textproduct: Juneau

SYNOPSIS

Key Messages:

- Low and frontal band moving into British Columbia Coastline just north of Vancouver Island Friday.

- The next big low (roughly in the mid 960mb range) to impact Southeast Alaska Sunday as it and the associated frontal band moves through the SE Gulf of Alaska on Sunday.

LONG TERM.../Monday through Friday/

The active pattern continues into next week, with the system impacting the panhandle during the weekend continuing to meander northwestward towards Prince William Sound and weaken by Monday morning. Multiple shortwaves will push across the Gulf Monday through Tuesday, keeping precipitation and elevated winds in the forecast with each wave passing through.

Some uncertainty in the forecast remains for midweek, however, on the synoptic setup and potential for a brief pattern change with snow going into the end of the week, with some model guidance suggesting high pressure building in the Gulf and over the panhandle Wednesday alongside a brief cooling and drying trend ahead of the next system. This solution would bring snow levels down across the northern panhandle and along the coastal range Wednesday into early Thursday morning, with snow levels down to 1000 ft or less, and bringing potential for snow at sea level for the northern panhandle Thursday as the next system moves into the area. However, there is a lot of uncertainty regarding this, as some guidance suggests warmer air and moisture with the next system moving in much sooner and not allowing as long of a period for cooling temperatures or lowering snow levels, with a much weaker ridge not holding the system back. Other guidance shows this ridge being strong enough to keep precipitation out of the area by the end of the week, though at this time this looks to be an outlier compared to other solutions. It will be something to watch as confidence increases in a specific solution, however there is a notable probability in seeing some snow or snow mixing in with rain at sea levels for Skagway and Haines, potentially down to Icy Strait Corridor, into the end of the week depending on how favorable the setup is for snow.

AVIATION

A low over the eastern Gulf of Alaska will continue moving north over the next 24 hours. The associated front arcs over SE Alaska and will move north with the low. While ceilings are mostly VFR for the region occasional MVFR is expected as the front moves through. Isolated IFR ceilings are possible during the overnight period this will mostly be at the more sheltered terminals as well as behind the main front. Any IFR conditions that develop should be short lived as gusty winds will keep the lower atmosphere fairly well mixed preventing widespread fog formation. However, the gusty winds will bring alongside the potential for LLWS, the magnitude and timing of LLWS is variable across all the SE AK terminals so consult TAFs and AAWU forecast for more details.

Ceilings and visibility will improve throughout the day Saturday from north to south, however, the improvement will be short lived because the next low pressure system will be moving in from the SW and will bring another round of lower ceilings, visibility and gusty winds Saturday evening/night.

MARINE

Outside:Fridays weather is currently being driven by a broad decaying storm force low located near 47N 135W, with the resulting surface pressure gradient drawing outflow of fresh to strong breezes out of the Panhandle. Along the coast, sea state is dominated by a trifecta of swell systems, with buoy 84 reporting stout SSW ground swell at 17 seconds being buried by southerly swell groups focused at 10 to 12 seconds. All combined, these groups are driving significant wave heights of 8 to 10 ft near the Fairweather Grounds, 12 to 14 ft near Cape Edgecumbe, and near 16 ft for waters west of Dixon.

Friday afternoon a disturbance is lifting north along the coast, with northeasterly winds breaking down and becoming southeasterly fresh to strong breezes thru the night. This wind shift foreshadows an approaching 963mb Storm Force low, which will be near 48N 140W Saturday morning. Conditions deteriorate thru Saturday becoming southeasterly gales along the coast of Prince of Wales and into Dixon; Cordova Sound and southern Clarence Strait will be particularly intense. This band of gales will lift north Sunday into Monday toward the Kenai, with conditions continuing to worsen along the northern coast.

Primary forecast challenge Friday was in the strength and direction of winds and resultant waves Sunday into Monday, with ensembles certainly suggesting southeasterly gale to strong gale force conditions for much of the eastern Gulf. For now, we continue to message winds somewhere between Gales (Force 8) and Strong Gales (Force 9), focused along much of our coast. Sunday fresh seas likely build to near 20-25 ft, becoming southwesterly Monday.

Powerful southwesterly wave energy from a decaying storm force system near 54N 154W will move toward the coast Monday into Tuesday, with buoys 83 and 84 likely reporting 15 to 20 ft significant wave heights near 13 to 15 seconds. Wont be clean, anticipate southeasterly fresh seas to ride over the swell creating rough conditions as the parent gale force low decays near the Kenai.

Active storm track continues for the Gulf next week.

Inside: Friday afternoon outflow winds are beginning to break down and become southeasterly as a system lifts along the coast. Expect Icy Strait and other east-west passages to start freshening up, with major north-south passages losing the northerly component for a few hours. The exception will be Lynn Canal where we will hold on to Strong Breezes to Near Gale Force, ebbing to moderate breezes at times, into the weekend.

By Saturday morning Clarence Strait to Sumner Strait will be see strengthening southeasterly winds, with fresh breezes becoming the dominant feel. Northerly winds will begin to get pulled out of Stephens Passage, as east-southeast winds continue to strengthen. Along and south of Sumner Strait, particularly in waters south of Gravina Island, winds will increase to gale force by Saturday late afternoon to evening.

Southeasterly Gale Force winds expand in Clarence Strait Sunday, with strong breezes to near-gale force conditions for waters along and south of Frederick Sound.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Wind Advisory from 6 PM Saturday to 6 AM AKST Sunday for AKZ328. Wind Advisory from 3 AM Sunday to 6 AM AKST Monday for AKZ330- 332. MARINE...Gale Warning for PKZ641-661. Small Craft Advisory for PKZ012-013-022-036-053-642>644-651-652- 662>664-671-672.