textproduct: Juneau

SYNOPSIS

Key Messages:

- A stronger weather system and weak atmospheric river will bring gusty winds, elevated seas, and moderate to heavy rainfall for the weekend.

- Unsettled conditions are expected to persist into next week.

LONG TERM.../Monday through Wednesday

Little change to the long term forecast and overall message as the pattern looks to stay unsettled. Low pressure will remain nearly stationary and very slowly weaken over south-central Alaska through the period. This will send multiple fronts across the panhandle and also work to reinforce persistent onshore flow. As a result, we will continue to see periods of rain, especially Monday into Tuesday with perhaps a bit less widespread precipitation for a time later Wednesday. As weak high pressure builds to our east over British Columbia and the pressure gradient tightens, we may see intervals of gusty winds, particularly in the favored areas over the northern panhandle. Model guidance is also suggesting that we could see a few thunderstorms, mainly over the coastal waters, but confidence was too low to include in the forecast at this time.

AVIATION.../Through 06z Sunday/

Behind a disturbance this morning bringing rain to the Northern Panhandle, a front is expected to bring MVFR to potentially IFR ceilings overnight tonight. As of now, the front is beginning to bring lower conditions for Sitka and Yakutat. As of now, the main impacts with this system look to be along and north of Fredrick Sound. South, there may be fog in Ketchikan and Klawock, but confidence in this occurring is low. By 15Z Saturday , there may be a brief break before another round of rain impacts the area.

A second warm front will approach Yakutat around 15Z Saturday. Through the afternoon and evening, this front will push east across Southeast Alaska. This system looks to increase rain chances area wide, and to increase winds as well. This front is expected to bring winds between 35-45 kt 2000 feet AGL. Low level wind shear appears most likely for:Yakutat, Gustavus, Sitka, Klawock, and perhaps Petersburg. However, confidence in this occurring in Petersburg was not high enough to include in this aviation update. Expect MVFR conditions toward the end of the TAF period across the Northern Panhandle, and MVFR ceilings and visibilities expected after 06Z for the Southern Panhandle.

MARINE

Outside: Current SITREP Friday morning across the coast is light winds, with seas an impressively low 4 to 5 ft along our coast. A short break. Upstream in the western Gulf a developing gale force low is rapidly shifting northeast, which will serve as the source for elevated winds/seas over the weekend. Expect easterly near gale force along Cape St. Elias by 2am to 4 am Saturday, with southeasterly strong breezes along the Chichagof/Baranof coast. Winds continue to quickly build Saturday morning, with sustained winds of strong gales, gusts to storm force, along Cape St. Elias and gale force near the Fairweather Grounds. Winds build to strong gales for much of the coast of the Alexander Archipelago Saturday night, with winds shifting to the south and slowly coming down through the day Sunday.

Touching on seas, our gentle sea state diminishes overnight Friday along the northern coast. Current forecast suggests fresh seas near 17 ft by 12 to 3 pm Saturday, potential reaching near 19 ft overnight Saturday into Sunday morning. For the remainder of the coast, expecting 15 ft seas to be the theme, with an area of 20 ft seas possible near the Fairweather Grounds to coastal waters south of Yakutat. Multiple wave systems will be present; large and confused seas. As we move into Sunday primary wave direction will begin to shift from the south, becoming southwest Monday night.

Inside: The northern inner channels continue to be a tricky forecast, with winds ramping up to near-gale force Friday morning in Lynn Canal. Thinking these winds are caused by a disturbance moving along the Yukon border helping to tighten up the pressure gradient. 20 to 30 knot winds should diminish to 15 to 20 knots Friday night for the north, including Point Couverden, northern Stephens, and Lynn Canal.

Moving past the northern challenge, primary focus for the inner channels is a front moving across the inside Saturday evening into Sunday. Primary theme will be strong breezes, with near gale to gale force for a few hours likely as the front moves over. At first, winds will flow up from Clarence Strait out of the southeast with easterly winds out of Icy Strait and Cross Sound. As the front moves over these southeast winds will become southerly, beginning to increase as they flow up Lynn Canal and Glacier Bay late Saturday night into early Sunday morning.

Moving into next week southerly fresh to strong breezes continue to impact the inside.

HYDROLOGY

A stronger system is expected to move into the panhandle Saturday into Sunday, bringing periods of moderate to heavy rain. During the peak of heavier rainfall during the overnight hours, rain rates could exceed 0.15 inches per hour. Moderate to heavy rates are expected to continue for any given location for a period of around 12-18 hours before decreasing. Total rainfall accumulations for the event are expected between 1.5 - 3.0 inches, with greatest amounts in the central panhandle. Upwards of 5 inches will be possible for higher elevations. Due to the short nature of the heavier rainfall, smaller creeks and streams will rise quickly, but are not expected to flood.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...Gale Warning for PKZ652-662>664-671-672. Small Craft Advisory for PKZ053-641>644-651-661.