textproduct: Seattle/Tacoma

SYNOPSIS

High pressure will bring continued warm and dry conditions across western Washington today. Onshore flow will increase on Tuesday ahead of an incoming weak front Wednesday, bringing in cooler temperatuers and chances for light rain. The remainder of the week will see near normal temperatures with morning clouds and afternoon sun breaks.

SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/

An upper level high pressure ridge will continue to shift inland today, bringing several degrees of warming to western Washington today. Temperatures are on track to peak in the upper 70s to mid 80s for most areas this afternoon under clear skies, except for cooler conditions along the coast with highs in the upper 60s. In addition, smoke from wildfires in British Columbia has filtered southward through the Fraser Valley, causing locally hazy conditions in Whatcom County.

An upper level trough moving southward from British Columbia will cause the ridge to break down tonight, generating onshore flow over the Pacific Northwest. An overnight marine push will bring in low stratus and high clouds early Tuesday morning. This will bring temperatures down several degrees, with highs Tuesday reaching the mid 60s to upper 70s. A weakening frontal system associated with the upper trough will swing across western Washington late Tuesday into Wednesday, increasing onshore flow and continuing a cooling trend. The northeastern Olympics and northern Cascades may even see some light rain as this frontal system works its way eastward on Wednesday. Outside of periodic westerly pushes through the Strait of Juan de Fuca, winds will generally stay light through the short term.

LONG TERM /THURSDAY THROUGH MONDAY/

Post-frontal zonal flow will develop aloft on Thursday with continued onshore flow at the surface. This will allow for another morning of cloudy skies with sun breaks developing by the afternoon and near-normal temperatures in the mid 70s. Towards the weekend, another upper low is set to drop southward over Vancouver Island, maintaining onshore flow over western Washington with morning low clouds and afternoon sun breaks. Chances for rain increase on Friday and Saturday as the low approaches, but models continue to show differences over the storm track.

By next Monday, a strong high pressure system is set to develop over the central US and is favored to amplify towards western Washington. This could bring in warmer temperatures by early next week, with chances for monsoon moisture to creep eastward of the Cascade crest.

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AVIATION

VFR conditions prevail this afternoon with some lower stratus at the coast. Forecasts support a return to MVFR ceilings tonight/Tuesday morning for the coast. There is also a 20-30% probability for the KSEA area to see MVFR ceilings between 12Z-17Z Tuesday, and this has been added to the TAF as a scattered layer. Winds are shifting to NW this afternoon and are in the 5-12 kt range. Breezy conditions are expected along the Strait of Juan de Fuca this evening with gusts to 25 kt. Surface winds transition to SW late tonight/early Tuesday morning.

KSEA...VFR expected through the TAF period with a few high clouds at times. Winds will transition NW this afternoon at 6-9 kt with gusts near 15 kt possible through 06Z. Winds then shift SW early Tuesday morning after 08-09z. There is a 20-30% chance for MVFR ceilings between 12-17Z Tuesday, and this has been added as a scattered layer through this time. After, VFR conditions with W to NW winds continue into Tuesday afternoon.

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MARINE

Winds are weakening, but seas linger around 7-8 ft today with a dominant period around 7-8 seconds, and the advisory continues through 5 PM. Small craft winds have began to reach the central and east Strait, and will continue through Tuesday morning.

Broad high pressure over area waters continues to weaken with a frontal system expected to move over area waters late Tuesday/early Wednesday. Stronger high end small craft westerlies are likely (70- 85% chance) Tuesday and Wednesday evenings. The highest probability for gale conditions (45-60%) will be from the Central Strait of Juan De Fuca and into the western portion of the East Entrance. Wednesday evening will have a slightly higher confidence for low-end gales. For now, a Gale Watch has been issued for Tuesday afternoon/evening. However, towards the end of the period (03Z Wed-06Z Wed), winds could weaken to bring a return of small craft conditions.

Later on Wednesday high pressure will rebuild in the wake of the front. Another front will move over area waters late in the week, weakening high pressure again. Onshore flow will continue through the Strait of Juan de Fuca throughout the week.

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FIRE WEATHER

Warmer and drier conditions across western Washington will peak today, with onshore flow increasing through the remainder of the week. This will bring in a cooling trend alongside good overnight humidity recoveries and periods of morning low stratus. A weakening frontal system will cross the region late Tuesday into Wednesday, with little in the way of rain or wind. Conditions heading into next week are favored to dry out and warm up as a strong upper level ridge builds into the region.

SEW WATCHES/WARNINGS/ADVISORIES

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

Gale Watch from Tuesday afternoon through Tuesday evening for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory until 5 PM PDT this afternoon 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.