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Southeast Alaska Forecast Discussion National Weather Service Juneau AK 318 PM AKDT Wed Sep 11 2024

SHORT TERM
/ through Thursday night / The frontal band from the next incoming moving across the gulf, with warm frontal like feature this evening into the Northeast Gulf Coast and Panhandle, and cold front approaches and moving into the area starting early Thursday. Periods of the rain may be heavier over the Northeast gulf coast and then to the northern panhandle through Thursday afternoon.

Marine winds increasing to Small Craft and Gale levels for the outer coastal waters and not quite a strong over the inner channels, however, should see higher wind speeds and locally gusty conditions Thursday afternoon into Thursday evening. Am not anticipating significant issues from the wind.

LONG TERM
Friday morning the negatively tilted trough that brought gale force winds to the coast will continue to weaken and expand, morphing into a much broader open longwave trough as it begins to transit south along the western seaboard. As the surface pressure gradient weakens, so will the wind. Expect rain to continue through Friday, tapering off through Saturday morning as a quick moving ridge of high pressure moves into the gulf.

While rain tapers off Saturday, an active pattern continues in the Bering Sea, which will allow another low and associated front to move into the western Gulf by early Sunday. Dynamics associated with this feature are limited aloft, helping to keep the surface pressure gradient from dropping below 990mb. With that said we still have anomalously high sea surface temperatures south of the Aleutians which could help strengthen surface frontal features and add some further detail to the forecasted winds.

Overall the main story for us is stout southwest winds south of the Aleutians and Alaskan Peninsula, forming a trapped fetch which will enhance winds and wave significant heights as this system propagates northeast into the Gulf by early Sunday. Ensemble guidance shows agreement with the location of this wind and resulting fetch but vary in strength. The current long range forecast is heavily dependent on the stronger GEFS solution to capture the higher winds speeds across the range of ensemble solutions. As wind and waves increase in the Gulf late Sunday expect light rain to fill in over the Panhandle, with 24-hour rainfall amounts well within the range of what we would consider normal for this time of year.
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