textproduct: Seattle/Tacoma

SYNOPSIS

A low pressure system is on track to bring rain, breezy winds, and chances for thunderstorms to the region on Monday. Showery weather continues on Tuesday, with a return to high pressure likely later in the week.

SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/

A pleasant day across western Washington today with scattered high clouds overhead and temperatures in the upper 50s to low 60s as of 1PM this afternoon. Through the next system is not too far offshore with clouds already starting to move in over Neah Bay. Most all the area should remain mostly sunny through the rest of the day with clouds increasing overnight. Highs should reach the upper 60s with a few low 70s in some spots.

Rain will start to move in along the coast early Tuesday morning before filling in across the interior after sunrise and into the late morning. Winds will also start to increase in the morning, with the peak winds expected late morning/early afternoon as the frontal system traverses the area. Wind gusts up to 25-35 mph will be possible for most, through for the coast and areas around/north of Whidbey Island, gusts up to 35-40 mph can't be ruled out. Behind the front, rain will devolve into scattered showers and a few isolated thunderstorms. The best chances for thunderstorms will be along the coast and across SW WA Monday afternoon and early evening, with probabilities of around 15-20%. With the rain, highs will be much cooler, in the upper 50s to low 60s.

Unsettled weather continues into Tuesday as the low center moves through the area. Scattered showers and a few isolated thunderstorms remain possible throughout the day. Highs a touch warmer, in the low to mid 60s.

Unseasonably large waves will begin to arrive at the coast late on Monday, before peaking early Tuesday morning to around 14 to 16 ft, bringing high surf conditions to the coast. Waves will slowly decrease throughout the day Tuesday.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

The low pressure system responsible for Monday and Tuesday's weather will continue to dig south, leaving the PNW in split flow to gentle ridging into the mid and late week. As such, temperatures begin to warm from Wednesday onward, reaching highs back into the mid 70s by Thursday. Ensembles and deterministic guidance are hinting at broader troughing over the NE Pacific late in the week for potential for more unsettled weather. Low pressure over the intermountain west will also begin to drift northward, pushing moisture from the east side over the Cascades, with chances for showers beginning Thursday through the end of the week. Upper level troughing over the area may provide enough instability for a slight (10-15%) chance of thunder over the mountains as well.

Long period swell will arrive to the coast on Thursday, which will pose a bigger threat for significant wave runup on coastal beaches.

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AVIATION

Flow aloft will become southwesterly tonight as an upper level trough approaches the Pacific Northwest from the northeastern Pacific. Satellite imagery shows stratus has mostly scattered across the area this afternoon, which has resulted in VFR conditions at all area terminals. High clouds will continue to stream in overhead and increase tonight ahead of a frontal system on Monday. VFR conditions will largely prevail through the overnight period, but expect a gradual lowering of the cloud deck heading into Monday as the system approaches. Surface winds will remain out of the southwest and persist between 5-10 kt.

KHQM will see conditions deteriorate first, with MVFR ceilings moving into the terminal around 12Z. Conditions look to be a bit slower to drop across the interior, with guidance suggesting VFR conditions hanging on into the afternoon with a BKN/OVC cloud deck lowering to around 4000-5000 ft. Rain will move inland along the coast between 11-14Z and into the interior roughly between 15-18Z. Southerly winds will increase across the area Monday morning as the system approaches, with gusts to 20-30 kt possible at times (especially for terminals along the coast and from KPAE northward).

KSEA...VFR conditions will prevail through the remainder of the day, with increasing high cloud cover expected at the terminal. Southwesterly winds will persist between 4-8 kt through this evening. Rain expected to move into the terminal between 16-18Z Monday as a frontal system moves into the area. Southerly winds will increase on Monday morning, and will persist at 8-12 kt with gusts to 20-25 kt possible at times. VFR conditions look to hold into Monday afternoon, with BKN/OVC cloud deck between 4000-5000 ft.

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MARINE

High pressure will remain offshore today keeping conditions relatively tranquil across the coastal waters. A low pressure system will begin the area tomorrow, with a cold front traversing the area waters through the morning and afternoon hours. Southerly winds will increase early tomorrow morning ahead of the front. Most of the coastal waters will see high-end Small Craft Advisory winds, but gusts to gale force will be possible over the northern-most areas, for which that has been upgraded to a Gale Warning. Through the interior coastal waters from Puget Sound up through the Northern Inland Waters, winds will increase slightly later in the morning and persist into the afternoon as the front moves through. Probabilities have decreased for gale force gust across most of the interior coastal waters, but a few gusts to gale cannot be ruled out in the East Strait of Juan de Fuca (30-60% chances).

Winds will decreased still remain elevated through much of the day, it isn't until Monday night into Tuesday when winds begin to calm down across the area as the low pressure center moves across the region.

High pressure quickly rebuilds as the system departs on Tuesday, with winds switch back to north/northwesterly Tuesday morning and increase to SCA criteria through the outer coastal waters by Tuesday evening. This pattern looks to persist through the end of the week. Beginning Thursday, lower pressure over land will increase the onshore gradient, funneling wind through the Strait of Juan de Fuca. Winds increase during the day, potentially reaching gale force by Thursday evening and into Friday.

Seas 5 to 7 ft will increase through the day Monday, peaking up to 14 to 16 ft Monday night into early Tuesday. Seas will slowly decrease throughout the day Tuesday and may briefly drop to around 8 to 10 ft on Wednesday before climbing back up to around 10 to 12 ft Thursday.

Steep seas through the outer coastal waters will likely return Tuesday night into Wednesday as the local winds increase and the dominant period decrease to around 8-10 seconds. Long period swells 7 to 10 ft with a period of 15-18 seconds will arrive to the coast on Thursday, pushing the significant wave height back up above 10 ft. Waves look to start to ease on Friday below 10 ft.

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HYDROLOGY

The daily hydrology discussion has ended until the start of the next rainy season; it will only be updated during this time as needed.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory from 2 AM Monday to 5 AM PDT Tuesday for West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 5 AM to 5 PM PDT Monday for Admiralty Inlet-East Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland Waters Including The San Juan Islands-Puget Sound and Hood Canal.

Gale Warning from 11 PM this evening to 11 AM PDT Monday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm.

Small Craft Advisory from 11 AM Monday to 5 AM PDT Tuesday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm.

Small Craft Advisory from 11 PM this evening to 5 AM PDT Tuesday for 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.