Marine Forecasts

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7 Day Forecast for Marine Location Near Anchor Point, AK

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Area Discussion for -

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FXAK68 PAFC 070230 AFDAFC

Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 530 PM AKST Fri Dec 6 2019

ANALYSIS AND UPPER LEVELS.

The first in a series of warm fronts is pressing in along the West Coast of AK. This will start the shift across much of the southern half of AK to a warmer and much wetter pattern. First, the weak shortwave that clipped through Southcentral AK last night is moving off through the Copper River Basin today. In general, it dropped anywhere from a trace to 1 inch of fresh snow. Out west, radar and satellite are showing the incoming snow well. Snow and blowing snow is already reducing visibilities a s low as one quarter mile across parts of the YK Delta. A Winter Weather Advisory is in place to address the snow and blowing snow out there. Meanwhile, there are signs of the warm air coming as observations across the Bristol Bay area are showing temperatures already into the upper 30s.

An impressive jet is helping to amplify this pattern. From west to east, we can see the 300mb (30,000’) jet moving under the Western Aleutians at 195 kts. This is helping to support the broad, cold trough over the Bering Sea. Further east, we can start to see signs of the jet strengthening over the North Pacific as transverse banding is very evident on satellite. This jet is currently around 115 kts. It is ushering much warmer air towards the southern mainland and will serve to creating a strong area of low pressure near Bristol Bay as we head into the overnight-Sat.

MODEL DISCUSSION.

Models have come into significantly better agreement in handling the various surface low pressure centers over the next couple of days. Generally, the American models have performed slightly better to this point. However, there are still key differences in the lows’ tracks and timing that will be key factors in the sensible weather through Tue. The depth and track of the low across Bristol Bay and the Western Capes tonight is much more certain. The remaining area of uncertainty surrounds how much of a coastal erosion/high surf impact this could be. Variables such as sea ice and duration of the fetch will make this a challenging forecast. Then for the next system moving towards Southcentral on Sat afternoon, the NAM has recently come in much stronger and further east. We have opted for a middle ground solution with that feature. Then finally, the 3rd system late Sun into Mon is the strongest. It will approach from the N Pacific into the Gulf of AK. This is a common source region for high model uncertainty.

AVIATION. PANC . VFR conditions should persist through the TAF period. Wind shear will become a concern by early Sat morning. Down-inlet north winds will hold at the surface, while southeast flow increases aloft in response to the approaching front.

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

A large stream of subtropical moisture will begin to move into the area this evening associated with strong southerly flow, east of a low tracking across the Alaska Peninsula. Brief snow and/or freezing rain is possible over the western Kenai Peninsula, however it will be light and quickly change to rain as the aforementioned southerly winds will warm surface temperatures above freezing. Winds along Turnagain Arm are expected to peak near 60 mph Saturday morning, but are not likely to affect the Anchorage Bowl. As flow will have an easterly component, much of the moisture will struggle to make it to the leeward side of the mountains. However as the low moves over Southcentral, downsloping will cease and snow/freezing rain is possible across Anchorage and the southern Susitna Valley late Saturday night into Sunday morning and temperatures briefly cool below freezing. Precipitation will gradually end through Sunday as the system departs to the north.

SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2). A very active weather pattern has moved into Southwest Alaska this afternoon and evening as a strong Pacific warm front is lifting north across Bristol Bay and into the Kusko Delta. Heavy snow and blowing snow is impacting the Delta and will gradually turn to rain or pockets of freezing rain in the late evening and early overnight. Rain has already changed over along the coast of Bristol Bay, although heavy snow will continue over higher elevation interior mountains. Attention quickly turns to a fast moving but strong gale force low moving north across Bristol Bay to north of Nunivak Island overnight through Saturday. This low will wrap up quickly and impact coastal locations with a strong onshore S-SW wind possibly gusting as high as 45-50 knots. Cold air wrapping around this low will likely result in a return to a mix of rain and snow, but given the onshore flow off the warm waters, no blowing snow is anticipated. A second area of enhanced precipitation will develop across the Alaska Range Saturday and Saturday night, bringing accumulating snow to that region and locations near the Alaska Range. Yet another low barrels into the Alaska Peninsula Sun eve, but the bulk of this system come overnight and Monday (see extended discussion).

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

A strong Pacific gale force warm front has reached the Southwest coast with a secondary trailing low moving north in between Dutch Harbor and Cold Bay, which will then quickly move into Bristol Bay and track toward the Strait through the day Saturday. This low will reach brief storm force over the marine waters south of the Eastern Aleutians/AKPEN, but will likely remain a powerful gale force low as it tracks along the coast as it moves northward. Thereafter, a series of weaker and smaller lows will move across the Western/Central Aleutians as broad cyclonic flow remains over the Bering Sea. Yet another low barrels into the Alaska Peninsula Sun eve, but the bulk of this system come overnight and Monday (see extended discussion).

MARINE (Days 3 through 5). Monday there is a potent low near Bristol Bay which has the potential to produce gale force winds and also produce light to heavy freezing spray near Nunivak Island. A second low which will be south of Adak also has the potential for producing small craft to gale force winds. As time elapses, the Bristol Bay low retrogrades towards NE Russia and the Adak low moves towards Kodiak and phases with another low. Expect the gusty winds and enhanced sea states to move into the Gulf Of Alaska. With this cold pattern in place, expect the sea ice to grow for both the Kuskokwim Delta and Bristol Bay.

LONG TERM FORECAST (Days 3 through 7).

The vagaries of the models continue to influence the confidence level in the long term forecast period. Looking at both deterministic and ensemble guidance categorically the confidence level is below average. There are a few items that can be gleaned. Expect a highly progressive pattern with the longwave pattern to retain residence over the Bering and the north Pacific. There are multiple lows from Kamchatka to the southcentral Alaska this forecast period. Although for the Bering and the NW Pacific the placement and the intensities of the lows are not in sync. The storm that will impact southcentral this weekend will break the cold snap with temperatures in the Anchorage Metro Area possibly getting back up into the 40s this Sunday. Also noteworthy and very plausible, the GFS at this time is suggesting an atmospheric river will move into southcentral on Monday.

AFC WATCHES/WARNINGS/ADVISORIES. PUBLIC . WSW 155. MARINE . Storm 155. Gales 119 125 130 139 150 160 165 170 172 177 178 180 181 185 414. FIRE WEATHER . NONE.



SYNOPSIS AND MODEL DISCUSSION . MO SOUTHCENTRAL ALASKA . AP SOUTHWEST ALASKA/BERING SEA/ALEUTIANS . JA MARINE/LONG TERM . PS

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Weather Reporting Stations

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Stations	Dist	Age	Wind	Air Temp	Water Temp	Waves	Pressure	DewPt
46108 - Central Cook Inlet - 175	12 mi	31 min			45°F	4 ft
OVIA2 - 9455500 - Seldovia, AK	24 mi	49 min			45°F		997 hPa
HMSA2	25 mi	19 min	E 6 G 12	40°F			995.1 hPa	33°F
HMRA2 - Kachemak Bay Reserve, AK	26 mi	31 min	E 9.9	39°F			996 hPa	35°F
FILA2 - Flat Island Light, AK	31 mi	31 min	NNE 15 G 19	39°F			996.7 hPa	36°F

Wind History for Nikiski, AK

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Airport Reports

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Airport	Dist	Age	Wind kt	Visibility	Sky/Weather	Temp	DewPt	Humidity	Pressure
Homer, Homer Airport, AK	20 mi	68 min	N 0	10.00 mi	Overcast	34°F	30°F	89%	998.1 hPa
Seldovia, Seldovia Airport, AK	24 mi	68 min	N 0	10.00 mi	Light Rain	37°F	32°F	82%	998 hPa

Link to 5 minute data for PAHO

Wind History from AHO (wind in knots)

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Tide / Current Tables for Cape Ninilchik, Alaska

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Tide / Current Tables for Ninilchik, 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

Other links: Northern Pacific     Contential US     Full GOES-East

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Ground Weather Radar Station Kenai, AK

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