Marine Forecasts

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7 Day Forecast for Marine Location Near Point Possession, AK

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Area Discussion for -

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FXAK68 PAFC 200215 AFDAFC

Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 515 PM AKST Tue Jan 19 2021

ANALYSIS AND UPPER LEVELS.

Three lows are in the Bering Sea region this afternoon, and while not part of a complex low, are interacting with each other. The first is an old low near Kamchatka which has a front extending into the northern Bering and then curves into the Kuskokwim Bay and Bristol Bay areas and then feeds into the second low which is just south of the Alaska Peninsula. This front is the one which will move into southwest Alaska tonight while the (second) low center tracks over Kodiak Island. A third low can be seen south of Adak and heading toward the Central Aleutians.

While the 250 mb jet stream is running south of the forecast area, it is controlling the fate of each of these lows. The old low near Kamchatka is far from any jet support and weakening. The low near the Alaska Peninsula is near the jet, but in an area the jet is weakening as well so it will weaken as it moves northward. The low south of Adak is the one that is in the upper-left exit region of a strong jet streak which is a favorable location for strengthening.

The last remnants from yesterday's storm are in the Copper River Basin this afternoon and heading eastward.

MODEL DISCUSSION. Models are in good synoptic agreement with all systems with no major preference for one over the other. Secondary model parameters such as surface to 850 mb temperatures will be important in sorting through precipitation types later in the week with the next set of lows moving toward southern Alaska.

AVIATION. PANC . VFR conditions and light winds will persist. There is a chance for some low level wind shear during the overnight hours as surface winds are northerly and wind aloft turn southeast. However, it looks like any wind shear level would be higher than 2000 ft should it occur so keeping it out of the TAF.

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2: Tonight through Wednesday) .

Quiet weather will continue for Southcentral through tonight as an upper level ridge is overhead. This upper level ridge will continue to move off to the northeast rather quickly this evening as the next storm system moves into the region. Expect a mostly clear sky for the early evening hours before the clouds out ahead of the next system move in later tonight. As a result, temperatures will be able to fall into the low to mid 20s across much of Southcentral with some spotty teens not ruled out. The low temperatures are actually expected to occur earlier in the night before the clouds move in as with the early sunsets yet, a decent radiational cooling situation will setup with light winds and clear skies to aid in dropping temperatures.

Next, the next storm system currently moving into Kodiak will be of minimal impact to much of Southcentral with mainly higher elevation snow and a mix or snow and rain for the low elevations. Kodiak is already beginning to see some precipitation out of this event with some light snow falling, though, this is expected to quickly changeover to all rain. With this being a colder system compared to the last one, Seward will actually see snow accumulation from this one with around 4 to 5 inches of snow expected tonight through Wednesday morning. Cordova is a rather tricky forecast for this event as the center of the low is expected to slide off just to the south and the east of there. Right now, expecting a rain/snow mix but there is the potential this can stay all snow but with temperatures at 33 to 34 degrees it will be a rather wet snow. Therefore, generally 1 to up to as much as 3 inches is possible. This could be more though if it ends up staying snow longer and colder.

Lastly, another storm system Wednesday night through Thursday will bring more rain to Kodiak and more higher elevation snow and low elevation rain to the typical areas of Prince William Sound and the east side of the Alaska Range. Downsloping is expected to be fairly prevalent with both these systems keeping the typical downslope areas dry.

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2/ Tuesday afternoon through Thursday afternoon) .

An active weather pattern continues across Southwest this week. Precipitation is currently moving inland over the Alaska Peninsula and interior Bristol Bay region as an upper level low tracks eastward. The biggest forecast challenge was determining precipitation type as this front pushes inland. Given enough cold air in place at the surface, and only mildly warmer air moving in aloft, precipitation is expected to fall as snow, though temperatures will continue to warm and approach freezing across the Bristol Bay region. Farther north over the Kuskokwim Delta, snow is expected as temperatures will remain cold enough during the overnight hours tonight.

As this first system departs and moves eastward overnight, a second low arrives over the Bristol Bay coast. This low will bring much warmer air aloft, with 850 mb temperatures approaching 1-2 degrees C. This warmer air, combined with gusty southerly winds throughout the midlevels of the atmosphere will work to erode any remaining cold air at the surface. As a result, thinking that there will be a brief period of mixed precipitation (rain/snow mix) Wednesday night before a change to all rain as temperatures continue to warm. Farther north over the Kuskokwim Delta, cold air will linger in place longer, delaying the change to all rain Thursday morning. Precipitation type will remain the biggest challenge as this next low arrives and brings warmer air to much of Southwest Alaska for the end of the week.

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2/Tuesday afternoon through Thursday afternoon) .

An upper level low over the western Bering will keep an active weather pattern in place through the week. A gale force low currently lifting northward over the central Aleutians this evening will move into the Bering Wednesday while its front tracks eastward along the Chain. With a warmer airmass wrapped into this low, rain and gusty southerly winds will continue to track eastward along the Chain through Wednesday. As colder air wraps around the backside of this low, expect storm force winds Wednesday afternoon as the low center lifts into the central Bering. By Thursday morning, the low center will gradually weaken and lift northward. Another north Pacific low approaches the western Aleutians late Thursday, though models are currently depicting this system as weaker and much less organized aloft.

MARINE (Days 3 through 5): Friday through Sunday.

Gulf of Alaska: Forecast confidence is good through the weekend. A band of southeast small craft wind and waves extends over the Gulf into the Barren Island Fri, and moves into the eastern Gulf Sat. A trough over the northern Gulf develops into a low in the northeast Gulf Sat, with a high-end gale force barrier jet over the North Gulf Coast. This low moves onshore Sun. A front moves across the Gulf Sat-Sun. Widespread small craft winds spread over the Gulf, increasing to high-end gale force winds late Sat into Sun. Wave heights over the Gulf range from 17 feet Fri to 23 feet Sat and Sun.

Aleutians/Bering: Forecast confidence is good through the weekend. A front extending from a Western Aleutian low stretches into the Gulf of Alaska through Sun. This low tracks into southwest Alaska late Sat. Widespread small craft winds and waves with gale force gusts wrap the low through Sat, diminishing to westerly small craft winds with the front across the southern Bering through Sun. Areas of gale force winds remain south of the Aleutians and Alaska Peninsula through Sun. A second low approaches the western Aleutians Sat with widespread small craft and local gale force winds over the western Aleutians and Bering through Sun. Wave heights to 18 feet across the Southern Bering and 23 feet south of the Aleutians and Alaska Peninsula.

.LONG TERM FORECAST (Days 4 through 7): Saturday through Tuesday .

A low moving over the western Mainland will keep a showery pattern across much of southern Alaska as the weakening front over southwest Alaska moves into Southcentral through Saturday afternoon. Most areas will see rainfall associated with this system as warmer temperatures continue across the region, aside from the Copper River Basin, which will remain below freezing. Southwest Alaska will see a brief period of drying before the next Bering low system extends its front over the Alaska Peninsula and coastal areas on Sunday continuing farther inland through Monday. Temperatures will start to drop below the freezing mark again, allowing for the return of snowfall with this system, though some of the southern locations as well as the Alaska Peninsula could see all rain or a mix of rain/snow. The active pattern continues across the western/central Bering and Aleutians with another low pressure system moving in on Tuesday morning moving towards the eastern Bering and Alaska Peninsula through late Tuesday.

AFC WATCHES/WARNINGS/ADVISORIES. PUBLIC . NONE. MARINE . Storm 170 173-176. Heavy Freezing Spray 185 Gale 130 132 139 150 155 160 165 171 172 177 179 180 181. FIRE WEATHER . NONE.



SYNOPSIS AND MODEL DISCUSSION . EZ SOUTHCENTRAL ALASKA . MV SOUTHWEST ALASKA/BERING SEA/ALEUTIANS . KO MARINE/LONG TERM . AH

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Weather Reporting Stations

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Stations	Dist	Age	Wind	Air Temp	Water Temp	Waves	Pressure	DewPt
ANTA2 - 9455920 - Anchorage, AK	25 mi	52 min	N 5.1 G 6	29°F	30°F		1013.6 hPa (+0.6)
NKTA2 - 9455760 - Nikiski, AK	66 mi	52 min	ENE 5.1 G 5.1	28°F	31°F		1012.6 hPa (+1.0)
SWLA2 - 9455090- Seward, AK	72 mi	52 min			42°F		1013.7 hPa (+1.8)

Wind History for Anchorage, AK

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Airport Reports

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Airport	Dist	Age	Wind kt	Visibility	Sky/Weather	Temp	DewPt	Humidity	Pressure
Anchorage, Ted Stevens Anchorage International Airport, AK	18 mi	59 min	NE 7	10.00 mi	Mostly Cloudy	28°F	22°F	78%	1013.1 hPa
Anchorage, Lake Hood Seaplane Base, AK	20 mi	59 min	ENE 4	10.00 mi	Fair	26°F	23°F	88%	1013.4 hPa

Link to 5 minute data for PANC

Wind History from ANC (wind in knots)

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Tide / Current Tables for Fire Island, Alaska

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Tide / Current Tables for Anchorage (Knik Arm), Alaska

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Weather Map

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GEOS Local Image of Alaska    EDIT
NOTE: East coast views moved to GEOS-16. They are experimental and not well supported by NOAA so they may not be correct so be warned. This change required redoing a large amount of the GOES code. If the image you are expecting is not showing, please let me know. You may need to use the EDIT function to update your location.
Link to Loop

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Ground Weather Radar Station

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