textproduct: Seattle/Tacoma

SYNOPSIS

An upper low will continue to linger over Western Washington through Friday for periodic showers in the lowlands, light snow shows in the mountains, and cooler temperatures. Conditions will trend drier over the weekend with temperatures remaining cool, especially overnight.

SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/

An upper level low continues to hover offshore maintaining showers around western Washington this afternoon. Cooler temperatures in the low 50s within the post frontal airmass. Additionally, there is chance (15-20%) of a thunderstorm or two late this afternoon due to the unstable environment. Thunderstorm chances greatly decrease early evening as the sun sets. Snow showers continue in the Cascades but has greatly decreased in coverage since this morning, and will continue as the Winter Weather Advisory remains out until 5PM. Most of the accumulations will be in and around Mount Rainier.

The aforementioned upper level low will not move much into Thursday and Friday, keeping scattered showers around in the lowlands and light snow accumulations in the Cascades. Overall precipitation will trend downwards, but can't rule out stray showers at times with most of the area remaining somewhat dry. Afternoon temps in the low to mid 50s.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Ensembles are agreeing in the low weakening into the weekend, with conditions becoming drier over western Washington. There may be a shower or two in the Cascades, but overall most of the interior looks to be dry over the weekend with high temperatures in the mid 50s. Overnight lows look to become cooler in the low to mid 30s, with some locations even seeing mid to upper 20s, particularly in the Southwest Interior. Weak ridging will allow conditions to likely remain dry heading into midweek.

Mazurkiewicz

AVIATION

An upper low remains over the region with widespread rain showers across the area through the evening. Expect continued breezy winds from the south/southeast with gusts to 20 kt this evening. An isolated thunderstorm remains possible (15% chance), but more likely impacts will be heavy rain and reduced ceilings/visibility under stronger showers as they move across the area. Otherwise, little change through the night with gradually decreasing showers after this evening. Stratus becomes increasingly likely with 30-40% likelihood for MVFR ceilings across much of the interior Thursday morning, while guidance suggests IFR conditions at KOLM.

KSEA...VFR conditions expected to prevail with gusty southerly winds through the evening. Showers remain around the terminal area and could bring a brief lowering if these move over the airport. Otherwise, winds easing overnight with showers decreasing. The potential for MVFR ceilings increases by 12z through the morning Thursday.

MARINE

Seas have peaked across the coastal waters earlier this morning, but remain quite steep with dominant periods around 8 to 9 seconds. As a result, a small craft advisory remains in effect for these areas through the evening. Expect both the seas to decrease and the dominant period to lengthen, so this should be good to expire by the end of the night. Elsewhere, conditions on the Grays Harbor bar are expected to worsen around a very strong ebb this evening as seas steepen and build, so an advisory has been issued here as well.

Looking ahead, seas will likely build early next week back to around 10 ft with the arrival of a long period swell into the coastal waters.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Winter Weather Advisory until 5 PM PDT this afternoon 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...None.