textproduct: Seattle/Tacoma

SYNOPSIS

Southwest flow aloft will maintain warm and dry conditions through Wednesday. A weak, dry trough will pass over the region towards the end of the week, promoting onshore flow and bringing in cooler temperatures through the holiday weekend. Zonal flow will develop by the beginning of next week, maintaining mild and dry conditions across western Washington.

LONG TERM /SATURDAY THROUGH TUESDAY/

Zonal flow aloft will develop over the Pacific Northwest over the weekend and into early next week as a cutoff low strengthens over northern California. This will result in continued mild conditions and mostly clear skies throughout the holiday weekend and beyond. With this pattern, this opens the door to the chance of a few light showers near the northern coast and the North Cascades over the weekend, although the chance of any precipitation remains fairly low at this point. Ensembles indicate some potential for high pressure to rebound over the western US towards the middle of next week, which could result in another warm-up across western Washington, but the exact details remain uncertain at this time.

15

AVIATION

Upper level ridge to the east with weak trough developing offshore giving southwesterly flow aloft over the area through Wednesday. In the lower level, there is increasing onshore flow this evening. It remains VFR across most of western WA this evening (with the exception of the coast as low stratus has already arrived into KHQM with BKN007 being reported as of 03Z). The low stratus with tonight's marine push will continue to advance eastward. IFR/LIFR conditions are expected along the coast (but no further than the Olympics), with a good chance that MVFR stratus will reach Puget Sound terminals early tomorrow morning (12Z-15Z). The stratus will clear out likely by 18-19Z due to southwest flow making it down to the surface overnight, with most surface winds switching from north to south overnight, and another push through the Strait of JDF will turn the winds northwesterly through the afternoon amd evening of 6 to 10 kt before becoming lighter and southwesterly through the evening.

KSEA...VFR with mostly clear skies this evening (might be some higher cirrus at times). Winds continue out of the north-northeast at around 10 kt with a couple gusts possible through dusk. Currently NBM gives a 30% chance of MVFR stratus reaching the terminal Wednesday morning between 12-15Z, with anticipated ceiling heights being from 1,500-2,000 ft. Given the switch of winds to the southwest (as flow aloft reaches the surface), skies will likely clear after 17-18Z. Diffluence from a marine push to the north will likely turn winds north after 00Z Thursday for a few hours through the evening, becoming light and back to southwest by dusk.

Kristell/HPR

MARINE

High pressure will remain in place across the coastal and offshore waters this week with thermally induced low pressure east of the Cascades. A weak front will dissipate over the offshore waters Wednesday.

Diurnal westerly pushes through the Strait of Juan de Fuca each evening. The gale warning tonight for the Central and Eastern Strait with small craft advisory northwesterlies in Admiralty Inlet have been left in place. Late day small craft advisory westerlies possible in the Strait each evening into the weekend.

21

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Gale Warning until 3 AM PDT Wednesday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory until 5 AM PDT Wednesday for Admiralty Inlet.