textproduct: Juneau

SYNOPSIS

Key Messages:

- A fast moving system Saturday bringing impactful winds to the outer coast and into the channels

- Cooler temperatures expected, aiding widespread snowfall with Saturday system and snow showers continuing into next week

LONG TERM

Simply put: -Continued snow showers through mid-week, heavy at times, creating a complex snow forecast. -Outflow build through the week, reaching peak intensity of gale force Thursday.

Monday two regimes will be present over the state of Alaska and Gulf: the first is a prominent ridge across the Bering Sea, the second a longwave trough across the ALCAN border stretching into the Gulf of Alaska. These systems will all contribute and influence weather across Southeast in the coming week into the weekend. Touching on the prominent ridge first, stout northerly flow downstream of the ridges axis will help reinforce cold air advection at 850mb, translating to relatively deep instability as cold air moves east across relatively warm ocean waters. This will serve as the catalyst for continued snow showers, some of them heavy at times. While snow showers move across the Panhandle Monday into Wednesday creating a complex snow forecast, a surface high strengthens in the arctic, with the longwave trough supporting a surface low in the gulf. As the systems develop the north-south pressure gradient will build, allowing outflow to increase across the northern inner channels. This cold and dry arctic air will help shunt snow further south through the week slowly, with showers coming to an end across much of the region by Thursday as gale force outflow reaches peak intensity. Friday outflow is expected to weaken slightly; however, winter will likely maintain its grip on Southeast as a closed low northwest of Hawaii lifts into the Gulf bringing moisture with it, which could result in an overrunning snow event.

AVIATION.../Until 00Z Monday/

With the storm force frontal system continuing to move in, expect winds to be quite strong/gusty through this evening as it continues to push through. Overnight, winds will begin their diminishing trend behind the front. Snow & rain with appreciable rates are expected to continue for a few hours over the area as the front approaches & pushes through. The highest snowfall chances are for the northern panhandle. Behind the front, showers that will give highly variable flight conditions are expected with the precipitation type being mainly snow. CIG & VIS conditions generally between the VFR & IFR range are expected as the front continues to approach & push through, after which showery conditions dominate. Flight conditions will generally improve through the period behind the front on average, but the heaviest of those snow showers may still periodically make conditions quite low. LLWS primarily centered aloft at up to around 2 kft with magnitudes up to around between 30 & 50 kt are anticipated around & out ahead of the front mainly this afternoon & evening.

MARINE

Outside (Gulf and Coastal Waters): A gale to storm force front is is making landfall along the coast of the panhandle through Saturday afternoon. The swath of strongest winds is currently pushing into the coast of Chichagof and Baranof Islands, following along the southern edge of the low center. Winds will steadily diminish along the coast as the front moves onshore Saturday night, though westerly strong breezes will continue through the weekend offshore in the southern gulf. Due to the fast moving nature of this front, wave heights are expected to drastically increase following the strongest winds and quickly diminish behind the front. An area of 20 to 30 ft waves is forecast to push into the central gulf coast, extending from Cape Fairweather down to Dixon Entrance. These will drop to about 15 to 18 ft going through Sunday morning and steadily decrease into early next week. The far northern gulf can expect a more consistent 12 to 16 ft Saturday and dropping to 10 to 13 ft through Sunday. Southwesterly swell will rapidly increase to up to 25 with the front, though will drop back down to a more consistent 10 to 15 ft at a period of about 12 seconds by late Saturday night into early Sunday morning.

Inside (Inner Channels): The gale to storm force front making landfall along the gulf coast of Chichagof and Baranof Island is expected to funnel the strongest winds and gusts into Cross Sound and partially down Icy Strait through Saturday afternoon and into the evening. The rest of the inner channels can expect to see southwesterly gale force winds with this front, with the strongest areas being in the southern channel entrances, near Five Finger Lighthouse, around Point Couverden, and up Lynn Canal. Winds will quickly decrease to strong breezes overnight into early Sunday morning, and then steadily diminish to moderate to fresh breezes through the rest of Sunday. The main impact from this system continues to be the quick switch to westerly to southwesterly gales as the front moves over. Sunday night into Monday, winds are expected to flip in the northern panhandle as outflow winds begin to increase. General wave heights of 4 to 6 ft are expected through the channels, with areas of strongest winds seeing closer to 7 to 9 ft. Channel entrances may see heights up to 25 ft pushing in with the front. Heights will drop to 1 to 3 feet into Sunday.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Winter Weather Advisory until 6 PM AKST this evening for AKZ317. Wind Advisory until 10 PM AKST this evening for AKZ317. Wind Advisory until midnight AKST tonight for AKZ320-321-327-328. High Wind Warning until 9 PM AKST this evening for AKZ322-323. Wind Advisory from 3 PM this afternoon to midnight AKST tonight for AKZ324-325. Winter Weather Advisory from 3 PM this afternoon to 4 AM AKST Sunday for AKZ325. MARINE...Storm Warning for PKZ022-643-644-663-664. Gale Warning for PKZ012-013-021-031>036-053-641-642-651-652-661- 662-671-672. Small Craft Advisory for PKZ011.