textproduct: Juneau

UPDATE

18z TAF issuance updated. Majority of the panhandle dealing with onshore shower regime bouncing from VFR to IFR in the snow showers. Conditionally unstable air rotating into the panhandle has sparked some stronger convection, including isolated Thunder, and could continue along the outer coast for the day.

Winter advisory for Ketchikan and Metlakatla expired but advisory for continued snow for the Sitka, Petersburg, Kake, Craig, Klawock, and Wrangell areas. Warning for Juneau continues to 1 pm. Snowfall amount can and have been wildly variable even in short area. For example in Juneau the airport, the WFO office at the back valley got 4 inches or less, while North Douglas, Lemon Creek, and Mountainside got roughly a foot of snow.

PREV DISCUSSION...ISSUED AT 623 am Mon Mar 9

UPDATE...A band of heavy snow set up overnight across parts of Juneau (Lemon Creek, Salmon Creek and toward downtown) and Douglas and reports of 6 to 8 inches of snow falling overnight. Have upgraded the Winter Weather Advisory to a Winter Storm Warning for Juneau/Douglas until 1pm Monday afternoon.

SYNOPSIS...

Key Messages:

- Scattered to widespread convective snow showers continue through Tuesday, shifting south mid to late week.

- Outflow conditions are developing today, steadily increasing through mid week and continuing through the end of the week. Outflow will bring colder, drier weather.

SHORT TERM.../through Monday night/...Persistent onshore flow with low pressure out over the eastern Gulf and upper level troughing and cold temps aloft continue to throw scattered to widespread snow showers into the panhandle from Icy Strait corridor on south. Upticks in shower coverage and intensity are expected as surface troughs continue to pivot around the low and into the panhandle. Winter Weather Advisories were issued for Juneau, Sitka and the southern panhandle last night and continue through this morning as an upper-level vorticity maximum worked into the panhandle and is bringing heavier snow showers, with visibilities dipping down to a mile or less. An additional 1 to 3 inches of snow is expected through this morning. Much like Sunday, snow accumulations may be limited during the day due heating and warmer surface temps. However, accumulations may pick up again after sundown and additional Winter Weather Advisories may be needed.

Further north, high pressure continues to build into the Yukon with cold, drier northerly outflow increasing for Haines and Skagway. A few snow showers may be heavy enough overcome the near surface drier air, especially at Haines, but any accumulations should be minimal.

LONG TERM...The main story for the mid to the end of week will continue to be northerly outflow with a chance of snow showers over the central to southern portions of SE AK. The upper level low over the gulf, along with the high pressure over the Bering Sea, will continue to allow for northwesterly flow to bring cold air over the panhandle. This will continue to slowly decrease temperatures as well as keep the precipitation type as snow. The southern panhandle will still see times of rain or a rain/snow mix, but snow will be the most likely precipitation type. With the low lingering over the gulf, snow showers are likely to continue, especially for central and southern SE AK. These showers will continue to be variable allowing the heaviest showers to bring moderate snow with reduced visibilities, and times of slightly increased winds.

Otherwise, winds will continue to become northerly across the inner channels with outflow winds building. Winds across the inner channels will slowly become northerly as the low pressure system moves south. All inner channel winds are anticipated to have northerly winds by Thursday. Strongest outflow winds will remain over Lynn Canal into Point Couverden, Stephens Passage, and Icy Strait with strong breezes to near gales (22 to 33 kts) through the weekend. Times of gale force winds (34 to 40 kts) are also possible, most likely occurring Wednesday and Thursday. For land winds, Skagway is likely to see strong winds with a 60 to 70% chance of wind gusts near 40 mph, and around a 20 to 30% chance for gusts near 50 mph, Wednesday.

This pattern looks to continue through the weekend into the start of next week. This means that the next system that pushes into the panhandle will likely bring more snow to the area due to the colder temperatures in place. We will continue to monitor for when the next low pressure system may arrive allowing for this change in pattern.

AVIATION...Snow showers continue this morning as the low continues to slowly move southeastward down the coast. Drops down to IFR and LIFR flight conditions from lowered CIGs and VIS associated with these showers is expected to last through the morning hours, particularly across the central panhandle where a more organized wave of precipitation is currently pushing through. This will continue to bring intermittent drops in CIGs to AoB 2000 ft and VIS from 3 SM down to 1SM or less during the heavier showers, lasting through around 16 to 18z. An improvement in flight conditions back to VFR is expected by late morning to midday for much of the panhandle. Some areas may still see some occasional drops to MVFR or lower during the day and into tonight, particularly across the southern and central panhandle, as showers are expected to continue throughout the TAF period. However, the showers will be less organized than the current band moving through this morning, and will allow for more breaks in the low cloud cover and duration of VFR flight conditions during the day.

The northern panhandle will continue to see northerly outflow that has begun earlier in the night, with 10 to 15 kt sustained winds and isolated gusts of 20 to 25 kts this morning and continuing through the TAF period. The rest of the panhandle will largely see winds 10 kts or less, with only some occasional gusts as showers move through. Still expecting no LLWS concerns.

MARINE... Outside (Gulf and Coastal Waters): Seas will remain hazardous to small craft over the coastal waters. The northern waters will see wave heights drop from 8 to 12 feet down to 6 to 10 feet through Monday night. Outflow conditions begin to develop today and will increase through midweek from Cross Sound on north off the coast. Winds and seas trend up as a result and look to become hazardous to small craft. Over the southern waters, wave heights drop from 12 to 16 ft to 8 to 12 ft through Monday night. Seas dip further through midweek.

Inside (Inner Channels): Winds will continue to flip to the north across northern channels as outflow develops. Outflow winds will increase through midweek, with strong to gale breezes expected through most of northern/central inner channels. Moderate to heavy freezing spray likely to develop for Lynn Canal and Glacier Bay. Channel entrances are currently seeing increased wave heights pushing in from the Gulf, but those are expected to decrease as outflow takes hold. Wave heights will trend up for Lynn Canal, Glacier Bay, Chatham Strait and Stephens Passage as persistent outflow brings more fully developed seas.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Winter Weather Advisory until 4 PM AKDT this afternoon for AKZ323. Winter Storm Warning until 1 PM AKDT this afternoon for AKZ325. Winter Weather Advisory until 10 PM AKDT this evening for AKZ326>329. MARINE...Small Craft Advisory for PKZ012-013-022-053-641>644-651-652- 661>664-671-672.