Marine Weather and Tide Forecast for Black Diamond, WA

SYNOPSIS
A passing disturbance will bring stronger onshore flow and additional showers across the region today. Transient high pressure builds late Wednesday through Thursday, but the next frontal system quickly follows. An unsettled weather pattern will remain in place across the Pacific Northwest this weekend through early next week, maintaining widespread clouds and rain showers.

SHORT TERM /TODAY THROUGH FRIDAY/
Widespread low clouds across the region this morning with some light rain showers evident in data from NWS radar this morning.
With the dominant upper trough remaining over the Great Basin, expect stronger onshore flow to again develop later this morning, aided by a shortwave dropping through southwestern British Columbia. Expect increased shower activity this morning near and east of northern Puget Sound, extending eastward through the Cascades. A Puget Sound Convergence Zone is likely to develop this afternoon and evening, bringing an additional focus for shower activity across central Puget Sound eastward into the Cascades. That said, QPF remains rather modest.

Expect some drying out to occur late this evening through early Thursday (outside of the previously mentioned PSCZ) as heights rises a bit with a transient upper level ridge in between the main weather features. That said, this will be a short-lived break, as the next frontal system will approach the coastline by early Thursday and bring yet another round of increased rain activity. This will knock a few degrees off of the daytime high temperatures, with the lowlands topping out in the mid 50s to lower 60s.

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
The long term period looks to feature an extended unsettled pattern, with an upper trough developing across the Pacific Northwest. There remains broad support in the ensemble guidance for this outcome, with fairly solid cloud cover and several rounds of showers. That said, the amounts aren't too impressive in any single time period, but the Friday night/Saturday period might be the wettest time period of the week ahead. The region will remain in a rather zonal pattern for the start of next week which will continue shower chances. Temperatures generally in the lower 60s through the interior lowlands for the start of next week.


AVIATION
Northwest flow aloft continues across Western Washington today as an upper level trough moving across British Columbia enhances low level onshore flow across the region. This is producing convergence across the interior lowlands with low MVFR or IFR ceilings and scattered showers. Showers will diminish toward afternoon, but ceilings will be slow to improve. Ceilings will lift to low end VFR most areas after around 22Z. A gradual deterioration back to MVFR is expected after 06Z this evening.

KSEA...Low MVFR or tempo IFR ceilings expected into midday with a convergence zone just north of the terminal. Improvement will be gradual at best with ceilings lifting to low end VFR by around 23Z.
Ceilings will fall back to 020-030 after 06Z tonight. Surface winds S/SW 8 to 13 knots this morning will shift W/SW this afternoon as the convergence zone dissipates just north of the terminal 22Z-00Z.
Winds may become variable for a period around 00Z before returning to a predominant southerly direction overnight tonight. 27

MARINE
Surface high pressure over the coastal and offshore waters will weaken late Thursday as a frontal system approaches the area.
This front will weaken as it moves onshore on Friday. Surface ridging will rebuild offshore on Saturday then shift into the coastal waters early next week.

Seas will generally remain under 10 feet through the weekend, but may approach 10 feet early next week as a swell train generated by a trough over the northern Gulf of Alaska arrives. 27



HYDROLOGY
The daily hydrology discussion has ended until the start of the next rainy season; it will only be included as needed.

SEW WATCHES/WARNINGS/ADVISORIES
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
Waters Strait Of Juan De Fuca.

Small Craft Advisory until 5 PM PDT this afternoon 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.