textproduct: Juneau

SYNOPSIS

Key Messages:

- A low pressure system pushes into SE AK Saturday bringing increased winds and precipitation.

- Outflow pattern allows for drier and colder weather Sunday into next week.

- The outflow pattern will bring strong winds over northern SE AK. These strong winds with colder temperatures will create moderate freezing spray over northern inner channels.

LONG TERM

/Sunday through next week/ One main area of interest going into this weekend and next week. That being the arctic cold front moving from north to south on Monday, bringing the panhandle finally back into cold temperatures.

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. Little change in overall message going forward for the Monday time range. Pressure gradients between Juneau and Skagway look to be around 8-9 mb, with large density differences look to bring forth up to 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. Similarly, gradients between Juneau and Ketchikan look to support up to gale force winds down Stephens Passage. Couple of caveats to this forecast: how fast and strong are the cold temperatures going to filter southward, and how long will the stronger winds stick around out of the north. At this time, not looking to see cold temperatures supportive of any moderate or greater freezing spray late Sunday night for the far northern inner channels. Then, expecting moderate freezing spray chances to move south over the day, making the most progress overnight. Looking to see freezing spray chances extend as far south as southern Stephens Passage and just south of Point Couverden.

Beyond Monday, things get a tad more complicated. At this point, there is around a 60% chance for pressure gradients to moderate, in part due to a flatter ridge aloft. While this would keep temperatures much colder, it would relax winds significantly even by up to 10 knots. Unfortunately, since temperatures are anticipated to be so cold at this point, moderate freezing spray is still a possibility, even with wind speeds less than 30 knots. That being said, there is a 40% chance, mainly represented in the GEFS, for a dominant high amplitude ridge, which would keep the stronger winds in place, and bringing down the moderate or greater freezing spray chances much further down than currently anticipated.

AVIATION

/through 12z Sunday/ Predominate MVFR to VFR flight conditions with isolated IFR CIGS ongoing across the panhandle this morning, CIGS generally AoB 4500ft as upper lvl ridging moves in aloft from stout high over the NW Pacific. Visibilities have improved overnight across the area, patchy dense fog near the Stikine Delta northward to PAPG has lifted to low stratus around 500 to 1500ft with widespread visibilities over the panhandle 3SM or greater. Moving into Saturday, preciptiation becomes more isolated and showery in nature, IFR CIGS improve to MVFR with predominate MVFR flight conditions prevailing with periods of VFR through 00z this afternoon. Conditions deteriorate after 00z from NW to SE across the panhandle starting with PAYA as a quick moving system pushes snowfall across the N Gulf and into the northern panhandle, reaching PAJN through 06z this evening. Given orientation of the approaching low, not anticipating much LLWS impacts from this system through Saturday night into early Monday. Surface winds through the TAF period will remain benign, around 12kts or less.

MARINE

Inside (Inner Channels): As broad ridging continues over the gulf, generally light winds remain across the inside waters. These lighter winds have allowed for areas of fog and low stratus to continue this morning reducing visibilities to below 1 nautical mile in some isolated areas. The one area that is seeing some stronger winds is near Cape Spencer with winds around 20 kts this morning. Winds across the area will increase later today as a low pressure system pushes into the NE gulf, eventually moving southeast across the panhandle. As this low moves southward, winds will become northerly and greatly increase due to a tightening pressure gradient. At the same time, high pressure builds over the Yukon starting what will be an extended period of outflow conditions. This will bring gale force conditions throughout many of the inner channels, with the strongest winds most likely over Lynn Canal on Monday. Along with these strong winds, decreasing temperatures will allow for freezing spray to develop.

Outside (Gulf and Coastal Waters): Ridging remains over the gulf allowing for west-northwesterly winds to continue this morning. Conditions will deteriorate starting Saturday night as the next system pushes into the NE gulf moving southeast across the area. This system will bring gale force northwest winds to the central gulf with seas building to around 15 to 20 ft lasting through Sunday. This low will is very likely to be a quick moving system, departing SE out of the panhandle by Monday morning. As this low moves southward, strong offshore and outflow conditions develop. Because of this outflow, mariners transiting along the N Gulf early next week should remain aware of areas of strong winds out of outflow prone areas like Cross Sound, Yakutat Bay, Disenchantment Bay, Alsek River Valley, and the Dangerous River Valley.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...High Wind Watch from late Sunday night through Monday morning for AKZ325. MARINE...Small Craft Advisory for PKZ022-053-641>644-651-652-661>664-671- 672.