textproduct: Juneau

SYNOPSIS

Key Messages:

- Northerly winds build across the inner channels Thursday, strongest marine winds expected in Lynn Canal. - High pressure returns through the end of the week with drier conditions, more sunshine, and high temperatures in the mid 60s to low 70s.

AVIATION.../through 12z Friday/

Quite a difficult aviation forecast has been unfolding overnight, with a broad stroke of flight conditions from VFR down to LIFR, ceilings ranging 100ft to SKC and visbys as low as an 1/8 mile at times. What started off the night as predominate LIFR/IFR vsby issues from fog formation has now transformed into a LIFR/IFR CIG issue as upper lvl clouds have moved in aloft in tandem with northerly winds beginning to build within the N inner channels. This combo of cloud cover and northerly winds have resulted in fog lifting into a low cloud deck AoB 1500ft across much of the interior inner channel terminals. Moving into the early afternoon, any lingering LIFR/IFR flight conditions will quickly diminish as day time heating gets underway with high forecast confidence of VFR flight conditions prevailing by 21z this afternoon with CIGS AoA 3500ft. Northerly winds will build across the inner channel terminals through the afternoon, sustained winds around 10 to 20kts, with strongest gusts up to 25 kts possible at Skagway. Will need to keep an eye on mountain wave and LLWS development near end of TAF period for PAJN as stronger northerly off-shore winds develop. Moving into the overnight hours, less confidence in overnight fog development this go around with the aforementioned drier northerly winds, but still expecting some development of a marine layer and patchy fog, albeit in less coverage.

MARINE

Outer waters: As an area of high pressure begins to slide into the Yukon, and a surface low slides to the south, northerly winds are going to become more prominent through our coastal waters. From Alsek west to Cape St. Elias, winds should remain largely at or below 20 knots. However, expect speeds to reach fresh to strong breezes just offshore of the Chichagof/Baranof Archipelago and out of Chatham Strait. Mariners attempting to round Cape Ommaney or Decision should be aware of this northerly wind component, especially during flooding tides. Favoring the coast will limit fetch potential.

Touching on seas, current buoy observations indicate a dominant WSW group 7 to 10 ft focused near 10 seconds from the Fairweather Grounds to Prince of Wales. A secondary wave system is out of the WNW, generated from near-gale force winds out of Cook Inlet, responsible for 10 ft seas in the central Gulf. These wave systems are burying southerly tropical swell focused at near 14 seconds.

Moving through the next 24 hours, WSW seas trend downward, with the focus shifting to the aforementioned W to NW wave system coming out of Cook Inlet and western Gulf. Expect this group to slowly diminish to 6 to 8 ft by Thursday afternoon. As we move into Friday, southerly forerunners from swell generated from Hurricane Lowell begins to reach the northern coast, with wave heights reaching 2 to 4 ft. Expecting peak swell conditions at 2 to 4 ft 15 seconds along much of the coast into Saturday. Riding on top of this system will be WNW wind waves, bringing some chop into the PoW coast and Dixon entrance.

Inside Waters: While winds are going slack across much of the inside this early Thursday morning, northerly winds will ramp up through the day. Mariners navigating the inner channels should be aware of this northerly threat, with sustained speeds reaching a minimum of fresh breezes for most waters along and north of Frederick by Thursday afternoon; Lynn Canal will see strong breezes by Thursday afternoon. Winds continue to escalate Thursday evening, with strong breezes for much of Chatham Strait and near-gale force conditions for Lynn Canal. These northerly winds will begin to increase as well for Clarence Thursday evening, likely reaching fresh breezes.

Of particular interest is the long fetch of Chatham and Lynn, where northerly winds will generate 4 to 6 ft seas. To reiterate the wave threat, mariners navigating Lynn and Chatham should be aware of the northerly winds and tidal cycles generating higher localized seas, especially near Point Couverden, Cape Ommaney, and Cape Decision. Our wave forecast does not take into consideration tidal influences.

Winds will come down slowly through the day Friday, with sea breezes becoming the primary focus into the weekend.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Dense Fog Advisory until 10 AM AKDT this morning for AKZ317-325- 326. MARINE...Small Craft Advisory for PKZ011>013-031>033-641>643-661>664-671- 672.