Marine Forecasts

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7 Day Forecast for Marine Location Near Seldovia, AK

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Area Discussion for -

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FXAK68 PAFC 190042 AFDAFC

Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 442 PM AKDT Sat Sep 18 2021

ANALYSIS AND UPPER LEVELS.

A shortwave trough is digging across the Copper River Basin this afternoon. This wave is progressing along the base of a broader trough of low pressure further north, which is currently shifting over the Alaska/Yukon border. Behind the trough axis large-scale subsidence or sinking motion has overspread much of Southcentral and Southwest with milder winds and clearing skies. Two areas, the Kuskokwim Delta and the Copper River Basin, remain under denser cloud cover. The Kuskokwim Delta is seeing moisture trapped from moving southeast by the Kuskokwim Range maintain cloudiness. The Copper River Basin remains downstream of the the aforementioned trough axis and thus in a region of convergence and diffluence aloft.

Meanwhile,a broad upper low continues to drift eastward across the Aleutians. Afternoon satellite imagery shows the center over or near Atka. This area of low pressure is promoting widespread cloud cover and areas of light rain over the Aleutian Chain with cloud cover slowly beginning to expand into the Alaska Peninsula. North to northeasterly winds are also gusting to gale force from Adak to Dutch Harbor. The low's occluded front stretches across the Alaska Peninsula with the intersection of a cold front and warm front noted to the south of Chignik. Additional easterly winds gusting to gale force are preceding the warm front. High pressure is slowly building into the Gulf with a few areas of northwesterly winds below gale force.

MODEL DISCUSSION.

Models remain in good agreement this afternoon depicting the continued progression of an Aleutian low into the Gulf over the next few days. All models suggest low pressure will set up along the coast just east of Cordova early on Tuesday, though there are differences in the evolution of the low. Guidance shows the low becoming elongated into two areas of low pressure Sunday into Monday with the leading edge of low pressure becoming the dominant low. While it looks like the higher outflow winds will be in the vicinity of Kodiak Island on Tuesday, any change in the low's track or speed could mitigate or enhance the intensity of said winds. Attention is also focused on the arrival of an arctic airmass into Southcentral on Tuesday and the potential for any snow. The Alaskan Range tends to modify colder temps this early in the year. Regardless, all the global models show 850 mb temperatures of -5 degrees Celsius or colder arriving with no issues into Southcentral on Tuesday. Models may be overdoing the freezing temperatures somewhat, thus limiting any threat for meaningful snow to the higher elevations and locations further north and east, and models will need to be evaluated closely over the next couple of days.

AVIATION.

PANC . VFR conditions will continue under high pressure with light northerly winds persisting through the TAF period.

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Tonight through Tue afternoon) .

An Arctic trough continues to move east this afternoon reaching the Alcan border by early Sunday morning. As a result, lingering cloud cover and some isolated showers remain possible through this evening. Some uncertainty remains as to how clear the Copper River Basin gets tonight which will impact how cold the temperatures get. Current thinking is mid to upper 20s but it could get a fair bit colder if it completely clears out. While light and variable winds are expected, cloud cover will play a role as to how cold it can get tonight for the Basin. If it does clear, low 20s to maybe even a few upper teens may be possible. The rest of Southcentral will remain clear with light and variable winds with the first widespread frost/freeze of the season remaining on track. The Susitna Valley, interior Kenai Peninsula, Matanuska Valley and especially East Anchorage can expect temperatures to drop to the upper 20s to low 30s overnight/early Sunday morning with near freezing to slightly above freezing for elsewhere. Therefore, make sure to protect those sensitive plants outdoors.

Next, Sunday will be generally quiet and dry for all of Southcentral as very weak upper level ridging remains in place. Temperatures are expected to rebound nicely during the day with most areas reaching into the low to mid 50s for highs with perhaps a few upper 50s in places. Due to the generally weak synoptic flow aloft and daytime heating, expecting at least a weak sea breeze for the Valdez area Sunday afternoon. The coastal ridge then begins to build some out ahead of the next system Sunday afternoon, therefore, expecting the Turnagain Arm to develop with some weak southeasterly winds maybe 5 to 10 mph making it into West Anchorage Sunday evening. However, any wind that does is expected to be brief before down Inlet flow develops as the next system moves northeast.

Lastly, onto the big story, a storm system currently south of the Aleutian Chain continues moving northeastward into Sunday. At this time, it appears most the precipitation with this misses Kodiak City to to the southeast remaining offshore but a few showers cannot be ruled out Sunday night into Monday morning. Then, a rather complex setup will occur for Southern Alaska Monday through Tuesday. Another Arctic trough dropping down from the northwest will bring the next stronger shot of cold air. This trough is expected to phase with the aforementioned low. Therefore, expecting any rain to change to snow overnight Monday into Tuesday morning for the Copper Basin with snow accumulations expected. There may be some snow showers for the Anchorage Hillside with any accumulation if any very minimal. Also, as the cold air comes in on the backside of this system late Monday night and Tuesday, expect a very windy day area-wide Tuesday, especially through the Seward area, Barren Islands, and Whittier as well as Valdez and Thompson Pass.

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Sat afternoon through Tue) .

Calm and cool weather is expected on Sunday as an upper level ridge breaks down. An arctic front will move in from the north dropping temperatures a solid five to ten degrees from Sunday into Monday. Lows will drop below freezing over the interior areas with coastal areas staying in the mid 30s due to oceanic moderation. A brief shot of light snow is possible overnight with little to no accumulation. Winds will also pick up during and after frontal passage with sustained winds ranging from 15 to 30 mph out of the north on Monday. By Tuesday, impacts from the front will be minimal with breezy winds and cool temperatures.

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3: Sat afternoon through Tue) .

The low over the central Aleutians is nearing peak intensity this afternoon. Fairly widespread gales have been measured on ASCAT imagery from the waters surrounding Unalaska west to Amchitka. As the low weakens and departs to the east-southeast, winds will diminish and become northerly throughout the eastern Aleutians and AKPen. By Sunday afternoon, a shortwave ridge will build over the Bering, leading to overall calm conditions through Monday night. By Tuesday afternoon, another low, taking a similar track to the one south of the Chain today, will bring gales and rain to the central Aleutians on Tuesday.

MARINE (Days Monday through Wednesday).

Gulf of Alaska . A gale-force front will be draped along the north Gulf coast, stretching east of Kodiak Island. As the responsible low pressure system sits in area, a cold arctic air mass will filter through the coastal mountains on Monday night into Tuesday which will drive gusty gale-force sustained winds through the gaps, with storm-force gusts, especially Kamishak Gap and Barren Islands regions. The next gale-force front rolls in from the Pacific quickly on Wednesday afternoon and evening.

Bering Sea . Monday starts with high pressure encompassing much of the Bering. The next system skirts the Aleutians to the south, so winds along the front in the southern Bering should be sub-gale force.

LONG TERM FORECAST (Monday through Friday). The big story with the extended forecast is an early Fall "winter" storm (even though it is still Summer until Wednesday morning). A cold front dropping southward will bring a very winter like air mass to the area. Guidance has been very consistent with digging the associated trough which will phase with a north Pacific low pressure. The combination of these two systems is needed to get the magnitude of arctic air this far south this time of year. The first trough brings the cold air through the Interior and to the edge of the Alaska Range, while the second system links up and pulls it through. Based on these factors, details have yet to determined, but there is increasing confidence of below normal temperatures, especially overnight minimums which will be below freezing in many locations.

On the subject of precipitation, the big question will be how much moisture is still in place when the cold air arrives. It will be difficult to get snow down to sea level this time of year, but for upper elevations of the Chugach it will be possible. Higher confidence for snow exists in the Copper River Basin and Thompson Pass where snow to the surface looks likely at this point along with some accumulation. The next facet of this system will be the first real "winter outflow" winds of the season. The arctic air mass being pulled through the gaps will make for gusty winds in the usual favored locations along the north Gulf coast.

The cold air mass remains in place, though moderated as the Gulf system exits quickly on Tuesday evening, but the next system comes into the Gulf on Wednesday/Thursday keeping precipitation along the coast and outflow wind in place. Definitely an active winter- like pattern.

AFC WATCHES/WARNINGS/ADVISORIES. PUBLIC . NONE. MARINE . Gale 155 170-177 FIRE WEATHER . NONE.

SYNOPSIS AND MODEL DISCUSSION . JPW/BL SOUTHCENTRAL ALASKA . MV SOUTHWEST ALASKA/BERING SEA/ALEUTIANS . CJ MARINE/LONG TERM . MTL

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Weather Reporting Stations

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Stations	Dist	Age	Wind	Air Temp	Water Temp	Waves	Pressure	DewPt
OVIA2 - 9455500 - Seldovia, AK	1 mi	53 min			51°F		1004.2 hPa (-0.3)
46108 - Central Cook Inlet - 175	12 mi	53 min		47°F	50°F	1 ft
FILA2 - Flat Island Light, AK	17 mi	23 min	E 8 G 8.9	46°F			1004 hPa	34°F
HMRA2 - Kachemak Bay Reserve, AK	19 mi	83 min	ESE 5.1				1004 hPa
HMSA2	19 mi	21 min	ENE 8 G 12	45°F				39°F
APXA2	23 mi	68 min	ESE 5.1	32°F			1005 hPa	29°F
AMAA2 - East Amatuli Light, AK	39 mi	23 min	N 5.1 G 8	53°F			1002.7 hPa	38°F

Wind History for Nikiski, AK

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N7 G12

NE5

NE6

E5

NE7 G11

NE8 G12

N1 G6

W1 G4

W4

W5

W4 G7

W5

W6 G9

W3

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NW1

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E8

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1 day ago

NE6 G10

NE5 G8

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W4 G7

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N4

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N8 G12

N3 G7

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N7 G10

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NE14 G22

NE14 G21

NE13 G20

NE14 G23

NE13 G19

NE13 G23

NE15 G22

NE15 G25

NE16 G23

NE19 G28

NE16 G26

NE15 G21

NE14 G20

NE14 G21

NE12 G20

NE12 G17

NE11 G15

NE11 G17

NE10 G14

NE9 G15

NE11 G15

NE10 G15

NE10 G15

NE9 G14

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Airport Reports

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Airport	Dist	Age	Wind kt	Visibility	Sky/Weather	Temp	DewPt	Humidity	Pressure
Seldovia, Seldovia Airport, AK	1 mi	60 min	N 0	10.00 mi	Fair	35°F	33°F	93%	1004.4 hPa
Homer, Homer Airport, AK	18 mi	60 min	NNE 3	10.00 mi	Fair	37°F	32°F	82%	1004.7 hPa

Link to 5 minute data for PASO

Wind History from ASO (wind in knots)

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Last 24hr

Calm

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Calm

NE5

N7

NE5

N7

N7

N7

3

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Calm

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Calm

Calm

S3

Calm

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1 day ago

Calm

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NE3

NE5

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2 days ago

NE5

N5

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N7

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N10 G18

N7

N5

N5

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Calm

Calm

Calm

Calm

Calm

Calm

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Tide / Current Tables for Seldovia, Alaska

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Tide / Current Tables for Port Graham, Alaska

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