Marine Weather and Tides
3/30/2021 -- ANZ330 has been split into ANZ331 and ANZ332. Click EDIT in Marine Forecast and select your new zone.
1/26/2021 -- The West Coast Satellite images havd been updated. They now use GEOS-17.
1/1/2021 -- The 7 day forecast are now working well. Thank you NOAA for your support.
|Sunrise 6:03AM||Sunset 6:50PM||Friday July 30, 2021 8:52 AM ChST (22:52 UTC)||Moonrise 9:59PM||Moonset 10:34AM||Illumination 70%|
7 Day Forecast for Marine Location Near Attu Station, AKHourly EDIT Help
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FXAK68 PAFC 291412 AFDAFC
Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 612 AM AKDT Thu Jul 29 2021
ANALYSIS AND UPPER LEVELS.
High pressure over the western Gulf continues to lift northeastward toward Southcentral Alaska this morning. A large upper-level low is situated over the Bering, with a slow moving front to its south. Satellite imagery is showing its front extending from the central Aleutians northeastward into the Kuskokwim Delta. Moisture associated with the front is spilling over the ridge and causing widespread cloud cover in Southcentral Alaska. Low level stratus and areas of fog are blanketing both sides of the Aleutians with the only breaks in cloud cover for the eastern Aleutians and AKPen occurring due to the downsloping of winds. Radar is showing several areas of light rain from the Mat-Su Valleys to the Chugach Mountains this morning. Much of this is not reaching the valley floors, with the exception of some very light rain reported in Anchorage and Talkeetna this morning. Out west, strong southerly surface winds continue to impact the west coast ahead of the front. These effects should wind down as the front moves farther east.
A few differences are present in the models for the short term, but overall agreement should persist through the end of the week. Model spread grows over the weekend with discrepancies concerning the placement of the trough located in the Bering and another subtle disturbance over the Aleutians. However, ridging over Southcentral will prevail into the end of the week, and will help to limit any meaningful movement of the front over the Bering. Over Southcentral, a transition pattern maintains with it being stuck between high and low pressure. This can cause uncertainty due to the models having difficulty picking up subtle weather features in this environment. Otherwise, forecast confidence remains high with the big picture.
MVFR conditions are expected to continue through at least this morning as low level moisture and clouds persist. An area of very light rain has also moved over the terminal this morning, but is expected to taper off over by mid morning. A ridge building in today should help scour out the low level moisture and break up the lower ceilings (with clouds remaining below 5,000 ft) by late afternoon afternoon or early evening. The 12z upper air sounding is showing some drying in the mid-levels (700 mb or ~10,000 ft AGL) Confidence remains low regarding the timing of this and the extent of clearing, though, as the overall wind flow remains weak and westerly. This could as the very least keep low clouds banked up along the hillside, just outside the terminal. MVFR conditions are expected again overnight as another system approaches from the west.
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2).
The main forecast challenge in the short term will be the extent of clouds cover across interior Southcentral, as there remains plenty of residual moisture lingering from the trough that moved through yesterday. Satellite imagery this morning shows a solid shield of low clouds encompassing much of the region. The exception to this is along Cook Inlet, where is more influence from a building ridge situated over Kodiak Island. It does appear that the ridge will continue to build northward, and, thus, should help lift and break apart clouds, especially from the western Kenai Peninsula north to the Mat-Su valleys. A weak westerly flow, however, could keep clouds banked up along the Talkeetna and Chugach Ranges.
Clouds will also begin to diminish across the Copper River Basin this evening, providing for clearer skies and milder temperatures for Friday. For eastern Southcentral, any clearing trend through the evening and overnight hours will be brief as clouds are expected to increase once again by Friday afternoon in advance of another advancing upper-level trough.
Fog is another concern. This morning's nighttime microphysics satellite imagery shows areas of low stratus and fog expanding over parts of the western and northern Gulf. With the ridge deepening, it is likely that this trend will continue, with low clouds and patchy fog spreading across the Barren Islands, southern Cook Inlet, and perhaps over eastern Kodiak Island through the end of the week.
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 2: Today through Saturday) .
The status quo over the next several days will continue with the same theme of wet, cloudy and cool conditions as deep southwesterly flow continues to stream across the entire Southwest on the upstream side of a ridge that remains parked over the Gulf and eastern mainland. A series of shortwave impulses tracking allowing the remains of a front sprawled between the Kuskokwim Delta and the Eastern Aleutians will continue to focus bands of steady stratiform rain inland, especially over the Y-K Delta through Friday morning. A much more potent shortwave and attendant surface low/front will come ashore by Friday evening, bringing another round of moderate rain and increased southwesterly winds across most of the Southwest. Fortunately, the onshore winds will remain well below levels observed during the past 24 hours and are no longer expected to result in any continued water buildup along the Kuskokwim Delta Coast. Therefore, the High Surf Advisory has been discontinued with this forecast package.
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 2: Today through Saturday) .
A weakening front will remain nearly stationary over the eastern Bering/Aleutians and continue to focus areas of rain along the eastern Aleutian Chain and AKPen, especially where moist southerly flow encounters steeper terrain and concentrates upslope lift. Showers will likewise linger near the Pribilofs along with areas of low marine stratus and fog for the next couple days. A new system will track across the northern and western Bering from late Friday to Saturday, bringing with it another round of moderate rain and southerly small craft winds to the far northern and western regions of the AOR. This low's trailing front will merge with the old front still meandering farther east, spreading another round of small craft strength winds and rain into the eastern Bering by Saturday morning. Generally, expect the early wet, misty and blustery fall pattern to continue into at least the first half of the weekend.
MARINE (Days 3 through 5: Saturday through Monday).
A series of lows will transit the Aleutians and Bering Sea. At the moment it looks like winds will top out at small craft advisory level. However, there could be some small areas of gale force winds, especially on Sunday as a low deepens over the south-central Bering Sea.
LONG TERM FORECAST (Days 4 through 7: Sunday through Wednesday).
A longwave trough digs into the Western Bering starting Sunday. A moderate low develops in the left exit region of the jet, where it crosses the Western Aleutians into the Bering through Monday. As the low becomes stacked and retrogrades towards Kamchatka on Tuesday, its front stalls across the Central Bering.
There is fairly good model agreement between the GFS, ECMWF, and Canadian on the development and general position of both the longwave trough and Bering low. Models remain consistent until Tuesday, when they begin to diverge more strongly on the strength and position of the low.
While rain and stronger winds are expected with the passage of the front in the Bering, conditions are expected to stay mostly dry in Southcentral Alaska due to lingering high pressure in the Gulf. Forecast confidence drops in the Tue/Wed time period, as models struggle with how long the upper ridge will hold on. In all likelihood, the ridge will at least weaken, leading to an increase in clouds and chance of rain as we head through the week.
AFC WATCHES/WARNINGS/ADVISORIES. PUBLIC . NONE. MARINE . NONE. FIRE WEATHER . NONE.
SYNOPSIS AND MODEL DISCUSSION . TM/NS SOUTHCENTRAL ALASKA . TM SOUTHWEST ALASKA/BERING SEA/ALEUTIANS . AS MARINE/LONG TERM . KZ/KC
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|Shemya, Eareckson AFB, AK||49 mi||57 min||Var 3||10.00 mi||A Few Clouds||60°F||49°F||66%||1013.4 hPa|
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Wind History from ASY (wind in knots)
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