textproduct: Seattle/Tacoma

SYNOPSIS

Dry conditions will continue across Western Washington through Friday, with a gradual warming trend expected over the next few days. Clear skies and cool overnight temperatures will allow for frost to form across portions of the region early Thursday morning. Cooler temperatures and precipitation chances return this weekend. Unsettled conditions may continue into early next week.

SHORT TERM /TODAY THROUGH FRIDAY NIGHT/

Overall the weather pattern remains fairly steady through Friday as dry, northwesterly flow aloft prevails as the ridge remains offshore and a cutoff low persists inches westward towards northern California. The ridge axis finally progresses across the area early on Friday as a trough begins to dig into the offshore waters from the Gulf of Alaska. All that said, skies will remain mostly clear through early Friday with temperatures warming up slightly each day. Highs today in the low to mid 60s, with 50s across the northern Salish Sea coasts and the immediate Pacific coastline. Another cool and clear night with calm winds will allow lows to drop into the mid 30s. This will allow for some isolated frost to develop, mainly across the Southwest Interior and lower Chehalis valley, and around the Arlington area in Snohomish county. Other localized areas may be possible in the interior western Whatcom County, and around Forks. Highs Thursday and Friday in the mid 60s to low 70s, with lows in the low to mid 40s.

LONG TERM /SATURDAY THROUGH TUESDAY/

The aforementioned trough will continue to dig southwestward along the west coast, moving inland down towards northern California. This will send not just much cooler temperatures but also some chances for rain showers through the weekend. Models are showing that rain could arrive as early as Friday afternoon or evening across southwest Washington, but the better chances to see more widespread rain across the area will begin overnight into early Saturday morning. Off and on precip chances will continue through Sunday and into Monday as well, at least for the higher elevations, as the system slowly moves into the southwestern U.S. Lowering snow levels early next week will allow for very light snow accumulations in the mountains and passes. The active pattern looks to continue into the middle of next week as another trough is on its heels Tuesday into Wednesday. Temperatures will drop back down into the low to mid 50s, with lows in the 40s.

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AVIATION

Northwesterly flow aloft will continue across western Washington tonight with an upper level ridge situated offshore, before becoming more westerly during the day on Thursday. Satellite imagery this afternoon shows clear skies across much of the region, with a few high clouds streaming overhead for areas south of the Sound. Conditions are VFR and will remain so through the remainder of tonight. Another round of fog will be possible for terminals along the south Sound and Chehalis River Valley (mainly impacting KPWT, KOLM, and KHQM) on Thursday morning. Latest probabilistic guidance indicates a 10-20 percent chance of LIFR conditions briefly developing for these terminals by around 12Z. Expect any fog that does develop to scatter by midday. Winds persisting out of the north this afternoon at 5-10 kt will become light at 6 kt or less between 03-06Z. Northerly winds will increase to 5-10 kt again between 18-21Z Thursday.

KSEA...VFR conditions expected through the TAF period. Northwesterly winds persisting between 5-10 kt this afternoon will become more northerly and ease again after 06Z. Northerly winds will increase to 5-10 kt again between 18-21Z and persist through the afternoon and evening.

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MARINE

North winds persist over the coastal waters through Friday with high pressure in place over the NE Pacific. A low pressure system will develop over the open waters on Friday before swinging south and east towards southern Oregon and northern California. High pressure will once again take its place over the west coast on Monday. A frontal system looks to move through the area Tuesday into Wednesday.

Overall little in the way of impactful weather. The diurnal cycle of westerly pushes down the Strait of Juan de Fuca may start to develop over the weekend into early next week. Seas remain 4 to 8 ft over the next week.

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HYDROLOGY

No river flooding is expected in the next seven days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Frost Advisory from 11 PM this evening to 9 AM PDT Thursday for Downtown Everett / Marysville Area-Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Thurston and Lewis Counties-Lowlands of Lewis and Southern Thurston Counties-Middle Chehalis River Valley-Olympia and Southern Puget Sound.

PZ...None.