textproduct: Seattle/Tacoma

UPDATE

A front is currently working its way throughout the region this evening as light rainfall spreads across western WA. Steadier rainfall will break into the showers overnight before conditions trend drier into Thursday morning. Precip amounts are not expected to be impactful with less than 0.25" expected for the interior lowlands and 0.25-0.50" for coastal areas. Overnight lows are to range throughout the 40s. The previous discussion is below along with an updated marine/aviation section.

SYNOPSIS

A weak frontal system moves across the area through tonight. A stronger system arrives Friday bringing steadier rain and locally gusty winds. Warm front moves northwards on Saturday with an associated cold front bringing another round of rain and gusty winds late Saturday into Sunday. A brief break early Monday before additional systems arrive into midweek.

SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/

A front is approaching the coast this afternoon with increasing mid and high clouds over western Washington. The front moves onshore late this afternoon and moves into Puget Sound this evening into tonight. A few hours of steadier rain is expected with this system. In addition, south winds will peak around 15 to 30 MPH along the immediate coast and Whidbey Island region this evening. Otherwise, this will be a weaker system with rainfall amounts up to 0.15" for most of Puget Sound, and 0.25-0.5" along the coast. Temperatures peak in the 50s today.

There will be a break in the precipitation on Thursday, with even a mix of clouds and sunshine. However, the break will be relatively short as the next frontal system approaches the region Thursday night with increasing rain early Friday. Steadier rain continues on Friday for most areas, with the heaviest QPF amounts focused in the Cascades and Olympic Peninsula. South winds also increase early Friday. Winds are expected to be strongest along the northern coast and from Whidbey Island northwards. NBM probabilities for gusts over 40 MPH range 50-90% for the majority of these areas, with higher probabilities on the REFS. Will need to monitor the potential for any Wind Advisory in these aforementioned regions on Friday. Winds elsewhere will be locally breezy, with gusts peaking between 20 to 30 MPH, especially near the water. The front weakens Friday night, but a warm front lifts northwards overnight, resulting in continued rain at times. Highs will reach the 50s again Friday.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

The majority of western Washington will be positioned in the warm sector on Saturday as the warm front lifts into BC during the morning. Most areas are expected to remain drier by Saturday afternoon, with exception being the Olympic Peninsula and near the BC border where there remains lingering precip potential. Otherwise, highs will be warmer on Saturday, peaking in the 60s for most areas.

A cold front progresses eastward Saturday night into Sunday bringing additional steadier rain and gusty winds. The bulk of the precip will be Saturday night, with precipitation more confined to the Cascades by Sunday afternoon, other than a few lingering showers. Another round of breezy south winds Saturday night with the front, with the strongest winds again along the coast and Whidbey Island northwards. However, winds will likely be a bit stronger elsewhere with this front compared to Friday, and thus more widespread gusts of 20 to 35 MPH may occur. In addition, seas build to near 20 ft along the immediate coast on Sunday, and will monitor for high surf conditions. Snow levels initially around 8000 feet Saturday fall towards 4000-5000 feet by later Sunday for higher elevation snow in the Cascades and Olympics. A brief period of drier weather then arrives Sunday night into Monday.

Uncertainty increases in ensembles later Monday into midweek. However, there is potential for a longer duration rain event during this period. Mean of ECMWF/CMC ensembles focus the moisture plume towards western Washington, with GEFS focused more into British Columbia. This will be something to monitor over the next few days with additional rain, winds, and increased waves likely at times next week. JD

AVIATION

Generally VFR this evening with areas of MVFR/IFR as rain showers continue to push inland with a cold frontal passage. Ceilings are expected to continue to lower this evening as heavier rain showers move inland, with a chance (30-35%) of IFR conditions over the Kitsap Peninsula and south of the Puget Sound. By early Thursday morning, the rain will have pushed east of the Cascades with MVFR ceilings expected to stick around across the region through much of Thursday morning. Models suggest VFR conditions returning by Thursday afternoon. Breezy south to southwest winds this evening from Puget Sound to the northern interior generally 5-12 kt, with gusts up to 20 kt possible between 04z-09z as the frontal system moves through the area.

KSEA...VFR this evening, with heavier showers expected this evening that will likely bring MVFR ceilings. While showers are expected to move east after midnight, MVFR ceilings are favored to hang on through Thursday morning with a slight chance (15%) for brief IFR ceilings between 14z-19z. Improvement to VFR is expected by 20z. Surface winds will generally stay south to southwest, with briefly breezy winds up to 18 kt between 06z-10z with the frontal passage.

29/15

MARINE

An active marine pattern will continue into next week with multiple weather systems expected to move over area waters. Increased south/southwesterly winds over the coastal waters will continue to ease this evening as a frontal system moves eastward. Winds expected to also increase across the interior waters with the passage of the front, with small craft conditions continuing for portions of the Strait of Juan de Fuca and Admiralty Inlet into early Thursday morning.

A stronger system will move over the waters Thursday night into Friday, bringing elevated winds and seas. Winds will increase area- wide overnight. A Gale Watch has been issued for the coastal waters, East Strait, and Northern Inland Waters due to increasing probabilities for gale force winds gusts. Winds will ease towards Friday evening. Seas will also increase Thursday night, climbing to 15-19 feet by Friday afternoon.

The weekend will remain active, with an even stronger frontal system moving through the area. Widespread gale gusts are possible across the waters Saturday afternoon through Sunday afternoon. The highest chances for gales are for the coastal waters with a 60-85% chance, while the interior waters have a 50-60% chance. Additionally, seas will build through the day on Saturday and peak Sunday afternoon towards 20 feet. There is a 40-50 chance for seas to exceed 20 feet. Seas will start to ease late Sunday into Monday.

Conditions look to remain hazardous going into next week, as additional frontal systems move near or through area waters. These frontal systems will bring additional chances for strong to gale- force winds.

29/15

HYDROLOGY

River flooding is not expected through the next seven days. However, a series of increasingly wet weather systems will bring rain (and high mountain snow) to the region, especially from Friday onward. While current forecasts are not expected to cause flooding, this will begin to saturate soils and raise base flows that could bring a concern with subsequent storms systems into next week.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 1 AM PST Thursday for West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory until 2 AM PST Thursday for Admiralty Inlet-East Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Watch from late Thursday night through Friday afternoon for East Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Watch from Friday morning through Friday afternoon for Northern Inland Waters Including The San Juan Islands.

Small Craft Advisory until 10 PM 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.

Gale Watch from Thursday evening through Friday 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.