textproduct: Seattle/Tacoma

SYNOPSIS

A dry and warm airmass associated with a strong upper level ridge will continue to remain over the area through Monday. Temperatures peaking in the 80s and 90s will bring widespread Moderate HeatRisk to the region again on Monday. Offshore flow will bring lower relative humidities and elevated fire danger. The ridge will weaken on Tuesday, resulting in increased onshore flow and seasonable temperatures through the rest of the week.

SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/

Clear skies and light offshore flow will continue across western Washington through tonight. As such, temperatures will continue to warm across the area today with temps as of 2 PM in the mid to upper 80s, except along immediate waterfronts where temperatures in the 70s continue. High temperatures today across much of the area remain on track for the upper 80s to low 90s. With the thermal trough along the coast, the sea breeze will struggle to get far inland, with only the immediate waterfront coastal areas remaining in the 60s and 70s. Low temperatures tonight a bit warmer, getting into the upper 50s near the water, with low 60s elsewhere. The thermal trough will then begin to weaken on Monday and get pushed inland by high pressure offshore. This will allow weak onshore flow to return to the coast, but this will take another day to reach the interior. Highs on Monday through the interior a touch warmer, but still in the 80s to mid 90s. The highest temperatures will be across the southern half of the metro and through the Southwest Interior. Highs on the coast will be dependent on the amount of recovery seen by the wind, but expecting 70s to low 80s farther inland into the foothills of the Olympics. It will also be a little less sunny on Monday with a thicker layer of high clouds overhead through much of the day.

Onshore flow gradients increase as high pressure builds along the coast. Tuesday will likely be noticeably breezy, with winds 15-20 mph with gusts up to 30-35 mph. The strongest winds will be through the Strait of Juan de Fuca. This onshore flow will also act to help reduce temperatures across the area, as high temperatures drop into the mid 70 in the interior, with 60s along the coast. Low temperatures will also drop Tuesday night, into the low to mid 50s. Areas along the coast will likely spend much of the day under the marine layer, with areas on the Strait clearing out in the morning.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Temperatures will generally remain seasonably warm but slightly above average with highs in the mid 70s to low 80s. Thursday and Friday will be the warmest days, with areas around the metro and the Southwest Interior potentially reaching Moderate HeatRisk. The overall pattern remains generally stable with morning clouds and evening sun and no precipitation forecast. Onshore flow will prevail with breezier conditions each afternoon. Model differences become greater next week with the evolution of the pattern with the potential for shortwaves moving through that may provide more unstable conditions.

AVIATION

High pressure and offshore flow will allow for dry and stable conditions to continue across western Washington. High clouds will begin to move in late tonight and persist through much of the day Monday, clearing out Monday evening. Northerly winds 5-10 kt will become light easterly to calm overnight. Winds resume tomorrow as W/NW 5-10 kt, except 15-20 kt through the Strait.

KSEA...VFR conditions prevail through the TAF period with high clouds tonight and tomorrow. N winds around 10 kt ease to E around 5 kt after 06Z tonight. Winds initially start as S around 5 kt or less by 15Z but switch to N between 21Z and 00Z Tue.

MARINE

Offshore flow continues through tonight with the thermal trough present along the coast. The trough will shift inland tonight, allowing onshore flow to resume tomorrow. Winds will increase through the Strait of Juan de Fuca tomorrow, beginning with Small Craft Advisory conditions with winds 15-30 kt. Winds then further increase on Tuesday for a period of gale force winds Tuesday afternoon and evening. Winds begin to decrease through the Strait late Tuesday.

Northwesterly winds will increase through the coastal waters beginning Tuesday and lasting through the rest of the week for an extended period of Small Craft Advisory conditions. Seas will also become locally wind-driven and become very steep. Waves will increase Tuesday night into Wednesday up to 10-12 ft with a dominant period of around 9 to 10 seconds. Seas may further increase late week/next weekend.

FIRE WEATHER

Dry conditions with much warmer than normal temperatures through tomorrow will bring elevated fire weather concerns across much of the area. Daytime min RH will dip below 20% across much of southwestern Washington and the southern Cascades--below 25-30% elsewhere. Even though fine fuels have not reached critical thresholds, this rapid drying will create elevated fire concerns especially for dry grassy/shrubby areas, as well as piles of dead fuels. Offshore flow today into Monday will prevent good relative humidity recoveries overnight. Relative humidities improve with the return of onshore flow Tuesday. Thursday and Friday may also of interested for additional attention, with slight warming leading to lower min RHs into the 25-35% range (despite continued onshore flow) and breezy conditions with gusts up to 15-25 mph, in particular on Friday. Fuels will continue to slowly dry with no precipitation forecast.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Heat Advisory until 5 AM PDT Tuesday 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-Lower Chehalis River Valley-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.

PZ...Small Craft Advisory from 1 PM Monday to 5 AM PDT Tuesday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.