textproduct: Juneau

UPDATE

update for the second release from Suicide Basin and the Flood Warning for Mendenhall River.

LONG TERM.../Saturday through Tuesday/

A low pressure system will enter the Gulf of Alaska this weekend, bringing gale-force winds to the outer coast along with periods of moderate to heavy rainfall associated with a weak atmospheric river. The initial wave of rain begins late Friday night into early Saturday morning as a front reaches the panhandle, impacting mainly the northern region and more so the NE Gulf coast. A stronger wave then follows, arriving by early Sunday morning. As the low slowly dissipates near south-central AK, it will meander and track multiple fronts across the panhandle. This setup, reinforced by a consistent slew of upper level troughs and divergent flow aloft, keeps precipitation in the forecast for the extended period, although overall impacts are expected to diminish gradually heading into next week. One thing of note is as the low dissipates, the pressure gradient over the northern panhandle becomes more north to south oriented, causing a potential increase in winds within Lynn Canal through Monday and Tuesday.

Impacts associated with this weekend system will initially start along the NE Gulf coast and as far south as Baranof Island, also upwind of higher elevations. From Sunday through Monday, heavier precipitation will push south across most areas, particularly targeting the Misty Fjords region. The highest confidence for 24- hour rainfall accumulations during Sunday's stronger wave ranges between 1.5 to 2.5 inches, with localized amounts reaching 4 to 5 inches over higher terrain. However, at this time there is a low (25%) chance that lower elevation areas surrounding Icy Strait, such as Juneau and Gustavus, could exceed 2.5 inches. A significant southerly jet will move along the coast Saturday, shifting southwesterly by Sunday morning and likely bringing 35 to 40 knot sustained winds from Cape Spencer north to Cape Suckling. Overnight Saturday into Sunday presents the greatest concern for elevated and gusty winds over the southern panhandle and inner channels, then trending on the decline Monday morning.

AVIATION...18Z TAFs

Scattered showers continue to affect parts of the northern and central panhandle, but ceilings and visibilities are generally VFR with just periodic and brief reductions to MVFR. The heaviest and most persistent shower activity will likely continue to be along the northern panhandle and outer coastline through the day. Mainly VFR to persist this evening, before MVFR becomes increasingly predominant after 09Z-12Z tonight under persistent onshore flow and a return to lower ceilings.

MARINE

Inner Channels: S winds of 15 to 20 kt for most areas of the inner channels north of Frederick Sound this morning. N Lynn is showing the highest winds with 25 to sometimes 30 kt overnight at Eldred Rock. These winds are expected to diminish through the day with most areas seeing 15 kt or less by this evening and then persist at that level through Friday night. N Lynn will be the exception as they could see 20 kt of wind that persists into Friday evening. Seas generally around 3 to 5 ft this morning with the highest seas in N Lynn. These seas will subside as the winds subside today.

Gulf Waters: Generally W to SW onshore flow around 10 to 15 kt remains the norm across the gulf this morning. This will not really be changing until Friday night as a new front approaches from the SW. The front will switch the wind direction to more of a SE and start to increase wind speeds as well. Gale force winds look likely by Saturday afternoon and evening along the near shore waters. Seas are generally around 5 to 7 ft with most of that being wind wave and very little swell. Not expecting much change in seas until Friday night when increasing winds from the approaching front and building SW swell starts to build seas above 10 ft.

Some isolated thunderstorm activity along the NE gulf near shore waters from Cross Sound to Yakutat Bay this morning. That is expected to diminish through the morning and should not be a concern by later Thursday afternoon.

Hydrology

A second release from Suicide Basin has started and levels will continue to drop through the day. Levels on the Mendenhall have started to rise and will continue to rise as the release continues. Current river level crest projection is around 10ft on Friday. At 10ft, water levels will inundate Mendenhall Campground with up to 3 feet of water covering low areas as well as up to 1.5 feet of water covering Skaters Cabin Road. Portions of West Glacier Trail will be impassable. Areas along View Dr will start to flood and cause minor flooding of yards. Closure of pedestrian pathways beneath Brotherhood Bridge and the trail system on the west side of Mendenhall River during outburst events. The water level on the Mendenhall River is expected to fall back below flood stage by Saturday morning.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Wind Advisory until 1 PM AKDT this afternoon for AKZ318. MARINE...None.