textproduct: Seattle/Tacoma

SYNOPSIS

High pressure will move inland today, with some patchy areas of dense fog this morning across the region. Some breezy east gap winds are expected in the Cascades as well today. The progressive pattern continues with a weak front bringing some showers tonight into early Thursday. A stronger system will bring precipitation this weekend into next week. This next set of systems looks to add substantial rainfall and accumulating snow in the mountains. Cooler temperatures are expected going into next week.

SHORT TERM /TODAY THROUGH FRIDAY/

Areas of low stratus and fog are present across much of the lowland interior this morning, but fog has lifted to low stratus already this morning. Low clouds and fog are expected to scatter out quickly this morning as east winds increase.

The high pressure/ridge will shift inland today, with a frontal system approaching the coast later tonight. The increased pressure gradient is expected to produce breezy east winds, with gusts of 25-35 mph at times today. An isolated pocket of 35 to 45 mph winds is expected in the North Bend area today (and the wind advisory for the area will continue). The coast and east Strait of Juan de Fuca areas may also see some gusts of 20 to 30 mph at times later today.

The previous mentioned front will split as it moves ashore, and will bring showers along the coast late tonight/Thursday morning. The coast is favored to see the most amount of QPF with this system (which is a light 0.25" or so of rain), while remaining areas see a few hundredths to a tenth of an inch. The precipitation drops to less than 30% chance the remainder of Thursday. Some areas of patchy fog will be possible again Thursday morning, potentially lingering for a good part of the day. Winds are expected to remain light on Thursday. Overnight temperatures will improve with increased cloud coverage (low 40s in the lowlands). Highs remain in the low 50s.

In addition to showers: along the coast, large long-period waves are expected to arrive Thursday afternoon. The latest NWPS/ensemble model guidance has waves approaching 14 to 16 ft Thursday afternoon with periods around 14 to 16 seconds. A future high surf advisory may be needed for the threat of beach erosion and significant run-up.

For Friday: This is the beginning of what is expected to be a series of progressive systems moving through the region into the weekend and next week. A front arrives Friday afternoon with increasing chances of precipitation. Snow levels will remain elevated around 6,000 ft. during the day, keeping initial significant snowfall to the peaks of the highest north Cascades peaks. The hydrologic concerns remain low at this time (see hydrology discussion below).

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

As mentioned, the progressive pattern is expected to continue through the weekend into next week. The heaviest of the QPF has shifted into Sunday-Monday night, but remains in the Cascades and in the Olympics/coast. Snow levels are expected to drop down to around 2,000 ft going into Tuesday. Accumulating snow will be possible at some of the more popular passes (Stevens, and Snoqualmie). Please continue to monitor travel conditions going into next week (especially if traveling for the Thanksgiving holiday).

Ensembles are split going into the middle of next week on if the pattern will become warmer or cooler (although CPC has western WA in a slight chance of below average temperatures next 8-14 days). The deterministic forecast favors cooler temperatures going into next week, with a few more lows in the 30s by midweek next week. Highs Tuesday only reach the upper 40s for most urban areas. Precipitation chances remain around 20% going into the middle of the week, but depending on how cool the air will get, any showers that do form during the cold hours will have the chance to mix a few snowflakes down to the surface.

HPR

AVIATION

An upper ridge over the region today with weak offshore flow developing this afternoon. Low level offshore flow will help to gradually erode the low clouds late morning onward for a return to VFR for most areas by early afternoon. Increasing mid/high clouds late tonight/early Thursday ahead of the next frontal system. Light rain moving inland overnight with MVFR conditions.

KSEA...Low clouds slowly eroding this morning with ceilings improving this afternoon due to drier east winds. East/northeast winds 5-7 kt increasing to 10-15 kt this afternoon. MVFR cigs by 12z Thu with light rain. 33

MARINE

High pressure will shift inland today, with a weak front expected to split moving across the waters/land tonight/Thursday. Some patchy dense fog is possible in the Puget Sound this morning. Otherwise. breezy east winds will turn more south/southeast later today ahead of the next front. Small craft advisories continue for the coastal waters, and the west/east Strait of Juan de Fuca areas for wind gusts up to 25 mph (up to 30 mph in the east strait). This progressive weather pattern is expected to continue through the weekend into next week, as models try to solve different paths for several systems expected to pass through our region.

Seas of 8 to 10 ft are expected in the outer coastal waters today (6 to 8 ft in the inner coastal waters). An increasing westward component will bring seas of 15 to 18 ft close to the shore, before dropping to 8 to 12 ft into early next week, decreasing to 8 to 10 ft.

HPR

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 Point Grenville To Cape Shoalwater 10 To 60 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.

Small Craft Advisory until 4 AM PST Thursday for Coastal Waters From James Island To Point Grenville Out 10 Nm- Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.