textproduct: Juneau

SYNOPSIS

Key Messages:

- A weak disturbance will slide south through SE AK late this afternoon into tonight, bringing a chance of showers.

- Quiet weather returns for Tuesday with more sun and dry conditions expected. Northerly outflow winds expected to increase through the inner channels and outer coastal waters.

- A return to a wetter pattern expected by the weekend.

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LONG TERM.../Thursday through Sunday/

A ridge of high pressure lasts over the Gulf and panhandle Thursday into Friday, however a pattern change begins Friday into the weekend with a return of a series of systems moving into the area. The first front will move in Friday from a low in the Bering Sea, with the front primarily looking to push into the northern Gulf coast Friday into Saturday morning, as the strong high pressure looks to keep the front further westward with lower chances of pushing into the rest of the panhandle until Saturday. The timing of this still looks to remain uncertain, largely dependent on how quickly the high pressure begins to break down with this strong low pushing eastward. It seems that more of the model guidance is keeping the front further west, slowing down the onset of precipitation. Alongside the uncertainty of timing, depending on when the front begins to push in will also affect the precipitation type expected; if the front moves in overnight into early Saturday morning, many locations across the northern panhandle may see rain with snow mixing in with the cold airmass in place and below freezing surface temperatures from overnight. However, if it moves in during the day Saturday and is delayed further on the timing, it is likely to begin as rain and stay predominantly rain, with the warmer air pushing into the area.

This more active pattern will continue through the weekend as a series of lows move into the Gulf from the south around this main parent low as it moves eastward towards the AK Peninsula by Sunday.

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AVIATION

Flight conditions over the central panhandle are poor at the moment, with a drifting marine layer reducing cigs to around 1-2 kft. As a pressure gradient gets set up, synoptic scale flow will become increasingly northerly and help to blow the last of the marine layer out of the area. Conditions will improve rather quickly, as exemplified by PAYA, which is rapidly changing from LIFR up to MVFR now that it is no longer covered. During the overnight period tonight, expect most if not all TAF sites to improve to VFR. The concern for the remainder of the 24 hour TAF valid period will be strong and gusty north winds, especially in the north where PAGY and PAHN could see gusts in excess of 20 kts during the day on Tuesday. When gusts get this strong we tend to look out for the occurrence of LLWS, but as the wind vectors are well aligned through the flight levels, there is little directional component to the shear, and thus likely will not become a concern.

MARINE

Outside (Gulf and Coastal Waters): High pressure dominates the Gulf of Alaska gradually shifting eastward Monday night into Tuesday, peaking around 1038 mb, centered near 50N, 150W. This feature is currently driving NW'ly 15 to 25 kt winds along the Gulf coast and in the offshore zones. Outflow winds from the inner channels will mainly impact the coastal zones from Cape Spencer southward. These elevated winds will likely persist through late Tuesday before diminishing Wednesday, with the Dixon Entrance region easing last. Seas will build alongside the winds, reaching 8 to 10 ft south of Cape Edgecumbe and 6 to 8 ft to the north. A low marine layer (1000- 2000 ft) has continued to push in along the NE gulf coast overnight, though is expected to be less impactful Tuesday morning due to increased winds along the coast.

Inside (Inner Channels): Light and variable winds persist this afternoon gradually increasing overnight. Outflow winds will strengthen across the panhandle beginning early Tuesday as a weak low slides south down the panhandle. This feature will tighten the pressure gradient between the high pressure in the Gulf and the interior high over the Yukon, primarily favoring N-S oriented inner channels. Winds begin picking up in the north, then spread southward. Lynn Canal will experience the initial increase, followed by Chatham Strait, Stephens Passage, Frederick Sound, and finally Clarence Strait by midday. Winds in these areas are likely to reach strong breezes to near gales, with gale force gusts possible in Lynn Canal and Chatham Strait. Wave heights will also increase, building to 4 to 6 ft, and 6 to 8 ft near ocean entrances. Winds and seas remain elevated across the region through the day Tuesday before diminishing Wednesday.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Wind Advisory from 9 AM to 8 PM AKDT Tuesday for AKZ318. MARINE...Small Craft Advisory for PKZ011>013-031>034-036-641>643-661>664- 671-672.