textproduct: Juneau

SYNOPSIS

Key Messages:

- This outflow pattern will strengthen Monday and continue through the week bringing strong winds, colder temperatures, and moderate to potentially heavy freezing spray over northern and portions of the central inner channels.

- Mountain wave activity increases Monday morning with the potential for wind gusts up to 45 mph for Downtown Juneau and Douglas. A Wind Advisory is in effect late Sunday night through Monday afternoon.

LONG TERM.../Monday night through Friday/

Over the week the primary threat continues to be outflow conditions, freezing spray, and very cold temperatures as cold arctic air infiltrates the panhandle, bringing a sudden return to true winter. Touching on wind first, we remain highly confident that we will see northerly winds of at least 25 to 30 knots spread across the northern inner channels through Tuesday, with a mountain wave event for downtown Juneau bringing frequent gusts of 40 to 50 mph. The main question is the potential of gale, to strong gale, force outflow winds ebbing and flowing through the week, which has serious implications on mariners safely navigating the inside. For now, the published forecast has strong gale force conditions in Lynn into Tuesday. Guidance continues to relax the north-south pressure gradient mid to late week, which would result in winds diminishing as low as strong breezes. However, do not let this catch you off guard. The winds will increase again to at least gales sometime by next weekend, as a strong north- south pressure gradient builds back. Freezing spray really becomes a threat for most inner channels through early Wednesday, before being mostly confined to the northern inner channels for late week. Heaviest freezing spray will be in Lynn Canal, Taiya Inlet, Stikine Inlet, and Unuk River Inlet.

It will become very cold, below 0F in the north, single digits in the Icy Strait corridor, and teens to low 20Fs in the central and south. Wednesday night there is some signal that a shortwave trough will rotate around a stout ridge in the Pacific, perhaps bringing some snow to the region Thursday. Guidance usually struggles with a strong ridge over the region, we approach cautiously.

For next weekend, models are trending towards the development of stronger high pressure over the interior driving much colder air southward into the panhandle once more. This has the potential to produce stronger outflow conditions than earlier in the week, with sustained storm force winds along the northern inner channels, namely Lynn Canal, and dangerous freezing spray Saturday into next Monday.

AVIATION.../through 12z Tuesday/

Offshore conditions have begun allowing for widespread VFR conditions and clearing skies. Ketchikan and Annette Island are the last areas to get rid of precipitation with times of light snow or a rain snow mix lasting into this morning. For these southern areas, conditions have improved over the last couple of hours with broken to overcast ceilings now around 3000 ft. There may still be short times of MVFR ceilings below 2500 ft, but overall conditions will continue to improve.

Otherwise, outflow begins across the panhandle throughout the day. Because of this, VFR conditions with clear skies will continue across a majority of SE AK. Main impacts will be increased winds and LLWS. Areas that will see wind shear, of 30 to 40 kts at 2000 ft, will be along the gulf coast, especially near Sitka, and areas that are affected by gap winds/outflow winds. Specifically those areas are mainly over downtown Juneau (from Taku Inlet) and near Wrangell (out of the Stikine River Basin). Those areas, along with Skagway and Haines, will see the strongest wind gusts today. Through this morning, wind gusts will increase to around 45 mph over Downtown Juneau and Skagway. Strongest wind gusts are likely this afternoon into this evening.

MARINE

Inside (Inner Channels): Wind are increasing across the inner channels, with sustained gale force winds already present in Stephen's passage, and gale force wind gusts across the central and northern inner channels as outflow winds continue to strengthen By this afternoon, sustained northerly gale force to strong gale force winds (34 to 47 kts) will have spread across Glacier Bay, Lynn Canal, Stephens Passage, and Chatham Strait. These stronger winds will last well into the week as outflow continues, although a bit of moderation is possible on Tuesday, as the gradient temporarily weakens. Along with these strong winds, decreasing temperatures will allow for freezing spray to develop. Freezing spray will also increase in intensity today with moderate freezing spray over the aforementioned areas. Areas of heavy freezing spray are also likely over portions of Lynn Canal and Glacier Bay.

Outside (Gulf and Coastal Waters): Near gale to gale force conditions will continue across the gulf as a low pressure system pushes SE across the panhandle. This system will bring gale force northwest winds to the central gulf with seas building to around 15 to 20 ft lasting through Sunday. Strong offshore and outflow conditions develop leading to mariners transiting along the N Gulf early next week needing to 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...Wind Advisory until 6 PM AKST this evening for AKZ318. Wind Advisory until 3 PM AKST this afternoon for AKZ325. MARINE...Heavy Freezing Spray Warning for PKZ011-012. Gale Warning for PKZ011>013-021-022-031>034-643-644-651-661>664- 671. Small Craft Advisory for PKZ036-053-641-642-652-672.