textproduct: Seattle/Tacoma

SYNOPSIS

The next disturbance will cross the area on Wednesday, bringing additional snow to the mountains and rain to the lowlands. After showers linger later in the week, primarily in the northern interior, a trend towards drier conditions emerge over the weekend and continue into the first half of next week.

SHORT TERM /TODAY THROUGH FRIDAY/

A stagnant pattern remains in the upper-levels of the atmosphere. Upstream, a rex block is the culprit as a high center stretches into the Bering Sea in concert with a cutoff low on the southern periphery of the area of high pressure. Closer to home, northwest flow regime aloft with high pressure at the surface. Today will start off dry with patchy low clouds and fog in the early morning. Then, the next frontal system will arrive from of the NW, bringing a glancing blow of lowland rain showers (primarily along the coast and Olympics) and mountain snow mostly for the North Cascades - Stevens Pass northward. Intense snowfall rates are not expected but instead rather steady with snow totals ranging close to a foot for areas such as Mt. Baker Ski area through Friday. Snow levels mainly 2,000 to 3,000 throughout the short-term forecast.

The upper-level pattern won't vary much for the next few days. Temperatures are forecast to remain seasonal with highs in the upper 40s to near 50 F. Overnight lows are forecast to fall into the mid 30s to lower 40s.

41

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

Ensembles suggests the upper-level pattern will progress in the long-term forecast. The aforementioned cut off low will become ingested in the mean-flow over the weekend as it tracks inland over N. California/S. Oregon. An upper-ridge will gradually position over the PNW by early next week. Daytime highs are slated to remain around average with cool overnight lows in the lower to mid 30s.

AVIATION

West to northwest flow over western WA today under moderate onshore flow. The low level air mass remains moist with BKN-OVC clouds around 3000-5000 ft, along with pockets of patchy fog and LIFR ceilings. Overall conditions are expected to improve to mainly VFR conditions this afternoon with showers developing primarily along the north coast, Olympics and northern Cascades. Ceilings will lower to around 3000 feet overnight with another round of lower ceilings possible at a few locations early Thursday morning. Gusty southerly winds will develop for many areas Thursday morning. 33

KSEA...VFR expected with ceilings between 3000-5000 ft later in the afternoon, lowering into Thursday morning but most likely remaining low end VFR.SE winds around 5 kt becoming S/SW 10 kt. Gusty southerly winds later Thursday morning with gusts 25-30kt possible.

MARINE

Moderate onshore flow prevails through Thursday with winds gradually easing on Friday. Seas will also build over 10 ft on Friday, primarily over the outer Coastal Waters. The flow will turn offshore over the weekend and continue into early next week. 33

HYDROLOGY

No river flooding is expected during the next seven days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Winter Weather Advisory until 4 AM PST Friday for Cascades of Snohomish and Northern King Counties-Cascades of Whatcom and Skagit Counties.

PZ...Small Craft Advisory until 4 AM PST Thursday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca-West Entrance U.S. Waters Strait Of Juan De Fuca.

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.