textproduct: Seattle/Tacoma

SYNOPSIS

Dry with warmer than normal daytime temps will linger through Wednesday. A weak system Thursday will bring increased clouds, near normal temperatures and a few light showers. Dry and continued near normal temperatures Friday, followed by a chance of a weak system over the weekend.

SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/

Dry with near-normal to slightly cooler than normal overnight lows tonight. Lighter winds into Wednesday morning will allow for more early morning patchy fog formation in sheltered locations. Morning shallow stratus/fog should lift and scatter late morning with another warm October day. A weak upper level system continues to be expected to brush the area Thursday. The main impact will be more cloud cover and near normal temperatures. High resolution ensembles like the REFS showing very limited, shortlived showers mainly in the Olympics and north Cascades Thursday afternoon and evening.

LONG TERM /FRIDAY THROUGH TUESDAY/

Ensembles in fair alignment with the overall pattern Friday becoming more zonal but dry Friday. For the weekend, ensemble clusters in good agreement with the overall pattern indicating an upper level trough moving across the NE Pacific and Gulf of Alaska Friday night, then shearing into a more consolidated trough moving into British Columbia Saturday and a trailing upper level low over the eastern Pacific. The grand ensemble showing good agreement on the overall idea of this upper level trough moving south and east through British Columbia itself or along west along the BC into Western Washington Saturday night into Sunday. Nearly half (48%) of the ensemble members favor the more direct approach with a more consolidated trough. The remaining 52% show either slower more northerly track or even offshore track for the trough. The more consolidated track would result in a more organized, but likely weak system moving through the area Saturday night into Sunday, where the northerly/offshore scenarios would likely result in more limited precipitation brushing the area Sunday or even delayed into Monday. The overall pattern early next week looks fairly evenly split with 49% of the grand ensemble showing some degree of ridging early in the week, and 51% some degree of troughing.

AVIATION

An upper level low continues to spin off CA with dry and stable conditions across western WA. The flow aloft is southwesterly. Patchy, shallow, fog will likely develop in the interior Wednesday morning for a brief period of LIFR conditions. Fog will scatter out by 18-20z for a return of VFR conditions. 33

KSEA...VFR conditions continue this afternoon and evening. A brief period of shallow/patchy fog is possible early Wednesday morning for LIFR conditions. Otherwise, VFR expected by the afternoon. N wind to 10 kt, becoming NE 5 kt overnight, then light and variable Wednesday morning. Winds Wednesday afternoon will be more W to NW around 5 kt. 33

MARINE

Weak high pressure will lead to generally light winds over the waters through Wednesday. Onshore flow will increase on Thursday as a cold front moves inland. Seas will build to 10-15 ft Thursday night then gradually subside under 10 ft on Friday. The flow will turn offshore this weekend as a thermal trough forms along the coast. Low pressure will weaken over the offshore waters early next week. 33

SEW WATCHES/WARNINGS/ADVISORIES

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