textproduct: Juneau

18z UPDATE

AVIATION

Conditions are generally VFR across the area. An approaching low pressure system will bring winds and rain to the Alaska panhandle. This system will bring deteriorating flight conditions across the Panhandle, with low-level wind shear concerns as well. As of now, LLWS in only mentioned for PASI and PAKW, but conditions across southern TAF sites will need to be monitored.

PREV DISCUSSION......ISSUED AT

SYNOPSIS...

- Rain and wind return through the weekend, with widespread forecast rainfall amounts 1 to 2 inches and wind gusts up to 45 mph across the Southern Panhandle. - Periods of gale force conditions are likely along the coast over the weekend. See Marine Section for further info.

SHORT TERM.../through Saturday night/... A major pattern change is underway, as the mid/upper level ridge which has been clinging to life across the southern panhandle is ejected eastward by an approaching low moving up from the south. Ahead of the bulk of the system, a weak warm front is is sweeping north through the panhandle Friday morning, bringing widespread cloud cover and areas of light precipitation through the panhandle. A stronger warm front sweeping up in the wake of the first arrives by Friday afternoon, bringing more widespread PoPs from midday Friday onwards. Many locations may only see drizzle or wetting rain with relatively light winds through the channels with the initial pair of warm fronts, with the bulk of the precipitation likely to arrive with the trailing cold front. The cold front will follow quickly behind the warm fronts, moving into the southern panhandle through late Friday afternoon before spreading through the rest of the panhandle overnight. The outer gulf coast will see a stronger area of winds move in and up Clarence Strait with the first band, though the main swath of strong winds will move into the panhandle and along the coast through late Friday night and into Saturday morning with the second band. Light to moderate rainfall is expected through Friday night as the system moves in, but periods of heavy rainfall will be possible through the weekend. Rainfall totals through the weekend will range from ~1-3 inches across the panhandle. See the long term discussion for more details.

LONG TERM.../Sunday through Tuesday/... Rain continues across the panhandle as we move out of the weekend and into the week. However, rain rates appear to be lightening up from moderate and persistent to light and showery over the day Sunday. There could be periods of heavier showers on the inner eastern part of the panhandle -- Juneau, Petersburg, Wrangell -- through the day Monday. Winds across the panhandle continue to diminish through the day Sunday as the low jumps onto land in the western gulf. High winds from channeling the previous day have the potential to linger in the inner channels across the panhandle with models picking up on Stephens Passage in particular. At the same time, winds in Lynn Canal look to increase through the day Sunday and be sustained around 20 mph as the pressure gradient over the panhandle squeezes.

AVIATION.../through 12z Saturday/... General VFR flight conditions ongoing as an upper lvl deck moves from S to N across the panhandle this morning with clear skies for much of the night at Yakutat. This clearing has allowed temps to plummet and for a low stratus deck/FZFG to develop with LIFR flight conditons. Expecting this to become more intermittent and dissipate over the next few hours as day time low level mixing begins.

Initial VFR conditions deteriorate to predominate MVFR through Friday afternoon and into the evening as a series of fronts move inland. Strongest of these fronts arrives into PAKW, PAKT by 00z this afternoon with stout SE-ly winds around 40kts near 2kft. Some LLWS expected near PAKW by Friday afternoon with increasing potential for some speed shear at PAKT however with sustained surface winds near 20kts and gusts up to 30kts, opted to leave PAKT LLWS out for 12z TAF issuance. This strong front will continue to move northward towards PAYA/PAGS/PAJN by 05z to 09z Saturday with MVFR to IFR flight conditions prevailing, however forecast confidence decreases in LLWS impacts as surface winds increase in unison to 2kft winds.

MARINE... Simply put, periods of near-gale to gale force easterly to southeasterly winds impact the majority of our coast Friday afternoon into the weekend, with seas building to 15 to 18 ft.

Outside: Friday morning winds will be easterly fresh breezes along the majority of our coast before a front associated with the low lifts through the eastern gulf, bringing a few hours of near- gale to gale force SE winds. Regarding timing, expect these frontal winds to reach the Prince of Wales coast by 2 to 4 pm Friday, Sitka Sound by 3 to 5 pm, and the Fairweather Range by 6 to 9 pm. After the frontal passage, southeast winds of strong breezes persist for the majority of our coast, with a more extensive period of near-gale to gale force winds for our coast Saturday late morning. Associated with this system is an excellent dynamic fetch responsible for southerly swell, along with the aforementioned fetch of southeasterly winds generating large southeasterly wind waves along the coast. Expect large and confused seas of 15 ft, to potentially as high as 18 ft, along the majority of our coast, with the focus of wave energy from the Fairweather Grounds to Cape St. Elias.

Inside: A low pushing into the central Gulf will drive southeasterly winds through many channels, beginning by late Friday morning for the far southern inner channels, before spreading northward Friday afternoon into Friday night. Given the low location, major east- west channels and passages like Icy Strait, Peril Strait, and Clarence Strait (to name a few) will see the strongest winds. By and large, expect sustained winds of strong breezes for many locations, with some favored areas (like Snow Passage in Clarence) seeing a few hours of near- gale force conditions Friday afternoon. Southerly winds of fresh breezes to strong breezes continues across many central and southern inner channels Saturday. Winds begin to diminish towards the second half of Sunday, though expect fresh breezes to remain for Lynn Canal and Stephen's Passage until Monday night.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Wind Advisory from 4 AM to 1 PM AKDT Saturday for AKZ332. MARINE...Gale Warning for PKZ644-651-652-661>664-671-672. Small Craft Advisory for PKZ022-031>036-053-641>643.