textproduct: Juneau

UPDATE

Aviation update for 06z TAF issuance.

SYNOPSIS

Key Messages:

- Multiple Winter Weather Advisories and Warnings are in effect for Sunday across the central Panhandle and the Icy Strait Corridor.

- Cold temperatures continue, with very cold wind chills near White Pass.

- Gusty outflow winds down Lynn Canal, Stephens Passage, near Point Couverden, and Downtown Juneau continue tonight.

- Snow will continue through tonight with decreasing snow rates ahead of the next round expected tomorrow. Numerous winter weather advisories and winter storm warnings in effect for Sunday.

- Moderate to heavy snow rates expected for the central panhandle on Sunday, with precipitation continuing into early next week.

LONG TERM.../Monday through Wednesday/

The active weather pattern continues in full force, with changes to the forecast significantly increasing chances of additional accumulating snowfall for the central panhandle and Icy Strait Corridor through Tuesday, before the primary band of precipitation moves further and southward through the remainder of the week and departs the area entirely on Friday.

The big change to the forecast has been the track of a strong low in the gulf Monday/Tuesday. This low was previously forecast to remain largely offshore and out over the central gulf, which would have encouraged weaker WAA across the southern panhandle alongside the better chances of PoPs in the same area. That situation has changed. Operational guidance, led by the Euro/Canadian models, have started falling in line behind a solution which would see this low moving NE, up into the panhandle directly on Tuesday. Ensembles have also begun to favor this scenario more heavily. This result would bring significantly more precipitation into the central panhandle Monday through Tuesday, with the greatest amounts between the Icy Strait Corridor and Petersburg/Wrangell. While confidence is growing in the potential for additional significant snowfall amounts across the Icy Strait Corridor through much of Tuesday as a result, the precipitation type from Kake southward is very much in flux. The low's much closer positioning to the panhandle means that WAA will be stronger than previously anticipated and could result in rain mixing in or even supplanting the snow entirely for these areas through parts of Monday and lasting through Tuesday. The final precipitation type for these areas will be dependent on the final trajectory of the low, with a track that takes it into the more northern section of the panhandle pushing the rain/snow line further north, while a track which would take it into the southern panhandle (as some ensemble runs are suggesting) would see the rain/snow line remain further to the south. The southern trajectory would increase chances of continued snow accumulations in places like Kake and Petersburg. Ketchikan, Annette Island, and southern PoW Island at least look set to largely remain rain during this time frame.

By Wednesday, precipitation will have largely ended across the Icy Strait Corridor, as the upper level trough over the Gulf shifts eastward, and northerly flow begins to win out and shift further southward. Chances of precipitation will continue in the southern half of the panhandle as the advance of the northerly outflow will finds itself eventually stalling as a low approaching the Dixon Entrance keeps chances of PoPs in the forecast through Thursday. Chances of PoPs finally depart through early Friday, as drier weather and northerly outflow prevail across the entire area, and we find ourselves on the W flank of the upper level trough through early next week.

Winds will remain elevated as well, with strong land-based winds especially prevalent across the northern panhandle as the strong northerly gradient accelerates cross barrier flow, and keeps the potential for elevated winds in Skagway and Haines, alongside the possibility for a mountain wave (Taku) wind event for Downtown Juneau, Douglas, and Thane. Temperatures begin falling from North to South once more through the latter half of the week.

AVIATION

/through Sunday evening/ The previous system that brought light to moderate snow to the southern and central panhandle has lifted inland over Canada. However some residual snow showers will continue over Sumner Strait and up to Juneau through late Saturday night. Starting for the north, from Yakutat eastward over to Skagway and Haines, VFR flight conditions continue with broken or overcast CIGS AoA 4000ft with Haines seeing very light snow. From Glacier Bay and Icy Strait southward, conditions have begun to improve with Petersburg and Wrangell still getting some snow showers dropping conditions occasionally to IFR. Another system bringing a secondary surge of moisture will push through the panhandle Sunday morning with another round of heavy snowfall expected for the central and northern TAF sites along the Icy Strait Corridor, including Sitka, Petersburg, Wrangell, Juneau, and Gustavus.

Strong winds for Skagway continue throughout the TAF period, with NE wind speeds between 25 and 35 kt, with gusts reaching upwards of 50 kt again later Sunday as the next system moves into the panhandle. LLWS remains a concern across the southern and central panhandle with southerly 30 to 40 kt winds at 1500 to 2000 ft remaining over the southern panhandle through the TAF period. The northern panhandle around Icy Strait Corridor including Juneau and Gustavus, as well as up along the NE Gulf coast near Yakutat, will see some wind shear with northeasterly winds of 30 to 40 kts at 2000 ft lasting through the TAF period, even as surface winds turn SE for Juneau and as surface winds remain relatively light for Gustavus and Yakutat.

MARINE

Outside Waters: Northeasterly outflow gap wind speeds remain elevated tonight. No real big changes as one low exits and the next one moves in. Some freezing spray remains possible for the northeastern gulf.

Inside: The outflow pattern continues into tonight across the northern panhandle, with continued wind speeds up to 25 to 40 kts. Wind speeds and gusts up to 50 to 55 kt continue for Lynn Canal. Wind directions will, more-or-less, remain unchanged through the short term across the northern panhandle. Freezing spray possibilities remain for Stephens Passage, Northern Chatham, Icy Strait Corridor, and Lynn Canal through, progressively getting heavier as we go into next week.

The biggest exception is the far southern panhandle, where south winds will be around 10 to 20 kts tonight wind higher south winds likely for Sunday.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Strong Wind through Sunday afternoon for AKZ318-319-322-325. Winter Weather Advisory from 9 AM Sunday to 6 AM AKST Monday for AKZ320-322-323. Winter Storm Warning from 9 AM Sunday to 6 AM AKST Monday for AKZ321-325. Winter Storm Warning from 6 AM Sunday to 6 AM AKST Monday for AKZ324. Winter Storm Warning from 3 AM Sunday to 6 AM AKST Monday for AKZ326-327. Winter Weather Advisory from 3 AM Sunday to 3 AM AKST Monday for AKZ329. Winter Storm Warning until 6 AM AKST Monday for AKZ331. Strong Wind Sunday afternoon for AKZ332. MARINE...Heavy Freezing Spray Warning for PKZ011-012-053. Storm Warning for PKZ651. Gale Warning for PKZ011>013-022-036-053-641-643-644-661>664-671- 672. Small Craft Advisory for PKZ021-031-032-034-035-642-652.