textproduct: Juneau

MID MORNING AND 18Z AVIATION UPDATE

VFR to MVFR conditions remain across most of the panhandle this morning as a weak low tracks across the area, though Gustavus has been experiencing CIGS around the IFR threshold. Generally, VFR conditions for the southern panhandle, with somewhat lower CIGS of 2k to 4k feet resulting in MVFR for the north through the morning, though expect improvements to VFR for most places this afternoon. Expect some scattered showers through the day, primarily for the north and central panhandle. Sea breezes of 10 to 15 kt are expected, especially for Ketchikan, Skagway, and Juneau, but otherwise winds will trend towards remaining under 10 kt near sea level for TAF sites.

For the northern panhandle, precipitation streaming from interior Canada westward has proven more persistent and widespread than previously forecast. An update has been issued regard this increase in coverage of light rain showers embedded in the easterly flow aloft impacting the far northern panhandle and northern gulf coast. Precipitation is expected to gradually diminish through the afternoon and evening hours, though isolated showers that develop over the Yukon could still advect southward through the evening. This will be analyzed further for the afternoon forecast package.

PREV DISCUSSION......ISSUED AT THURSDAY JUNE 18 AT 551 AM

SYNOPSIS...

Key Messages:

- Isolated showers and mostly cloudy skies continue across SE AK through early Thursday as an upper level system moves across the panhandle.

- Warmer temperatures, sunny skies, and drier conditions are anticipated for this weekend as an area of high pressure remains over the gulf, with high temperatures reaching into the 70s.

- A region of good heating Friday may lead to stronger convection along the Chilkat range and north to British Columbia border. and the remains of an upper level features on Saturday cloud develop the stronger convection for the Misty Fjords north to about Ernest Sound.

SHORT TERM.../Through Saturday night / A weakening low pressure weather system will move to the panhandle and track across it Friday before taking the remains into British Columbia. Showers nearly over the for SEAK, however, some afternoon convection possible wit afternoon heating. High temperatures warming for the most part warming form the 50s t upwards of the 70s, with warmest sections along the mainland and inner channels. A marine layer still evident based on satellite imagery in the gulf and near the coast. Patchy morning fog this morning should be going away by mid morning and anticipate that it could reform overnight again.

LONG TERM.../Saturday through Tuesday/...(written Wednesday afternoon) With the ridge in the Gulf of Alaska strengthening Saturday, drier and warmer weather is still expected across the majority of the panhandle for the upcoming weekend. With this pattern, a marine layer is also likely over the gulf, though as of this forecast it is not expected to push into the inner channels due to flow largely parallel to the outer coast. With the location of the ridge axis, descending drier air should help suppress cloud development over the inner channels Saturday and Sunday, with high temperatures looking to reach the low to mid 70s. Temperatures aloft are not particularly warm, therefore as of this forecast, daytime highs are not expected to meet or exceed any records.

Winds across the panhandle and southeastern Gulf of Alaska will generally drop off as the ridge axis rotates over the region. Clearing skies will allow for sea breeze development in the usual areas, though the lackluster surface gradient should limit strength of these developing breezes.

As is often the case, model guidance begins to diverge as we head into early next week and energy in the western gulf attempts to erode the ridge over the eastern gulf and panhandle. Forecaster confidence is low for the ridge backing down so easily, with dry and warm conditions expected to continue through early next week as of this discussion. The area with the highest uncertainty would be the northern gulf coast, as it will be on the back end of the ridge axis by that time.

AVIATION... Locations across the panhandle vary from MVFR to IFR CIGs as lingering low clouds move through the area. MVFR CIGs boarder on 3,000ft, except for PAGS sitting around 1,500ft, and are expected to improve to VFR conditions over the rest of the morning. Winds are also expected to pick up this morning with daytime heating and resemble typical sea breeze directions as the day goes on. Winds are then expected to calm again tonight, bringing the possibility of borderline MVFR CIGs back across the panhandle. Most guidance is indicating the likelihood of VFR conditions to persist through the period with little to no precipitation. The only exception is Yakutat, with guidance indicating IFR conditions overnight. This could be due to the expected clearing through the day and anticipated light winds overnight bringing the possibility for patchy fog. However, offshore flow in the upper levels is directing drier air towards Yakutat, so confidence is low that fog will develop.

MARINE... Outside (Gulf and Coastal Waters): A weak low makes it's way onto land this early morning, causing mostly light and variable winds to the gulf. A stronger high pressure center just south of the area looks to bring west to northwesterly winds through the day today once the low moves through the area. These northwesterly winds are expected to be accelerated by the coastal terrain, specifically around prominent capes, causing winds to reach up to 20-25kts by this evening. In the northern outer waters, 15-20kts are more likely to be expected around Cape Fairweather and Cape Spencer, while winds in the southern outer waters will have more time to accelerate up to 20-25kts. This phenomena is expected to continue through the day Friday before diminishing through the day Saturday. Through the period , waves are expected to sit around 4-5ft and build up to 8 ft in the southern outer waters with the acceleration of wind along the coast.

Inside (Inner Channels): Thursday brings generally lighter winds to the inner channels, reaching 10kts with typical sea breeze directions. Lynn Canal and Clarence Strait look to be the outliers for this trend are expected to reach up to 15-20kts (SE in Lynn and NW in Clarence). Winds are also expected to increase in Cross Sound and Icy Strait as terrain forced channeling around prominent capes causes surface winds to accelerate, up to 10-15kts with a westerly direction. This trend is expected to continue again on Friday before winds diminish across the area and become calm and variable on Saturday.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...Small Craft Advisory for PKZ641-661.