Marine Weather and Tide Forecast for Glennallen, AK

.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days 1 through 3: This afternoon through Friday evening)...

Currently, an upper-level low along the Arctic Coast of Northern Alaska extends a trough southward across Western and Southwestern Alaska. This is helping showery activity persist across Mainland Bristol Bay today. There continues to be cold air that lingers across the Alaska Peninsula (AKPEN) with northerly flow in the middle levels in the eastern Bering Sea. This is helping some snowflakes to mix in with rain across Port Heiden and Pilot Point.
The trough axis continues to slide eastward tonight into Wednesday as the showery activity will taper off by then.

High pressure across the central and eastern Bering today will drift eastward and nudge in across Southwest and the AKPEN Wednesday and persist into Thursday. This will promote relatively drier conditions and light winds across the area both days, but especially Wednesday. The upper-level low, currently along the Arctic Coast of Northern Alaska, will begin to dig southward Wednesday and begin to make its presence felt over the Kuskokwim Valley and along the Western Alaska Range Thursday afternoon into the evening hours and Friday. This upper low will be accompanied by cold air aloft and elevated instability. Thus, diurnally-driven showers will be possible mostly along the Western Alaska Range Thursday afternoon and evening. For Friday, a North Pacific low sends its front and moisture northward through the Gulf of Alaska.
The upper-level low, now over the lower Yukon Valley, will interact with this moisture and help to draw more of it over interior portions of Southwest, including interior Bristol Bay along the Aleutian Range and portions of the Kuskokwim Valley, in the form of Friday afternoon and evening showers. Despite the instability and cold air aloft from the upper-level low over the lower Yukon Valley, surface temperatures, in the middle 40s, look to be too cold for thunderstorm formation along the Kuskokwim Valley, interior Bristol Bay, and along the Western Alaska Range.

Farther out west, a low pressure system near Kamchatka has sent its gale-force front to the western Bering and Western Aleutians today. Shemya has reported misty conditions for most of the day along with gusty southeast winds. However, steady light rain is currently moving in over the area. Light rain and gusty southeasterly to southerly winds will continue into tonight with winds turning southwesterly across the far Western Aleutians by Wednesday morning. The front continues drifting east to Kiska and Amchitka Wednesday as it weakens. At the same time, the previously mentioned strong central/eastern Bering ridge will drift eastward.
This will allow a little more eastward progression with the weakening front with light rain making it over Adak for Wednesday morning. Atka will remain mostly dry through the first half of Wednesday. A weak North Pacific low lifts to south of Adak/Atka Wednesday afternoon and evening. This will spread rain across Atka during Wednesday afternoon and evening and help to keep rain going across Adak. Rain becomes more showery across Adak/Atka by Thursday morning as this low weakens in place south of the area.
Expect continued cloud cover showers from time to time Friday across Shemya and Adak/Atka as additional shortwave move eastward to the Bering from Kamchatka.

.LONG TERM FORECAST (Days 4 through 7: Saturday through Tuesday)...

Models have come into better agreement regarding the long term forecast. The global models all have a large North Pacific low entering the southern Gulf and moving northeastward through Sunday morning. If current trends continue, the low pressure system itself moves to Southcentral's east, but does bring with it precipitation, mainly for coastal Southcentral areas. Looking aloft, watching a digging trough or closed low move over Southwest Alaska, though the question of if/when these two features interact is still rather uncertain. If they do in fact interact, the much larger upper trough with the "right" orientation could help tug/retrograde the low back to the northwest, which would increase precipitation chances for coastal Southcentral. The next order of business is a strong front that moves across the Aleutians and eventually into the western Gulf from Sunday afternoon to Monday afternoon as its parent low situates itself across the southern Bering. After the front pushes into the Gulf, details become fuzzy. All said, the pattern looks to remain active through the end of the long term.

-AM

AVIATION

PANC...VFR conditions will prevail this evening under weak southeasterly low level flow. The low level flow will then shift to southwest overnight ahead of an upper level short-wave trough approaching from the west. This will lead to lowering ceilings and development of showers in the vicinity, with high confidence in dropping to MVFR between 09 and 15Z. As the upper trough gets closer steady light rain will develop Wednesday morning. Most likely ceilings will stay in the MVFR category, but there is a small chance of IFR ceilings at the terminal or in the vicinity.

Meanwhile, the terminal will remain right along the northerly edge of the Turnagain Arm jet this afternoon and evening, making it a challenge to determine timing of gusty southeasterly winds moving in. The most likely period for gusty winds is 03 to 06Z, but it could be a little longer than that. Once winds die down, they will remain light through Wednesday.

-SEB