textproduct: Juneau

SYNOPSIS

Key Messages:

- Onshore flow and a weak disturbance sliding through the panhandle today and bring light rain showers and continued cool temperatures.

- Slightly stronger system to impact the panhandle by the end of the week, bringing increased rain rates, especially over the southern panhandle.

- The Taku River is expected to reach bankfull later Wednesday morning due to ongoing glacial lake outburst. While flooding is not expected, debris in the water and colder than normal water temperatures are possible.

LONG TERM.../Friday through Monday/

A series of lows approach & slide southeastward past Southeast Alaska for the forecast period, bringing decent chances for appreciable rainfall to southeast alaska & enhanced winds less than Small Craft Advisory criteria values(23 kt or greater) to the eastern Gulf of Alaska & Inner Channels. Seas for the Outside Waters look to build to Small Craft Advisory criteria values(8 ft or more) as the lows approach & pass by the region.

The series of aforementioned upper level troughs passing over the region, combined with a southward positioned jet stream, will assist the formation of several weak surface lows throughout next week. Seasonably cooler 850mb temperatures are expected to persist, preventing significant surface warming. A weak low entering the Gulf on Friday morning is forecast to bring enhanced southwesterly winds along the coast, followed by the formation of another weak low Saturday night into Sunday. This sequence of Gulf lows will lead to moderate rainfall across the southern panhandle, with the highest intensity expected from Friday night through Saturday morning, supported by moderate mid to low level instability. A subsequent wave of rain showers is anticipated to move through the coast Sunday night, with precipitation persisting across the southern panhandle through Monday. While continuous cloud cover and rain showers throughout the weekend will keep temperatures cooler, a potential break in showers on Saturday and intermittent clearing could allow for slight temperature increases, with a trend toward drier conditions appearing after Monday.

AVIATION.../through Wednesday night/

Fairly disorganized marine layer across the Gulf of Alaska this morning has brought ceilings as low as 500 feet to Yakutat. A weak low pressure system west of Cape Spencer has helped mix out the marine layer from the past couple of nights. The low may bring some showers this afternoon, but chances look generally less than 30%.

With daytime heating, ceilings are expected to generally improve to VFR areawide. After 06Z, ceilings are expected to decrease to MVFR. With weak winds, fog appears possible in Petersburg towards the end of the TAF period. Since confidence in this occurring is low, it was not included in the 12Z TAFS.

MARINE

Outside (Gulf and Coastal Waters): With a weak area of low pressure to the west of Cape Spencer, winds and waves are fairly benign this morning. As an upper-level disturbance passes over the area, the fairly benign pattern will persist before a front and low pressure system arrives Friday morning. Along the front, winds up to 20 kts and seas up to 6 feet are expected. The disturbance is expected to weaken and move southeast toward Haida Gwaii by early Saturday morning.

Inside (Inner Channels): Winds are fairly calm in the inner channels this morning, but there are some stronger southerly winds in Lynn Canal and northwesterly winds in Clarence Strait. Through the day Wednesday, the pressure gradient is expected to decrease, so winds are expected to weaken through the day and turn southerly in Clarence Strait. Friday morning, a front will arrive in the Gulf of Alaska. Based on the current projected track of the low pressure system, the main impact in the inner channels looks to be coverage of rain.

HYDROLOGY

River gauge observations as of early Wednesday morning indicate a release from Lake No Lake is ongoing. Based upon basin estimates and current river levels, flooding is not expected with the river forecast to reach bankfull conditions by late Wednesday morning with elevated flow up to around 80 kcfs. As a result of the release, debris in the water is possible on the Taku River, extending down Taku Inlet, & into Stephens Passage, particularly for Wednesday. Furthermore, the water temperature near the Taku River may be much colder than normal, possibly by more than 10 degrees. Typically a release of this type along the Taku River lasts from 1 to 3 days. The National Weather Service and Alaska River Forecast Center will continue to monitor conditions going forward and update this statement as necessary.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...None.