textproduct: Juneau

SYNOPSIS

Key Messages:

- Numerous marine storm warning have been issued for tonight and Thursday over the eastern Gulf of Alaska and along the near shore waters of the outer coast from Sitka southward.

- Winter Storm Warnings and Winter Weather Advisories have been issued for the northern inner channels for snow potential. Highest accumulations are expected on Haines Highway, including areas like Klukwan.

- Multiple high wind warnings and wind advisories have been issued for the panhandle, with highest winds from Sitka to Kake and southward.

- Possibility for thunderstorms with highest likelihood near Prince of Wales Island and the surrounding areas on Thursday.

LONG TERM

Onshore flow will continue for the start of the long term period with a weakening low remaining in the northern Gulf for the end of the week. This onshore flow will continue to bring moisture into the area allowing for showers to continue. Most of these showers should remain on the lighter side but could potentially have some periods of moderate to heavy rain mixed in. Going into the weekend, high pressure builds over the Yukon and Interior Alaska before shifting to the south and east. This shift will strengthen the pressure gradient between Canada and the Panhandle. With this increasing gradient, winds out of gaps in terrain are expected to increase with outflow winds. Temperatures are also expected to start to decrease going into this weekend with a lot of locations expected to drop below freezing for the northern and central panhandle by Saturday morning.

With the dropping temperatures and continued onshore flow, some snow showers are likely to occur but would result in light snow accumulations at this time. Heading into Sunday, an area of low pressure is expected to form near Prince William Sound before moving into our area. This low will bring an increase in upper level dynamics as well as a more organized area of snow. This would be the first return of snow to most of the panhandle since we moved out of the cold and snowy pattern in January. Right now, accumulations for this system on Sunday look to be around a couple inches for most places. But those locations that are at elevation could of course see higher snow totals. Going into the middle to end of next week, we look to continue to the cold trend with near normal to below normal precipitation.

AVIATION

For the late afternoon update, generally MVFR to VFR has worked in across the central and northern portions of the Panhandle with MVFR to locally IFR across the southern areas where bands of rain and a zone of lingering higher winds off the surface are producing LLWS. We will see the LLWS weaken a bit in the south this evening, then winds in the 2-5 thousand foot layer will increase across the southern half of the Panhandle tonight as a strong storm force low deepens over the eastern Gulf of Alaska. By morning, we do expect to see MVFR to IFR across the southern 2/3rds of the Panhandle with an area of snow to the northeast of the weakening low during the morning over Haines and Skagway areas (lighter snow around Yakutat), with mostly rain from Elfin Cove to Juneau and southward. LLWS for areas from Elfin Cove to Juneau south will be an issue tomorrow morning with east winds at the surface quickly increasing and becoming more southeast to southwesterly in the 2-4 thousand foot layer.

MARINE

A dangerous storm is moving toward the eastern gulf, bringing storm force conditions to the central and southern coast and widespread gale force conditions in the inside. Mariners are advised to seek safe harbor now. Make ready for strong southwesterly winds. If along the Chichagof, Baranof, or Prince of Wales coast large southwesterly seas will build overnight to 30 to 40 ft.

Outside (Gulf and Coastal waters): As of Wednesday afternoon, one system and associated front is pushing into Canada, with southwest winds starting to diminish from their overnight peaks. Sea state is dominated by southwest energy, with multiple wave systems bringing a combined period near 7 to 10 seconds and significant wave heights of 10 to 12 ft.

Main focus is on a developing hurricane force low, at 52N 150W as of 2 pm Wednesday, which will quickly march northeast toward the Gulf over the next 12 hours, reaching a minimum pressure near 974mb. On the eastern flank of this system, there is high confidence that sustained southwesterly winds will be at or above 45 knots, with increasing confidence in storm force conditions being realized. Another consideration is a deep mixed layer, allowing strong winds aloft to mix down to the surface, bringing frequent gusts of violent storm force to hurricane force. These winds will generate seas of 35 ft.

Right now, current forecast consensus is that Lisianski Strait south to Prince of Wales will get hit the hardest, with damaging southwesterly winds at a prime direction to move up Sitka sound. This will depend on the storm track. If the storm shifts south winds will be much less for Sitka.

Inside (Inner Channels): Winds are slowly responding across the inner channels as a storm force low approaches, with gales being maintained in southern Clarence Strait. Winds will continue to ramp up Wednesday night, with gale force conditions across many inner passages by 3am Thursday. One exception will be Lynn Canal, where we will likely hold on to northerly winds of moderate to fresh breezes for areas north of Vanderbilt Reef. We approach with caution as areas south of Pt. Retreat and Douglas are likely to maintain easterly near-gale to to gale force conditions. Wind and seas subside Friday morning bringing better conditions until outflow begins Sunday.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Winter Weather Advisory from midnight tonight to 3 PM AKST Thursday for AKZ318. Winter Storm Warning from midnight tonight to 3 PM AKST Thursday for AKZ319. Wind Advisory from 3 AM to 6 PM AKST Thursday for AKZ320>322-324- 325. High Wind Warning from 3 AM to 6 PM AKST Thursday for AKZ323- 326>330-332. Wind Advisory until 3 PM AKST this afternoon for AKZ330-332. MARINE...Storm Warning for PKZ033-035-036-641-642-661>663. Gale Warning for PKZ013-021-022-031-032-034-643-644-664-671. Small Craft Advisory for PKZ011-012-053-651-652-672.