Increasing low level onshore flow will bring cooler air into western Washington today with highs 10 to 20 degrees cooler. An upper level ridge centered well offshore with northwesterly flow aloft and light low level onshore flow will keep temperatures a few degrees above normal along with dry conditions through the weekend. An upper level ridge building early next week will bring relatively warmer temperatures back into the region.

SHORT TERM /TODAY THROUGH THURSDAY/

Satellite imagery shows stratus filling in along the coast with some middle level clouds over the Northwest Interior. Mostly clear skies elsewhere. Temperatures at 3 am/10z were in the mid 50s to mid 60s.

Much cooler today with low level onshore flow increasing. Stratus along the coast not getting very far inland. Weak low level convergence could produce some cloud cover over the Central Puget Sound this afternoon. Marine air filling up the interior this morning with high temperatures dropping into the 70s for the interior and 60s for the coast.

Little change in the pattern tonight through Wednesday night. Upper level ridge centered well offshore with northwesterly flow aloft. In the lower levels onshore flow will weaken tonight through Wednesday night. Lows in the upper 40s to mid 50s. Highs in the 60s on the coast and upper 60s to mid 70s inland.

Northwesterly flow aloft continuing Thursday with the low level flow going light. This will give the area a little warmer day with highs in the upper 60s to mid 70s coast and 70s and lower 80s inland. Felton

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/

Upper level ridge remaining well offshore with northwesterly flow aloft through the weekend. Weak system moving by to the north Sunday could produce a shower in the North Cascades. Light low level flow becoming onshore at times. With the lack of offshore flow temperatures will not get too warm. Highs Friday in the mid 70s to lower 80s for the interior cooling to the 78s over the weekend with a little more onshore flow. Highs on the coast in the mid 60s to lower 70s. Upper level ridge building over the area Monday with low level flow going light. High temperatures warming into the mid 70s to mid 80s interior and lower to mid 70s coast. Lows through the period in the 50s.

AVIATION

As the upper level ridge continues to flatten, prevailing west/northwest winds persist. Gusty westerly winds are expected today near the coast as well as in and adjacent to the Strait of Juan de Fuca. Satellite and surface weather observations as of 17Z Tuesday showed low marine stratus at the coast, bringing high-end IFR to low-end MVFR ceilings. Cloud cover at the coast is expected to scatter out later this afternoon, bringing a brief period of VFR conditions. That said, low marine stratus is expected to fill back in at the coast by 03-06Z Wednesday (60-75% chance).

Although inland areas remain mostly clear this morning, additional clouds are expected to develop this afternoon/evening with a few hours of low-end VFR ceilings likely over the greater Seattle Metro area.

KSEA...VFR conditions are expected through the TAF period. As onshore flow continues today, a Puget Sound Convergence Zone may briefly materialize early this afternoon, with southwesterly to south-southwesterly flow at SeaTac from 18-22Z. Scattered to broken ceilings as low as 3000 ft could occur as clouds develop this afternoon. Chances for ceilings down to 3000 ft range between 20-35% this afternoon, with a 65-80% ceilings wind up closer to 4000 ft or higher. After 22Z, northerly flow will dominate into the overnight hours, allowing for clouds to clear out. Winds should eventually become light and variable after 08Z Wednesday, before becoming northwesterly near 7-9 kt by 21Z Wednesday. -23

MARINE

Onshore flow continues today as the surface thermal trough moves east of the Cascades into eastern Washington. Northwesterly winds will gust to 25kts over the coastal waters, with a Small Craft Advisory in effect from this afternoon through early Thursday morning. Seas will become locally-wind driven and become very steep. Wave heights will increase throughout the day Tuesday up to 10 to 13 ft with a dominant period of around 10 seconds. Waves in the outermost waters may reach up to 15 ft by late week.

A Gale Warning is in effect for the central and eastern waters of the Strait of Juan de Fuca, with gusts up to 40 kts expected today associated with a strong marine push. Small Craft Advisory winds will also funnel down into Admiralty Inlet by this afternoon. Marginal Small Craft Advisory wind gusts up to 25 kt are also expected over the west entrance of the Strait of Juan de Fuca Winds this afternoon and evening, mainly to the east of Neah Bay. Winds will ease by late tonight. -23

FIRE WEATHER

The return of low level onshore flow today will ease fire weather concerns west of the Cascades. Elevated fire weather concerns return on Friday and Monday as a warmer and drier airmass will be in place at that time. Minimum relative humidity values are forecast to drop to around 30 percent both days along with some breezy conditions in the afternoon and evening hours. -Felton/23

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 11 PM PDT this evening for West Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Warning until 11 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 2 PM this afternoon to 11 PM PDT this evening for Admiralty Inlet.

Small Craft Advisory until 5 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.