textproduct: Juneau

UPDATE

The easterly wave moving out of northern British Columbia across the coast mountain into the north central Panhandle over night starting between about Midnight and 4 am, is looking fairly moist and the majority of the High resolution models were indicating a shift to wetter pattern. So the dry weather that was in the forecast got a refresh. Expect PoPs of 30 to 60 Saturday with the best chances in the early to mid afternoon.

AVIATION...As mentioned above, the primary change in forecast that could impact aviation is an easterly wave moving over from British Columbia. There is increasing confidence that showers will make it over the mountains by Saturday morning. The most likely impact from these would be locally heavier showers late morning into early afternoon which could briefly reduce VIS to 5sm or less. Otherwise primary impacts overnight into Saturday morning remain a resurgent marine layer that will likely bring lowered CIGs AoB 1500 ft which should begin to rise by mid morning.

PREV DISCUSSION......ISSUED AT 335 pm Friday Jun 26

SYNOPSIS...

Key Messages:

- Strengthening marine layer will bring low clouds for most of the panhandle and fog chances for the outer coast and Icy Strait.

- Rain chances increased to around 20% for the far inner channels, including Juneau, Petersburg, and Wrangell, due to an easterly wave from Canada. Highest chances in the morning timeframe.

- Moderating temperatures, more cloud cover, and drizzle are possible late weekend and going into the workweek.

SHORT TERM.../Through Sunday night/...Tonight the primary concern will be fog potential and a marine layer setting up offshore from the northern coastline near Yakutat down along Baranof Island. Currently it does not seem like it will advance very far inland, moving into Cross Sound up to around Gustavus, and over some of the towns along the outer coastline, even potentially setting up along the west coast of PoW by the early morning hours. Confidence is low on it pushing in further to around the Juneau area, or curving up into Clarence Strait to near Ketchikan if the winds shift SW enough overnight. The fog and low stratus along the outer coastline may linger longer into the morning.

Cloud cover will return for the weekend across the northern half of the panhandle and along the coastline as a system in Canada pushes some waves into the panhandle tonight through Saturday. These will largely continue to keep cloud cover across the area, with slight chances for showers possible for areas near the coastal mountains. The highest chances (15-25%) of these showers pushing into the panhandle will be during the day on Saturday when an easterly shortwave pushes along the coastal mountains, bringing slight chances of showers from around Petersburg/Wrangell northward to Juneau. Parts of the southern panhandle, however, will begin to see some clearer skies on Saturday, with much of the cloud cover either being pushed northward into the central/northern panhandle from the easterly wave, or along the outer coastline from the ridge siting offshore. These clearer skies are expected to last through Sunday even as the northern panhandle continues to see shower chances throughout the day, as any showers moving in from the Gulf will largely stay just offshore of the southern panhandle. Overall the temperatures will stay more moderated across the panhandle as cloud cover lingers.

LONG TERM.../Monday through Thursday/... Conditions remain relatively benign across the panhandle with the potential for lingering showers to start off the week. Onshore flow in the upper levels, combined with a high pressure in the northern Pacific, is expected to keep a persistent marine layer in the gulf and bring damper, overcast conditions to the panhandle. Precipitation chances look to remain below 40% with little to no accumulation through at least Tuesday. Some time during the day on Tuesday, a low pressure center or well defined negatively titled trough is expected to bring an offshore shift in flow. This is expected to clear out conditions across the panhandle through Tuesday which are anticipated to last through the rest of the period. Winds in the gulf are likely to have a strong NW component with sea breezes driving winds in the inner channels.

AVIATION...Mainly VFR conditions are expected this evening, although a marine layer will slowly advance inland overnight and bring the return of IFR ceilings. Minor sea breeze influences will continue at Skagway and Ketchikan through early evening, but sustained wind speeds will generally remain less than 15 kts. Ceilings will again rise after about 14Z Saturday, but an easterly wave may result in a few scattered showers, especially at PAPG and PAWG.

MARINE... Outside: A low level ridge over the Gulf of Alaska will remain in place and slowly weaken through the weekend. This ridge will result in persistent northwesterly winds reaching SCA level for the southern zones. With southwesterly swell continuing, combined seas of 5 to 7 feet are expected for most of the outside waters, with higher waves (8-11ft) for the waters south of Port Alexander. The other thing of note for the outer waters would be the set up of a more persistent marine layer and fog set up for along the coast.

Inside: The diurnal winds will be the main area of interest over the next several days for the Inner Waters. Conditions are expected to remain below SCA criteria, however for channels that are E-W oriented and near ocean entrances will see windier conditions with sustained winds 15-20kts. Similar to the outer waters, the marine layer will move in during the over night hours, however, this will be more of a stratus deck with only truly isolated areas of fog during the early morning hours.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...Small Craft Advisory for PKZ022-641-642-661>663.