textproduct: Juneau

SYNOPSIS

Key Messages:

-No major weather concerns expected into the weekend however marine layer low clouds will persist over the eastern Gulf and inner channels.

-A weak front will be moving north through the central and northern panhandle Friday night bringing possible periods of light rain.

-Suicide basin glacier dammed lake continues to fill at this time. It is expected to be full sometime late this weekend or early next week.

LONG TERM

Ensemble models have reached greater consensus on the track of the main system for next week. A weak upper-level trough is expected to move over the area Monday and Tuesday, bringing light, and generally unimpactful precipitation. A mid-level low will supply vorticity to the region Monday and Tuesday, amplifying anticipated rain showers before tapering off as high pressure builds on Wednesday. A significant upper-level ridge will build on Wednesday, while the low-level ridge strengthens early next week as the low tracks south and east toward the AOR. High pressure remains the dominant feature, keeping the main low to the west as it tracks over the Aleutians, digs south, and moves into the Kenai Peninsula. While the current expectation is for the main frontal precipitation to push through on Tuesday with a mean 24 hour accumulation of 0.25 (supported by the 75th percentile NBM and GEFS/EC ensemble agreement), there remains a risk that if the low shifts further east, Yakutat and surrounding areas could experience heavier bands of rain showers between Thursday and Friday. For now, the expected track will keep the Northeast Gulf Coast under light rain showers, but nothing unseasonable. After the midweek system pushes through, the central and southern panhandle are expected to see clearer skies, and therefore warmer temperatures. Current thinking puts inland and southern areas with highs in the low 70s for Wednesday and Thursday.

AVIATION

Conditions have improved more than expected, with many areas as high MVFR to mostly VFR. The weak front aloft is currently in the central panhandle, slowly working its way northward. Still expecting the moisture wrapping around the upper level low to bring in moisture into Canada, which in turn streams over the Icy Strait corridor and Haines and Skagway. With plenty of moisture already present, could see visibilities less than 5 SM with high IFR to low MVFR cloud decks this evening. Furthermore, looking to see an intrusion of marine deck overnight for the gulf waters and outer coast, dropping CIGs to AoB 1500 ft.

MARINE

Outside: High pressure once again remains constant through the next 3 days, with the main threat for the outside waters being low clouds and poor visibility. These threats look to be localized around the Cross Sound entrance and south of Cape Decision. Visibilities could drop to below one statute mile.

Inside: Similar story for the inside waters, with the main difference being Taiya Inlet. As some clearing is expected north of the AOR, expecting a mild thermal gradient to develop in the aforementioned area, although this does not look to exceed 15 knots. Otherwise, expect winds to be lighter through the weekend, with speeds and directions largely affected by local effects rather than large scale movements in the atmosphere.

HYDROLOGY

Suicide basin glacier dammed lake continues to fill. The pool elevation as of 1 pm was at 1343 ft with a rate of rise of around 2 ft over the last few days. The overflow channel is at an elevation of around 1350 ft so the lake has another 7 ft to rise before it starts to overflow across the side of the glacier. With the rate of rise over the last few days and weather conditions expected to remain mostly consistent with cloud cover and near normal temperatures the lake is expected to likely become full around August 10th or 11th. Once that point is reached, in the past it has taken up to 6 days before the lake starts releasing.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...None.