textproduct: Seattle/Tacoma

SYNOPSIS

A warm front will bring widespread lowland rain and mountain snow for the highest elevations tonight with showers lingering into Saturday. A cooler system remains on track early next week with heavy mountain snow and the potential for an early morning rain/snow mix for parts of the interior lowlands.

SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/

A warm front continues to influence conditions over W WA this evening as radar remains active with much of the CWA seeing light to moderate showers. Temps this evening have been slow to cool with most obs hovering right around 50 degrees or just a degree or two cooler. With dewpoints in the upper 40s, overnight lows may not budge too much from what is currently being observed. Inherited forecast remains on track with activity becoming more scattered overnight and into Saturday...but never fully ending...before more uniform and consistent precip returns with the anticipated cold front starting Sunday night.

No evening updates are anticipated. For additional forecast details, please refer to the Previous Discussion section below. 18

From Previous Discussion...A warm front is clipping the area today for light precipitation. With the warmer air mass the snow levels are higher and around 5,000 ft. We're in the warm sector tonight and Saturday as the front lifts north and stalls over southern B.C. Temperatures on Saturday will be mild and in the lower to mid 50s. Rain chances increase on Sunday a cold front sags south into western WA. It will be breezy as well with gusts to 15 to 30 mph. Snow levels will drop Sunday night with a few inches of snow in the Cascades including both Stevens and Snoqualmie Pass. 33

LONG TERM /MONDAY THROUGH FRIDAY/

The weather pattern is cold and wet moving through next week with low snow levels. Strong, moist, westerly flow will hammer the mountains with potential for several feet of snow. Rates increase on Wednesday and Thursday which could make travel over the mountains difficult. Across the lowlands, with low snow levels, there is a rain/snow mix in the forecast Mon-Fri. The low level flow will remain onshore, though, which will help temperatures mostly stay above freezing and thus limit impacts. Snow levels will be rising on Wed and Thu and any snow would mostly affect areas close to the mountains. 33

AVIATION

A surface warm front will continue to pass through the terminals through the afternoon into tonight. Flow aloft will continue to remain northwest with this system with an upper level high well offshore. A mix of ceilings ranging from MVFR to LIFR as light rain moves through the terminals, continuing into Saturday. Ceilings expected to continue deteriorating overnight with the majority of terminals expected to go IFR/LIFR after 09Z. Improvement to MVFR for most terminals likely by Saturday late morning/early afternoon. Southwest winds 8-15 kt gusting to 20-25 kt for Puget Sound terminals tonight and will continue into Saturday.

KSEA...IFR cigs with lowered vis as light rain moves across the terminal tonight. Improvement into MVFR likely after 19Z. Light rain will continue through Saturday morning with activity tapering throughout the day. Southwest winds 10-15 kt gusting to 20 kt tonight into Saturday morning. Winds will increase Saturday afternoon with gusts greater than 25 kt likely (80-85% chance) after 21Z.

HPR/29

MARINE

A surface warm front will pass through the waters today into Saturday. No significant weather is expected with this first system, but rain and mist may lower visibilities to mariners at times. The flow pattern will remain largely onshore this weekend into next week. The next likelihood of impactful weather will come with the first trough of a progressive pattern later this weekend into next week. The next system Saturday night through Monday will send strong westerlies through the Strait of Juan de Fuca, with a medium chance of gale gusts occurring. The gusty winds are also expected to spread into the coastal waters, and the Admiralty Inlet with more confidence in the gusts affecting small craft at this time. Another system midweek next week will also produce gusty winds across all waters.

Seas through Saturday will range from 6 to 8 feet, further increasing to 9-12 ft Sunday through next week.

HPR

HYDROLOGY

Heavy precipitation over the Olympics will force rises on the Skokomish River with the potential for flooding late next week. No other river flooding is expected during the next seven days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...None.