textproduct: Juneau

SYNOPSIS

Key Messages:

- Multiple weak fronts look to move over the panhandle, 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.

- Another front moves into the panhandle Saturday into Saturday night. Not expecting any wind gusts exceeding 40 mph nor rain rates exceeding a tenth of an inch per hour. Winds look to not exceed strong breezes to near gales.

- 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

Mid and extended range forecast has not changed all that much as the panhandle is mainly locked into a warm wet pattern well into next week. The main driver of this continues to be the upper level pattern which features a broad trough over mainland Alaska, Bering Sea, and the northern Pacific while an upper ridge is parked over the US west coast and western Canada. This leaves much of the gulf of Alaska and the Panhandle under S to SW flow aloft with the pacific storm track directed at the Gulf for much of the period.

Lower in the atmosphere, the dominate S to SW flow will bring in a series of lows and fronts into next week with the strongest of which expected sometime mid next week. The first of which in the mid range will be moving in from the south Sunday night. This feature will bring more rain and some wind mainly to the southern panhandle, but is not expected to be outside the norm for rain (around an inch for each front or wave) or wind (gusts to 40 mph on land/30 kt marine winds) for this time of year. The mid week system is another story. That system has the markings for another atmospheric river with the potential for up to 2 to 5 inches of rain for many areas Tuesday into Wednesday, but it will mainly be focused on the southern panhandle. The extreme forecast index from the ECMWF is painting a bullseye for extreme rainfall over the southern inner channels from around 0z Wed to 0z Thu lending more confidence on this. This system also looks like it will be a wind maker as well with widespread gale force winds for the gulf waters possible while the inner channels could see winds of 25 to 35 kt. The timing of this system has improved with the main effects from the system starting to be felt by late Monday evening or very early Tuesday morning. Guidance is also indicating a rather strong followup system on Wednesday, but certainty on that is worse with wildly different possibilities for track and strength on that feature at the moment.

In addition while most low elevation areas of the panhandle will be warm enough for rain, the higher elevations of the Klondike Highway will still be cold enough for snow. Snow levels will be hovering around 1500 to 3000 ft along the Klondike into next week. While there is not much potential for significant snow through the weekend since most of the precip will be south of that area, the more substantial system mid next week could bring more substantial precip (and more substantial snow) to the Klondike Highway and will continue to be watched.

AVIATION

For the late afternoon (00Z) aviation update, we kept the general trend of MVFR most locations going through the evening as the weak frontal occlusion washes out over the central Alaska Panhandle...with a clearing trend (initially south) and residual areas of light rain (north) gradually diminishing through early evening. Model soundings and the current short term forecast supports the idea of some areas of fog and low stratus late tonight across the southern 2/3rds of the Panhandle (going IFR then for a period of time 09Z-15Z LIFR)...then clearing out towards 19Z before the next batch of rain and lower ceilings comes up from the south for the southern 1/3rd of the Panhandle mid to late afternoon Saturday. 05/Garmon

MARINE

Outside (Gulf and Coastal locations): Friday afternoon seas and winds continue to diminish as a weak low lifts across the Panhandle and a ridge builds aloft. 18z ASCAT passes along the eastern gulf reported winds less than 20 knots across our area, with altimeter wave heights matching coastal buoys, 10 to 13 ft, dominant direction out of the south focused at a period of 10 to 12 seconds. Seas will continue to relax through early Saturday morning. Saturday late morning a gale force low lifts into the eastern gulf, with easterly near-gale force winds increasing out of Dixon Entrance, impacting the west coast of Prince of Wales and Cross Sound. Sea state will increase late Saturday, with significant wave heights reaching 11 to 13 ft along the northern coast by Sunday. An active pattern continues into next week, with an extensive gale to strong gale force low lifting into the Gulf by Tuesday, increasing seas to near 25 ft, with multiple rounds of significant southerly wave energy impacting our coast through the week.

Inside (Inner Channels): Forecasted winds Friday afternoon did not come to fruition given the track of the responsible low, with only strong breezes impacting Clarence Strait and for a short period of time in Lynn Canal. We are still watching winds become southerly across the inner channels as this feature lifts north, but not seeing much impacts, with moderate to fresh breezes anticipated for a brief time. Main threat will be the potential for areas of dense fog settling again tonight as winds relax, persisting into Saturday morning. Saturday late morning a gale force low will lift into along the coast, helping to freshen winds up to moderate to strong breezes, mainly in waters south of Frederick Sound, especially on the exposed coast of Prince of Wales and southern Clarence Strait.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...Small Craft Advisory for PKZ036-053-641>644-651-652-661>664-671- 672.