textproduct: Juneau

UPDATE

After the 06z TAF issuance. No big changes to the plans. Mainly VFR flight conditions to start the night, and may briefly lower to marginal in the 1500 to 3000 ft range. Not expecting any major flight hazards through the Tuesday evening.

PREV DISCUSSION......ISSUED AT 312 pm Mon August 10

SYNOPSIS...

Key Messages:

- Suicide Basin glacier dammed lake continues to fill. At this time, the most likely time to see a full basin will be sometime Tuesday, August 11th. In the past, it has taken up to 6 days for the main flooding event to start after the basin is full. Visit weather.gov/ajk/suicidebasin for more information.

- Warming trend for the week with highs in the 70s. Lower 80s will be possible, especially across interior locations across the south for mid to late week.

- The warm and dry conditions will bring elevated threat for fire starts across much of SE AK. A few small fires have been observed already over the past week.

SHORT TERM.../Through Wednesday/...Cloud cover has mostly cleared for the northern panhandle with broken to overcast skies remaining for the southern panhandle. Because of these clearer skies to the north, temperatures increased into the high 60s to low 70s. This trend of warming temperatures will continue into this week as high pressure continues to build over the gulf. There is a chance again this evening for thunderstorms to push north of Haines and Skagway this evening. Confidence remains low with a less likely chance than yesterday, although a few cells have begun to develop.

As we continue into the week, the stronger area of high pressure will create northwesterly and offshore flow. This will continue to help to clear out upper level cloud cover and decrease any chances for lingering light showers and drizzle. This will increase the chance for afternoon and evening sea breezes to develop bringing periods of gusty winds to land areas touching the inner channels or gulf waters. Sea breezes will also help to keep temperatures on the cooler side. Warmest temperature, into the 70s, will occur over more inland and protected areas.

LONG TERM...Primary focus continues to be on warm/dry through the end of the week along with the uncertainty of equatorial tropical storms and subsequent moisture transport into the N/Pac. Starting off, for the end of the week clusters still show strong agreement in a ridge dominating the western seaboard, limiting major surface lows from moving into the Gulf and serving as the source for abnormally warm temperatures aloft. LREF 850mb temperature histograms have shifted to more normal distribution, translating to increased confidence for 12C to 14C at 5000ft by Thur/Fri. For folks at sea level, this means warm temperatures, with afternoon highs likely in the mid-70s to mid-80s, depending on where you are in the Panhandle. Thunderstorms might make an appearance Thur/Fri across the central and southern area; however, this will ultimately depend on where the ridge axis sets up and a shortwave moving down from Canada along the coast range, something to watch.

Moving through the weekend guidance breaks down the ridge suggesting cooler temperatures and some moisture; however, guidance continues to break down the ridge too soon. Thinking we hold on to warmer temperatures into Saturday, with cooler temperatures and moisture arriving by late Sunday and/or start of next week. With that said, there are a variety of outcomes in various ensemble system solutions; current forecast Monday afternoon sticks with troughing setting up in the Gulf and an increase in clouds and light rain.

For the maritime environment, anticipate northwest winds to continue along the coast, with daily sea breezes moving through the inside, peak afternoon speeds likely moderate to fresh breezes. By Sunday/Monday northwest winds along the coast give way to southerlies as a series of lows moves into the Gulf. Will need to watch for the potential for fresh to strong breezes along the northern coast.

AVIATION...VFR conditions continue for most of the panhandle this afternoon with the exception of the southern panhandle. These ceilings should break up but may persist for the rest of the afternoon. A marine layer is expected to redevelop this evening bringing lowered ceilings with ceilings dropping to MVFR and potentially IFR similar to what we saw this morning. With the continued offshore flow, we will see clearing skies especially during the daytime hours although some cumulus clouds could develop in the afternoons off the terrain.

MARINE... Outside (Gulf and Coastal Waters): Light breezes continue to be reported by the observations across the Gulf this afternoon. Winds will continue to from the W-NW as high pressure remains across the area. With the high pressure expected to shift, the NW winds are expected to increase Tuesday evening into Wednesday for the Cape Decision down to Dixon Entrance region with moderate breezes possible starting Wednesday morning and continuing through the week. By the latter half of the week, these winds could be up to fresh to strong breezes.

Inside (Inner Channels): Light to moderate breezes continue this afternoon as high pressure continues to influence the area. 15-20 kt winds are expected for the afternoon hours as sea breezes increase in strength before diminishing during the overnight hours. With the weather pattern we are in, conditions should stay similar to what we have seen the past few days. Seas during this time could get up to 3- 4 ft with the strongest winds. Some fog formation may be possible during the overnight hours with the marine layer.

FIRE WEATHER...High pressure continues to sit over the area this afternoon with no real signal for a pattern change likely until the weekend. With the persistent weather, we have started to see temperatures jump into the 70s and some pockets of 80s for the inland areas. Relative humidities have fallen down to the 30s to 40s for some areas during the daytime hours but should rebound during the overnight hours. With the continued lack of rain, fine fuels such as grasses will continue to dry. Some lightning strikes were also noted along the northern border with Canada yesterday and is likely possible again today.

HYDROLOGY...Suicide Basin continues to fill this afternoon with water levels sitting around 1,345' as of the time of writing. We currently expect the basin to fill within the next day before water starts to go over the spillway. With water flowing over the spillway, a release is expected to occur within 2 to 6 days. We will continue to monitor conditions in the basin as well as the Mendenhall River and will makes updates as they are needed.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...None.