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PKZ723 Passage Canal- 310 Am Akdt Tue Oct 3 2023
Today..W wind 20 kt. Gusts to 30 kt near whittier in the morning. Seas 3 ft.
Tonight..W wind 15 kt diminishing to 10 kt after midnight. Seas 2 ft.
Wed..Variable wind less than 10 kt becoming E 10 kt in the afternoon. Seas 2 ft.
Wed night..E wind 10 kt. Seas 2 ft.
Thu through Fri..E wind 15 kt. Seas 2 ft.
Sat..Variable wind less than 10 kt. Seas 2 ft.

PKZ700
No data

FXAK68 PAFC 031307 AFDAFC

Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 507 AM AKDT Tue Oct 3 2023

ANALYSIS AND UPPER LEVELS

An upper-level trough and its attendant surface low continue to track east into the Panhandle. As a result, precipitation tapers off across eastern Southcentral this morning. High pressure across the central and eastern Aleutians and Bering, Southwest Alaska, and much of Southcentral is keeping conditions generally dry and benign. The pressure gradient between the high pressure to the west and low pressure to the east has been promoting gusty northwesterly gap winds along the Alaska Peninsula and through the Barren Islands. Winds begin to gradually diminish this morning and will continue to do so during the day. Further west, a Kamchatka low extends its surface front across the western Bering and Aleutians. Steady rain and winds up to gale force are associated with the front.

MODEL DISCUSSION

Models remain in good synoptic agreement through most of the week. There is strong consensus for an upper-level low and surface front to enter the western Bering and Aleutians this morning. A surface low will track from the North Pacific into the front and enhance precipitation for the western and central Aleutians this afternoon through tonight. Another upper-level low will reach the Alaska Peninsula and eastern Aleutians Wednesday into Thursday.
Model agreement begins to diverge by Friday and beyond with regards to the depth and placement of this low, ultimately affecting precipitation placement and intensity.

AVIATION
PANC...VFR will prevail for the TAF period. Light northerly winds will persist through the day.

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3; Today through Thursday night)...

Snow is slowly coming to an end from west to east across the Copper River Basin this morning as a compact surface low moves south of Kayak Island and the upper-level trough slides east toward the Al-Can border. A drier airmass advecting over Southcentral in the wake of the aforementioned trough will bring mostly clear skies and slightly below normal temperatures to much of the region today through Wednesday. A weak shortwave clipping the Alaska Range and extreme northern portion of interior Southcentral this afternoon may bring some clouds and isolated snow showers to the higher elevations of the Talkeetnas and Wrangells this afternoon and evening.

The bigger story will be a return to an active weather by the second half of Wednesday as a North Pacific low pushes its gale- force front northward over Kodiak Island. Gusty winds and moderate rain with pockets of heavier precipitation overspread the island Wednesday afternoon. The front will continue to lift northward and reach the northern Gulf Coast Thursday morning. In doing so, an area of northeasterly storm-force winds will be possible in the vicinity of the Barren Islands Thursday morning, with easterly and northeasterly gales elsewhere along the north Gulf Coastal waters. Deep southerly flow and warmer air will accompany this front. Confidence is high that coastal locations will see mostly rain with this event. However, there should be enough cold air in place across the Copper River Basin for at least a couple of inches of snow before the snow mixes with or changes over to rain Thursday afternoon. A similar scenario is also possible for the Susitna Valley; however, there is a higher level of uncertainty as to how much cold air will be in place at the start of the event. Currently, it looks like areas around Willow and Skwentna could see some snow before a changeover to rain.



.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days 1 through 3)...

Mostly dry yet cooler conditions are forecast for Southwest Alaska over the next few days as weak high pressure gets shunted from the eastern Bering into the Seward Peninsula through Wednesday. Below freezing temperatures associated with a polar low over the Arctic Ocean have spilled all the way into Southwest and Southcentral. The end result is the first prominent bout of colder temperatures into Southwest this Fall. Overnight lows through Wednesday night are forecast to dip into the 20s and 30s, though daytime highs should warm to above freezing for most areas each day. Dry weather will last into Wednesday afternoon.
Thereafter, a North Pacific low brings a warm front into Southwest Alaska late Thursday along with a plume of deep moisture. Showers are forecast to spread northward across Southwest throughout the day on Thursday as the front makes a trip to the Arctic Circle.

Across the Bering an occluded front is overspreading the Western Aleutians this morning. Southerly gales and numerous showers will linger through late Tuesday while also moving into the Central Aleutians. Enhanced winds with potential storm force gusts will taper off early Wednesday morning as the front is carried northwestward into Kamchatka and its parent low begins to shear apart over the Western Aleutians. Late on Wednesday will see redevelopment of potential gales, this time along the Alaska Peninsula as the N Pacific low moves from the Pacific side of the AKPEN into Bristol Bay.



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

An upper-level longwave trough, with embedded closed low centers, will remain in place across southern mainland Alaska for the long term forecast period. At the surface, model guidance suggests this corresponds to a broad low pressure centered near the Alaska Peninsula gradually shifting into the Gulf of Alaska. However, the surface details are highly uncertain, with different model solutions depicting differing low strengths and various individual waves propagating through the flow.

At the beginning of the long term on Friday, a low centered over the Alaska Peninsula is accompanied by a front spreading precipitation across much of southern mainland Alaska, while northeasterly winds are drawn from Interior Alaska out across the Kuskokwim Delta. These winds are a point of disagreement in the model guidance, as a result of uncertain strength in the pressure gradient between the Alaska Peninsula low and high pressure over the Chukchi Sea. As a result, while strong northeasterly winds are likely to set up through the Kuskokwim Delta, there is moderate uncertainty in what their intensity will be. Low end guidance suggests sustained winds peak out near 25 mph, while the higher end suggests gale force winds (>39 mph) are possible. The current forecast favors the mid to higher end of this range.

Northeasterly winds flow out across much of the Bering Sea for the end of the week, before a ridge moves in from the west and low pressure shifts into the Gulf by Sunday. This reorients the winds more northerly, while they become more limited to the eastern Bering Sea, but affect a greater portion of Southwest Alaska. The front over southern mainland Alaska weakens, leading to more showery conditions, while southerly onshore flow continues to wring out precipitation along the coast from Kodiak to Cape Suckling through Sunday. The front may linger over Southcentral as it pivots in response to an Arctic trough dipping southward across Southwest Alaska. Model inconsistencies abound, so generally expect continued above seasonal normal rain chances, with no particular geographical focus among inland locations.

For Monday, there is moderate potential for winds out of gaps along the Alaska Peninsula and western Gulf coast as low pressure increasingly focuses in the Gulf and cold air looks to push south across the Aleutian Range. Models also generally indicate a weak (below gale force), disorganized low entering the western Bering Sea at the start of next week.

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Tue -- 06:18 AM AKDT     -2.21 feet Low Tide
Tue -- 08:09 AM AKDT     Sunrise
Tue -- 11:14 AM AKDT     34.70 feet High Tide
Tue -- 03:37 PM AKDT     Moonset
Tue -- 06:20 PM AKDT     3.74 feet Low Tide
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Tue -- 11:05 PM AKDT     35.32 feet High Tide
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