Marine Weather and Tide Forecast for Valdez, AK

.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days 1 through 3: Thursday through Saturday)...

Key Messages:

* Ex-Choi-wan will bring active weather through the end of the workweek, with conditions gradually improving through Saturday.

* Wind Advisories remain in effect for Unalaska and Dutch Harbor through 1 PM today, and for Kuskokwim Delta/Nunivak Island through 1 PM Friday. High Wind Warnings have been cancelled.

* A High Surf Advisory remains in effect for Kuskokwim Delta coast through 3 PM Friday.

Discussion:

With Ex-Choi-wan curving towards Eastern Russia, the highest winds (>= 75 mph) have exited our forecast area. Peak winds reached 75 mph at Shemya yesterday, and topped out at 69 mph in Adak and 61 mph in Atka. While the low center itself has moved out of the area, strong southerly to southeasterly winds continue along the storm system's front, which is currently moving over the Pribilof Islands. The latest observations show peak winds of 63 mph in Saint Paul and 69 mph in Saint George. In Unalaska/Dutch Harbor, a gust to 41 mph was observed, though the strongest winds aren't set to arrive until later this morning.

The front will move into Southwest Alaska and across the Alaska Peninsula by late morning/early afternoon, then stall as it runs up against a ridge over the Mainland. As such, there will be a decently long duration of southerly onshore winds, bringing the potential for high surf to the Kuskokwim Delta coast. While the front will begin weakening tonight, an incoming shortwave will reinvigorate it, bringing another round of strong winds for Friday morning. The latest model runs have shown some variance in how far west or east this front will shift as that shortwave moves in; the current forecast reflects a more westerly track (stronger winds for Kuskokwim Delta coast), but other models are showing strongest winds a bit further east, which could lead to greater impacts for Bristol Bay. This will bear watching over the next few model cycles.

By Friday evening, the center of low pressure will begin to gradually move eastward across the Northern Bering as it continues to weaken. This will allow the front stalled over the Southwest coast to progress toward the interior, shifting the core of heaviest rain to the southern AKPen and western Alaska Range. A series of weaker shortwaves will round the low, leading to showery conditions for much of the region through Saturday. Winds will remain elevated through the Bering, with widespread small-crafts, but will gradually diminish as the low fills in.

-LM/KC/CW

.LONG TERM FORECAST (Days 4 through 7)...

A deep upper low in the northern Bering Sea with an upper level ridge over the Southcentral starts to breakdown Sunday, allowing for moisture advection under southwesterly flow through southern mainland. Winds begin to diminish, but showery precipitation will linger for Southwest Alaska as the front moves inland. A surface low will develop along the front in the Gulf of Alaska, with strong, southeasterly surface winds. Ample moisture is expected to move through the Gulf and Southcentral. Most of the precipitation will be focused toward Kodiak Island, the northern Gulf coast, and Prince William Sound. The bulk of the moisture looks to move into the northeastern Gulf Monday. Southeast flow would promote precipitation enhancement through orographic lift along the windward slopes and downslope drying to the leeside. The amount of precipitation will depend on the progression of the front, the amount of precipitable water in the vertical column, and the location/time of the surface low the Gulf.

Confidence decreases early next week as the main upper level trough starts to phase with a potentially vigorous low emerging from the North Pacific, south of the Aleutians. Some data suggests that this low tracks more north into the Bering (20 to 30 percent chance), but another batch of data (and the current forecast with 50 to 60 percent confidence) suggests a track that remains to the south of the Aleutians, toward the western Gulf. There will be plenty of moisture with this system, but the amount of precipitation for the Aleutians and Alaska Peninsula will depend upon the strength of this low as it approaches the Aleutians. As this combined trough moves east midweek, we start to see additional breakdowns in model consensus (and therefore confidence) for the wind forecast, especially as the front approaches the Gulf and Southcentral. Although the current guidance suggests sustained gale force winds with storm force gusts along the front, this system has the potential to produce sustained storm force winds (20 to 30 percent chance) across the Gulf and along the northern Gulf coast into Prince William Sound.
This will be dependent upon not only the strength of low pressure system, but also its placement in relation to the geographic features across southern mainland Wednesday and Thursday. The forecast is expected to evolve - check back for updates.

AVIATION

PANC...Generally VFR with variable winds around 5 kt or less through much of the day. Lingering low-level moisture, weak lift, and little to no wind flow in the boundary layer as resulted in the development of scattered showers around the terminal this morning. Given the weak wind flow, it will be tricky to pin down the exact movement of these showers through the morning hours. As such, there is a chance (25-35%) that a rain shower moves over the terminal between 5 AM and 11 AM AKDT. Any rain shower near or over the terminal will likely (60-70%) lower ceilings to MVFR. Ceilings improve later today as a light southerly wind aloft helps to drive any shower activity toward the lower Susitna Valley and away from the terminal. MVFR ceilings are likely again (60-70%) by early Friday morning as a wind flow up Cook Inlet develops bringing another round of low-level moisture toward the terminal