textproduct: Seattle/Tacoma

SYNOPSIS

Shower and thunderstorm chances expected to ease tonight. 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 NIGHT/

Thunderstorm activity has dwindled this evening and just a few showers along the US/Canada border remain. Stubborn low- level cloud cover hindered thunderstorm development over the Cascades this afternoon/evening. Showers and thunderstorm chances will continue to 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 /SUNDAY 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. Thunderstorm activity has moved north into Victoria, and the thunder threat has ended for the evening across western WA terminals. Showers to the north near KBLI will continue to move north and exit into B.C. this evening as well. In wake of the convection, most terminals are VFR this evening with the exception of the coast, where IFR stratus has begun to take shape with the low level moisture. This stratus will advance inland, reaching the interior by 12Z. There is a 50-60% chance of the stratus dropping to MVFR for the interior/Puget Sound, and a 20% chance for brief IFR early morning. Probabilities increase westward for IFR and LIFR conditions out to the Pacific/Strait of Juan de Fuca coasts, as well as for visibilities down to a quarter of a mile as the stratus mixes to the surface for fog/mist. The interior will see clearing from 18-20Z. 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. Winds become more west Friday with diffluence from the strait turning winds to the north after 00Z through the northern portion of Puget Sound.

KSEA...VFR through the evening, with a 60% chance of MVFR stratus arriving by 12Z, and lasting through 18Z. There is a 20% chance of this stratus dropping to IFR by early Friday morning. Skies will clear late Friday morning/afternoon. Southwest winds 8-12 kt will decrease to 5 kt or less through Friday morning. Winds to turn more west Friday afternoon, with north winds remaining north of the terminal for now in the evening.

14/HPR

MARINE

Thunderstorm activity has subsided across the coastal waters and chances for thunderstorms will continue to dwindle into tonight.

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.

14/29

FIRE WEATHER

The thunderstorm threat has diminished this evening across western Washington as convection exits north into B.C.. The Red Flag Warning will be allowed to expire at 10 PM this evening.

The low offshore will make its way over the region, and dissipate as it moves onshore. This will result in 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/HPR

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.