textproduct: Juneau

UPDATE

Aviation Discussion for 18z TAF issuance

SYNOPSIS

Key Messages:

-Snow and mixed snow/rain showers training along the northeast gulf coast or just off shore. Keeping a close watch on the Yakutat area. If they train over the top of Yakutat proper a few overnight ( 2 to 4 possibly ) could fall.

- Occluded front from the Bering Sea parent low to move into the panhandle area late Friday to Saturday. This will spread the next band of organized precipitation into region Saturday.

- Brief break possible Sunday as ridging builds over the Gulf of Alaska.

LONG TERM.../Sunday through Wednesday/

Minimal changes to the Sunday forecast as the low moves southeast and ridging begins to develop over the Gulf and panhandle. This will still bring a period of lower PoPs, with some clearing in the cloud cover. The drier weather expected to last longer for the central and southern panhandle into early Monday morning, while some showers linger over the NE Gulf coast and northern panhandle, before the next front begins to move in from the west Monday morning. The winds during this period will remain lighter across the panhandle, and stay more northerly bringing some cooler temperatures particularly for Sunday night, dropping minimum temperatures down to around freezing for much of the northern panhandle and areas further from the coast.

The forecast remains largely the same for the front moving through Monday into Tuesday, with the biggest change in the forecast being in the precipitation types and amount of snow on the highways. Model guidance has been trending more warm at the surface, with 850 mb temperatures staying around -4 to -5C and surface max temperatures nudging up to the high 30s to low 40s over the central and northern panhandle as onshore flow returns to the panhandle Monday with this next system. Snow levels are also increasing this week, from 500 to 600 ft Monday morning further north and far from the outer coastline, to over 1000 ft by Tuesday morning across even the northern panhandle. This warmer air brought in by this system and higher snow levels and wet bulb temperatures correspond to more rain being expected as the precipitation type Tuesday and Wednesday with the exception of the highways. Monday morning there will be possible mixing Icy Strait corridor northward due to the lower temperatures from overnight as the moisture moves in, but transitioning to rain during the morning to midday.

The greatest amount of QPF is expected along the NE Gulf coast for this system, with around 1 inch in 24 hours Monday and expecting another 0.5 to 1 inch Tuesday and Wednesday as precipitation continues to move into the panhandle. The rest of the panhandle should see amounts of 0.25 to 0.50 inches per 24 hours as rain lingers even after the front moves through, and as another wave moves through Tuesday night into Wednesday. Overall this system will bring between 1.5 and 3 inches of snow to the Haines Highway and between 3 and 5 inches of snow to the Klondike Highway in 48 hours. The winds for this system remain largely the same in the forecast, aside from some increases to 15 to 20 kts Wednesday across the inner channels as the second wave moves through. Otherwise, no other wind impacts across the inland areas.

AVIATION

Low CIGs from a front pushing north through the panhandle have begun to lift for the central panhandle and will continue to do so up through Lynn Canal through the next few hours. Light northerly winds along the surface have allowed for snow to continue down to the surface at Haines and Skagway through 9 am leading to much lower VIS. This precipitation should diminish into the late morning hours, eventually transitioning to showers with a mix of more rain then snow later. For the entire panhandle, precipitation should clear out by early Sunday morning, with overall improvement to VFR conditions and diminishing clouds, particularly for the southern panhandle. No LLWS expected for the TAF period.

MARINE

Main marine concerns in the short term forecast are centered around the low pressure that is moving through the Gulf. As of this morning, the low pressure center is approaching the central Gulf and is tracking southeast. The associated front has been swinging south-to-north overnight, bringing rain and snow to the panhandle. By this afternoon, the low will reach the eastern Gulf and will continue to move southeast Saturday evening.

Outside waters: As the low center travels through the area today, the winds on the south side will be strongest at around 15 to 25 knots.

Lighter westerly winds are likely Sunday, at around 5 to 15 knots.

Inner Channels: Southerly winds around 5 to 15 knots are likely with pockets of higher wind speeds. For now, expecting those stronger winds to be near Icy Strait, Near Point Couverden, and southern Stephens Passage. But as the front pushes northward tonight, wind speeds in the inner channels should lighten up to around 5 to 10 knots by late tonight.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...Small Craft Advisory for PKZ022-031-053-641>644-651-652-661>664- 671-672.