textproduct: Seattle/Tacoma

SYNOPSIS

Dry tonight and Monday as surface high pressure weakens. Next system moving down the British Columbia coast arrives on Tuesday. Weak upper level ridge building Wednesday. Possible system moving by to the north later Thursday into Friday. Strong upper level ridge building Saturday with the low level flow trying to turn offshore.

SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/

Latest satellite shows mostly clear skies across the CWA with split-flow aloft and surface high pressure. Cloud coverage will remain limited tonight as efficient radiation cooling ensues across the area. Patchy fog, primarily across river valleys is favored to develop with widespread overnight lows in the 40s. Can't rule out few areas flirting with the upper 30s.

Dry weather is favored to remain on Monday as surface high pressure weakens. High temperatures won't stray too far from average, typical for late September with highs in the 60s. On Monday night a frontal system will enter as rain develops along the coast and northern interior. Winds will become breezy with southerly gusts up to 25 to 35 mph with gusts near 40 mph across western Whatcom.

The aforementioned frontal system will progress through the remainder of the area on Tuesday as rain spreads over the region during the morning. Windy conditions continuing over the Northwest Interior. There is a chance wind advisories made be needed. Highs in the lower 60s. Rainfall will gradually diminish into the evening hours as conditions trend drier overnight.

McMillian

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Latest ensembles show a warming and drying trend through the end of the week into the weekend. An upper level ridge will build over the area for high temperatures in the mid 60s likely throughout the end of the week. Potentially, could even see even a 70 degree day over the weekend. Stay tuned!

Mazurkiewicz

AVIATION

A weak upper trough will shift east tonight with the flow aloft over western WA becoming more zonal. Skies are VFR with the trend continuing overnight for the interior. At the coast, expect shallow marine layer clouds pushing inland for MVFR conditions. Patchy low clouds or fog may form around the south sound early Monday. Increasing clouds Monday afternoon with rain reaching the coast after 00z Tue. 33

KSEA...VFR conditions through the period. N wind around 10 kt easing to 5 kt after 03z. 33

MARINE

The next frontal system arrives late Monday into Tuesday with increasing southerly winds over all waters - Small Craft Advisories are in effect. Winds will turn more westerly through the strait Tuesday afternoon. Meanwhile, expect elevated seas with swells reaching 10-11 ft. Onshore flow will ease late Tuesday night. The flow will then turn offshore on Wednesday with a thermal trough along the coast. Light offshore flow continues through the end of the week. 33

SEW WATCHES/WARNINGS/ADVISORIES

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