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PKZ761 Bristol Bay From Port Heiden To Cape Chichagof Out To 15 Nm- 402 Am Akst Mon Dec 11 2023
Today..NW wind 20 kt. Seas 6 ft. Freezing spray. Snow showers.
Tonight..N wind 20 kt. Seas 6 ft. Freezing spray. Snow showers.
Tue..N wind 20 kt. Seas 6 ft. Freezing spray. Widespread snow showers.
Tue night..N wind 30 kt. Seas 11 ft.
Wed..N wind 35 kt. Seas 13 ft.
Thu..NE wind 20 kt. Seas 7 ft.
Fri..SE wind 20 kt. Seas 3 ft.

FXAK68 PAFC 111421 AFDAFC

Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 521 AM AKST Mon Dec 11 2023

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...

A winter storm remains in progress across much of southcentral Alaska. Latest satellite imagery shows the deep, broad cyclone gradually shifting eastward across southern Alaska. The attendant warm front with this cyclone is currently lifting through the Chugach Range, with the cold/occluded front extending southward through the Kenai Peninsula. The atmospheric river behind the warm front of this system has brought a fetch of very warm, moist air from the North Pacific into the Central Chugach eastward. A winter storm warning remains in effect for this area, specifically Thompson Pass and the adjacent area where 2-3 feet of snow is likely be the time this system wraps up on Tuesday.

Elsewhere, PAHG and PAIH radars show (mostly) snowfall moving northward across the Kenai Peninsula into Anchorage and the Mat-Su Valley. A rather strong downslope shadow on the west side of the Kenai and Chugach mtns has kept precipitation limited overnight, but latest radar trends show that the this precip shadow is now diminishing as cross-barrier flow subsides. Snowfall in the vicinity of 1-2 inches is possible for the Kenai northward into Anchorage and the Matanuska Valley today, with locally higher amounts. Heavier snow is expected for the Susitna Valley, where another 6 to 10 inches is possible from Talkeetna north.

For tonight night and beyond, much of the forecast remains highly in flux. Models continue to mostly trended towards a more east solution for the next low expected to lift northwest into the Gulf around the nearly stalled upper trough centered over the Alaska Peninsula, and this low should reach the coastline by Tuesday morning as it follows along a wavering frontal zone stretching over the Gulf. A near continuous stream of moisture firing into the mainly eastern sections of the Gulf coastline will result in near continuous snow (low-level coastal rain) for mountainous areas, with blizzard conditions possible in susceptible areas such as Thompson Pass. A big forecasting challenge with this next system will be the degree of 'inland' (including much of the Copper Basin) precipitation and the amount of warm air trying to filter into valleys that could cause some mixing with rain between Monday and Tuesday, including near McCarthy and Chitina. Farther west out towards the Kenai Peninsula and Mat-Su Valleys, the potential for additional snowfall past Monday morning has down- trended, with the majority of scenarios (now reflected in this forecast package) are keeping this region mostly dry through Tuesday night.

Yet another low pressure will join the parade of systems arcing north and west from the North Pacific on Wednesday morning. While details are again not clear-cut, it looks like there will be better chances this time around for light snow to spread back over to eastern parts of the outlook area, while another batch of moderate snow (and again possible mixing with rain near the coast)
moves into the Prince William Sound and Copper River Basin. Stay tuned for the forecast and for more updates to come as this very active winter pattern continues.

-Brown/AS

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Today through Wednesday)...

An amplified pattern continues over the Bering and Southwest Alaska this morning with a deep upper low situated over the Alaska Peninsula. An upper level front is pushing into the Western Aleutians with downstream ridging immediately west of the Central Aleutians. Northerly flow ahead of the ridge and on the backside of the AKPEN low is allowing cooler air (sub 32 degrees) to spill southward, uninhibited. Water vapor imagery reveals just how far south the colder air mass has traveled. Convective showers from the cooler air moving atop warmer sea surface temperatures extend as far south as 40N and along 170W. Cooler temperatures will continue to filter southward, including Southwest Alaska, over the next few days.

Short term updates include the tail-end of a blizzard warning over Bristol Bay and a Winter Weather Advisory over the Lower Kuskokwim Valley. While the upper low over the Alaska Peninsula will continue to promote periods of snow through the afternoon and evening hours, winds are already steadily decreasing. This will see any threat for blizzard conditions come to an end. Even without the wind threat, morning visibilities range from a 1/2 mile to 1 1/4 miles across Dillingham, New Stuyahok, and Koliganek as snow continues to fall.

This bring attention back to the temperature forecast. Overnight lows across the Kuskokwim Delta dropped to briefly below zero last night. Bethel reached -3 degrees before warming to 2 degrees. The daytime hours will promote little warming, if any, before nighttime befalls the region and sees temperatures once again dip below zero. Northerly winds gusting to around 25 mph will see wind chills range from -25 to -28 degrees during the morning hours on Tuesday and again on Wednesday. Precipitation largely comes to an end across Southwest by late Tuesday into Wednesday.

Finally, a Kamchatka low is expected to bring the next frontal system into the Western and Central Aleutians by midweek. This will bring a wedge of warmer and above freezing temperatures across the Aleutians, along with a changeover from snow back to rain.

BL

.LONG TERM FORECAST (Days 4 through 7)
Thursday through Sunday

The long-term forecast remains on track for the continued unsettled and active pattern for Southern Alaska, the Bering Sea, and the Gulf of Alaska. For Thursday and Friday, an upper level low in the Gulf opens up into trough as it progresses eastward to Southeast Alaska. Any snow showers should be confined to the coastal mountains through Friday. Another deep trough moves eastward to the central Bering Sea and becomes stationary by Sunday. A gale to storm-force low pushes its front eastward from the Central Aleutians to the coast of Southwest Alaska through Friday. There will be a warm push of air with this front. Thus, while precipitation could start as snow ahead of the front, precipitation will quickly change to rain as the warm air works in. Precipitation type is a little more uncertain for Southwest Alaska Friday due to timing differences in when the parent low in the western Bering occludes as well as when a secondary low forms along the front. Regardless, precipitation overspreads Southwest during the second half of Friday and makes it into Southcentral Friday evening and Saturday. Coastal locations of Southcentral look to again see the most precipitation with more uncertainty for inland locations due to downslope drying flow. Cold air continues to spill into the Bering Sea Saturday and Sunday as the occluded low remains in the Bering with snow showers a good bet for Aleutian Chain. Sunday for Southcentral features a lot of uncertainty with regard to the track of a potential Gulf low.

AVIATION

PANC...Gusty northerly winds over the terminal will persist into the early morning hours before shifting southerly by 15Z. Snow moving over the terminal will similarly persist into the early morning hours Monday, with areas of loose snow blowing around possible. The chance for snow will be low Monday with some showers pushing up and over the mountains possible, however diminishing throughout the day. Showers will then persist in the vicinity through the day Monday. Most likely ceiling/vis will bounce up and down as snow showers move over the terminal. There is a small chance of low level wind shear sometime between 09Z and 12Z as easterly flow strengthens along Turnagain Arm and the front range Chugach.

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Middle Bluff, Kvichak Bay, Bristol Bay, Alaska, Tide feet

Kvichak Bay (off Naknek River entrance)
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Mon -- 12:48 AM AKST     -0.00 knots Slack
Mon -- 04:22 AM AKST     -2.45 knots Max Ebb
Mon -- 08:25 AM AKST     0.00 knots Slack
Mon -- 09:26 AM AKST     Moonrise
Mon -- 10:10 AM AKST     Sunrise
Mon -- 10:47 AM AKST     2.90 knots Max Flood
Mon -- 02:30 PM AKST     -0.00 knots Slack
Mon -- 03:04 PM AKST     Moonset
Mon -- 04:34 PM AKST     Sunset
Mon -- 05:58 PM AKST     -1.98 knots Max Ebb
Mon -- 09:30 PM AKST     0.01 knots Slack
Mon -- 11:02 PM AKST     1.33 knots Max Flood
Tide / Current data from XTide NOT FOR NAVIGATION

Kvichak Bay (off Naknek River entrance), Alaska Current, knots

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