textproduct: Seattle/Tacoma

SYNOPSIS

A weak front will move inland tonight into early Thursday but will fall apart as it does so. Some chances for rain on the coast tonight but will become mostly dry by the time it moves inland. Broad high pressure rebuilds Friday across the south while a weak system over B.C. brings back showers chances to the northwest portion of the area. A stronger system will bring more substantial chances for rain and mountain snow area-wide Sunday into Monday. Cooler and drier conditions expected Tuesday into the middle of next week.

SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/

An upper level ridge will continue to shift eastward as an elongated trough moves towards the region tonight into Thursday. This will bring an associated surface front towards the coast tonight, but it is expected to rapidly weaken as it moves inland. This will allow for easterly gap winds to east tonight. There will be chances for light rain along the coast tonight, but little in the way of precipitation is expected for the rest of the area through early Thursday morning. Most of the rest of the day should remain dry. Temperatures Thursday will be a bit warmer, with highs in the low to mid 50s and lows in the upper 30s to low 40s. On Friday, the jet stream strengthens and takes aim at British Columbia. This will bring renewed chances for rain for the far northwestern portions of the region starting Friday, for places including the northwestern tip of the Olympic Peninsula, the North Cascades, and Whatcom County, while the rest of the area should remain mostly dry. Snow levels above 5-6000 ft will keep snow accumulations confined to the highest peaks. Temperatures should also remain similar compered to Thursday.

Along the coast, large long-period swells will arrive on Thursday. The current forecast keeps conditions just short of high surf criteria, but will need to continue to be monitored for the potential for an advisory. Regardless, localized beach erosion and significant wave run-up may be possible on Thursday.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

The overall upper air pattern remains consistent from Friday into Saturday until an embedded shortwave trough moves through the area on Sunday. This will generate a surface system that will bring the most substantial chances for precipitation across the area that will linger into. Snow levels will lower to around 3000 to 4000 ft Sunday night, allowing for accumulating snow across most of the mountain passes into Monday. Confidence is beginning to increase for a cooler and drier trend for the first half of next week with highs sinking into the 40s and lows in the 30s. Many locations could se lows below freezing by Tuesday night.

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AVIATION

High pressure shifts east tonight while a trough digs along the coast. The flow aloft is southerly. Increasing clouds overnight with light rain and MVFR conditions Thursday morning. VFR conditions returning by 21z with drier conditions.

KSEA...VFR tonight with easterly winds to 10-15kt. Increasing clouds with MVFR and light rain by 12z. Cigs gradually improving with VFR returning by 18-21z. 33

MARINE

E/SE offshore flow tonight with highest wind/seas over the coastal waters and entrances to the strait. Winds will ease early Thursday. Meanwhile, seas will build to 13 to 17 feet Thursday afternoon. Southerly winds prevail over the waters Friday and into the weekend. A stronger push down the strait is forecast Sunday night and Monday with gales possible. 33

HYDROLOGY

No flooding is expected through the week ahead. Stronger weather systems moving into the region early next week could bring periods of heavier rain (or mountain snow) and will be the next time frame to watch with respect to hydrologic concerns.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory until 10 PM PST this evening for Foothills and Valleys of Central King County.

PZ...Small Craft Advisory until 4 AM PST Thursday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm-West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 6 PM this evening to 10 AM PST Thursday for East Entrance U.S. Waters Strait Of Juan De Fuca.