textproduct: Juneau

SYNOPSIS

Key Messages:

-Suicide Basin glacier dammed lake continues to fill. At this time, it is expected to be full sometime August 11th or 12th. 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.

-Some areas of clouds and a gradual warming trend expected through the week for the panhandle.

LONG TERM

Wednesday, a closed low south of the Aleutian chain will reach full maturity, beginning to decay as it lifts north. Three primary features of interest as this system moves into the Gulf are: strength of the accompanying surface low, clear/warm over the Panhandle for the mid to end of the week, and moisture transport into the region by the weekend. Touching on the low first, ensembles show agreement that this system will make landfall along the AK Peninsula, with southerlies building in the central Gulf; winds remain below gale force. Our stubborn high over the eastern Gulf cedes territory, making a slight retreat into the Panhandle, with north-westerlies still impacting much of the coastal waters. Overall, little concern for major marine impacts with continued focus for northwest winds of moderate to fresh breezes along the Alexander Archipelago and sea breezes thru the inside.

As this high shifts into the Panhandle Thursday, warm and dry once again becomes the theme. Digging into the 850mb temps, the LREF shows a left-skewed distribution based around 7C to 15C, with the mode around 13C, translating to 75F to 85F surface temps, about 10F above normal for this time of year. The Extreme Forecast Index shines more light into this, with agreement in abnormal warmth increasing its footprint over the Panhandle into the end of this week. A note, its not just about the afternoon high temperatures, nightly low temperatures also likely remain about 10F above normal for most of the region.

Moving onto moisture, by the end of the weekend this pattern will begin to break down the dominant high, or at a minimum, push the ridge further east, with southwesterlies picking up on some equatorial moisture and funneling it into the Gulf. A few ensemble outliers want to bring a quick hit of moderate AR conditions; however, overall modest Integrated Vapor Transport values suggest just an increase in clouds, and perhaps some light rain, by the end of the weekend.

AVIATION.../through 00z Tuesday/

Upper level system remains stationary over the Panhandle this afternoon with CIGs having lifted to predominantly VFR with some weak localized sea breezes finally developing as of this discussion. With the surface high parked over the central Gulf in tandem with the upper level low, broken to overcast skies and unsettled weather are still expected to continue through the TAF period though probability of any impactful showers reaching the panhandle remains low. Conditions will remain benign through the afternoon and evening, however diminish routinely overnight AoB 2000ft as marine layer settles in and light rain or drizzle returns, particularly for the outer coast sites.

Similar to previous days, winds of sustained 10 to 15 kts will continue through this afternoon, with the highest chance of seeing any gusts reaching 20 kts being in the vicinity of Taiya Inlet. No LLWS concerns through the TAF period.

MARINE

Outside: A 1023mb high pressure remains stationary over the central Gulf into early next week, keeping generally overcast skies with light and variable winds along in the outer waters. Wave heights remain largely benign through the early week, around 4ft or less 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 down to Dixon Entrance around 10 to 15 kts or less, with the strongest winds expected in the vicinity of Cape Spencer and Cape Decision, particularly by the afternoon hours. 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 afternoon with only a few areas seeing winds above 10 kt, namely near ocean entrances as well as localized sea breezes. This pattern of relatively benign conditions with marine layer influence and patchy fog in the morning giving way to increasing winds and sea breezes by the afternoon will hold true through at least midweek. Wave heights remain 4 feet or less through early week as well with no significant systems to break down the influence of high pressure out in the gulf.

HYDROLOGY

Suicide basin continues to fill. With the cloudy and somewhat cool weather we have had over the weekend as well as the calving event on Friday night, we have moved the expected most likely date for a full basin to be August 11th-12th. The overflow channel is still around 1350 ft and we still expect the release to start up to 6 days after the basin has reached full status.

AJK WATCHES/WARNINGS/ADVISORIES

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