textproduct: Juneau

SYNOPSIS

Key Messages:

- In the short term, on the downward swing with impactful weather as a front weakens over the Coast Range of SE Alaska. Heavy rain and significant wind impacts have diminished.

- Brief break in the persistent rain is possible Sunday night into Monday, however another front and round of heavier rain and wind push across the Gulf by Monday night.

- Increasing potential for a more impactful/strong area of low pressure developing over the Gulf of AK Tuesday and Wednesday.

LONG TERM.../Monday through Thursday/

An active fall-time weather pattern will continue across SEAK next week. Monday will start off with a ridge of high pressure over most of the panhandle, which could lead to fog development, with weaker onshore flow and light showers ahead of the next system. A progressive low and cold front will trek across the Gulf and reach Yakutat Monday afternoon before sweeping southeast across the panhandle Monday night into early Tuesday before weakening and stalling across southern panhandle, with onshore flow behind bringing steady rain into the panhandle. Total precipitation with this initial system will remain relatively limited, though a brief period of moderate to heavy rain and increasing southerly winds will develop ahead of the frontal boundary. Behind this initial system, a stronger low is forecast to deepen rapidly (~960 mb) as it lifts northeast into the northern Gulf of Alaska on Tuesday, stalling through midweek before gradually weakening and dissipating on Thursday. This strong low will quickly send another front and deeper moisture feed toward and through SEAK Tuesday into Wednesday, bringing moderate to heavy rain and strong gusty winds, along with severe marine hazards. South to southeasterly winds will intensify significantly on Tuesday, producing gale-force conditions in inner channels such as northern Lynn Canal and Clarence Strait, with gales (34-47 kt) and possibly storm-force winds (4855 kts) and combined seas exceeding 20 feet along outer coastal waters, mainly from Cape Spencer northward. By Thursday, conditions will improve behind the frontal passage and as the low in the northern Gulf weakens, though lingering onshore flow will sustain rain showers, while winds and seas slowly subside.

Persistent onshore flow with mainly cloudy skies and rain will keep temperatures cool and consistent through the period, with daytime highs in the mid to upper 40s (low 50s possible on Tuesday) and overnight lows in the upper 30s to low 40s.

MARINE

Outer waters: The low pressure system sitting in the northern gulf is swinging across yet another frontal system, generating 25-30 knot southerlies in the gulf waters through tonight. A shift to the southwest with similar wind speeds is expected during the early morning hours for the coastal zones before diminishing through Saturday night. Wave heights associated with the southwesterlies are expected to build to around 15 ft offshore between Cape Spencer and Cape Edgecombe. May also see some convective cells with some lightning strikes and stronger wind gusts. The low pressure, then vertically stacked, should slowly fill and move southeast, keeping up to 20 knot westerlies for Sunday morning before diminishing. Going into next week (Tuesday/Wednesday), a potent low moves into the central gulf, as noted in the long term section. Current guidance indicated a barrier jet looks to form along the NE gulf coast, generating storm force winds east of Cape St. Elias. Currently, there is good confidence on the strength of the system; however, confidence on timing and placement is moderate to low. There is evidence in ensembles that new low centers will generate along the negatively tilted shortwave aloft, which would move around the low. These types of scenarios would shift highest wind speeds much further down the coast, to around Cape Spencer at the furthest with current guidance. For waveheights, very strong southwesterly swell upwards of 22 ft will contribute to wave heights exceeding 25 ft in the gulf waters. Stay tuned for more information regarding this system.

Inside Waters: Leading into the front, building high pressure in the southern panhandle in wake of the stronger front that moved through the southern portion of Clarence Strait may decouple winds. This combined with clearing skies and abundant moisture from recent showers may generate some fog overnight tonight ahead of the incoming front. The front from the aforementioned low pressure in the central gulf is expected to bring up southeast winds early Saturday morning to around 20-25 knots. Highest wind speeds, and associated small craft advisories, look to be for Lynn Canal and Stephens Passage. Definitely possibly to see an upgrade to 25 knot winds for northern Chatham Strait, but did not have the confidence for this forecast package.

HYDROLOGY

With the end of the larger atmospheric river system this morning, flooding concerns are no longer expected, even as some showers continue into the weekend. Rivers and creeks may still be at their crest into this evening, but overall most streams have crested by the morning / afternoon and all are expected to continue to fall into tonight and the weekend. Any showers that continue this weekend will be largely light, and even if some more productive cells bring periods of higher rainfall amounts, they will be quick moving and not persistent, with longer breaks between even the more organized bands of showers.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...Small Craft Advisory for PKZ012-013-022-031-053-641>644-651-652- 661>664-671-672.