textproduct: Seattle/Tacoma

SYNOPSIS

A brief break in the active weather tonight before the active pattern return with the system arriving tomorrow. Weather systems will traverse across the area throughout the week. Snow levels and temperatures will increase tomorrow night into Monday through the week as well.

SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/

Showers have dissipated this evening with partly cloudy skies under increasing high clouds. A couple spots may see patchy fog/freezing fog tonight with the light winds, but the high clouds will likely hinder any widespread development. The temperatures will be on the chilly side, with most of western WA at or below freezing tonight (temperatures in the upper 20s to low 40s, with low 20s and teens in the mountains). A few shady spots that stay damp tonight may see slick spots form Sunday morning (especially if untreated).

The ridge flattens Sunday, with the next jet streak & moist conveyor belt setting up to the north of the states in Canada. There is a warm front that will approach the coast late Sunday morning and afternoon. Snow levels will increase to over 9,000 ft on Sunday. The next round of precipitation does not arrive along the coast until late Sunday morning/early afternoon, and does not reach the remainder of the interior until late Sunday evening. Snow will be limited to the Cascades and Olympics, and just the peaks as the snow levels rise. A couple early showers Sunday morning that come ashore may produce a couple snowflakes. The precipitation continues into Monday, with a few heavier areas of QPF being focused in the Cascades, the Olympics and coast. There are expectations that rivers and streams will rise with the additional rain falling on top of the melting snow next week (see the hydrology discussion below for further details). Highs increase into the mid and upper 40s Sunday and Monday, with lows well above freezing Sunday and Monday night. The coast and north interior have the potential to see windy conditions, with gusts most likely at this time approaching 30-35 mph.

HPR/62

LONG TERM /TUESDAY THROUGH SATURDAY/

The warm and wet pattern will continue through the week, with a couple additional rounds of moderate precipitation expected in the mountains and the coast at times through the week. The precipitation begins to scale back on Friday, with some disagreement if the warm pattern continues into the weekend, or if it becomes cooler. The temperatures will warm gradually through the week, with lowlands seeing highs approach the upper 50s to low 60s.

HPR

AVIATION

Northwesterly flow aloft as upper level ridging continues to build over the eastern Pacific. Surface winds largely light and variable with speeds less than 5 kts.

Earlier convergence zone has largely fizzled out by this point with generally quiet conditions emerging. VFR conditions in place areawide with patchy high clouds overhead. This should be enough to maintain VFR conditions for most terminals for the TAF period, however locations more prone to lower cigs, especially OLM and PWT, will run the risk for MVFR to IFR conditions developing overnight and into Sunday morning. VFR conditions are expected to return to these two terminals by 18Z Sunday morning. Rain from a warm front will reach the coast Sunday morning and the interior during the afternoon. PoPs showing enough confidence for inclusion in the 06Z TAFs, but precip amounts expected to be light. As such, may opt for more of an -SHRA approach than indications of something more stratiform. This front will lift north Sunday night. 18/33

KSEA...VFR conditions will prevail. Light variable wind becoming S to SE by 06Z. Patchy low clouds or fog in the vicinity early Sunday, but not much confidence on them intruding on the terminal. Cigs lower with approach of warm front, but should still remain VFR with light, scattered precip starting in the 21-00Z time frame. 33/18

MARINE

High pressure will shift inland tonight. Southerly flow will increase on Sunday as a strong warm front shifts north into southern British Columbia. Moderate south winds will continue into Monday and Tuesday with Small Craft Advisories possible for the interior waters. Seas will build to 10-12 ft by Tuesday. 33

HYDROLOGY

River flooding continues for rivers across the Chehalis basin. Rivers currently in flood stage include the Skookumchuck River near Bucoda /already crested and on its way down/, and the Chehalis River near Grand Mound and at Porter. The Chehalis and Grand Mound is cresting at the time of this writing, getting very close to moderate flood stage but remaining just under. Porter is still expected to crest by Sunday afternoon before 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.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 11 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca-West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 11 AM Sunday to 5 PM 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-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.