textproduct: Juneau

UPDATE

Update to the Aviation Section to include the 06z TAFs.

PREV DISCUSSION......ISSUED AT 433 PM AKDT Mon Apr 13

SYNOPSIS...

- Tuesday is expected to see a clearing from north to south, with increased chances of sun and warmer temperatures.

- Showers return late on Wednesday and into Thursday.

SHORT TERM...

A broad area of low pressure in the Gulf is bringing with it rain and snow showers across SE AK, driven by continuing onshore flow and conditional instability. 850 mb temperatures are between -6C and -8C, and 1000 to 850 mb thickness values of 1285-1290 decameters would normally indicate the potential for accumulating snow under these conditions. However, diurnal heating has proven sufficient to hold most of the accumulations at bay, with the bulk of the snow melting almost as quickly as it can falls in areas under heavier bands of showers.

Overnight, the low will begin to traverse SE and showers will diminish across the northern half of the area. This will set the stage for fog development for areas north of Sitka. Showers continuing across the southern panhandle could drop minor snow accumulations of less than an inch during the same timeframe as diurnal heating subsides. Tuesday will see showers dwindle across the remainder of the area and drier weather take hold. Some locations will likely climb into the 50s. Tuesday night will see returning chances of fog, this time reaching further into the southern panhandle, but drier weather will continue through most of Wednesday until a shortwave manages to race over the axis of the ridge and into SE AK Wednesday night.

LONG TERM...The low impacting the southern panhandle Tuesday will continue to dip south into Wednesday, allowing for skies over the rest of the panhandle to clear out. A broad upper level ridge develops, with the associated surface level ridging positioned to continue onshore flow into the panhandle. Mid level moisture looks to move into the northern panhandle with a shortwave trough on Wednesday night, allowing for light snow in Yakutat and parts of the far northern panhandle Thursday morning. Snow is not really expected to stick for these locations as temperatures remain around freezing, though higher elevation areas and the Klondike and Haines Highways may see up to an inch. This precipitation will be a mix or all rain for the rest of the northern and central panhandle Wednesday, moving into parts of the southern panhandle through Wednesday night into Thursday. Showers are expected to continue until Thursday night, when a more organized front moves into the panhandle from northwest to southeast. This will bring widespread precipitation to the panhandle Friday into Saturday, though QPF remains on the lower side. Again, Yakutat and the northern highways may see snow with this front, though daytime temperatures should only allow for minimal, if any, accumulation. Precipitation is expected to taper down through Saturday, though it may not completely stop until Sunday. The only real wind issue is expected near the typical hot spots from Thursday into Friday as the front moves inland, with Lynn Canal, southern Stephens Passage near Five Finger Lighthouse, and around Point Couverden potentially seeing small craft advisories through this period.

AVIATION.../Until 06z Wednesday/...Showers across the panhandle continue to bring MVFR down to IFR conditions this evening with rain and snow. These showers have been starting to end from north to south and will continue to diminish through the overnight hours into Tuesday. With the clearing skies, there in an increasing potential for some fog development, especially across the northern panhandle should winds continue to diminish. Farther south, the showers are expected to persist into the morning hours as the low bringing these showers to the area starts to work to the south. With the showers, AAWU forecasts for icing show a broad area for potential icing from FL040 to FL100. This area of icing is expected to decrease in size as over the southern panhandle going into tomorrow morning.

MARINE...

Outer Coastal Waters: As a low treks off to the south, winds will turn out of the NW through Monday night. Anticipate winds will strengthen to fresh to strong breezes across the outer coastal waters, with the strongest winds south of Kruzof Island. Waveheights of 5 to 7 ft are expected for areas north of Kruzof, while waveheights of 6 to 9 ft are expected for areas south. Through Wednesday, winds will shift out of the W before becoming SW on Thursday. SW swell with wave periods of 7 to 10 seconds.

Inner Channels: Winds in the inner channels remain out of the south through the evening hours on Monday, with fresh to strong breezes, especially for Lynn Canal and Stephen's Passage. As a low tracks south through the night, winds weaken and eventually flip out of the North. Winds will strengthen again to fresh breeze - although this time out of the north - through the day on Tuesday. Winds will flip back out of the S on Thursday as the pressure gradient once more flips.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...Small Craft Advisory for PKZ012-022-641>644-661>664-671.