textproduct: Juneau

SYNOPSIS

Key Messages:

- Multiple High Wind Warnings and Wind Advisories remain in effect for the panhandle.

- Increasing potential for thunderstorms Thursday afternoon and evening for southern panhandle, highest likelihood near Prince of Wales Island and the surrounding areas.

- Weather pattern change begins on Friday, with showers diminishing in coverage through the day.

- Drier and cooler weather for start of next week with outflow pattern for the northern panhandle.

LONG TERM

Two areas of interest going into this weekend and next week. The first being a fast moving "clipper" system Saturday night into Sunday. The second being an arctic cold front moving from north to south on Monday, bringing the panhandle finally back into cold temperatures.

Ultimately, both areas of interest are caused by the same phenomena, a broad ridge over central to western Alaska, which, in turn, digs a trough down from the northern Gulf of Alaska down to Haida Gwaii. The associated baroclinic zone from the persistent warm temperatures look to spin up a low pressure at the surface, passing south along the northeastern and eastern gulf coast. Good deal of uncertainty with how this system may play out, particularly when an arctic boundary is involved. A majority of the guidance, roughly 70% chance, indicate this system does not look to produce too much liquid equivalent precipitation, as little moisture is associated with it and it moves too quickly south for any one area to receive too much; however, there is around a 30% chance for a slower solution, stagnating around the southern panhandle. Given the arctic air associated with this trough, precipitation type is expected to transition from initial rain to all snow. From the faster solution, not expecting to see much accumulation greater than 2 inches; however, with the slower, less likely solution, could see up to 5 inches at this time.

Beyond this, by Monday, a stout inversion in Canada, enhanced from the sharp ridge and NW flow aloft, look to bring forth strong katabatic flow to the northern half of the panhandle. Pressure gradients between Juneau and Skagway look to be around 8-9 mb, with large density differences look to bring forth strong gales. At this time, there is around a 25% chance of storm force winds based on similar historical pressure gradients in this channel. Expecting to see similar conditions in the upper arms of Glacier Bay. Expecting to see near gales to gales extending down Stephens Passage and Chatham Strait as well. Combined with the single digit lows, looking to see at least moderate freezing spray concerns in all aforementioned channels.

AVIATION

/ through Friday afternoon / Frontal band pushing through, with landfalling low over north central panhandle. Mostly clear near Yakutat in the dry slot will collapse are precip band move into and over the area this evening. Rain/snow and ceiling below 3000 ft northern panhandle winds main issues this evening and probably into early Friday. South central, gusty winds leading to LLWS issues through the evenings. Conditions will be improved Friday with less intense turbulence. Winds for the far south have start lightening as well and with light winds overnight, the possibility of patchy fog for the southern third to half of the panhandle may be possible.

MARINE

Outside (Gulf and Coastal Waters): Thursday afternoon observations highlighted storm force conditions along our coast, with the highest winds focused near Cape Ommaney. Given satellite wind passes, able to narrow down the 35 ft seas, likely aimed toward Chatham and Sumner ocean entrances. Along the northern coast, buoy observations from 46082 and 46083 reported significant wave heights near 10 to 12 ft. However, one item of note was prominent WSW swell at 14 to 16 seconds, masked by the fresh seas generated from the strong low. Moving into early Friday morning wind and seas begin to diminish along our coast. Next system will be a low that will take a southeast transit along our coast Saturday night, bringing gale force northwest winds to the central gulf and fresh seas increasing. Mariners wishing to transit from Cross Sound to Cape St. Elias will see winds less than 30 knots and seas less than 12 ft if they favor the coast.

Inside (Inner Channels): Thursday afternoon high winds are shifting east into the Panhandle, driving gale to storm force for most of the central and southern passages. Stephens Passage looks particularly intense, with a few hours of storm force conditions through the evening. Moving through Thursday night, wind and seas begin to subside, bringing light winds Friday. As these winds decrease Friday, dense fog is becoming more likely Friday night into Saturday morning. Sunday an extended period of outflow conditions begins, with gale force conditions ebbing and flowing through the coming week.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Winter Weather Advisory until 3 PM AKST this afternoon for AKZ318. Winter Storm Warning until 3 PM AKST this afternoon for AKZ319. Wind Advisory until 6 PM AKST this evening for AKZ321-323-324. High Wind Warning until 6 PM AKST this evening for AKZ325>330- 332. MARINE...Storm Warning for PKZ031-033-035-641-642-661-662. Gale Warning for PKZ032-034-036-663. Small Craft Advisory for PKZ012-013-021-022-053-643-644-651-652- 664-671-672.