Marine Weather and Tide Forecast for Mercer Island, WA

SHORT TERM /TODAY THROUGH SUNDAY/
Satellite imagery shows upper level ridge axis just east of the area this afternoon with high clouds ahead of the next trough moving into the northwest portion of the state. Already have some 70 degree plus temperatures in the south Puget Sound and Southwest Interior at 3 pm. Temperatures over the remainder of the area in the 60s. It's a warm day today but not as warm as it was 9 years ago on this day. Seattle, high of 89 degrees, Olympia, high of 88 degrees and Bellingham, high of 83 degrees all set records for the warmest day ever in April.

Upper level ridge continuing to move east tonight with the upper level trough moving inland early Saturday morning. Cloud tops with the trough axis already warming this afternoon. A good sign the feature is weakening. Increasing clouds later tonight with just a slight chance of showers late this evening into early Saturday morning. Cloud cover will keep lows in the lower to mid 40s.

Not much going on Saturday with Western Washington in between troughs. Air mass slightly unstable by afternoon combined with weak convergence over the Central Puget Sound could produce a light shower. The main weather story Saturday will be more cloud cover and much cooler temperatures with highs only in the mid 50s to lower 60s.

Another upper level trough sagging south along the British Columbia coast Saturday night will arrive in Western Washington Sunday. Shower activity increasing late Saturday night into Sunday morning with the showers continuing into the afternoon hours.
Northwesterly flow aloft will rain shadow the Central and Southern Puget Sound initially. Cooling trend remaining intact with highs only in the 50s. Lows Sunday morning in the lower to mid 40s.

Post trough convergence zone forming Sunday evening. With the northwesterly flow aloft, the zone will be a little further south than its favored location, settling up right over King county.
Snow levels down to at least 3500 feet by this point. Could see a couple of inches of snow at Stevens Pass and maybe Snoqualmie Pass if the precipitation rates drive the snow level down a little further. Folks coming back to Western Washington late Sunday evening over the passes should be prepared for winter driving conditions. The convergence zone will dissipate early Monday morning. Lows in the mid 30s to lower 40s.

LONG TERM /MONDAY THROUGH THURSDAY/
Extended models in good agreement with little in the way of weather Monday. Northwesterly flow aloft over the area with the air mass beginning to dry out.
Could see isolated showers lingering in the morning hours especially in the Cascades otherwise just a mostly cloudy day.
Highs in the 50s.

Dry upper level trough moving down from the north Tuesday, we saw one of these earlier this week, will actually dry the air mass out over the area. Even with the sunny skies highs will just be near normal, mid 50s to lower 60s. Lows on the cool side Tuesday morning with colder locations in the Southwest Interior having the potential to drop to freezing. For the remainder of the area mid 30s to lower 40s.

Upper level ridge building Wednesday with northwesterly surface gradients. Highs a little bit warmer, in the upper 50s to mid 60s.
Another cool morning with lows mostly in the 30s.

Models having trouble with the Thursday and Friday time frame.
Solutions varying between and upper level ridge over the area and a negatively tilted trough moving into the area from the south Friday. The negatively tilted trough scenario was in the models a few runs ago, disappeared for a couple of runs and now it's back again on the 12z run. Ensemble solutions trending towards a wetter solution for Friday, especially the GFS. There is a small, less than 10 percent, number of the ensemble solutions indicating heavier precipitation Friday hinting at possible thunderstorm activity. At this point with much uncertainty will go with the old mostly cloudy chance of showers forecast Friday and keep Thursday dry with highs in the 60s. Felton

AVIATION
A departing upper level ridge will be followed quickly by a subtle shortwave trough moving through tonight into Saturday morning. Winds aloft primarily W to NW. VFR conditions will prevail through this evening for all locations.

MVFR conditions will develop on the coast as early as this evening ahead of an incoming front. For the interior terminals, ceilings will slowly lower this evening, becoming MVFR overnight as the front moves through. VFR conditions look to quickly return to the coast behind the front (around 12-15Z Saturday), with low clouds hanging on through the interior through 18Z Saturday before conditions return to VFR. Overall, this front will be mostly dry with no significant precipitation expected.

Most terminals seeing light southwesterly winds this afternoon. A westerly push down the Strait of Juan de Fuca this afternoon will allow for winds reaching 10-15 kt with gusts up to 20-25 kt possible at CLM. Winds look to remain west to southwesterly going into Saturday, but will increase to 8 to 12 kt.

KSEA...VFR conditions through this evening. High-end MVFR cigs develop early Saturday morning with the frontal passage, slowly breaking up and lifting to VFR after 18Z Saturday morning. Light southwesterly winds look to switch to light northerly to northeasterly this evening. Winds return to west/southwesterly tomorrow, increasing to around 5 to 10 kt.

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MARINE
A weak front across the northeast Pacific will move southeastward across the coastal waters tonight into early Saturday morning. A westerly push down the Strait of Juan de Fuca this afternoon and evening ahead of the front, which will spill into Admiralty Inlet as well. Northwesterly winds will begin to develop tonight across the coastal waters, as well as in the Strait of Georgia north of the San Juans. Winds will peak in these aforementioned locations Saturday morning and will ease Saturday evening. Another westerly push, behind the front, down the Strait of Juan de Fuca looks possible again Saturday afternoon.

Small Craft Advisories have been issued for these winds through Saturday evening.

Another weaker system looks to traverse the area waters on Sunday, which may prompt another round of headlines for the coastal waters and Strait of Juan de Fuca. Following, broad high pressure looks to regain control, maintaining light north-northwest winds across the waters going into next week.

Seas 5 to 7 ft this afternoon will build to 10 to 13 ft early Saturday. Seas will be steep with a dominant period of 8 to 9 seconds. Seas ease to around 6 to 7 ft early Sunday. The front on Sunday afternoon may push seas back to around 8 to 10 ft. Seas will ease into next week, remaining around 4 to 6 ft.

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HYDROLOGY
No river flooding in the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES
WA...None.
PZ...Small Craft Advisory until midnight PDT tonight for Central U.S.
Waters Strait Of Juan De Fuca.

Small Craft Advisory until 2 AM PDT Saturday for East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 6 PM this evening to 8 AM PDT Saturday for Northern Inland Waters Including The San Juan Islands.

Small Craft Advisory from 6 PM this evening to 2 AM PDT Saturday for Admiralty Inlet.

Small Craft Advisory from 8 PM this evening to 11 PM PDT Saturday for Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.

Small Craft Advisory until 11 PM PDT Saturday for 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.