textproduct: Juneau

UPDATE

06z Aviation Discussion

LONG TERM.../Monday through Saturday/

Key messages: - Dry and partly cloudy conditions through the week - Potential for rain to return Thursday and Friday - Warming temperatures mid week

Details: Ridging moving north through the gulf will push the previous low out of the panhandle and set up for drier weather Monday. Clouds are expected to linger through the week, though the potential for skies to clear out keeps growing every day. The panhandle is expected to see partly cloudy conditions for much of the week, though periods of more or less clearing are possible throughout the day. Typically after there has been sufficient surface heating a marine boundary layer may develop, bringing clouds back to the northern panhandle. The southern panhandle will continue to get more and more clear through the week, with outflow winds picking up to moderate to fresh breezes coming out of Clarence Strait. Clearing skies and warmer temperatures aloft should allow for temperatures to rise near 70 degrees at the surface for a majority of the panhandle Tuesday and Wednesday, with the highest chances for the southern panhandle and communities in the inner channels. These temperatures could be offset in many areas by the development of an afternoon sea breeze. In the interior, Hyder could even see temperatures reach near 80 degrees during this time.

A disorganized surface level low with associated upper level troughing looks to bring precipitation back to the northern panhandle Thursday, spreading south through Friday. Model spread leaves much to be desired at this point, with many aspects of this system varying from run to run including timing and associated precipitation amounts. The GFS depicts a more organized system that will send a stronger frontal band over the northern panhandle with lots of precipitation, while most other models stay relatively dry and calm Thursday. Friday's condition remains dependent on this track; if the system reaches the panhandle Thursday morning that could mean Friday would be more dry, vs if Thursday is clear Friday could receive the precip instead. Stay tuned for further updates as we go through the weekend.

AVIATION.../Until 6z Monday/

The remains of the weather system pushing though the southern panhandle with northern edge of the precipitation line has pushed to Sitka, where the line of precipitation is expected to fall apart through this evening. South of the line, westerly onshore moist flow will keep low ceilings between IFR and LIFR for much of the night. Areas on the windward side of mountains facing the west are particularly prone to poor CIGs. Similarly, lighter winds and recent rainfall has made visibilities particularly variable between 2-4 NM. Not expecting much improvement for conditions south of Sitka.

Sitka is by far the most uncertain TAF site, as it sits directly on the boundary line between dry and moist air. Velocity radar returns show the winds aloft shifting southerly slightly, which is currently bringing down VIS from rain. However, as it moves SEerly with the low feature falling apart and dipping south, mountains look to block some precipitation.

Otherwise, look for all sites to improve drastically tomorrow, from north to south. Dry air from the north looks to sap away any residual moisture aloft, clearing skies and returning the panhandle to what is left of its summer. Expect sea breezes to develop with Skagway expected to increase to 15 knots by midday.

MARINE

Outside: As the incoming system hits the panhandle and weakens, expect moderate to fresh northerly breezes along Baranof Island and the NE Gulf coast. Special mention to Cross Sound, as a tip jet developing will provide the highest magnitude wind speeds for the northern half of the coastline in our AOR. In the southern panhandle, there is the possibility of a short lived gale at the entrance to Clarence Strait due to some terrain influences (barrier jet), but not expecting anything as drastic, with a swift change to westerly fresh breezes as the cold front pushes eastward into the panhandle.

Inside: Lynn Canal has been stubborn today to become light as a result of light troughing in the Yukon, but the gradient is expected to relax in the coming hours. Otherwise, southern Stephens Passage, Icy Strait, and Chatham Strait have all shift north to northeast and have begun to increase, reacting to the incoming low pressure off the coast of Baranof Island. Expect speeds to increase to around a moderate breeze before relaxing overnight. In Clarence and Sumner Strait, fresh to strong breezes are expected to pick up shortly in response to the warm front extending out from the low pressure. Looking towards Sunday, expecting comparatively warmer temperatures and sea breezes to develop. This means that Icy Strait, Point Couverden, Point Craven, and Lynn Canal are expected to increase up to 15-20 knots.

A marine layer could develop tomorrow evening, causing changes in wind speed in Icy Strait and visibility impacts to the outer coast and entrances to the inner waters; however confidence is low at this time.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...Small Craft Advisory for PKZ036.