textproduct: Juneau

UPDATE

Aviation section update following 06z TAF issuance.

SYNOPSIS

Key Messages:

- Strong north and northeast winds continue slightly diminishing throughout the day Tuesday. Winds will relax late Tuesday into Wednesday.

- Temperatures continue to trend down through the week.

LONG TERM

Wednesday night the axis of a ridge aloft will continue transiting east into B.C, with the stout pressure gradient which was responsible for our strong outflow weakening, leaving much lighter winds for the inner channels. Westerly flow upstream of the ridge axis will begin to transport some moisture into the Panhandle early Thursday, helping drive some snow Thursday into Friday. Current forecast shows the best snow potential along the northern coast and in the central and southern Panhandle, with a range of 3 to 7 inches possible; 2 inches or less for Juneau north. Friday the longwave trough begins to dig south, forming into a closed low along the western seaboard over the weekend. As this feature transits south, a very tight surface pressure gradient forms again between an arctic high in Canada and the relative warm waters of the Gulf, increasing the confidence that strong gale force outflow winds return for many inner channels through the weekend with the associated colder weather and freezing spray.

Into early next week, outflow diminishes again as the Yukon high weakens and a new weather system moves in from the W. The possibility of precipitation returns for most areas by Tuesday with most of the areas likely still cold enough for it to be mostly snow.

AVIATION.../through 06z Thursday/

Widespread VFR conditions continue with clear skies across the panhandle as weakening outflow continues. The trend of decreasing winds continues into tonight, though some areas will hold onto the elevated winds and gusty conditions for longer into the morning. Skagway will continue to see sustained winds of 15 to 20 kt with gusts to 30 kt tonight through around 20z Wednesday morning. There is potential for it to hold onto these stronger winds for longer into the day, but will regardless decrease into the end of the TAF period. For Juneau, the first few hours of the TAF period will continue to see the strongest winds and highest gusts alongside the most LLWS concern before winds begin to decrease overnight. Stronger cross barrier flow exists across Gastineau Channel from the elevated NE to N winds, however the strongest appear to be above 3000 ft with 45 to 60 kt observed at Sheep Mtn. Overall both the surface and higher elevation winds will diminish by Wednesday morning for the Juneau area.

Wrangell and Klawock will also hold onto the wind for longer, with gusts of 20 to 25 kt expected to last through Wednesday evening, dropping off by the end of the TAF period tomorrow night. Surface wind for other locations will largely remain less than 10 kt throughout the TAF period, with potential for occasional isolated gusts to 15 to 20 kt for Haines, Gustavus, and Sitka overnight and into the morning. LLWS, mainly speed shear, at around 1000 ft is still hanging around near typical outflow exits, such as Taku Inlet or the mouth of the Stikine River, though are expected to gradually diminish by tomorrow afternoon to evening.

MARINE

Outside: Offshore flow from the channels diminishes through Tuesday night. Seas are on their way down, with residual NW seas, masking SW swell generated from a system a few days ago south of the Aleutians. Significant heights less than 12ft by Tuesday evening, and between 5- 9 feet on Wednesday, with the highest seas over the open Gulf.

Inside: Tuesday dawns with gale force winds howling across the northern and central inner channels, along with usual outflow areas. The current forecast maintains sustained winds of strong gale force in Lynn Canal, with widespread gales along and north of Sumner Strait through Tuesday evening. These winds will generate freezing spray, with moderate to heavy freezing spray for prime areas like northern Lynn and Taku Inlet. Expect winds to slowly diminishing Tuesday night into Wednesday, with moderate to fresh breezes expected Wednesday afternoon through Friday morning. However, Friday evening winds are expected to ramp back up to gale force for most central/northern channels with the threat of heavy freezing spray becoming more extensive.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Cold Weather Advisory until 9 AM AKST Wednesday for AKZ318-319- 323-325-327-331-332. Cold Weather Advisory from midnight tonight to 9 AM AKST Wednesday for AKZ326. Cold Weather Advisory until 6 PM AKST Wednesday for AKZ328. Cold Weather Advisory until 3 PM AKST Wednesday for AKZ329. Cold Weather Advisory until noon AKST Wednesday for AKZ330. MARINE...Heavy Freezing Spray Warning for PKZ011-012-031. Heavy Freezing Spray Warning for PKZ013-053. Gale Warning for PKZ012. Small Craft Advisory for PKZ011-013-021-022-031-032-034-643-644- 661>663.