textproduct: Seattle/Tacoma

SYNOPSIS

Another round of onshore flow and stratus clouds are expected today, with light drizzle expected at times. High pressure noses back in Wednesday and Thursday for clearing skies and warming temperatures. Increased cloud cover is again expected late in the week as a dry front moves through the region. Stronger high pressure and offshore flow is indicated for next week.

SHORT TERM /TODAY THROUGH THURSDAY/

Nighttime satellite products show lower clouds and stratus across western Washington as onshore flow continues. Expect another day of clouds and isolated pockets of drizzle today with cooler temperatures in the upper 50s and low 60s. Afternoon highs from Wednesday through the end of the week are suggestive of minor HeatRisk. After today, high pressure builds into the area for the middle of the week, gradually decreasing the cloud cover and bringing the temperatures back into the upper 60s and even low 70s by Thursday. Outside of diurnal westerly winds through the Strait of Juan de Fuca, much of the Puget Sound region should see light northerly winds.

A dry front will progress through on Thursday as the high pressure scoots east, bringing clouds back in the later half of the day.

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/

After the dry front moves through late Thursday, clouds and onshore flow are expected to linger into Friday, cooling the temperatures a few degrees into the mid 60s. Skies clear and conditions quickly warm up over the weekend, with temperatures near 80 possible by Sunday. Probabilistic HeatRisk guidance is suggestive of those temperatures corresponding to at least a 20-30% chance of the moderate category in the Seattle-Tacoma Metro area, with greater chances west of Olympia and into the western Puget Sound region. This forecast can and will change and the corresponding HeatRisk metrics will continually be assessed.

The extended range forecast is suggestive of the development of an amplified ridge along the west coast that extends into next week. As the high strengthens, a thermal trough will develop along the coast and aid in those temperatures getting up to around 80 through Monday, gradually cooling off into the 70s on Tuesday.

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AVIATION

High pressure remains offshore today with low level onshore flow at the surface. A weak disturbance in the north flow may generate isolated light showers, mainly along the coast and in the mountains. Ceilings are a mixed bag with VFR and pockets of MVFR conditions. The trend is for lifting and scattering of low clouds today but still remain SCT-BKN around 5000 ft. Clouds will continue to lift and gradually scatter overnight and into Wednesday morning. 33

KSEA...SCT-BKN ceilings around 5000 ft today with brief MVFR conditions possible this morning. S/SW wind around 10 kt becoming W and NW/N around 5 kt after 00z. 33

MARINE

High pressure remains offshore with lower pressure inland, maintaining onshore flow. A stronger onshore push is forecast down the Strait of Juan de Fuca Thursday afternoon and evening with cold front. 33

HYDROLOGY

No river flooding is expected over the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES

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