textproduct: Seattle/Tacoma

SYNOPSIS

Scattered thunderstorms continue offshore, with the potential for additional development this afternoon. An upper level trough offshore will then push inland over the weekend, bringing cooler temperatures to the area and additional chances of showers. Troughing will persist through early next week, allowing for temperatures to trend just below to near normal.

SHORT TERM /TONIGHT THROUGH SATURDAY/

Satellite and radar continue to show scattered thunderstorms along portions of the Washington coast and across the coastal waters. These will continue to move to the north-northwest this afternoon. Additional development will be possible this afternoon, with the best chances being over the Cascades and Olympics. Showers and thunderstorm chances should ease tonight as the trough offshore beings to lift northward. Marine stratus will likely fill back in tonight, allowing for low temperatures to reach the mid 50s to near 60. Stratus should give way to mostly sunny skies on Friday, allowing for high temperatures to bump up a bit compared to today, reaching back into the low to mid 80s across the interior, with 70s elsewhere.

The upper trough offshore finally traverses the area Friday night into Saturday, bringing stronger onshore flow and more clouds, as well as chances for showers along the coast and the mountains. This will also help to push high temperatures below normal, with high temperatures in the mid 70s.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/

Chances for showers will continue Saturday night into Sunday as another shortwave trough moves through the area. Temperatures on Sunday similar to Saturday, in the mid 70s. Looking forward into next week, upper level troughing remain the dominant influence across the area as several systems move down from the Gulf of Alaska. Some model solutions show the upper level high over the Four Corners region retrograding westward, which may allow highs to warm towards the end of the week, otherwise temperatures generally remain around climatological normals with mostly dry conditions after Monday.

AVIATION

An upper level low will continue to spin offshore the Pacific Northwest tonight. This low has been responsible for bringing mid level moisture over western WA this afternoon- and showers and thunderstorms to portions of the coast and Olympic Peninsula. Thunderstorm chances will remain possible through the remainder of the afternoon, but will mainly remain confined to the Cascades, Olympics, and the coast. Latest guidance continues to suggest showers tapering between 00-03Z. Satellite this afternoon shows some low clouds lingering across the central and south Cascades and along the coast. Expect another strong push of onshore flow in the low levels to bring marine stratus inland to the Puget Sound terminals by 12Z Friday for another round of MVFR to localized IFR conditions. Expect conditions to gradually improve back to VFR for the interior terminals around 18Z Friday as stratus retreats back to the coast. Southwesterly winds will generally persist between 8-12 kts (with some gusts to 20 kt) across the interior terminals through this evening, before easing and becoming light and variable tonight around 06Z.

KSEA...VFR conditions this afternoon with some FEW and SCT low to mid clouds. Expect another round of stratus to push into the terminal by 12Z Friday and lower conditions back to MVFR. West- southwesterly winds will persist at 8-12 kt through this evening, before easing and becoming light around 06Z.

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MARINE

A low pressure system offshore will continue to bring chances of showers and thunderstorms to the coastal waters through this afternoon. Latest radar this afternoon shows a line of scattered thunderstorms currently moving northward across the central and northern coastal water zones. Gusty winds, lightning, reduced visibilities, and brief heavy downpours are likely within the vicinity of these storms.

A low pressure system will remain offshore the Pacific Northwest on Friday, before tracking back into the area and dissipating on Saturday. Onshore flow will prevail over the next few days, with strongest winds expected to be along the Strait of Juan de Fuca. Another low pressure system will track southward from Gulf of Alaska and will stall a frontal boundary offshore on Saturday before it moves inland on Sunday night. This may bring some small craft southerlies to portions of the area waters over the weekend. Another front will follow on Tuesday.

Seas will generally range between 4-7 ft over the coastal waters on Friday. A brief uptick in seas to 6-8 ft will be possible on Saturday, before seas subside back to 4-6 ft again on Sunday. Seas will then persist within the 4 to 6 ft range into early next week.

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FIRE WEATHER

The Red Flag Warning for lightning and gusty outflow winds continues as the thunderstorm chances will remain into this evening. There have been several reports so far of fire starts from yesterday's lightning which number in the hundreds of flashes overland. Rainfall with the storms was sparse. Where it did fall, it was mostly just a few hundredths to less than a tenth of an inch. The strongest concentration of thunderstorms and heaviest rain was along the Cascades from the southern Lewis County border to the King - Snohomish County border with amounts ranging from about a quarter to six tenths of an inch.

Overhead clouds and the onshore flow today has brought low clouds and stratus that is stubborn to burn off and hampering firefighters efforts to locate and attack the new fire starts. The cooler temperatures and higher humidities today will give way to warm and dry conditions Friday as the upper ridge expands over the area once again. This will be short lived as the low center off the coast makes its way over the region though dissipating in the process. the result will be cool temperatures and shower chances through the weekend into the first part of next week easing fire weather concerns. Additional thunderstorms are not likely but can't be ruled out at this time. JBB

SEW WATCHES/WARNINGS/ADVISORIES

WA...Red Flag Warning until 10 PM PDT this evening for Black Hills and Southwest Interior Lowlands-Central Coastal Lowlands- East Portion of the Olympic Mountains-North Coastal Lowlands-North and Central Coastal Strip-West Portion of the Olympic Mountains-West Slopes of the Central Cascades Generally above 1500 Feet.

PZ...Small Craft Advisory until 5 AM PDT Friday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.