textproduct: Seattle/Tacoma

SYNOPSIS

High pressure aloft will begin to rebuild across Western Washington on Wednesday and remain in place into Friday for a return to some sunshine and warmer temperatures. The ridge will weaken over the upcoming holiday weekend for a cooling trend and a chance of rain by Memorial Day.

SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/

A building upper ridge on Wednesday will lead to clearing skies and warmer temperatures. The ridge remains firmly in place offshore into Thursday with low level onshore flow weakening. Interior temperatures will warm a few degrees, but coastal area temperatures will likely stay fairly static with night and morning clouds hanging around and an afternoon sea breeze.

LONG TERM /FRIDAY THROUGH TUESDAY/

The upper ridge axis offshore begins to weaken on Friday with low level onshore flow picking up a notch late in the day. Interior temperatures should be similar to those of Thursday...upper 60s to mid 70s...while coastal areas remain mostly in the lower 60s. The ridge is expected to flatten by Saturday for slightly cooler temperatures to begin the weekend.

The weekend looks like a tale of two halves. Ensemble height anomalies agree that a deepening upper trough over the Northeast Pacific will begin a transition toward cooler temperatures and possible precipitation, but the speed of transition is up for debate. In general, the Euro and Canadian suite of solutions are more agressive with the troughs arrival while the GFS is less so. Sunday should feature additional cooling and cloud cover with precip chances increasing areawide Sunday night into Memorial Day.

27

AVIATION

Upper ridging offshore will continue to lead to N/NW flow aloft over western Washington for the entire TAF period. Some differences in surface flow...while the majority of terminals are seeing westerly to northwesterly winds, PWT is favoring an easterly direction while BLI is more southerly. Speeds ranging 4-8 kts although HQM is running closer to 8-12 kts this evening. A universal transition to north to northwesterly winds expected by 06Z tonight and remaining that way into late Wednesday morning with speeds generally 5 kts or less. Most terminals expected to remain northerly, with some variations to the NE or NW, but will see speeds increase to range mostly 5-10 kts.

VFR conditions hold court over the eastern half of the CWA while MVFR cigs in place from CLM and points west. Low clouds expected to push westward through the night with widespread MVFR expected by 12Z Wednesday morning /IFR for terminals more prone to lower cigs/. Lifting looks to kick in during the 18-20Z time frame with widespread VFR conditions returning. The strengthening ridge will make life difficult for any low-level clouds, scattering out the lower altitudes leaving only SCT to BKN high clouds by Wednesday evening.

KSEA...VFR conditions this evening into tonight with W to NW winds 4 to 8 knots, becoming more northerly after 06Z. Mid to high level clouds before MVFR conditions return late tonight and lasting throughout Wednesday morning. VFR conditions returning around 18z- 20z.

18/Mazurkiewicz

MARINE

Surface high pressure offshore will continue onshore flow throughout the area waters through majority of the week. A small craft advisory remains in effect for all outer coastal water zones, mainly for elevated seas. Can expect another westerly push down the Strait of Juan De Fuca tonight, where a small craft advisory is also in effect. Diurnally driven pushes down the Strait expected through the end of the week. A system on Friday and Saturday could bring a round of elevated seas and winds to the coastal waters.

Coastal seas 6 to 8 feet this evening will increase to 8 to 10 feet tonight into Wednesday. Seas will then level to 7 to 9 feet throughout Thursday, before rising above 10 feet Friday and into the weekend.

Mazurkiewicz/18

HYDROLOGY

The daily hydrology discussion has ended until the start of the next rainy season; it will only be updated during this time as needed.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 5 AM PDT Wednesday for Central U.S. Waters Strait Of Juan De Fuca-Coastal Waters From Cape Flattery To James Island 10 To 60 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-East Entrance U.S. Waters Strait Of Juan De Fuca.