textproduct: Seattle/Tacoma

SYNOPSIS

Zonal flow aloft into Friday with precipitation chances along the northern portions of Western Washington. Warm, dry conditions over the weekend as an upper ridge builds over the Pacific Northwest. Onshore flow returns early next week with the return of near normal temperatures but continued dry conditions.

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/

West flow aloft continues into Friday with a building upper level ridge across the majority of the Western US. A weakening weather system will move across the northern periphery of the ridge into BC into Friday, resulting in continued mid and high clouds at times. Although the majority of precipitation will remain in BC, light rain at times may occur along the northern Olympic Peninsula and Whatcom County into midday Friday. Otherwise, temperatures remain near to slightly above normal through Friday.

The upper ridge builds further across Western Washington Friday night into the weekend resulting in dry conditions and warming temperatures. Stratus and areas of fog are expected Saturday morning around Puget Sound with relatively light north winds. Clouds will clear for sunny conditions in the afternoon. Temperatures Saturday will peak in the mid 60s to mid 70s, and even in the low 80s in the Cascade Valleys under light offshore flow.

LONG TERM /SUNDAY THROUGH THURSDAY/

The upper ridge will remain in place over the majority of the Western US on Sunday, resulting in temperatures being a few degrees warmer by Sunday afternoon, and continued dry conditions. Ensembles are consistent in the ridge beginning to flatten over Western Washington on Monday, with onshore returning, and a slight cooling trend in temperatures along with increasing morning stratus. Dry conditions are expected into midweek though with continued ridging influence. JD

AVIATION

Westerly flow aloft continues through Friday with an upper ridge across the Southwest US and a weakening frontal system moving into British Columbia. Widespread VFR mid and high clouds this afternoon with light rain along the BC border. VFR cigs into this evening with IFR/LIFR stratus developing late tonight along the coast. Stratus will slowly slide into southern Puget Sound early Friday morning. At this time, MVFR/IFR stratus is expected to mainly remain from the Kitsap Peninsula westwards, with lower probabilities for stratus east of Puget Sound. Otherwise, clouds will lower towards MVFR Friday AM at KBLI near the front. Mainly VFR Friday afternoon, with continued stratus along the Olympic Peninsula. Light winds increasing from the S/SW Friday afternoon.

KSEA...VFR high clouds into tonight. Stratus will move inland towards southern Puget Sound early Friday AM. At this time, MVFR/IFR stratus is expected to remain west of the terminal. However, there is a 20% probability of IFR cigs between 13 to 18z Friday. Otherwise, VFR mid and high clouds on Friday. Light NW winds, less than 5 kts, into tonight, before winds transition S/SW between 07-09z and increase Friday. JD

MARINE

High pressure continues across the waters this week. A weak front will move north of the area into Friday, but little in the way of wind impacts are expected. A thermal trough builds Saturday bringing northerly to offshore winds Saturday and Sunday. Onshore flow returns late Monday with a westerly push through the Strait of Juan de Fuca Monday evening. Generally light flow then returns into midweek. Seas are expected to remain between 4 to 6 feet through early next week. JD

FIRE WEATHER

Fire weather concerns remain minimal through the next few days. Developing high pressure aloft this weekend with a thermal trough building up the coastline will bring warm temperatures and light offshore flow. This could result in locations in the Cascades and adjacent valleys seeing minimum RH values approach 30% on Sunday. This will be short lived, with onshore flow returning early next week to boost humidity values and cooler temperatures.

SEW WATCHES/WARNINGS/ADVISORIES

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