textproduct: Seattle/Tacoma

SYNOPSIS

Upper level ridge axis and thermally induced surface trough over the area today shifting east tonight. Low level flow turning onshore tonight. Western Washington still on the backside of the ridge through Saturday with just slight cooling Friday and Saturday. Upper level flow becoming zonal Sunday. This combined with increasing low level onshore flow will give the area a few days of normal first half of August weather.

SHORT TERM /TODAY THROUGH SATURDAY/

Satellite imagery shows stratus along the coast moving down the Strait of Juan de Fuca and moving inland through the Lower Chehalis Valley. Smoky skies elsewhere. Temperatures at 3 am/10z were in the mid 50s to mid 60s.

Upper level ridge over the area today. Ridge axis along the coast will move inland today. At the surface, thermally induced surface trough over the interior. Stratus will retreat back to the coast then dissipate by midday. High temperatures cooler along the coast today, near 70. High temperatures inland similar to Wednesday, in the 80s to lower 90s. Light flow in the lower levels will keep smoke over the area today with degraded air quality.

Increasing low level onshore flow tonight as the upper level ridge axis and the thermally induced trough move east of the Cascades. Stronger onshore flow will help scour out the low level smoke while increasing west southwesterly flow aloft pushes the upper level smoke out of the area as well. Stratus reforming along the coast spreading inland in the early morning hours but remaining west of Puget Sound. Lows in the 50s and lower 60s.

Low level onshore flow Friday but temperatures aloft remain warm. 500 mb heights still in the upper 580 dms. Shallow marine layer will have a tough time getting east of Puget Sound and with the warmer air remaining aloft high temperatures will only cool by a couple of degrees over the interior into the upper 70s and 80s. Highs along the coast remaining near 70.

Slow cooling trend continuing Friday night into Saturday. Temperatures aloft cooling slightly with a little bit deeper marine layer. Stratus will still have a tough time getting east of Puget Sound. Best chance will be in Snohomish county with the stratus coming down the Strait of Juan de Fuca. Lows in the 50s and lower 60s. Highs over the interior in the mid 70s to mid 80s. Highs along the coast in the upper 60s. Felton

LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/

Extended models continue to show good consistency with 500 mb heights slowly falling in response to an upper level low well to the northwest. Low level onshore flow each day. Stratus developing along the coast in the evening spreading inland in the early morning hours each morning. Stratus most of the time only making it as far inland as the Puget Sound. Stratus dissipating in the late morning/early afternoon hours. Highs inland in the 70s and lower 80s and in the upper 60s along the coast. Lows mostly in the 50s.

The normal high in Seattle is currently at its peak of 79 degrees. It will drop to 78 degrees Monday the 10th. The first step in lowering down to bottoming out at 46 degrees December 19th. Felton

AVIATION

An upper level ridge will move across the terminals today into Friday, with flow aloft southwest to west. A weak onshore push has commenced along the coastline this morning as ceilings drop to IFR/LIFR, but given the weaker gradients towards the thermal trough moving inland, probabilities remain the greatest along the immediate coastline. Haze/smoke continues in the interior this morning, and there remains a 20-40% chance of visibilities dropping to MVFR (3-5 SM) this morning into the afternoon as some residual near-surface smoke slowly begins to clear out today into tonight. The smoke will continue to affect horizontal visibilities, but slant-wise visibility impacts should decrease as smoke is removed. Early indications for Friday morning has the push advancing a little further to this morning, but remaining west of Puget Sound. Winds will pick up out of the north/northwest 5-10 kt today.

KSEA...VFR generally expected through the TAF period, though there remains a 30% to 40% chance of visibility reductions to MVFR due to wildfire smoke/haze that will slowly clear out today. Stratus expected to remain west of the terminal this morning, and likely Friday morning too. Winds picking up from the northwest late this morning/afternoon 5-10 kt, then decreasing to 5 kt or less tonight from the northeast.

HPR

MARINE

A thermal trough will begin to move inland today, with higher pressure remaining offshore through the end of the week. Onshore flow will slowly begin to trickle back into the waters through the end of the week/weekend. This will primarily affect the Strait of Juan de Fuca as early as Friday night, with beginning chances of daily occurrences of winds/gusts over 20 kt into next week. Coastal waters may also see wind increases towards 20 kt, but likely below until Saturday night/Sunday, and Thursday as a couple of weak troughs move through.

Seas at 4-6 ft today through Friday at around 8 seconds. This increases to 6-8 ft this weekend into Monday, and decrease back to 4- 6 ft Tuesday and Wednesday before increasing again to 6-9 ft.

HPR

FIRE WEATHER

Elevated fire weather concerns across the area the next couple of days with warm and dry weather. Minimum relative humidity values lowering into the 20s in the drier locations like the Southwest Interior and Cascade foothills. While no significant wind or instability is expected today for a red flag warning, maximum caution over new fire starts still should be emphasized.

The thermally induced trough will shift into Eastern Washington tonight. Some uncertainty still remains over potential instability and incoming wind in combination with the eastward movement of the thermal trough. This may briefly promote fire growth late tonight into early Friday morning. Hot and dry conditions hold Friday for most of the interior. Elevated fire weather concerns continuing through the day.

Increased onshore flow Saturday into into next week will bring cooler temperatures and increased moisture with much better humidity recoveries across the region.

Wildfire smoke over the area today could cause localized impacts to fire operations. Felton

SEW WATCHES/WARNINGS/ADVISORIES

WA...Heat Advisory until 10 PM PDT this evening for City of Seattle- Downtown Everett / Marysville Area-Eastern Kitsap County- Eastern Strait of Juan de Fuca-Eastside-Foothills and Valleys of Central King County-Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Snohomish and Northern King Counties-Foothills and Valleys of Thurston and Lewis Counties-Foothills and Valleys of the North Cascades-Foothills of the Western and Southern Olympic Peninsula-Island County-Lake Crescent Area Including US 101-Lowlands of Lewis and Southern Thurston Counties-Lowlands of Pierce and Southern King Counties-Lowlands of Western Skagit and Northwestern Snohomish Counties-Lowlands of Western Whatcom County-Middle Chehalis River Valley-Northern Hood Canal-Olympia and Southern Puget Sound-Port Townsend Area- San Juan County-Shoreline / Lynnwood / South Everett Area- Southern Hood Canal-Willapa and Black Hills.

Air Quality Alert until 5 PM PDT this afternoon for Cascades of Snohomish and Northern King Counties-Cascades of Southern King County-Cascades of Whatcom and Skagit Counties-City of Seattle-Downtown Everett / Marysville Area-Eastern Kitsap County-Eastside-Foothills and Valleys of Central King County-Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Snohomish and Northern King Counties-Foothills and Valleys of the North Cascades-Foothills of the Western and Southern Olympic Peninsula-Grays Harbor County Coast- Lower Chehalis River Valley-Lowlands of Pierce and Southern King Counties-Lowlands of Western Skagit and Northwestern Snohomish Counties-Lowlands of Western Whatcom County-Middle Chehalis River Valley-Northern Hood Canal-Olympia and Southern Puget Sound-Olympics-Shoreline / Lynnwood / South Everett Area-Southern Hood Canal.

Air Quality Alert until 11 PM PDT this evening for Cascades of Pierce and Lewis Counties-Foothills and Valleys of Thurston and Lewis Counties-Lowlands of Lewis and Southern Thurston Counties-Willapa and Black Hills.

PZ...None.