textproduct: Juneau

LONG TERM.../from Thursday onward/

Confidence is increasing in a frontal feature and associated atmospheric river bringing moderate to heavy precipitation to the panhandle late Thursday night and into Friday. Moderate precipitation is expected to continue into the weekend from this system. A hydrologic outlook has been issued highlighting the increasing confidence and potential impacts from this synoptic pattern. For more information on potential hydro concerns, see the hydrology section below.

Continuing from the short term, the leeside low pressure system in the vicinity of Kodiak Island will throw multiple waves rotating outward from it and towards the panhandle into Thursday bringing modified arctic air. This is expected to lead to a transition to exclusively snow showers by Thursday along with falling temperatures. Daytime highs for Thursday will range from the upper 30s in the south to mid to upper 20s in the far northern panhandle.

For the end of the week, an elongated trough extending from an Aleutian low is expected to develop into a closed low feature and steer a plume of moisture towards the panhandle Friday. Ensemble guidance is trending toward an amplifying upper level ridge that will punch northward into the central gulf before sliding eastward over Canada Friday night into Saturday. The source region for this plume and orientation of surface and upper level winds increases the likelihood of snow levels rising rapidly from south to north through the day Friday and into Saturday, with the greatest change occurring in the southern panhandle. Concurrent rising temperatures leading and a transition to rain/snow mix and straight rain will progress from south to north Friday, though some snow accumulations are likely initially, particularly for the central and northern panhandle. Gale force winds will spread into the gulf as well as the inner channels, particularly Clarence Strait.

As is often the case, the major forecast challenge over the coming days will be how strong the system is and its track, which will determine how far the warm southerly progresses up the inner channels as well as the extent and duration of highest precipitation rates. Overall there is increasing confidence that next weekend a majority of the panhandle will see daytime high temperatures approaching 40 degrees, with the far southern panhandle reaching the mid to upper 40s Saturday. These above normal temperatures are expected to stick around through the weekend and into early next week.

AVIATION

Showers continue across the panhandle allowing for variable flying conditions between MVFR and VFR into tomorrow. Snow showers over the far northern panhandle have ended with increasing temperatures, allowing for flying conditions over Yakutat and Haines to greatly improve. Temperatures and precipitation type will continue to be a forecast challenge for areas north of the Icy Strait Corridor throughout the TAF period. Temperatures will once again decrease tomorrow allowing for precipitation to change back to snow and a rain/snow mix over the panhandle.

The strongest winds continue to be over the northern panhandle, especially over Skagway. These strong winds will continue throughout the TAF period. The strongest winds will occur this evening into early morning with wind gusts up to 40 kts possible.

With continued onshore flow and showers, convection along the central and southern gulf coast will continue. There has continued to be short times of lighting near Baranof and Prince of Wales Island. These showers will also allow for times of sporadic and gusty winds as they move over the area.

MARINE

Outer Coastal Waters: Waveheights remain elevated to ~25 feet for the outer Gulf, and 15-20 feet for the outer coastal waters through Wednesday as a decaying low remains anchored over the northern Gulf. The highest wave heights will be for areas south of Cross Sound. By Wednesday night, an improving trend starts takes hold, and by Thursday afternoon, wave heights have diminished to 7-11 feet, with the higher wave heights for areas south of Sitka Sound, with winds likely dropping to fresh breeze by Thursday afternoon. Conditions deteriorate once more on Friday, as another front moving up from the South

Inner channels: Winds hover around fresh to strong breeze, remaining out of the south across many of the inner channels through Wednesday as bands of showers continue to cross the panhandle. Lynn Canal may switch out of the north Wednesday night.

HYDROLOGY

Off and on showers will continue through mid week as a low in the NE Gulf sends waves of precipitation across the area. Looking towards the end of the week, the next organized system will push an atmospheric river into the panhandle late Thursday night through Friday. This system will bringing rounds of moderate to heavy rainfall and rapidly rising freezing levels for communities across the panhandle.

For the northern panhandle, current forecast rainfall amounts are around 1 to 2 inches, with locally higher amounts approaching 3 inches at higher terrain. This rainfall in combination with rapidly rising freezing levels around 2000 to 3000ft by Friday afternoon into the weekend. This rainfall in combination with rapidly rising freezing levels around 2000 to 3000ft through Friday afternoon will lead to localized flooding concerns like ponding on road ways and poor drainage due to snow blocking drains along and north of the Icy Strait Corridor, including but not limited to Juneau, Gustavus, Hoonah, Yakutat, Haines, and Skagway.

For the central and southern panhandle, current forecast rainfall amounts are around 2 to 4 inches, with locally higher amounts approaching 5 inches at higher terrain. This rainfall in combination with rapidly rising freezing levels around 3000 to 5000ft will lead to localized flooding concerns like rapid river rises on small streams, ponding on road ways and poor drainage due to snow blocking drains along and south of a line from Sitka to Angoon to Petersburg.

For all of the panhandle, any existing snowpack will become more dense and hard to move by Friday. Additionally, hard pack snow on driveways, parking lots, and sidewalks will become very icy. Preparations should begin for an expected rain on snow event going into the weekend. Stay tuned for further forecast updates on this system moving through the week.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...Small Craft Advisory for PKZ012-013-022-031-036-053-641>644-651- 652-661>664-671-672.