textproduct: Juneau

SYNOPSIS

Key Messages:

- Pattern change on the horizon as a weather system approaches tonight, bringing a return of rain and elevated winds across the panhandle through midweek. Gales for Northern Lynn Canal.

- Multiple systems to impact the region late week into the weekend, with the potential for heavy rain, gusty winds and increasing seas.

LONG TERM.../Thursday through Tuesday/

Upper level features continue to show a rather active pattern through the long range period. We start out with overall zonal W to E flow over much of the region that will gradually transition to a broad upper trough stretching from the Russian Far East to NW Canada by the weekend. The transition is set in motion by an upper low moving out of Russia late week that eventually anchors itself over SW mainland Alaska. The broad trough stays in place into early next week, but several short waves are evident rotating around the southern edge of it.

The active weather pattern is still apparent at the surface with a series of fronts expected to move through the region late week, through the weekend, and into early next week. First the low and front that is approaching on Friday that was a new feature in the guidance yesterday is still there, but details are still being worked out. Guidance has been somewhat split on whether this system will track S to N farther west and stronger or farther east and weaker. The trend so far looks to be toward the latter, but it will still be a wet (up to 1 to 2 inches of rain Fri morning to Sat morning) and breezy (winds of 15 to 25 kt for the SE gulf and inside waters) Friday regardless.

The weekend is looking interesting as well with a strong broad area of low pressure moving into the gulf from the SW and heading toward the northern gulf coast. In addition to the stronger onshore SW flow it will bring, it its wake is a shot of cooler air that will be coming in from the west. Forecast convective indices are already indicating that Sunday into Monday may be rather convective/showery in nature as the cooler air moves in and the potential is there for some thunderstorms across a large area of the gulf and outer coast at that time. I have added a broad area of slight chance of thunder at that time with the potential that areas along the outer coast could see more frequent thunderstorms from the interaction with the terrain. We will keep monitoring these systems as more details emerge.

AVIATION

MVFR and VFR conditions continue this afternoon as parts of the marine layer have dissipated while other parts continue to linger. This layer is expected to move back in this evening bringing lowered conditions again for parts of the panhandle. For the northern panhandle, marine layer will attempt to move in as we also start to clouds from the next system to impact the area move closer. This could limit the development of marine layer during the overnight hours. As the front approaches the area tomorrow, we will see conditions start to deteriorate down to MVFR and potentially IFR. For the Icy Strait area, LLWS will be a possibility, especially during the morning hours as the front moves through.

MARINE

Outside Waters: As the incoming system pushes in over the panhandle this evening from the west, high pressure in the Gulf has begun shifting southward. Winds this afternoon predominately from the NW, with gentle to moderate breezes observed along the coastline. In the central Gulf, winds becoming W to SW-ly and picking up this afternoon to 15 to 20 kt. Expecting winds to increase to a fresh to strong breeze, with near gale to gale force gusts, for the central and northern Gulf late Tuesday evening through Wednesday morning with the passage of this system. Prominent capes exposed to NW flow have a high likelihood of seeing increased channeled winds. Wave heights at 4 to 5 ft this afternoon building to 8 to 11 ft in the central and northern Gulf by early Wednesday morning, before diminishing Thursday ahead of another system moving in by late week, all with a W-ly swell.

Inside Channels: Winds at generally light to gentle breezes across the panhandle have begun gradually picking up this afternoon as the pressure gradient tightens with the incoming system. Predominately southerly winds will continue to increase this evening through Wednesday morning across the northern and central inner channels, with the exception of 20 to 25 kt westerly winds within Cross Sound and Icy Strait. The highest of these winds will be in Lynn Canal with S winds picking up to between 25 to 35 kt tonight with gusts to 40 kt, and a period of gales expected in Northern Lynn early Wednesday morning through Wednesday afternoon. As this system exits the region, winds are expected to decrease across the panhandle, but remain elevated longer over Lynn Canal with the tightened gradient persisting ahead of another system moving in by late week.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Wind Advisory from 7 AM to 7 PM AKDT Wednesday for AKZ318. MARINE...Gale Warning for PKZ012. Small Craft Advisory for PKZ013-022-643-644-651-652-662>664-671- 672.