textproduct: Juneau

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.

LONG TERM

/through Sunday night/ 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

/through 12z Wednesday/ Surface low remains situated over the central Gulf this morning and resulting marine layer stretched across the panhandle with CIGS AoB 5000ft. Southern panhandle terminals once again seeing the redevelopment of an IFR layer around 500 to 7000ft has worked its way in with CIGS 500 to 800ft over Prince of Wales, Ketchikan, and Annette. Similar to yesterday, expecting gradual improvement through the early afternoon to predominate VFR across the panhandle with a general rinse and repeat forecast. Conditions improve during the afternoon to VFR with CIGS AoA 5000ft, however diminish routinely overnight has marine layer returns.

Winds are primarily sea-breeze driven, expected to increase through the afternoon and into the evening reaching sustained 10 to 15kts, isolated gusts up to 25 kts possible. No LLWS concerns through the TAF period.

MARINE

Outside: Overall marine forecast and weather pattern remains the same as previous days. A 1023mb high pressure over the central Gulf expands and strengthens to 1028mb through end of the week as it moves over the panhandle. Wave heights remain largely benign through the week, around 3 to 5ft along the coast with a persistent southerly swell of 2ft or less. Accompanying this high pressure is broad westerly to northwesterly winds in the NE gulf coast from Cape Spencer down to Dixon Entrance. Winds generally remains around 15 kts or less, with the strongest winds expected in the vicinity of Cape Decision to Dixon Entrance up to 20kts through Wednesday afternoon. Main marine concern for outer and coastal waters will be nightly return of marine layer, dropping visibilities potentially as low as one quarter mile each morning.

Inside: Conditions across the inside waters remain relatively benign this morning with winds largely 10kts or less. Isolated spots across eastern Icy Strait from Sisters to Rocky Island seeing the strongest winds of the morning, around 15kts. Main hazard this morning is an area of dense fog near the entrance of Cross Sound, with visibilities 1nm or less as evident by FAA webcams near Cape Spencer. Light to moderate breezes expected once again this afternoon as high pressure continues to influence the area. Strongest inner channel winds up to 15 to 20 kts are expected for the afternoon and evening hours as sea breezes increase in strength before diminishing during the overnight hours.

HYDROLOGY

Suicide Basin continues to fill this Tuesday morning, with water levels around 1,345' as of 4am AKDT. 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 then 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.

FIRE WEATHER

High pressure continues to sit over the area with no real signal of a pattern change likely until the upcoming weekend. With the persistent weather, we have started to see temperatures rise into the 70s with some pockets of 80s for the inland areas with warm temperatures expected to continue through the week. Looking at the past few days, relative humidities have fallen down to the 30s to 40s for some areas during the daytime hours with rebounding during the overnight hours into the 90s. With the continued lack of rain, fine fuels such as grasses will continue to dry. Isolated thunderstorms are once again possible this afternoon across the far northern panhandle border of Canada.

Overall, expecting the dry and warm conditions to continue through the week with fire weather conditions continuing to develop, the main variable to watch for will be daytime winds. As of now, expecting the worst fire weather conditions to be Thursday and Friday afternoon, however given the persistent pattern can't rule out this extending further into the weekend.

AJK WATCHES/WARNINGS/ADVISORIES

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