textproduct: Seattle/Tacoma

SYNOPSIS

Shower activity will gradually taper across western Washington throughout the day today. Drier conditions are expected on Sunday morning, before the next round of precipitation moves into the region Sunday night into Monday. An atmospheric river will brush the area early next week, then looks to slowly sag southward. This will bring much warmer temperatures and periods of widespread rain to western Washington at times throughout the next week.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

A warmer and wetter pattern looks to persist through much of the next week. While uncertainty still remains in the exact positioning of the atmospheric river, latest guidance does indicate the axis of the moisture slowly sagging southward on Tuesday and bringing additional rounds of rain to the area through Thursday. The main concern next week will be potential hydrological impacts from higher snow levels and from rain on snow in the mountains. See the hydrology section below for additional details on river flooding. Temperatures will climb throughout the week, with highs approaching the upper 50s to low 60s Thursday and Friday.

14

AVIATION

Westerly flow aloft will continue before flow transitions more NW this afternoon. Post frontal showers are lining up early this morning through Whidbey Island through KPAE, moving generally toward the SE. RA/SN showers cannot be ruled out early this morning. Fog has settled into central Puget Sound and is likely to remain in place with low cigs until around 18-19Z. Probabilities of cigs below 030 are between 35-45% for areas KSEA south. Winds will remain light throughout the period, increasing along the coast as onshore flow kicks back in around midday.

KSEA...Significantly reduced visbys and cigs are present at the terminal early this morning due to fog setting up in the wake of the snow and moisture. Some additional rounds of drizzle (and around a 15-20% chance of light -RA/SN) are possible through 16Z this morning. Fog will remain in place until 18-19Z before conditions rebound into MVFR to VFR criteria. Expect southerly winds throughout the period.

21

MARINE

Surface ridging will build today and gradually reduce area precipitation down to isolated showers this morning. This will lead to increasing onshore flow over the coastal waters and in the Strait of Juan de Fuca today. This morning, expect some marine fog in central Puget Sound, dissipating likely after 18Z. Inherited SCA products will remain in place for stronger winds along the coast and in through the Strait of Juan de Fuca. The ridge will shift onshore tonight and Sunday as a strong warm front approaches the offshore waters. The warm front will lift northward across area waters Monday into Tuesday for increasing winds and seas.

21

HYDROLOGY

River flooding continues for rivers across the Chehalis basin this morning. Rivers currently in flood stage include the Newaukum River near Chehalis, the Skookumchuck River near Bucoda, and the Chehalis River near Grand Mound. The Chehalis River at Porter continues to rise and will likely reach flood stage by late this morning. Meanwhile, the Deschutes River near Rainier has crested just below flood stage overnight. With widespread precipitation ending across the area, expect rivers to crest today into Sunday and to start receding.

Attention will then turn to an atmospheric river expected to move inland to the north of the region early next week before gradually sagging southward into our area. Higher snow levels and rain on recent snows in the mountains could bring additional flooding concerns to portions of the area as several rivers are forecast to rise into Action Stage. For now, the only river forecast to reach flood stage is the Skokomish River- but river forecasts will bear watching over the coming days.

14

SEW WATCHES/WARNINGS/ADVISORIES

WA...Winter Storm Warning until 11 AM PDT this morning for Cascades of Pierce and Lewis Counties-Cascades of Snohomish and Northern King Counties-Cascades of Southern King County.

Flood Watch through Sunday afternoon for Cascades of Pierce and Lewis Counties-Foothills and Valleys of Thurston and Lewis Counties-Lowlands of Lewis and Southern Thurston Counties-Olympia and Southern Puget Sound-Willapa and Black Hills.

Winter Weather Advisory until 11 AM PDT this morning for 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.

PZ...Small Craft Advisory until 11 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca-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.

Small Craft Advisory until 3 PM PDT this afternoon for East Entrance U.S. Waters Strait Of Juan De Fuca.