Marine Weather and Tide Forecast for Halibut Cove, AK

.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING SEA/ALEUTIANS (Monday afternoon to Thursday afternoon)...

The Winter Weather advisory remains in effect in the Pribilof Islands until Tuesday morning as snow and gusty winds continue to impact the islands. This is due to an occluded front that is impacting the Bering from a low south of the Aleutian Islands. In the Aleutian chain itself, temperatures are too warm for snow at lower elevations, so precipitation falling there is mostly in the form of rain. Over the course of the day, the low will split into two and the new one will move into the mainland by Tuesday evening. This will set the stage for another round of precipitation for the southwest mainland. However, due to the orientation of the winds (southeasterly), parts of the Bristol Bay region (a triangle from King Salmon, Dillingham, to Iliamna) will be downsloped which means lower chances for precipitation and less accumulations. Furthermore, the southerly flow will allow warmer air to continue filtering into the southwest, meaning precipitation will be mostly in the form of rain at lower elevations. Gusty winds will also impact the southwest mainland as the low moves through. Areas of precipitation and gusty winds will continue until Wednesday afternoon when a small ridge moves in. Cooler air will accompany the ridge, so high temperatures will drop below freezing mainly north of Dillingham by Wednesday.

Out in the Bering, a Kamchatka low moves into the western Bering by Wednesday morning. A trough attached to the low will dip into the Aleutian Islands as the low travels along the Kamchatka coastline. This will bring precipitation and high-end gale force winds to the Bering as the trough tracks eastward. Cold air will wrap around the back of the system, so snow showers may follow behind the trough. Come Wednesday night/Thursday morning, a compact low within an atmospheric river will barrel into the Bering, quickly pushing the Kamchatka low northwards and driving the trough into the mainland. The mainland could see some snowfall before warmer air filters in behind the trough. Wind speeds will soar into storm force category in the central Aleutians by Thursday afternoon. Heavy precipitation mostly in the form of rain will also accompany this low. Looking a bit ahead reveals that this core of storm force winds will track into the Kuskokwim coast, which could drive coastal flooding into communities such as Kwigillingok and Kongiganak by Thursday night into Friday. Behind this low and atmospheric river is a cold air mass that will move into the western Aleutians from Siberia by Thursday evening. This much colder air could have implications for the near future.

-JAR

.LONG TERM FORECAST (Days 4 through 7: Friday through Monday)...

KEY POINTS:

- A highly amplified and potentially impactful weather pattern is expected to affect much of the forecast area from Friday into this weekend.

- Strong winds, heavy precipitation and very warm temperatures will be possible over much of southern Alaska from Friday to Monday as a strong frontal system moves across the region.

- Much colder air will move in from the northwest behind the heavy precipitation early next week.

An extremely active, highly unusual and potentially highly impactful pattern will be well underway at the start of the period on Friday morning. A very strong longwave ridge is expected to be in place over the Northeast Pacific on Friday morning, with the crest of this ridge extending well up into Mainland Alaska. To the northwest, a deep longwave trough with an embedded closed low is expected to be moving up into the far northern Bering Sea and up into far northeastern Russia. Two dramatically contrasting air masses will be building under the main upper trough and Pacific ridge. A very warm air mass will be in place under and towards the upstream side of the ridge, including much of the southern Mainland out to the eastern Aleutians. Meanwhile, a much colder, Arctic air mass will be building under the longwave trough across much of the northern and western Bering up into Siberia.

The gradient in terms of temperature and pressure fields between the two synoptic features outlined above, both near the surface and the upper levels, will be quite impressive for even Alaska standards. For example, the highest surface pressure under the ridge in the northeast Pacific could be as high as 1045 mb, contrasting with a surface low moving into the Bering that could deepen to around 980 mb or lower - a difference of at least 65 mb. A strong baroclinic zone (an area of strong temperature and pressure gradients) will exist between the main high pressure and the low/trough in the Bering Sea, initially in place Friday morning along an axis from the central Aleutians to the coastline of western Alaska. This effective frontal zone will slowly advance southeast with time throughout the weekend into early next week, and this will largely be the focus of the most inclement conditions with this pattern. The strong pressure gradient setting up along this boundary, plus at least two distinct stronger areas of low pressure that will move north along it, will support intense southwest winds, initially over the eastern Aleutians and Southwest. Stronger winds could also affect parts of Southcentral on Saturday and Sunday as the second low moves up from the Pacific into Southwest, but this potential for strong wind will be highly dependent on a still very uncertain low track.

An anomalous moisture plume, or atmospheric river, is also likely to stream north along and ahead of the main frontal zone, initially expected to be impacting parts of Southwest and much of the Alaska Peninsula and eastern Aleutians on Friday. This deep moisture tap will help support rather intense precipitation rates for much of Southwest and later Southcentral compared to what is typically possible for late January. Temperatures in many areas of Southwest close to sea level will likely initially be warm enough for rain at lower elevations, and this will likely also be the case as the atmospheric river and front shift into Southcentral between Saturday and Monday. There could be a transition over to snow across both Southwest and Southcentral as cooler air begins to move in behind the front between Sunday and Monday.

Lastly, it looks increasingly likely for a significant, sudden temperature drop to advance west to east across the southern Mainland early next week as the front moves through and as the Arctic air mass cascades south and east. There is still a fairly large spread in terms of when it looks like the colder air will arrive for any given location, but there is a strong signal in both deterministic and ensemble guidance that this cold air mass will eventually make it into our outlook area early next week.
This could lead to more weather impacts due to the sudden switch from warm temperatures and rain/snow to bitter cold. Stay tuned as we follow this very active pattern and resolve details for timing, precipitation amounts and wind magnitude for this setup in the coming days.

-AS

AVIATION

PANC...Fog and low stratus apparently will continue to be an issue through the night in the very moist airmass over the area. The light and variable winds will probably turn light northerly late in the evening which may also help keep some of the fog and stratus in the vicinity. This has the look of a situation where it is in and out throughout much of the night. Toward morning, the winds aloft will increase from the southeast. That, and thickening mid-level clouds may help to increase the mixing in the atmosphere and decreasing the radiational cooling at the surface so fog and stratus are expected to be less of an issue later tonight and into tomorrow.