textproduct: Juneau

UPDATE

Updated 06z aviation section.

SYNOPSIS

Key Messages:

- Cooler with rain spreading north across the panhandle, wind gusts 25 to 35 mph expected within Northern Lynn Canal northward to Haines and Skagway through the evening.

- Multiple systems move through the area next week, bringing rain to the area. Best potential for rain will be across the southern panhandle.

LONG TERM

A persistent, positively tilted upper-level low will linger over the region through the end of the week and into the weekend. As an upper-level ridge over the Alaska Peninsula tracks eastward, this trough will evolve into a closed-off low before weakening and moving out of the region by Sunday. Simultaneously, a surface low originating from Prince William Sound will stall just west of Haida Gwaii, gradually weakening as its upper-level support wanes. This pattern will result in bands of rain pushing northward, primarily impacting the southern Panhandle and Coast Range, though precipitation totals are expected to remain seasonably normal, with the highest QPF amounts on Wednesday and possibly Friday. While the southern Panhandle remains predominantly wet and showery under persistent SE'rly flow, the North Gulf Coast is expected to see a break in heavier rain showers towards the end of the week. As the surface low dissipates southward over the weekend and a ridge attempts to build, northerly winds and warming 850mb temperatures over the northern and inland parts of the panhandle may lead to down sloping and warmer surface temperatures in the mid 70s near Yakutat, Skagway, Haines, and Hyder. Model guidance is in general agreement regarding the evolution of the low, though there is some uncertainty in resolving local wind convergence through Dixon Entrance into southern Clarence Strait. While winds will likely see their most significant push northward on Wednesday, current thinking is that wind speeds will remain around 20kts or less, gradually diminishing afterwards.

AVIATION

A front is exiting into the Yukon, currently working its way over Haines and Skagway at time of writing. The thermal gradient that has plagued the aforementioned areas with stronger winds is expected to fully collapse in the next few hours, decoupling to light winds overnight. With continued rainfall however, there is the possibility of a developing cloud deck AOB 1000 ft. For the NE gulf coast, higher confidence for a cloud deck AoB 1000 ft with IFR conditions from persistent southwesterly onshore flow. For the Icy Strait corridor, should have some clearing tomorrow with the possibility of sea breezes developing. For the far south, continued rain showers with breezy conditions specifically for the ketchikan area. Biggest concern are the heavier showers, with may bring CIGs down to low MVFR for both CIGs and VIS for short periods of time.

MARINE

Outside (Gulf and Coastal waters): Sunday late morning, our suite of observations showcase southeast winds of moderate breezes across most of our coast, with Cape St. Elias reporting northwesterly winds of moderate breezes. Sea state is currently dominated by three wave systems, the dominate is south swell of an impressive 20+ seconds, a secondary southeast swell at 15 seconds, and wind waves at 7 to 9 seconds. Combined these groups are bringing significant wave heights of 3 to 5 ft. Moving through the next 24 hours southeasterly winds expand across our coast as a surface low moves toward Haida Gwaii. For areas north of Cape Edgecumbe, expecting winds to remain at or below moderate breezes, with the low beginning to pull northerly winds out of Chatham Strait Monday evening. For areas south of Cape Decision expect east to southeast winds of moderate to fresh breezes, with easterly winds building Monday night across southern PoW and Dixon Entrance.

Touching on waves, anticipate a building wind wave regime, particularly west of the Sitka coast and Prince of Wales Island. This wave group will try to mask underling prominent southerly swell; however, significant wave heights should remain near 4 to 6 ft, with 6ft more likely west of Dixon Entrance and the PoW coast.

Inside (Inner Channels): Primary challenge Sunday morning was the timing for southeast winds in Lynn Canal as a weak front moved across the area. As of this writing, southerly winds have finally pushed through Lynn, with speeds of moderate to fresh breezes bring reported. For the remainder of the inside, winds are largely at or below moderate breezes, with the exception being Clarence Strait, with southerly winds continuing to build to fresh breezes.

As we move into Sunday night and into Monday, southerly winds slowly diminish across the inside but remain south, with the exception of southern Clarence Strait with continued moderate breezes from the south. As a surface low moves toward Haida Gwaii Monday evening, winds become northerly again through the central and northern inner channels, with building northeast to east winds in southern Clarence/Dixon. Mariners transiting the Inside Passage late Monday night/Tuesday morning should be aware of building northeast winds of moderate to fresh breezes for Southern Clarence Strait and Revilla Channel (Revillagigedo Channel). Furthermore, northerly winds of fresh breezes is forecasted in southern Chatham early Tuesday morning.

AJK WATCHES/WARNINGS/ADVISORIES

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