textproduct: Juneau

UPDATE

After 06z TAF issuance and adding a new long term discussion.

SYNOPSIS

Key Messages:

- Showers will steadily diminish Wednesday, with clearing skies expected from North to South Thursday into Friday

- A system may clip part of the southern panhandle Thursday, but should move out of the area fairly quickly.

- Clear skies expected to persist into the weekend, with precipitation potentially moving back into the northeastern gulf coast Sunday

LONG TERM

/ Friday to Tuesday / At the mid and higher level steering levels of the atmosphere the upper level trough which was in the gulf travels east in British Columbia by Friday morning, as a building mid level ridge builds and moves east over the gulf. The ridge axis should shift east of the panhandle by early Sunday. A weakening closed low over Bering Sea moves east to be north of the Pribilof Islands and stalling by Sunday as well. A trough about this low will rotate south over the Aleutians and into the North Pacific, then to the western gulf Mon-Tue time frame depending on the model solution following.

So what does this mean weather wise for Southeast... showers from the midweek into Thursday, tapering off/ending as improvements Friday - early Saturday period due to the ridge moving through and clearing weather out. Models beginning to come to agreement of fairly organized from to push through the eastern gulf Sunday to Monday. Gusty winds for the coastline Sunday, and then likely showers to start the upcoming week. The very long forecast is showing hints that will be need to watched closely to see how that situation develops.

Temperature-wise at or just below normal values, with higher elevations of the Klondike and the higher Canadian Haines Highways to possible see snow or snow rain mix for the weekend period.

AVIATION

Showers continue to bring intermittent CIG and VIS drops across the panhandle tonight, with most areas seeing CIGs falling to 2000-3500 ft with the showers pushing in. Some parts of the northern panhandle and outer coastline may continue to see CIGs down to 1500 ft, with the area around PAHN and northern Lynn Canal seeing some lower 800-1000 ft CIGs on and off into tonight. Showers will also continue to bring some gusty winds and VIS drops to 4-5SM, however the larger VIS concern tonight will be for the southern and central panhandle as the shower chances diminish from S to N into tonight, allowing for some patchy fog development. Already PAPG has seen fog develop with VIS down to less than 1 SM, however any fog will be less widespread / persistent overnight and the main area of concern for fog development will remain over the PAPG to PAWG area.

Winds remain elevated over northern Lynn Canal, with PAGY still seeing 20 kt winds with gusts to 30 kt into this evening, though this will gradually diminish into tonight to around 10-15 kt by 15z, and continue to decrease through the morning hours. However, these winds may hold on for longer into tonight and keep some gusty conditions through Wednesday morning. Otherwise, areas begin to clear from S to N into the day Wednesday back to predominant VFR conditions. The break for the southern panhandle appears to last until after 00-03z Wednesday evening, as a feature moves south of the panhandle and brings another round of rainfall, deteriorating flight conditions across the S panhandle by the end of the TAF period.

MARINE

Outside: As of Tuesday afternoon, blustery onshore flow continues as a low weakens over Prince William. ASCAT passes highlight winds of moderate to fresh breezes out of the WSW. Altimeter wave heights indicate seas of 10 to 15 ft; highest seas in the central Gulf. Winds continue to weaken across the Gulf, allowing wind seas to begin to diminish and underlying WSW swell to flourish. Thinking we maintain WSW 9 to 12 seconds near 10 ft along the majority of our coast.

Overall, Wednesday should be much better conditions across the Gulf with winds at or below moderate breezes and swell diminishing. Light winds and lower sea state persist into Thursday afternoon, as a low develops and moves into the British Columbia coast while a surface high shifts into the Gulf. For us humble folks in Southeast Alaska, expecting a tight north to south pressure gradient to develop, driving northerly winds across the coast, inner channels, and into Dixon Entrance. Main impact for the eastern Gulf will be along coastal waters as northwest winds build to fresh to strong breezes, driving stair master fresh seas of 10 to 13 ft, focused from Cape Edgecumbe to Dixon Entrance, highest northwest seas impacting western Dixon.

By Thursday, underneath the northwest fresh seas will be westerly ground swell from Typhoon Choi Wan, followed shortly by additional westerly ground swell from an extra-tropical transitioning Choi Wan, likely about 1 ft near 17 to 19 seconds.

Inside: Certainly, a breezy few days across the inside; however, winds should be on their way down Wednesday afternoon as the supporting low in the northwest Gulf dies out, leaving behind a weak surface pressure gradient. Expecting much better conditions Thursday morning with light winds, some fog in the mornings, and lighter rain. Thursday afternoon into Friday northerly winds build across the inner channels, particularly impacting north-south orientated channels like Lynn, Stephens, Chatham, and Clarence. At this time northerly winds should hold near moderate to fresh breezes, with Lynn Canal likely picking up a few hours of near-gale force conditions Friday. Forecast was based on surface pressure gradient between Whitehorse/Juneau and Skagway/Juneau, with a stable but warmish boundary layer profile to the north of the coast range, limiting wind potential. No freezing spray concerns as water temperatures are still above 45F, with air temperatures above freezing.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...Small Craft Advisory for PKZ022-053-641>644-651-652-661>664-671- 672.