textproduct: Seattle/Tacoma

SYNOPSIS

Precipitation will return to the area today, with lowland rain and mountain snow before becoming mostly rain throughout the day Wednesday. Unsettled weather is expected through the holiday before drier conditions start to emerge for the weekend. The trade off for the calmer weather will be colder overnight temperatures.

SHORT TERM /TODAY THROUGH THURSDAY/

The lull in activity continues over W WA this early morning. Current satellite shows plenty of high to mid level clouds overhead while latest radar imagery suggests that there may be some low clouds in play as well. However, the former is preventing the latter from creating widespread fog...even though some areas may experience some patches here and there.

Models remain in good agreement with activity likely holding off until the late morning for much of the area...although along the coast could see rain start in the mid-morning hours /perhaps toward the tail end of the morning commute period/. From there, soggy conditions settle in for the rest of the day before tapering off overnight and brief dry conditions emerge by Wednesday morning. Now, the main concern with this initial system will be wintery precip in the Cascades. QPFs have increased from solutions 24 hours ago, even while the timing for snow levels to lift has remained generally on track. This looks to give rise to the prospect where amounts will overpower temps, at least initially, not only allowing for snowfall hanging on a little bit longer than one would typically expect, but also a transition over to mixed or icy precip. That said, inherited Winter Weather Advisory for the Cascades of Snohomish, King, Pierce and Lewis counties looks good, with the higher snowfall amounts expected to focus on Snohomish and King counties. These two areas could see 6-8 inches of snow accumulation while the remainder max out around 6-ish.

Wednesday morning starts off ridge-ish, but a secondary upper level low shifts toward the coast bringing a return to rainfall in the mid to late afternoon. Models seem to have finally reached a consensus with the track of this system, guiding it almost directly over the Columbia river. This will keep not only the remainder of Wednesday but also the bulk of Thursday wet. It is worth noting that rainfall amounts with this secondary system do not appear to be as much as today's system, with the ensemble mean Wednesday proving to be half of the value of today. That said, the precip is more drawn out with the secondary system, over the span of 36 hours, give or take.

Temps today will be akin to yesterday, perhaps a degree or two cooler with much of the lowlands still stuck in the mid to upper 40s. The benefit of the passing warm front, aside from the rising snow levels discussed above, will be a slight boost to the daytime highs for both Wednesday and Thursday, with each day finding themselves in the upper 40s to lower 50s.

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LONG TERM /THURSDAY NIGHT THROUGH MONDAY/

Precip activity expected to taper off throughout Thursday night and into Friday morning before becoming generally dry by noon. This is thanks to an upper level ridge building over the eastern Pacific. Deterministic long range models and ensembles remain in sync with each other, keeping the remainder of the extended period fairly inactive as this ridge continues to hold court and remain almost stationary. That said, there are hints of shortwave systems potentially bringing Slight Chance to low-end Chance PoPs to the area toward the end of the forecast period...Sunday to Monday-ish. NBM /and thus the forecast/ hang on to PoPs perhaps a little bit longer than current solutions suggest, which is fine given that only 24 hours ago solutions were utterly scattershot. Should the current solutions remain consistent, future forecasts will likely see these PoPs erode.

The trade off for the less active weather will be cooler temperatures. Daytime highs only take a minor hit, generally staying in the mid to upper 40s for the remainder of the forecast cycle. The impact will be felt in the overnight lows, which will see temps get down into the lower to mid 30s...aside from water adjacent locations, which will be just a touch higher in the mid to upper 30s.

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AVIATION

Moist, W-SW flow aloft, today with rain increasing across western WA. With the rain, expect lowering clouds and MVFR conditions. Rain eases after 09-12Z tonight, then increases again by 18-21z Wednesday as the next frontal system lifts north through western WA. 33

KSEA...Lowering clouds, MVFR and rain today. Easterly surface winds around 5 kt. Moist low level air mass overnight with IFR conditions likely. 33

MARINE

South winds will increase today as a stronger Pacific frontal system moves in - Small Craft Advisories are in effect. Winds will ease late tonight into early Wednesday. Expect elevated winds and seas on Thursday as another strong system reaches western WA. The flow will turn more northerly and offshore late in the week, with Fraser River outflow winds possible over the weekend. 33

HYDROLOGY

A stronger weather system will move into Western Washington today, with continued precipitation at times through Thursday. Between the relatively quick flash of precip today and the more drawn out event Wednesday and Thursday, QPF amounts remain generally consistent, perhaps a little increased. This will still allow for area rivers to see rises the rest of this week. However, the breaks in activity could be an offsetting measure. For that reason, the flood threat for most rivers remains minimal. The Skokomish remains the outlier, as forecasts continue to advertise river levels cresting just at flood stage or a little lower. Given the borderline nature of latest forecasts, inherited Flood Potential Outlook for Mason County continues to look on track and will remain unaltered at this time. This, as well as other rivers, will continue to be monitored.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...Winter Weather Advisory from 10 AM this morning to 4 AM PST Wednesday for Cascades of Pierce and Lewis Counties- Cascades of Snohomish and Northern King Counties-Cascades of Southern King County.

PZ...Small Craft Advisory until 1 AM PST Wednesday for Admiralty Inlet-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- East Entrance U.S. Waters Strait Of Juan De Fuca.