textproduct: Seattle/Tacoma

UPDATE

Satellite imagery shows plenty of breaks in the cloud cover especially over the North Coast, Strait of Juan de Fuca and Central Cascade foothills. Marine layer is shallow with light onshore flow. Expect the July sunshine to dissipate the layer in the afternoon. Southwesterly flow aloft with upper level trough offshore will continue to throw middle and high level clouds over the area through the weekend. Marine layer reforming over the interior tomorrow morning but like today the layer will be shallow making for a sunny afternoon. Current forecast on track. No updates this morning. Previous discussion follows with updated aviation and marine sections. Felton

SYNOPSIS

An upper level trough will produce varying amounts of cloud cover through the weekend along with near seasonal temperatures. High pressure will rebuild into the region Monday and Tuesday for a warming trend. A weak system may briefly cool temperatures around the middle of the coming week before a longer term dry and warm spell returns toward next weekend.

SHORT TERM /TODAY THROUGH MONDAY/

A upper level trough just offshore will send a series of weak disturbances across the area into early Sunday. For the most part, dry conditions will prevail though a couple light showers will be possible at times across the Olympic Peninsula, North Interior, and North Cascades. Temperatures through Sunday will hover within a couple degrees of seasonal normals for most spots. The upper trough will lift back into British Columbia later on Sunday as strong upper ridging centered over the Rockies and North Great Plains expands a little westward. With weaker onshore flow and modest height rises, temperatures on Monday will edge upward several degrees with plenty of sunshine.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

The dry and warm trend continues into Tuesday. Low level onshore flow will increase a notch or two which will cool coastal areas a bit, but interior temperatures will remain warm with areas around Seattle metro seeing a 30-50% probability of moderate HeatRisk.

Uncertainty remains in the temperature trend for the later half of the upcoming week as a number of ensemble members retain some degree of upper troughing just offshore. Based on the trends of the last few days, the main effect of this weak trough may be to simply delay an impending lengthy period of above normal temperatures that most guidance points toward commencing by next weekend.

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AVIATION

VFR across the area so far this morning with the exception of isolated MVFR lingering. Any lingering low clouds should improve to VFR by 17-20z. Winds generally remain light and southwesterly, increasing to 8-10 kts after 18-21z Sat through around 06z Sun.

KSEA...VFR conditions prevail. Southwest winds continue below 8 kt. Gusts near 20 kt after 00z.

MARINE

A weak surface trough will remain over the offshore waters today before high pressure broadly rebuilds into the coastal and offshore waters Sunday and Monday and remains in place into midweek. This will promote a fairly typical summer pattern with varying degrees of onshore flow promoting a diurnally driven increase in westerlies through the Strait of Juan de Fuca nearly daily. Northwest winds over the coastal waters are likely to increase later Monday into Tuesday as thermally induced surface low pressure expanding over the interior of Western Washington tightens the onshore gradient.

FIRE WEATHER

The current onshore pattern will continue through the weekend which will lead to continued excellent nightly RH recoveries. There's a 30-40% chance of rain showers today, mainly for the Olympics and northern Cascades, but rainfall amounts during this period would generally total less than 0.10". A ridge of high pressure rebuilds into the region Monday and Tuesday. While the onshore pattern will largely remain in place, warmer daytime temperatures and clear skies will likely lead to RH values dipping into the 20-40% percent range, with the lowest values in the south interior and Cascades Valleys. This will allow fine fuels to continue to dry with elevated fire weather conditions. Some modest cooling is slated to arrive by the middle of next week, but may well be short-lived.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory from 5 PM this afternoon to 3 AM PDT Sunday for Central U.S. Waters Strait Of Juan De Fuca- East Entrance U.S. Waters Strait Of Juan De Fuca.