Marine Forecasts

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7 Day Forecast for Marine Location Near Nikolski, AK

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FXAK68 PAFC 181307 AFDAFC

Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 507 AM AKDT Sun Apr 18 2021

ANALYSIS AND UPPER LEVELS.

The stretch of very quiet and generally dry conditions continues across much of the region this morning. The large scale upper levels also continue to display a sluggish, blocked regime across the breadth of Alaska and beyond. A roughly 575 decameter 500 mb omega ridge centered over the Yukon now extends southeast all the way to the far western CONUS. This is the primary driver of the normal to above normal temperatures recently observed across mainland AK, particularly across the Mat-Su Valleys. Both Willow and Talkeetna surprisingly managed to breach 60 F on Saturday despite the now rapidly melting snow cover in place. Farther west, a deep, complex longwave with several embedded lows and shortwaves continues to sit along an axis stretching from the Bering to well south of the Gulf across the North Pacific. An easterly wave transiting the Western Gulf and AKPen is also helping to advect a plume of mid to upper level moisture into the Southwest. This is bringing a broad swath of mainly altostratus and cirrus cloud cover across the Southwest and AKPen within this zone of southeasterly flow, along with a few scattered rain showers drifting northwest.

Out west across the Bering/Aleutians, a stalled front draped from the far northern Bering to near Adak continues to disintegrate as the winds weaken to small craft or lower on both sides of the boundary. An axis of mainly light rain still follows much of this weakening front, but the brunt of the impacts from this system or otherwise diminishing. Elsewhere, amorphous patches of low marine stratus are drifting across the Bering underneath ridging present both west and east of the front.

MODEL DISCUSSION.

Models remain in good agreement for most large scale features through midweek. Some differences do begin to crop up with the progression of a wave digging southeast from the northern interior, with models depicting varying degrees of interaction between this shortwave and another easterly wave tracking across the AKPen on Monday and Tuesday. Depending on how far south and west the trailing portion of the shortwave move across, showery precipitation potential may briefly return to interior Southcentral late on Tuesday. This could then be followed by a shot of somewhat colder air, especially through the Copper River Basin, by Tuesday night. The NAM and GFS are currently the most aggressive with the cooling/CAA going into Tuesday and Wednesday. The ECMWF/Canadian show only modest cooling, arcing the shortwave into the Yukon much farther north. This could lead to some challenges in resolving temperatures over Southcentral later this week.

AVIATION. PANC . VFR conditions and light winds will continue.

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

A strong upper-level ridge remains anchored along the Al-Can border and is one piece of the now well-advertised blocking pattern that has set up over the state. The ridge will remain in place through late Monday before retreating south over the Canadian Rockies. The second piece is an upper-level low situated over the Northern Pacific. This feature will lift northwest toward the AKPEN by Monday in the wake of a weaker shortwave moving north out ahead of the main low.

This first shortwave will continue to bring clouds and occasional showers to Kodiak Island through the morning hours before it lifts into Southwest Alaska. By Monday, a second wave and associated surface front will move north into the Gulf with another round of light rain for Kodiak. The upper-level shortwave extending from the low moves over the northern Gulf along with the surface trough by Monday night, bringing a chance for light rain along the Southcentral coast. The southerly flow across the Gulf will keep clouds and precipitation along the coast through late Tuesday as the surface trough and upper-level shortwave stall.

For the interior, the ridge will keep conditions clear and dry, with only occasional high clouds passing overhead. High temperatures Sunday and Monday will again push into the 50s, with lower 60s possible in parts of the Mat-Su Valleys. An upper-level trough and associated cold front will dive southeast across the interior beginning Monday night as the aforementioned ridge retreats. The front will likely bring a few mixed rain/snow showers, especially for the higher elevations. The best chance for precipitation looks to be over the Talkeetna Mountains and Copper Rover Basin on Tuesday. This system will exit the region by Wednesday morning taking the stalled trough along the coast with it. High pressure builds back in by mid-week as the blocking pattern looks to re-establish itself.

SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2).

A North Pacific low moves towards the Eastern Aleutians, forcing the upper level ridge north late Monday morning. A tighter pressure gradient sets up between the ridge and trough, producing gusty easterly winds through the gaps of the Alaska Range and across parts of Bristol Bay. This will also allow for stronger northerly winds across the Kuskokwim Delta. Daytime temperatures look to remain in the mid-40s to mid-50s across Southwest Alaska through the forecast period, with overnight lows in the mid-30s. Moderate chances for rain continue along the AKPen and Coastal Bristol Bay today, with the highest chance in the early morning. Precipitation will most likely be all rain for these areas and will be relatively short-lived.

SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2).

The N-S frontal boundary over Adak continues shearing apart today, allowing precip probabilities across the Western/Central Aleutians to continue to decrease. Winds become northerly across most of the Bering beginning Sunday night when a North Pacific low moves just south of the Eastern Aleutians. This will create gusty northerly winds through the bays and passes of the Central and Eastern Aleutian Islands, as well as gale force winds south of the AKPen, especially out of Shelikof Strait. Rain showers across the Eastern Aleutians and Southern AKPen are expected to persist over the next couple days, with Unalaska looking to get the brunt of the precipitation. Most of the impacts will be confined to the southern Bering and North Pacific. Widespread small craft winds out of the northeast are expected across the Bering north of the low. Additionally, gales are likely in the Northern Bering between Saint Matthew Island and Nunivak Island Monday night.

 MARINE (Days 3 through 5: Tuesday through Thursday).

There is a chance for some Gales to develop south of the Alaska Peninsula and Eastern Aleutians Tue through Wed. Other than that, expect winds less than 35 kts and seas less than 20 ft for the Day 3 through 5 period.

.Long Term Forecast (Days 4 through 7: Wednesday through Saturday) .

Subsident dry air and increased warmer temperatures will persist as a result of a dominant presence of a surface to high pressure over the region. Short-lived gales from a frontal system extending over the central Aleutians will gradually taper off Wednesday afternoon. Overall, it will be a quiet forecast period.

AFC WATCHES/WARNINGS/ADVISORIES. PUBLIC . NONE. MARINE . Gale Warning: 131,132,138,150,155,173-176. FIRE WEATHER . NONE.



SYNOPSIS AND MODEL DISCUSSION . AS SOUTHCENTRAL ALASKA . TM SOUTHWEST ALASKA/BERING SEA/ALEUTIANS . KM MARINE/LONG TERM . CB

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Weather Reporting Stations

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Stations	Dist	Age	Wind	Air Temp	Water Temp	Waves	Pressure	DewPt
OLSA2 - 9462450 - Nokolski, AK	16 mi	51 min	NNW 5.1 G 7	41°F			1021.9 hPa
NKLA2	17 mi	27 min	NNW 11 G 19	37°F				31°F

Wind History for Nikolski, AK

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N5

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Airport Reports

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Airport	Dist	Age	Wind kt	Visibility	Sky/Weather	Temp	DewPt	Humidity	Pressure
Unalaska, Unalaska Airport, AK	155 mi	43 min	N 13	10.00 mi	Overcast	39°F	34°F	82%	1021.4 hPa

Link to 5 minute data for PADU

Wind History from ADU (wind in knots)

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N7 G20

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N12 G22

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NE11 G20

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Tide / Current Tables for Adugak Islands, Umnak Island, Alaska

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