textproduct: Juneau

SYNOPSIS

Key Messages:

- Multiple weak fronts look to move over the panhandle through early next week, bringing increases in wind and precipitation chances, with breaks in between.

- After this front moves past any given area, periods of clearing and fog potential increase.

- A possible atmospheric river could move into the southern half of the panhandle by mid next week. Flooding and an increase in winds are possible, with a hydrologic outlook issued in response. Accumulating snow near Haines and Skagway highways are also a concern.

LONG TERM

An unsettled pattern of above normal temperatures and continued moist onshore flow remains on tap for SE AK heading into next week. This is being driven by an upper level pattern featuring a broad trough over the Bering Sea and northern Pacific, with an upper level ridge over the US and Canadian west coasts. This ridge will be amplified in the early week as an embedded short wave trough rotates into the Gulf of Alaska and deflects the jet stream northward, bringing increased southerly and southwesterly flow aloft over the region.

Lower in the atmosphere, this will result in predominantly south/southwesterly flow, with energy from a broad surface low in the western gulf throwing multiple fronts and short wave features towards the panhandle. The strongest of these features is expected to be a gale force front Tuesday that will also be directing an atmospheric river, primarily towards the southern panhandle, with the potential for 2 to 5 inches of rain over 48 hours. The ECMWF extreme forecast index continues to paint a target over the southern panhandle for extreme rainfall from 0z Wednesday through 0z Thursday, as well as highlighting above normal temperatures across a majority of the panhandle throughout most of the week. With the ridging aloft and down to the surface over interior western Canada, the approaching gale force front will lead to increasing winds out of east/west facing gaps and valleys such as around the Stikine Delta and also Taku later on. The orientation of the front as it approaches will be key not only in the moisture transport and thus timing of heaviest precipitation, but also when and where the strongest winds will set up Tuesday.

As of this forecast discussion, the strongest winds are expected along the outer coast and in the area of Dixon Entrance Tuesday, increasing late Monday night into Tuesday morning. By late Tuesday night, the front is expected to have pushed northward and begun to lift inland, with surface winds beginning to drop off across the board, though likely holding on a bit longer around Dixon Entrance and along Hecate Strait. While most of the panhandle will see warming temperatures and thus moderate to heavy rainfall from this system, the higher elevations of the Klondike Highway may still remain cold enough for snow. Snow levels are expected to range between 1500 to 3000 feet and will largely depend upon how strong the southerly surge is coming up Lynn Canal. With the parent low remaining far to the west, there is a good chance for continuing accumulating snow at the highest elevations, particularly with the initial front on Tuesday. This will continue to be evaluated in the coming days.

AVIATION

/06Z to 06z/ Areas of fog has moved out of downtown Juneau but still seeing 1/2SM as of 6z Saturday night at PAJN. PAGS has had some fog as well, however with the frontal band actively tracking northward have visibility improving when rain arrives in the next couple hours. To the south, where light to occasionally heavy rain has been falling, CIGs have been MVFR to VFR due to the easterly component of the wind aloft with this front. Can already see the breaks behind the front on radar and think this will lead to some patchy fog across the south when things break out before dawn on Sunday. LLWS at several TAF sites with the frontal band tonight looking slightly weaker than predicted, but have observed 35kt at 2kft on the Biorka Radar VAD wind tonight out of the ESE. Within the next 24hrs another frontal band will track northward, in a similar fashion to tonight's, and cause another round of rain and LLWS. Timing of this next round of LLWS could be as early as 16-18z across the southern sites.

MARINE

Inside waters: Low wind conditions at the moment across the inner channels though expect winds to increase this evening as the next front moves in from the south. Clarence Strait will see the highest winds from the south with around 25 to 30 kt winds expected. Meanwhile Lynn Canal will see the highest northerly winds ahead of the front with 25 to 30 kt winds expected there this evening. Otherwise most areas will see winds of 15 to 20 kt as the front moves through. Expect another break in the winds Sunday before they start to increase again Sunday evening as the next wave moves in. Clarence Strait again will see the higher winds with 25 to 30 kt winds expected again from the S.

Gulf Waters: Mainly S to SE winds expected though the next 48 hours. Two periods of higher winds expected (Saturday night and Sunday night) with the first of the two periods showing the higher winds. Expecting around 35 to 40 kt min gale force winds with the first system that moves through, main for the southern half of the gulf. Only expecting around 30 kt winds with the second system on Sunday night. Seas are still high with 8 to 11 ft seas being common (with a 7 ft SE swell at 12 sec period). Expect seas to increase tonight to 11 to 14 ft with the incoming front and will likely stay that high into early Monday with the continued active weather over the gulf waters.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Dense Fog Advisory until 6 PM AKST this evening for AKZ325. Wind Advisory from 6 PM this evening to midnight AKST tonight for AKZ325. Wind Advisory until midnight AKST tonight for AKZ328. MARINE...Gale Warning for PKZ641-661>664-671. Small Craft Advisory for PKZ012-013-022-035-036-642>644-651-652- 672.