textproduct: Seattle/Tacoma

SYNOPSIS

A period of very active weather will dominate the week ahead as a series of frontal systems produce cascading impacts across Western Washington. In addition to ongoing river flood concerns, another period of windy conditions is expected tonight into early Wednesday. Snow levels will tumble to the passes by early Wednesday with blizzard conditions expected in the mountains. Cool, unsettled conditions will remain in place through the remainder of the week with substantial additional snowfall in the mountains.

SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/

A brief lull this morning will be short and sweet, with a secondary, stronger system arriving later this evening and overnight, bringing mountain snow, lowland rain, and breezy conditions through much of the area. Active weather looks to continue throughout the short term, with the hazards listed down below.

The following key messages with this secondary system and week ahead are outlined below.

* RAIN: With this secondary system, we will see rain amounts generally in the mountains around 1 to 3 inches, with an inch or less in the lowlands through Wednesday evening. Initially this evening, the snow levels will remain high, generally around 8000 to 9000 feet, which will keep the landslide risk elevated. There is also a very slight chance of an isolated thunderstorm or two developing Wednesday morning, but the likelihood of any thunderstorm remains low. For more information regarding hydrology and river flooding, please refer to the .HYDROLOGY section down below.

* SNOW: This secondary system moving later this evening will have snow levels initially start at 8000 to 9000 feet, slowly lowering them, especially after midnight, down to 2000 to 2500 feet. Ample moisture from this system will result in significant mountain snowfall for the Cascades and Olympics. Snow will be heavy at times along with breezy winds up to 45 mph, therefore, a Blizzard Warning has been issued for late tonight into Wednesday afternoon. We could see totals around 10 to 15 inches at Snoqualmie Pass, with 15 to 20 inches at Stevens, and upwards to 2 to 3 feet at Mount Baker and Mount Rainier. A convergence zone will set up over the Cascades which could locally drive amounts up further. With upslope flow and additional systems, snow will continue at the mountains through Thursday, with additional winter headlines likely needed for the Cascades.

* WINDS: Winds will continue to increase this afternoon and evening, with widespread gusts up to 50-55 mph along the coast and up to 40- 45 mph across the interior. Southwesterly winds this afternoon will shift west to northwesterly later this evening, with the highest gusts later tonight through the Strait of Juan de Fuca and inland into western Snohomish County. The breezy winds, combined with deeply saturated soils, raises the risk of downed trees and localized power outages.

* COASTAL HAZARDS: Minor coastal flooding remains possible along the San Juan County island coastlines during Wednesday's high astronomical tide. The threat of minor coastal flooding shifts to along the Pacific Coast on Thursday and Friday. Seas will also build along the Pacific Coast Wednesday morning, generating large breaking waves that may pose a danger to beachgoers and cause localized coastal erosion.

LONG TERM /FRIDAY THROUGH TUESDAY/

Active weather looks to continue throughout the long term, with a series of systems arriving throughout the weekend and into the first half of next week. Lowland rain and mountain snow will continue as snow levels remain near or just below pass levels. Cool and unsettled conditions will remain.

Mazurkiewicz

AVIATION

A strong frontal system with an atmospheric river will continue to impact terminals rest of today into Wednesday. Moderate to heavy precipitation continues to move across the central and northern terminals. Visibilities and/or ceilings have dropped to IFR with this activity. There is a 15-20% chance of thunder along the coast/south interior terminals rest of today into Wednesday (tops are expected to be low with CB's less than 20,000-25,000 ft.). The precipitation will continue in the region tonight into Wednesday. Strong SW winds will continue to increase with gusts up to 35 to 45 kt in most terminals tonight/Wednesday morning. Strong NW outflow through the Strait of Juan de Fuca may result in a shift of winds to the NW in and around KPAE (wind shear is possible with this push). In addition, snow levels will drop to around 2,000 with blizzard conditions in the Cascades & Olympics through late Wednesday morning. Outside of areas of precipitation, MVFR ceilings are likely tonight, with a gradual lift up to VFR Wednesday morning before dropping back down to MVFR in the afternoon.

KSEA...Complex of moderate to heavy rain is moving over the terminal as of 22Z (reducing visibilities/ceilings down to MVFR/IFR). Additional bands of moderate to heavy precip will move through the terminal through 12Z. Outside of the precipitation, ceilings will drop to MVFR through the evening into Wednesday morning, then improve to VFR/overcast early Wednesday morning, before dropping back to MVFR in the afternoon. A few showers will be possible late Wednesday morning into the afternoon. Strong SW winds will increase to 10-20 kt with gusts to 30-40 kt possible overnight (strongest gusts expected between 06Z and 12Z tonight. Winds decrease back down to 10-15 kt gusting to 25 kt later in the morning/afternoon.

HPR

MARINE

A strong frontal system will continue to cross the Pacific Northwest late tonight into early Wednesday, bringing elevated winds and seas to the region. Gale force winds will cover all area waters by this evening, with the strongest winds through the central and eastern Strait of Juan de Fuca early Wednesday morning reaching storm force. Winds will remain elevated but will gradually ease into Wednesday afternoon with SCA winds continuing over the coastal waters and through the Strait of Juan de Fuca. A low pressure system will cross the region on Thursday, keeping small craft advisory winds across the coastal waters.

Seas around 11 to 14 feet will continue to build to 15 to 21 feet by early Wednesday morning. Seas will gradually subside to 10 to 14 feet by Thursday, where they will remain through Friday. Seas will subside to below 10 feet over the weekend.

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HYDROLOGY

Major flooding is possible on the Skagit river beginning Wednesday morning in the upper reaches with the flood crest reaching Mount Vernon Wednesday night. Several other rivers are forecast to reach minor to moderate flood but there is a fair amount of uncertainty with the crests, especially due to how quickly and and how low the snow level gets.

A flood watch is in effect through Thursday afternoon across the lowlands.

The landslide threat remains very elevated will continue to be high through at least tomorrow.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory from 4 PM this afternoon to 6 AM PST Wednesday for City of Seattle-Eastern Kitsap County-Eastside- Foothills and Valleys of Central King County-Foothills and Valleys of Pierce and Southern King Counties- Foothills and Valleys of Snohomish and Northern King Counties-Foothills and Valleys of the North Cascades- Lowlands of Western Whatcom County-San Juan County- Shoreline / Lynnwood / South Everett Area.

Coastal Flood Advisory from 2 AM to 8 AM PST Wednesday for San Juan County.

Flood Watch through Thursday afternoon for Cascades of Pierce and Lewis Counties-Cascades of Snohomish and Northern King Counties-Cascades of Southern King County-Cascades of Whatcom and Skagit Counties-City of Seattle-Downtown Everett / Marysville Area-Eastside-Foothills and Valleys of Central King County-Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Snohomish and Northern King Counties-Foothills and Valleys of Thurston and Lewis Counties-Foothills and Valleys of the North Cascades-Foothills of the Western and Southern Olympic Peninsula-Grays Harbor County Coast- Lower Chehalis River Valley-Lowlands of Lewis and Southern Thurston Counties-Lowlands of Pierce and Southern King Counties-Lowlands of Western Skagit and Northwestern Snohomish Counties-Lowlands of Western Whatcom County-Middle Chehalis River Valley-Olympia and Southern Puget Sound-Olympics-Shoreline / Lynnwood / South Everett Area-Willapa and Black Hills.

Blizzard Warning from 2 AM to noon PST Wednesday for Cascades of Pierce and Lewis Counties-Cascades of Snohomish and Northern King Counties-Cascades of Southern King County- Cascades of Whatcom and Skagit Counties-Olympics.

Winter Storm Warning from 4 PM this afternoon to 10 PM PST Wednesday for Cascades of Pierce and Lewis Counties- Cascades of Southern King County-Olympics.

High Wind Warning from 4 PM this afternoon to 6 AM PST Wednesday for Downtown Everett / Marysville Area-Eastern Strait of Juan de Fuca-Foothills of the Western and Southern Olympic Peninsula-Grays Harbor County Coast- Island County-Lake Crescent Area Including US 101-Lower Chehalis River Valley-Lowlands of Pierce and Southern King Counties-Lowlands of Western Skagit and Northwestern Snohomish Counties-Middle Chehalis River Valley-Northern Hood Canal-Northern Washington Coast-Olympia and Southern Puget Sound-Port Townsend Area-Southern Hood Canal- Western Strait of Juan de Fuca.

High Surf Advisory from 1 AM to 10 AM PST Wednesday for Grays Harbor County Coast-Northern Washington Coast.

PZ...Small Craft Advisory until 4 PM PST Wednesday for Grays Harbor Bar.

Gale Warning until noon PST Wednesday 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-West Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Warning from 4 PM this afternoon to midnight PST tonight for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Storm Warning from midnight tonight to 6 AM PST Wednesday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Warning from 6 PM this evening to 6 AM PST Wednesday for Admiralty Inlet-Northern Inland Waters Including The San Juan Islands-Puget Sound and Hood Canal.