textproduct: Seattle/Tacoma

SYNOPSIS

Spotty precipitation will linger into Friday followed by drier and cooler conditions this weekend into early next week before the next chance of precipitation returns around midweek.

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/

Not a lot of significant variability in the the upper-level pattern through the short-term. An negatively tilted upper level low off of the northern California coast will remain in just the right spot to let some of the precipitation streaming into British Columbia slip into western Washington - mainly the Olympic Peninsula and North Cascades into Friday. This has been spotty showers - rain over the low elevations and mountain snow above 3000 feet. Breezy southerly winds this afternoon through much of the interior are expected to ease through the evening hours. The upstream upper level low will slowly move east of 140 W by Saturday morning, boosting upper level heights over the Pacific Northwest and helping shift the precipitation fully to the north into British Columbia through the day Friday.

Conditions will continue to dry Saturday as cooler air begins to spill in the region, with snowlevels dipping to around 2000 feet Saturday morning. Low level flow will become weakly offshore. Morning low temperatures Saturday will range from the mid 30s near the water and low 30s for interior locations south of Puget Sound and in the Cascade Foothills. Late February will help high reach into the upper 40s to near 50 F.

LONG TERM /SUNDAY THROUGH THURSDAY/

Ensemble clusters continue the trend of no significant variability in the upper level forecast well into early next week. The upper level low will open up and move into central California Sunday, maintaining the dry northwesterly flow over the Pacific Northwest. Variability in the forecast starts to creep back into the ensembles as an upper level low moves into the northeast Pacific Tuesday. This continues to look like the next shot at precipitation for the region with roughly 53% of the ensemble members hinting at a faster, more progressive system, and the remaining 47% a slower trend. This system looks to affect most of the Pacific Northwest midweek, likely resulting in lowland rain and another round of needed mountain snow. Daytime highs are expected to remain near normal with cool overnight lows in the lower to mid 30s.

AVIATION

West to northwest flow aloft continues across Western Washington into Friday as the region remains on the periphery of a frontal system moving into British Columbia. The low level flow is onshore. MVFR ceilings are expected to lift to VFR most areas this afternoon. Ceilings are then expected to sink back to MVFR across the region again overnight into Friday morning. A return to VFR areawide is expected again Friday afternoon and evening. Locally gusty south to southwest surface winds will ease this evening.

KSEA...High end MVFR ceilings are expected to lift to BKN040-060 this afternoon into the evening hours. Ceilings will deteriorate again tonight with a general OVC020-030 layer expected 09Z-20Z Friday before lifting again. Surface winds S/SW 10-15 gusting 20-25 knots easing to 8 to 11 knots after 00Z.

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MARINE

Surface high pressure will build into the coastal and inland waters on Friday allowing onshore flow to gradually relax. High pressure over the interior of British Columbia and lower pressure to south of the waters will turn the flow more northerly or weakly offshore over the weekend. The first of a series of frontal systems is expected to approach the waters on Tuesday.

Coastal seas will hover near 10 feet...especially across the outer waters...into Friday before subsiding back to the 4 to 7 foot range and remaining as such through Tuesday.

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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 PM PST Friday for Central U.S. Waters Strait Of Juan De Fuca-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 Point Grenville To Cape Shoalwater 10 To 60 Nm-West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory until 10 PM PST this evening for East Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland Waters Including The San Juan Islands.

Small Craft Advisory until 8 PM PST this evening for Puget Sound and Hood Canal.