Marine Weather and Tide Forecast for Des Moines, WA

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/
Radar is picking up a few residual showers near the coast this evening, but these should diminish as a weak upper ridge just offshore begins to build into the area. Current frost advisories look on track. We could see another round of chilly temperatures in the same areas again Saturday morning before temperatures moderate over the weekend. No change in the short range forecast as upper low cuts off to our southwest this weekend. That's spring for you.
Previous forecast discussion follows with updates to marine and aviation portions. 27

Dry conditions return this afternoon with a mix of sunshine and cumulus. Temperatures will remain in the cooler side today, with highs in the 50s. Temperatures will fall again tonight into the low 30s to low 40s, with the coldest temperatures from Olympia southwards. Have issued a Frost Advisory for portions of the Southwest Interior and southern Cascade Foothills and Valleys as temperatures drop between 33 to 36 degrees. Low clouds may also develop early Friday AM which may inhibit frost development elsewhere, however, additional Frost Advisories will need to be monitored. Otherwise, weak ridging continues to build into the area on Friday resulting in dry conditions, and some sunshine.

An upper low will approach the Pacific Northwest well offshore on Saturday. Dry conditions will likely continue for the majority of western Washington through Saturday afternoon.
However, precip potential begins to increase late Saturday into Saturday night along the Olympic Peninsula with the aforementioned upper low offshore. High clouds will spread overhead on Saturday as temperatures warm into the 60s. JD

LONG TERM /SUNDAY THROUGH THURSDAY/
The upper low will slide southwards offshore Sunday into Monday. At this time, precipitation is expected to be confined to the Olympic Peninsula on Sunday, with dry conditions continuing for interior locations. Predominantly drier conditions on Monday with the upper low positioned well to the south along the northern California coast. Precipitation chances increase slightly Tuesday and Wednesday with wrap around moisture associated with the upper low as it moves inland. Ensembles then suggest drier conditions begin to prevail late next week. Temperatures will warm into the mid 60s to low 70s Sunday and Monday, with areas of minor HeatRisk across southern and central Puget Sound.
Otherwise, conditions cool a few degrees for midweek. JD

AVIATION
Northerly winds aloft in the wake of an exiting upper trough and as an upper level ridge builds over the eastern Pacific. Surface winds generally southwesterly, however CLM, OLM and HQM favoring a more westerly to even northwesterly direction at times this evening.
Increased winds in the Strait will have some impact on PAE as winds will shift northerly late this evening/early tonight. More widespread northerly are expected for most terminals by late Friday morning.

Widespread VFR conditions this evening, although there is medium to high confidence (40-80%) that MVFR cigs will return tonight into Friday morning. Highest chances for MVFR conditions will be north of PAE. All terminals expected to recover to VFR after 18Z Friday.

KSEA...VFR cigs this evening and into tonight. MVFR cigs possible (40-60% chance Friday morning) between 11Z-18Z. While some models have backed away from this solution for the terminal, there is at least enough uncertainty to warrant high-end MVFR in the TAF at this time. VFR cigs return by Friday afternoon. SW winds this evening at 6-10 kt will shift SE overnight at 4-6 kt. becoming northerly after 16Z-18Z Friday.

18/29

MARINE
Confidence has increased, now greater than 70%, with the latest high- resolution guidance for the westerly push through the Strait of Juan de Fuca meeting small craft criteria. Therefore, a Small Craft Advisory remains in effect for the Central and Eastern portions of the Strait of Juan de Fuca. Some spillover could impact portions of the Admiralty Inlet zone, so they will remain in the inherited SCA as well. High pressure will continue building over area waters through early Saturday, before it weakens later that day with the next frontal system arriving. Conditions with this system look to remain below small craft criteria at this time, with current probabilities ranging between 30-50% of winds exceeding 21 kt for the coastal waters. Seas will build slightly this weekend and into early next week to 4-7 ft this weekend, with the highest seas over the outer coastal waters. While seas will remain below 10 ft, seas will be steep as the dominant period will be around 7 to 8 seconds.

Grays Harbor bar is expected to enter a period of very strong ebb currents over the next few days. While seas will continue subsiding, seas may remain rough around the ebbs the next few mornings.

29/18

HYDROLOGY
No river flooding is expected over the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES
WA...Frost Advisory from 1 AM to 9 AM PDT Friday for Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Thurston and Lewis Counties-Lowlands of Lewis and Southern Thurston Counties-Middle Chehalis River Valley-Willapa and Black Hills.

PZ...Small Craft Advisory from 5 PM this afternoon to 3 AM PDT Friday for Central U.S. Waters Strait Of Juan De Fuca- East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 8 PM this evening to 3 AM PDT Friday for Admiralty Inlet.