Marine Weather and Tides
12/16/2019 NOAA is having trouble with requests that include wind gusts. I am posting graphs without wind gusts until it gets fixed.
10/9/2019 Updated the Marine Zones.
9/4/2019 Fixed the weather maps due to NOAA moving them.
7/25/2019 New feature in the Airports section gives a link to 5 minute updates for data reports.
|Sunrise 6:46AM||Sunset 6:16PM||Wednesday January 22, 2020 4:14 AM ChST (18:14 UTC)||Moonrise 5:09AM||Moonset 1:03PM||Illumination 12%|
7 Day Forecast for Marine Location Near Attu Station, AKHourly EDIT Help
Area Discussion for -  (on/off)  Help NOTE: mouseover dotted underlined text for definition
FXAK68 PAFC 211629 CCA AFDAFC
Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 357 AM AKST Tue Jan 21 2020
ANALYSIS AND UPPER LEVELS.
A mainly zonal flow aloft extends from the Bering into southwest Alaska this morning, turning more southwesterly for Southcentral. Closer to the surface, infra-red satellite imagery shows a low moving ashore across eastern Prince William Sound, with a pair of meso (small scale) lows near the southern tip of Kodiak Island, and also near Saint Matthew Island. Showery type precipitation is seen in various data sets with all of these features, with the nighttime microphysics imagery showing low stratus and/or fog hanging just west of Anchorage in the Cook Inlet, and also across portions of the Copper Basin and Bristol Bay regions.
The models remain in good agreement through Friday evening, before some differences begin to show up. Even then, they remain in fairly decent agreement aloft with the overall theme of the synoptic features. The main differences lie with regard to where the center of a very deep mid-level low sets up. This occurs as high amplitude negatively tilted ridging develops from the tip of the Alaska Peninsula to the Pribilof islands. A disturbance riding the top of the ridge dives into south central or southwest Alaska, allowing for a 490-492 dm low to develop, as very cold air dives south.
Initially, all models agree on this developing just south of Seward. As the pattern amplifies due to shortwave energy diving into the base of the trough on Monday, the low repositions to either Shelikof Straight (European), central Bristol Bay (GFS), or north of King Salmon (Canadian Global). This dictates who gets the coldest of the air as 850 mb temps are projected to be around -26 deg. C. These are similar values, with a similar setup, to what was seen across southwest Alaska around New Year's Eve, when wind chills pushed or exceeded -40 deg. F. This is also a pattern where several rounds of cyclogenesis (low pressure development) would occur in the Gulf of Alaska, probably just south of Prince William Sound. Should this occur, snowfall potential would increase for Southcentral.
PANC . Stratus clouds seen on satellite imagery, likely around 1500 feet, continues to lurk just west of the airfield. Model guidance has been split on whether this will make it into the terminal. For now, plan to cover this with a tempo group and see how things unfold. Light winds will prevail through the period.
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2). An upper level short wave trough will slide across Southcentral from southwest to northeast today. Some showers and considerable clouds will linger over the area. Tonight through Wednesday night a long wave trough will slowly dig into southern Alaska. This will bring increasing offshore winds and usher in a drier air mass. Some showers could still occur in the Copper River Basin and along the coast from Prince William Sound eastward. Temperatures should also start to cool on Wednesday and Wednesday night as the long wave trough slowly slides east into Southcentral.
SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3).
Snow showers continue to linger across the Kuskokwim Delta area this morning. While showers will eventually taper off, lingering moisture in the area will keep low level stratus and patchy fog around through Tuesday morning. By midweek, a broad upper level trough arrives over Southwest. This will initiate a plunge in temperatures across Southwest for the rest of the week as the trough deepens and pulls down plenty of cold Arctic air from the northwest. With a building ridge in place over the eastern Bering Wednesday night into early Thursday, northerly winds are expected to increase (especially along the coast and usual gaps and passes along the southern Alaska Peninsula) through Thursday night. This translates into a generally clear, but cold end to the work week for southwest Alaska.
SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3).
An unstable airmass over the Bering continues to allow for showery conditions this morning. Scattered snow showers are expected to continue over most of the northern Bering through early Wednesday. The next storm arrives over the western Aleutians Wednesday morning, bringing southeasterly gales. Snow will start initially with a quick change to rain as warmer air moves in. As the low lifts northward, the front spreads across the Bering through Thursday. Expect high end gale force winds with this next system. Storm force gusts are possible and will likely be concentrated over the western Bering. This low will eventually move northward as a blocking ridge remains in place over the eastern Bering through the end of the week.
MARINE (Days 3 through 5: Thursday through Saturday).
Gulf of Alaska:
A low over the eastern Gulf Thursday will turn westward and move to near Middleton Island by Friday morning. The low will stall out and remain nearly stationary through Saturday morning, then dissipate or get absorbed into a new low moving into the eastern Gulf Saturday evening. This will keep gales ongoing continuously across the Barren Islands and through bays and passes southwest of Kodiak Island through Friday. The gales may weaken to small craft winds on Saturday, depending on where the low is at that point and where the next low moves into the eastern Gulf. Significant forecast uncertainty persists on Saturday.
Bering Sea and Aleutians:
A strong and nearly stationary low centered south of the western Aleutians will keep widespread gales with occasional embedded storms ongoing across the central and western Bering through Friday. Seas of 20 to 35 ft are expected over a large area of the central and western Bering and Aleutians through Friday night. By Saturday the low will move to near Kamchatka, which will result in gradually diminishing winds over the western Bering on Saturday. Strengthening high pressure over the eastern Bering will cause gale force offshore winds to develop Friday night through Saturday from the Southwest Alaska coast. The gales will extend south through the bays and passes of the Alaska Peninsula and eastern Aleutians by Saturday evening.
LONG TERM FORECAST (Days 3 through 7: Thursday through Monday).
The stagnant weather pattern intensifying on Thursday will persist through the weekend, and potentially last even longer. A strong and nearly stationary low centered south of the western Aleutians will keep gale force winds and rain ongoing across the central and western Aleutians through at least Friday night. On Saturday, the low moves off to the Kamchatka Peninsula, but another North Pacific low may move in to the same area to replace the old one into Monday. There is significant model uncertainty about where the new low tracks, however.
Meanwhile, across the eastern Bering and mainland Alaska, high pressure will strengthen with time through at least Saturday. After that there is some model disagreement as to how quickly the high pressure moves westward into the Bering. The GFS is much faster moving the high westward than the foreign models. Either way, the high will support increasingly cold air flooding southward on strong winds across Southwest Alaska, the eastern Bering, and the gaps and passes of Southcentral from Saturday through Monday. This will be a favorable pattern for another round of wind chill hazards in these same areas.
Across the Gulf, the weather will remain unsettled as a low over the eastern Gulf on Thursday moves to near Middleton Island on Friday morning, then parks itself there and spins moisture, very likely in the form of snow given the cold air around, into coastal areas. Since the low will be relatively weak and hardly moving, any snow that falls is not expected to become heavy, but it looks to persist in some areas through Saturday. There is considerable uncertainty on who gets what amount of snow and when, so stay tuned for future forecast updates. By Monday, with the high gradually drifting west over the Bering, the storm track may begin to shift westward along with it into the Gulf and Southcentral, which, if it occurs, would bring back more seasonably cold temperatures, and much greater threats for snow into Southcentral.
AFC WATCHES/WARNINGS/ADVISORIES. PUBLIC . NONE. MARINE . Heavy Freezing Spray Warning 160 185 Gale Warning 176 177 178 FIRE WEATHER . NONE.
SYNOPSIS AND MODEL DISCUSSION . PD SOUTHCENTRAL ALASKA . BL SOUTHWEST ALASKA/BERING SEA/ALEUTIANS . KO MARINE/LONG TERM . JW
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|Shemya, Eareckson AFB, AK||49 mi||19 min||SSW 14||7.00 mi||Partly Cloudy||31°F||22°F||72%||1006.8 hPa|
Link to 5 minute data for PASY
Wind History from ASY (wind in knots)
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