textproduct: Juneau

UPDATE...to add 06z aviation discussion/

LONG TERM

The active pattern continues through the medium range with most of the guidance tracking a strong low (and associated gale to potentially storm force front) over the eastern Gulf of Alaska Tuesday through Wednesday with a fairly deep moisture transport from the central Pacific. This will bring periods of heavy precipitation (mostly rain) and strong winds across SE Alaska midweek (latter half of Tuesday through Wednesday). This will continue to result in the potential of impacts across SE Alaska in this midweek timeframe, with potential for flooding, downed trees, and the potential for sporadic power outages. Things start to quieten down somewhat after Wednesday with Thursday and Friday looking to be a bit more benign for the southern 2/3rds of SE Alaska as a rather robust ridge builds northward across SE Alaska in the ensemble means. The exception to this will be the areas from Yakutat northward where yet another strong tap of Pacific moisture associated with another low pressure system (moving north but farther to the west) will take aim on South Central Alaska and the northern sections of SE Alaska (Yakutat to Icy Bay) late in the week.

AVIATION.../Until 06Z Monday/

Primarily MVFR flight conditions, on average, are expected through the period. As for SFC winds, for the northern half of the panhandle, breezy conditions will continue through the night & into the early morning hours. For southern areas, it looks to remain rather breezy through the period. Centered up at around 2 kft, southerly to southeasterly LLWS magnitudes up to between around 30 & 55 kt are anticipated through the TAF period.

MARINE

Inside waters: Active weather continues with mostly southerly and easterly winds to 25 kt through the inner channels late this afternoon. Winds are expected to increase again this evening with many areas reaching 30 kt (some isolated areas could reach min gale force) as a new short wave comes up from the south. Winds are then expected to diminish across the northern channels Sunday, but the southern channels will see winds continue to increase to mid gale force of around 40 kt especially in Clarence Strait as another new short wave moves north behind the first one. Southerly winds of 25 to 35 kt will likely linger in the southern channels through at least Monday before diminishing. Seas will mostly be wind waves with the highest being up to 7 to 8 ft in Clarence Strait Sunday through some southerly swell will cause some higher seas up to 15 ft near ocean entrances exposed to the south.

Gulf Waters: Active weather continue as a series of short waves move south to north through the central and eastern gulf over the next 24 hours. The first is currently in the south central gulf and will be spreading gale force conditions through the eastern half of the gulf this evening. That feature is expected to move out late tonight, but a second short wave will be moving north farther east spreading another area of gale force conditions to the SE gulf and Dixon Entrance area for Sunday. Expect southerly winds of 25 to 35 kt to persist in that area through at least Monday before diminishing Monday night. Seas are rather high with 15 to 20 ft seas being rather common, driven by a 12 to 14 ft S swell with a 15 sec period. Seas overall are expected to remain rather high (in the 10 to 20 ft range with higher seas in the SE part of the gulf) through Monday at least with persistent high S swell through that entire period.

HYDROLOGY

Sunday sees another low pressure move up along the moisture feed, bringing an additional surge of rain primarily for the southern half of the panhandle. Expecting IVTs to be somewhat lower, less than 500 kg/ms, but with healthy divergence aloft, strong low level flow, and high freezing levels, rain to be fairly efficient. The southern and central panhandle could see 1.5 to 3.0 additional inches with higher amounts near Ketchikan and Metlakatla, and rainfall rates could exceed 0.2 inches per hour during the Sunday morning and early afternoon timeframe. Main concerns right now are ponding of water in low lying areas, along with rapid increases in creeks and streams. What is particularly uncertain at this time is the current state of the snowpack at higher elevations. As snow levels look to rise to above 4000 ft in the south, cold rain will fall on these higher snowpacks. If the snowpack is primed or near primed, additional runoff could be wrapped up into existing rainfall, adding to the fuel for any flooding in the area.

Additionally, Tuesday looks increasingly likely to have additional moisture move into the area. While IVT values look to exceed 500 kg/ms, details regarding location and magnitude of moisture are not fully clear at the moment. Stay tuned for details.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Winter Storm Warning until 9 AM AKST Sunday for AKZ318. Flood Watch through Monday morning for AKZ326>332. Strong Wind from 3 AM AKST Sunday through Sunday afternoon for AKZ328-330-332. MARINE...Gale Warning for PKZ033-036-641>644-651-661>664-671. Small Craft Advisory for PKZ011>013-021-022-031-032-034-035-053- 652-672.