textproduct: Juneau

UPDATE

Updated aviation section for 18z TAF issuance.

SYNOPSIS

Key Messages:

-No major weather concerns expected through the late week, however marine layer low clouds will persist over the eastern Gulf and inner channels.

-A front advances into the southern panhandle Friday and into the northern half of the panhandle by Friday night, bringing a round of light rain to the area.

-Suicide basin glacier dammed lake continues to fill at this time.

LONG TERM

Not expecting to see any major weather events this coming week. However, as high pressure in the Gulf breaks down, several minor disturbances will move through the area, leading to the development of showery precipitation. By Sunday, the lingering remnants of a front will support rain showers primarily in the northern panhandle. 24 hour rainfall amounts on Sunday are expected to be around 0.1, with the highest rates occurring overnight into Sunday morning. Most precipitation will be isolated to higher elevations.

Something of note, some models are indicating favorable lower level lapse rates along the international border, which may help thunderstorm development at higher elevations from Sunday through Tuesday. However, limited shear and a lack of instability in the mid to upper levels should inhibit deep convection. Most if not all storms are expected to remain in Canada rather than crossing the Coast Range into our AOR.

Through the weekend, a weak upper level trough is expected to move over the eastern Gulf, followed by the formation of a jet streak south of the region by Tuesday. This, combined with a low- pressure center tracking east from the Bering Sea across the Gulf, may provide sufficient energy for widespread rain showers and higher QPF amounts as a front pushes northward on Tuesday. While guidance is beginning to agree on the track of the Gulf low, there is still large spread in rainfall totals, which will likely be more influenced by local effects than anything else.

AVIATION

Mixed bag of conditions this morning as a weak front moves in from the south, combined with lingering marine layer clouds in the central panhandle and Icy Strait corridor. As this front moves northward, generally MVFR CIGs with occasional rain will shift nortward to the Icy Strait corridor. Currently expecting for a brief period of VFR conditions for the central and Icy Strait corridor towards the late morning to afternoon timeframe, as easterly flow aloft over the mountains offers a bit of drying. Beyond this timeframe though, the moisture wrapping around the upper level low looks 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.

MARINE

Outside: Weakening but constant high pressure over the gulf is expected to be the primary forcing of winds through the weekend and beginning of next week. 15 kt winds along the northern gulf coast are expected to diminish through the day to light and variable. Light and variable winds are expected across the gulf through the weekend. A weak shortwave moving up from the south may shift winds northwesterly to westerly in the waters to the west of Prince of Wales Island on Friday. Otherwise, conditions are relatively stagnant with wave heights 4 ft or less. Virility is also expected to be reduced, especially in the overnight hours due to fog development, low clouds, and misty or drizzly conditions Prince of Wales Island and near Cross Sound.

Inside: We see a relative downward trend in wind speeds today through the weekend, with Lynn Canal being the location of most concern. A thermal gradient between Southeast AK and the interior of Canada is expected to bring increased winds to Taiya Inlet, up to about 18kts SE which will reach into northern Lynn Canal. This trend is expected to continue through the weekend, although winds are not expected to exceed 15kts. As for the rest of the inner channels, winds are not expected to exceed 10kts and remain mainly light and variable through the weekend.

AJK WATCHES/WARNINGS/ADVISORIES

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