textproduct: Seattle/Tacoma

SYNOPSIS

Dry conditions will continue across Western Washington through Friday, with a gradual warm up in temperatures peaking on Friday. Clear skies and cool overnight temperatures will allow for frost development across portions of the region this morning. Cooler and precipitation chances return this weekend. Slightly drier conditions early next week before a stronger system arrives on Wednesday.

SHORT TERM /TODAY THROUGH SATURDAY/

Satellite imagery shows clear skies early this morning. Current temperatures are in the upper 30s to low 40s across Western Washington. Clear skies and light winds will promote effective radiational cooling, allowing temperatures to continue decreasing this morning. The coldest spots will be locations in the southern interior and Cascade foothills, where temperatures are expected to decrease into the mid to low 30s. As a result, frost development is expected this morning, with a Frost Advisory remaining in effect through 9 AM.

Weak upper level ridging over the region will keep conditions dry and warmer through Friday. Temperatures will rebound this afternoon and give way to a nice afternoon with clear skies and temperatures in the low 60s along the coast and upper 60s to low 70s in the interior. Temperatures on Friday will be similar to Thursday, but expect cloud cover to increase throughout the day.

Ensemble guidance has come to good agreement that a low pressure system descending from the Gulf of Alaska will move into northern California. As this system moves through California, it will advect moisture into Western Washington and bring precipitation back into the region. In addition, expect cooler temperatures with this system. High temperatures will be in the low 50s along the coast and upper 50s to low 60s in the interior.

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LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/

Unsettled conditions will continue through the weekend as the previously mentioned low pressure system continues to move through California. Snow levels with this system will remain above pass level. On Saturday snow levels start around 6000-6500 ft and by Sunday will drop down to 5000-5500 ft. Precipitation with this system is expected to be light.

Slightly drier conditions on Monday as weak ridging builds over Western Washington. There is some uncertainty on Tuesday regarding the upper level pattern. However, the majority of ensemble members favor the upper level ridge to remain in place through Tuesday. As a result, this has pushed the next system to arrive on Wednesday, with guidance being in good agreement for a trough to move through the region. High temperatures next week will be in the low to mid 50s and low temperatures will be in the 40s.

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AVIATION

An upper ridge remains offshore with continued north to northwest flow aloft today. Flow will transition more southerly tonight into Friday as an upper low slowly moves towards the CA coast. VFR conditions continue through the TAF period with high clouds at times. Localized fog may develop in valley areas this morning, mainly impacting PWT, OLM, and HQM. However, latest probabilistic guidance keeps LIFR conditions only around 10% for these sites this morning, peaking between 12 to 16z. Light north winds will increase towards 5 to 10 kts by midday.

KSEA...VFR conditions through the TAF period. North winds around 5 to 8 kts this morning, increasing to around 10 kts by midday and continuing through the afternoon. JD

MARINE

North winds will continue over the coastal waters through Friday with high pressure over the NE Pacific. A low pressure system will develop over open waters on Friday and move south into northern California. High pressure will rebuild on Monday. A frontal system will then move through area waters Tuesday into Wednesday. Guidance is hinting at a low to moderate chance (40-60%) for small craft winds for the coastal waters, and West and Central Strait of Juan de Fuca.

A diurnal push of westerlies through the Strait of Juan de Fuca will begin to develop over the weekend and into early next week. There is a low to moderate chance (35-55%) of winds reaching small craft thresholds on Monday.

Seas will remain below 10 ft into early next week before approaching 10 ft on Wednesday.

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HYDROLOGY

No river flooding is expected in the next seven days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Frost Advisory until 9 AM PDT this morning for Downtown Everett / Marysville Area-Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Thurston and Lewis Counties-Lowlands of Lewis and Southern Thurston Counties-Middle Chehalis River Valley- Olympia and Southern Puget Sound.

PZ...None.