textproduct: Seattle/Tacoma

SYNOPSIS

A low pressure system will descend from British Columbia tonight into Sunday, bringing precipitation to Western Washington. Conditions look to remain cooler and unsettled next week as additional systems move through the area.

SHORT TERM /TODAY THROUGH MONDAY/

High clouds starting to stream overhead across Western Washington early this morning. Temperatures continue to drop as well, with the latest observations showing temperatures in the low 30s to low 40s. A frontal system associated associated with a low pressure system just off the coast of British Columbia will move south into Western Washington this evening. Light precipitation is expected with this system, with rain reaching the coastline this evening and then filling into the interior by Sunday morning. The bulk of the precipitation is expected along the coast and the Olympics. The parent upper level low is expected to continue its southward track Sunday into Monday. The majority of models favor the center of the low pressure system moving into Oregon, which should render drier conditions for the region. However, shall center of the low track more towards the Oregon/Washington border, it may keep light showers in the forecast for Monday.

High temperatures in the mid to upper 50s. Low temperatures in the in the low 30s to low 40s increasing to the upper 30s to mid 40s by Monday.

29

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Conditions look to remain generally unsettled into Friday. There is general agreement among ensemble guidance a broad upper level trough will remain situated over the region Tuesday with a low pressure system to the north. Models are now trending wetter on Wednesday and Thursday, as the low pressure system moves southward. Cooler temperatures expected next week, with the coldest temperatures expected late in the week; high temperatures in the low to mid 50s and low temperatures in the low 30s to low 40s.

29

AVIATION

Westerly flow aloft will shift southwesterly and increase today as an upper trough digs southward into the Washington offshore waters. Areas of LIFR low clouds and surface visibilities below 3SM along the coast and across the Southwest Interior will dissipate by around 18Z as high and mid level moisture increases areawide ahead of the incoming system. Ceilings will lower to MVFR in light rain at times along the coast and across the far North Interior by around 00Z. After low clouds dissipate this morning, ceilings are expected to remain VFR across the interior from around KPAE southward into this evening.

KSEA...Confidence in VFR conditions this morning remains fairly high as temp/dew point trend and arrival of high clouds with incoming system limit any low cloud development. High and mid level clouds will lower and thicken through the day, but are expected to remain well within VFR thresholds. Surface winds southeasterly generally 7 knots or less this morning are expected to back to a more E/NE direction later this afternoon and evening as offshore system gets a little closer to the region.

27

MARINE

A surface low southwest of Haida Gwaii will shift southward today into tonight and an associated occluded front will clip the coastal waters on Sunday morning. Increasing easterly or southeasterly gradients will lead to small craft advisory winds across the coastal waters as well as the Strait of Juan de Fuca. Seas will build to 10 to 12 feet over the coastal waters late today into Sunday. The surface low is expected to move onshore over northwest Oregon Sunday night into Monday with winds easing and seas subsiding back below 10 feet. Another frontal system will shift southward into area waters on Wednesday.

27

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory from 11 AM this morning to 5 PM PDT Sunday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 5 PM this afternoon to 5 PM PDT Sunday for Central U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 8 PM this evening to 5 PM PDT Sunday for East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 3 PM this afternoon to 5 PM PDT Sunday for Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.