textproduct: Seattle/Tacoma

SYNOPSIS

Zonal flow to weak ridging aloft and onshore flow at the surface will maintain seasonably warm conditions across western Washington through much of the week, with morning clouds and fog followed by afternoon sun breaks. Chances for rain increase towards Friday into the weekend alongside cooler temperatures as troughing develops over the Pacific Northwest.

SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/

The overall weather pattern look to remain fairly similar through Thursday as mostly zonal flow trends towards slightly higher 500 mb heights by mid-week as the ridge over the southwestern U.S. expands. What that translates to for the Pacific Northwest is a routine pattern of morning clouds and fog, giving way to sunnier afternoons with high clouds overhead. Chances for fog will be greatest today as light winds will this afternoon and tonight, and continued moisture will help promote the redevelopment of the marine layer and areas of dense fog. Slightly stronger winds Tuesday and Wednesday may help to trend things towards stratus and less fog by mid-week, but areas of patchy fog will still remain possible in the sheltered valleys.

Temperatures will remain seasonably warm across the area with highs in the mid 60s to low 70s. Lows remain in the upper 40s to mid 50s.

LONG TERM /THURSDAY THROUGH MONDAY/

Upper level ridging looks to gain its greatest influence across Washington on Thursday, therefore also forecast to be the warmest day of the week with highs in the upper 60s to mid 70s.

Most models agree on the development of an upper level trough digging into the Pacific Northwest Friday into the weekend. There will be some slight chances for showers across portions of the area but widespread rain does not look very likely with this system. There remains some uncertainty in the exact timing but Friday into Saturday have the best chances at this time. But an increase in clouds and an increase in winds is to be expected. Cooler temperatures also looks to be in store with highs dipping into the upper 50s to low 60s this weekend, with lows in the upper 30s to mid 40s.

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AVIATION

Onshore flow will continue through the TAF period. This morning's fog and low clouds continue to clear this afternoon, though a few pockets of MVFR ceilings remain in the south interior, the Pacific Coast, and north interior terminals. Conditions will continue to improve to VFR through the evening. Overnight: another round of fog/low stratus is likely with the next marine push, beginning as early as 06-10Z in west/central terminals, and likely lasting through 18-21Z before clearing. Winds will switch to the north/northeast at 4-6 kt for most south of the Strait of Juan de Fuca this afternoon/evening. A few gusts to 16 kt will continue in portions of the north interior through the evening. Light/calm winds are expected tonight/Tuesday morning before increasing out of the north 4-8 kt.

KSEA...Conditions improving to VFR this afternoon/early tonight with high clouds. Winds will switch to the north/northeast this afternoon at around 5 kt before becoming light/calm. Fog/low LIFR stratus remains likely to reach the terminal again as early as 10Z, and likely lasting through 18-21Z before improving to VFR.

HPR

KSEA...

MARINE

Onshore flow will likely continue through the week with high pressure remaining offshore. Several areas of fog will be likely next couple of mornings with ample moisture in each of the pushes. A weak push this afternoon is expected to bring wind gusts up to 15-20 kt in the central Strait of Juan de Fuca. The southwestern coastal waters will also see pockets of similar wind gusts through the first part of the week. The next organized frontal system on Friday will likely bring small craft winds to the coastal waters, and a chance for gale gusts to portions of the Strait of Juan de Fuca.

Seas through Wednesday hold at 4-6 ft, and increase to 6-10 ft late this week with the late week systems passing through.

HPR

SEW WATCHES/WARNINGS/ADVISORIES

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