textproduct: Juneau

SYNOPSIS

Key Messages:

- A weakening low in the northern gulf will keep persistent snow showers spreading across the panhandle Thursday night, gradually tapering off from north to south through Friday. Localized heavier showers and gusty winds are expected.

- Winter weather advisory remain in effect for Prince of Wales Island. - Outflow conditions increase through Friday morning, with gale force winds in Lynn Canal and freezing spray expected within the northern panhandle inner channels through Friday.

LONG TERM

With the cold air in place from the outflow conditions experienced during the short term, we will start to see the potential setup for a significant overrunning snow event. Current thinking is that the most significant snow is expected to be from Petersburg northward to the Icy Strait corridor including Juneau. The big question for this overrunning event is where does the Arctic boundary set up in comparison to the moisture moving into the area. For places around Petersburg, the cold air is expected to persist before being mixed out and warmer temperatures allow for a switch to rain. Farther south, warmer temperatures are expected to persist that will minimize the amount of snow that is expected across the area while places to the north such as Haines and Skagway are expected to remain on the dry side due to the cold, dry air that will have moved in. Current thinking is that the Icy Strait corridor including Juneau could be the target for the heavy, prolonged snow event across the area. There is still some exact uncertainty regarding just how much snow could fall. But confidence continues to increase in seeing significant snow, especially as ensembles come into better agreement for the location of the low moving into the Gulf. This pattern is expected to persist into the middle part of next week.

Headed into the later half of next week and into the weekend after, a return near normal temperatures and precipitation is expected for the region.

AVIATION.../through 0z Friday/

Snow showers continue to stream over the panhandle bringing highly variable flight conditions down to LIFR at times. As of the Thursday afternoon, a band of overrunning showers continues to persist over the Icy Strait area bringing more consistent IFR and occasional LIFR conditions to the area primarily due to VIS restrictions. This band of more organized showers is expected to last into the early evening hours Thursday before gradually diminishing as northerly flow wins out and the low in the gulf weakens and continues moving southward. Coastal communities could see showers last a bit longer from continued onshore flow. MVFR and VFR conditions will become more common Thursday evening and night as cloud cover starts to lift and thin out a bit.

Elevated winds remain blowing at Haines and Skagway with gusts up to 30 kt. These winds are expected to subside late Thursday night as the gradient slackens with the low sliding southward in the gulf. The strongest winds are expected in the vicinity of Lynn Canal with sustained northerly winds of 20 to 30 kt and gusts up to 45 kt. Winds aloft will also shift more out of the north through the period as the low departs.

MARINE

Inner Channels: Northerly outflow conditions have started up in the northern inner channels. Lynn Canal is already blowing min gale force with outflow winds reaching Cross Sound (E wind of 25 kt) and central Stephens Passage (n wind of 20 kt) as of 1 pm. Farther south winds are still mostly out of the S and W at around 15 kt or less. The outflow winds are expected to continue to spread southward through the night with the furthest extent being down to Frederick Sound and Southern Chatham Strait by Friday morning. Max winds will still be in Lynn Canal and should not exceed moderate gale force overnight. Expect the outflow to then diminish through the day Friday and nearly shutting off completely by Friday night. Freezing spray has also returned for the northern channels, especially Lynn Canal and that should diminish on Friday as the outflow diminishes. Seas are around 4 ft or less for most areas except for Lynn Canal where the northerly gale force winds are producing 7 to 8 ft seas currently, and at ocean entrances exposed to the W where a W swell of 10 to 15 ft are enhancing seas there.

Gulf Waters: Winds and seas are on the downward trend after peaking at moderate gale and nearly 30 ft seas in the central and southern gulf last night. Currently Westerly winds have diminished to 30 kt or less across the gulf with seas of 20 ft in the south and 10 ft seas in the north (W swell of 13 to 15 ft in the south gulf with a 12 sec period). Winds and seas expected to continue to diminish into Friday with most of the gulf below 15 kt of wind and seas 8 ft or less by late Friday afternoon. The NE gulf will have some gusty winds out of interior passes tonight, but those should not last beyond Friday morning before diminishing. Seas should continue to diminish into Saturday. Winds will be switching direction Friday night from a W direction to a S direction and will likely start to increase again to around 20 to 25 kt across the south gulf by Saturday.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Cold Weather Advisory from 6 PM this evening to noon AKST Friday for AKZ318-319. Winter Weather Advisory until 4 PM AKST this afternoon for AKZ320-321-323-325-330. Winter Storm Watch from Saturday morning through late Saturday night for AKZ320>322-325-326. Winter Weather Advisory until midnight AKST tonight for AKZ322- 328. MARINE...Gale Warning for PKZ012-013-053-651. Small Craft Advisory for PKZ011-021-022-031-032-641>644-652- 661>664-671-672.