textproduct: Seattle/Tacoma

SYNOPSIS

Lingering showers mainly over the mountains today, with more widespread precipitation returning to the area tonight into Friday. A cooler system remains on track for late in the weekend into early next week, bringing needed mountain snow and some potential for an early morning rain/snow mix for parts of the interior lowlands.

SHORT TERM /TODAY THROUGH SATURDAY/

The Winter Weather Advisory in the Cascades will expire at 10 Am as planned with showers winding down. 33

Previous discussion...Post-frontal showers will linger over the Cascades today. Precipitation associated with warm front will spread into the area again this evening and loiter through much of the day Friday. The warmer air mass will boost snow levels to over 5,000 ft by late Friday morning and 6000 to 7000 ft by Saturday morning. Precipitation should generally taper off Saturday morning, lingering over the higher terrain. Temperatures will run in the ballpark of normal with highs in the low 50s and lows in the upper 30s to low 40s.

LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/

An upper level trough moving across south central Alaska Saturday evening will help nudge a frontal system south along the British Columbia coast into western Washington Sunday morning. This will bring widespread precipitation through the day Sunday into Monday morning - as well as much cooler air mass. Snow levels are expected to drop to pass levels by early Sunday evening and to 1000 to 1300 feet by early Monday morning. Low level flow is expected to remain onshore, but there remains a chance for a window with a rain/snow mix for some lowland locations early Monday morning before temperatures moderate for rain. The cooler air mass looks to remain in place through the early part of next week, with the NBM showing 70-80% odds at low temperatures Tuesday morning at or below 32F for many locations outside of the urban areas. Periods of lighter precipitation remain possible, especially over the higher terrain Monday and Tuesday. Longer range ensemble guidance hinting at the next, more organized system mid week which will most likely result in another round of needed mountain snow.

AVIATION

Onshore/westerly flow aloft continues behind yesterday's front. Majority of interior terminals are seeing low VFR or MVFR ceilings this morning (with isolated pockets of IFR). Isolated shower activity will continue over higher terrain this morning with mountain obscuration. Outside of precipitation, low clouds will continue filling in across the western Washington terminals with some brief improvement to VFR by later this afternoon/evening. Conditions will lower again later tonight to widespread MVFR to IFR in cigs and vis as another frontal system brings in widespread lowland rain and mountain snow. Surface winds generally south to west 8 kt or less this morning increasing to 5 to 12 kt this afternoon with gusts to 20 kt. Higher westerlies possible through the Strait of Juan de Fuca and over the Cascades.

KSEA...MVFR is expected to continue this morning, with a slow improvement to low end VFR into the afternoon. Steady rain will move inland this evening, and probabilities have increased for lower-end MVFR conditions (both cigs/vis) with a chance of IFR for a majority of the day Friday. Winds generally southerly 5 to 10 kt overnight. South to southwest winds increasing this afternoon with gusts to 25 kt possible.

15/HPR

MARINE

Winds over the coastal waters have eased this morning - seas will remain elevated through the morning - dropping to 7 to 8 feet through the afternoon. Onshore flow will linger through the period with small craft advisory westerlies through the strait easing during the afternoon. The flow will remain onshore Friday and Saturday, with the increasing winds and seas Sunday/Monday.

HYDROLOGY

No river flooding is expected over the next seven days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Winter Weather Advisory until 10 AM PST this morning for Cascades of Pierce and Lewis Counties-Cascades of Snohomish and Northern King Counties-Cascades of Southern King County.

PZ...Small Craft Advisory until 6 PM PST this evening for Grays Harbor Bar.

Small Craft Advisory until 10 AM PST this morning 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 1 PM PST this afternoon 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.