Area Forecast Discussion

SYNOPSIS

Slow moving front offshore will move inland later today and dissipate tonight into Monday. Light showers will be possible across the north and western portions of the area. Briefly warmer on Monday before another weak front arrives Tuesday. Dry and warmer weather Wednesday into Friday as an upper level ridge centered over the Southwest builds back towards the Pacific Northwest. Another weak front will try and move into the area Saturday.

SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/

A very slow moving front continues to sit just offshore this afternoon. Light showers continue to persist across portions of the western Olympic Peninsula as well as areas north of Whidbey Island. This will continue to be the case through tonight as the front attempts to inch westward before just falling apart and dissipating by Monday. Elsewhere in western Washington, partly to mostly cloudy conditions persist, through there's some more sun down closer to White Pass. High temperatures will be below normal, with highs in the 60s under rain, with low to mid 70s in areas without rain.

A brief increase in the upper level heights during the day Monday should allow for just enough subsidence to clear out skies at least in locations west of the Salish Sea by the afternoon. This should for highs in the interior to reach back up closer to normal. in the mid 70s to near 80. Lingering clouds and slight chances for light showers/drizzle will keep highs in the 60s there.

Another frontal system looks to reach western Washington early Tuesday as a shortwave trough moves through the larger trough over the British Columbia coast. Another day similar today, though with slightly higher chances of seeing some light precipitation across the interior. Expect most places south of Everett and east of Olympia/I-5 to remain mostly dry, through. Highs back down into the 60s to low 70s in the interior. Winds may gust up to 20-25 mph around the Salish Sea and the Kitsap Peninsula with an increase in west/southwesterly winds.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

The question for the long term forecast will be the evolution of the forecast for next weekend. Models have been consistent and still are, through the end of the week, on the high sitting over the Four Corners region to retrograde and build up towards the Pacific Northwest. Heights will rise, but with onshore flow remaining, temperatures will slowly rise back around to near or slightly above normal by Friday. By Saturday, the closed low over the Gulf of Alaska will start to drift back southward and pinch the upper level jet stream across the area. Deterministic forecasts are showing the potential for a shortwave moving through that may send chances for light showers across the area once again through the weekend. Looking at the ensemble forecast space, it's about a 50/50 split whether the ridge remains strong enough to keep us dry and warmer or if the trough can win out and keep cooler and cloudier conditions in the forecast. It's not the typical forecast for late July/early August, but will continue to monitor model trends and see if trends favor one solution over the other.

62

AVIATION

A weak front will dissipate over the interior of Western Washington tonight. Southwesterly flow continues aloft. Areas of IFR along the coast in light rain will lift to MVFR this afternoon as precipitation diminishes. VFR ceilings will continue across most interior areas.

KSEA...VFR ceilings expected to continue at or above 040 into Monday morning before lifting further Monday afternoon. Surface winds southwesterly 6 to 10 knots becoming light southerly overnight then increasing to southwesterly 6 to 10 knots again Monday afternoon.

27

MARINE

A slow moving front will move inland and dissipate tonight over the inland waters. High pressure will build in behind the front Monday. Another front will move into the area waters Tuesday. High pressure will build in again behind the front Tuesday night and remain over the waters through Thursday night.

Diurnal westerly pushes through the Strait of Juan de fuca could produce small craft advisory westerly winds in the evening Wednesday through Friday.

Felton/27

FIRE WEATHER

Onshore flow with generally cooler conditions and elevated RHs will linger through Tuesday. A weak system will clip the area Monday night into Tuesday, with a good shot for wetting rain for the north coast and West Slopes of the Olympics. REFS has a 60-80% chance of 0.25 in or more for the north Coast and northwest Olympics, and NBM showing as much as a 92% chance. Dry and warmer conditions return Wednesday through Friday. MinRHs start to dip into the 30 Thursday and Friday, but persistent low level onshore flow will help maintain good humidity recoveries in the overnight hours.

SEW WATCHES / WARNINGS / ADVISORIES

WA...None. PZ...None.