textproduct: Seattle/Tacoma

SYNOPSIS

Weak ridging will start to build into the region today for drier and warmer weather. The pattern will change again over the weekend as an upper- low digs over the offshore waters, bringing several rounds of lowland rain, mountain snow and gusty winds through early next week.

SHORT TERM /TODAY THROUGH SUNDAY/

Recent radar imagery shows some scattered showers along the offshore waters, along with some showers in the Olympics. Low temperatures this morning have been in the mid to upper 20s across much of the interior, with lower values especially in western Whatcom county where a Cold Weather Advisory continues this morning and with wind chill values between 15-20 F. Along with the cool temps this morning, with the isolated shower activity at the coast and the Olympics - could see a brief mix of rain/snow in these locations, but with showers continuing to dry out as a ridge builds, this chance will decrease in the next couple of hours.

Drier weather in store this afternoon along with relatively warmer afternoon temperatures in the mid 40s. Ensembles continue to show a pattern progression heading into the weekend, as the ridge axis will move eastward, allowing a upper level low to dig southward from the Gulf of Alaska and to meander over the waters of the west coast. This upper level low will push shortwave disturbances into the area, especially on Saturday, with the return of lowland rain and mountain snowfall with snow levels generally around 2000 to 3000 in the mountains. Winds will also increase on Saturday, with breezy easterly winds in the Cascade Gaps and along the coast. Temperatures will also feel warmer on Saturday, with afternoon highs in the upper 40s, maybe even reaching the lower 50s in some spots.

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/

The aforementioned low looks to continue to stay around Sunday and Monday, allowing precipitation to continue in waves. High temperatures will generally be in the low 50s for most of the region. The pattern continues to remain unsettled with multiple rounds of precipitation throughout the long term, especially with continuous mountain snowfall.

28

AVIATION

North to northwesterly flow aloft will more become westerly through the day as a weak transient ridge moves onshore. Conditions are VFR for all the terminals early this morning, with a drier airmass place in the lower levels. Should any MVFR ceilings develop this morning, they will likely remain south of KSEA, mainly impacting terminals like KOLM for a few hours. Otherwise, expect mostly VFR conditions to persist for the majority of the terminals through the day with mid to high cloud covering streaming in overhead. A few showers are expected to develop later this morning into this afternoon, but look to stay mainly west of Puget Sound. As a result, terminals along the coast may briefly see conditions drop to MVFR in any heavier shower activity. Surface winds are light this morning and have started to back to the east and southeast. Winds will remain light across the majority of the area, with a slight uptick to 8-12 kts expected along the coast.

KSEA...VFR conditions expected through the TAF period. A few light showers may drift into the vicinity of the terminal this afternoon, but do not expect much in the way of impact. Surface winds have started to transition back to the SE and remain light at 6 kt or less and look to remain so through the day.

14

MARINE

Light offshore flow will continue today with a broad surface trough over the coastal waters. Seas will generally hover between 4-7 ft. A strong system will move into the area waters over the weekend, increasing offshore flow and likely bringing gales to the coastal waters and portions of the inland waters throughout the weekend. Seas will build as a result, with the latest probabilistic guidance suggesting between a 60-80 percent chance of seas building into the 18 ft or larger range over the coastal waters this weekend, with a significant southerly contribution.

An active pattern will continue through the middle of next week as additional disturbances move across the area waters. Though not as strong as the system over the weekend, these system will likely bringing additional headlines to the area waters.

14

HYDROLOGY

No river flooding is expected over the next seven days but later next week chances increase significantly for flooding on the Skokomish River. Starting this weekend through next week there will be multiple rounds of widespread precipitation along with warming temperatures to raise the snow level. With the thin mountain snowpack and existence of low elevation snow, rain on snow could produce enough snow melt getting added to the otherwise unimpressive forecast precipitation amounts to result in flooding.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Cold Weather Advisory until 10 AM PST this morning for Lowlands of Western Whatcom County.

PZ...Gale Watch from late tonight through Sunday morning for Central U.S. Waters Strait Of Juan De Fuca-West Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Watch from late tonight through Sunday afternoon for East Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Watch from late tonight through late Saturday night 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 James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.