textproduct: Seattle/Tacoma

SYNOPSIS

Showers persisting tonight. The next weather system will move into the area on Tuesday, bringing lowland rain, mountain snow, and breezy winds to western Washington. Precipitation will linger into Wednesday, with drier weather expected Thursday into the weekend. Cold, near-freezing morning lows are expected for portions of the south Sound and Chehalis Valley on Thursday. Chances of precipitation return late in the weekend into early next week.

SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/

Plenty of clouds on latest satellite while there are still some lingering showers on latest radar. The largest patch is currently over Snohomish and Skagit counties but there also appears to be a new wave of activity making its way onto the Olympic Peninsula. This fits well with inherited forecast showing activity ramping up overnight as incoming frontal system draws closer to W WA.

That said, since current forecast is handling conditions well, will not need any evening updates tonight. For additional forecast details, please refer to the Previous Discussion section below. 18

From Previous Discussion...Showery and unsettled conditions will continue through the remainder of the day today. Cloudy conditions and afternoon highs will generally be in the low to mid 50s across the area.

The next system will then move into the area on Tuesday, bringing the next round of lowland rain, mountain snow, and breezy winds. Mountain snow will continue into Wednesday and isolated chances of thunderstorms will be possible in the wake of the system. Additional details on the hazards have been outlined below:

Winds: Southerly winds will increase across western Washington through the morning hours on Tuesday. Wind gusts will generally be between 25-40 mph, though isolated gusts to 45 mph will be possible at times. With new foliage on trees, tree damage may be possible with any gusts between 35-45 mph. Winds will gradually ease area-wide again late Tuesday night into Wednesday morning.

Mountain Snow: Snow levels will start out between 3000-4000 ft on Tuesday, but will fall to 1000-1500 ft by Wednesday, bringing accumulating snow for the mountains- especially for the Cascade passes. The heaviest snow will occur Tuesday night into Wednesday morning and will be for elevations generally above 2500 ft. Snow will linger through the day Wednesday, before tapering late Wednesday night into Thursday.

Rain: This system will bring the next round of lowland rain to the region. The most likely rainfall amounts for the interior lowlands look to be between 0.50-1 inch, with the typical shadowed areas generally expected to see a little less- between 0.25-0.50 inches. Areas along the coast will see the most rain, with rainfall amounts generally expected to range between 1-1.25 inches from Tuesday morning through Wednesday night.

Thunderstorms: A slight chance of thunderstorms will be possible in the cool post-frontal airmass on Wednesday. The most likely areas for any thunderstorm development will be along the Pacific Coast. Any isolated thunderstorms that do develop may produce dangerous lightning, gusty winds, small hail, and brief heavy downpours.

LONG TERM /THURSDAY THROUGH MONDAY/

Drier conditions are expected the second half of the week with high pressure building back into the region. Clearing skies overnight will allow for temperatures to dip into the low to mid 30s across much of the area by Thursday morning. Most likely spots to approach freezing will be areas around the south Sound and the Chehalis Valley- where frost will also be possible. Dry conditions will persist through Saturday as the ridge of high pressure moves overhead. Afternoon high temperatures will warm a few degrees each day- topping out in the upper 50s to low 60s across the region by Saturday. An upper level low will then approach the region on Sunday, bringing the return of shower chances to the region. Showers then look to linger into early next week.

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AVIATION

Northwest flow becoming westerly tonight into Tuesday as an upper- low tracks along the BC coast. Most terminals remain VFR except those under the convergence zone over Snohomish County. Ceilings are beginning to slowly lower across the area this evening. Scattered/occasional MVFR cigs are expected through much of tonight before widespread rain begins to move in across the area tomorrow morning, which will bring more widespread MVFR to IFR ceilings and visibility. This will persist through the remainder of the TAF period. Winds south southwesterly 8 to 12 kt with occasional gusts 15 to 20 kt will remain like so through much of the night, with winds increasing after 18Z up to 15 to 25 kt with gusts 25 kt to 35 kt, primarily between 21Z Mon - 03Z Tue. Winds will begin to ease behind the frontal passage at the very end of the TAF period.

KSEA...Low-end VFR cigs will continue to persist this evening, with period of scattered MVFR cigs possible overnight. Rain beings to move over the terminal 15-17Z after which ceilings will more consistently lower to MVFR with lowered visibility in moderate rain as well. S/SW winds 8 to 12 kt with gusts 15 to 25 kt will persist tonight, increasing after 18Z up to 15 to 20 kt with gusts 25 to 35 kt. Winds, rain, and ceilings all look to start improve towards the end of the period after 06Z Tue.

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MARINE

Surface high pressure resides well offshore in the NE PAC. Onshore flow continues over the area waters as well for the small craft advisory in the Strait of Juan De Fuca for enhanced westerlies. A stronger frontal system is still on track to enter the area late tonight into Wednesday morning for breezy conditions and elevated seas. A small craft advisory remains in effect for all of the coastal water zones starting early Tuesday as S/SW winds increase ahead of the front. New SCAs have also been added for the inland water zones of Puget Sound, Admiralty Inlet, and the Northern Inland waters. Can't rule out the brief the potential for gale strength gusts, particularly in the strait.

Coastal seas 4 to 6 ft tonight before increasing upward to 9 to 12 feet on Tuesday evening. Seas 8 to 10 ft through Thursday before decreasing by Friday to 3 to 5 feet.

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HYDROLOGY

With rain moving into the area Tuesday into Wednesday, slight rises on area rivers will be possible. The Skokomish River is expected to rise into Action Stage with the additional precipitation. Snow levels will fall mid week to 1000-1500 ft, but no river flooding is expected at this time.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...Winter Storm Warning from 11 AM Tuesday to 11 PM PDT 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.

PZ...Small Craft Advisory until 5 AM PDT Tuesday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 5 AM Tuesday to 5 AM PDT 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.