Marine Weather and Tides
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 7:34AM||Sunset 6:46PM||Monday March 8, 2021 6:32 AM AKST (15:32 UTC)||Moonrise 5:48AM||Moonset 11:46AM||Illumination 25%|
7 Day Forecast for Marine Location Near St. George, AKHourly EDIT Help
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FXAK68 PAFC 081432 AFDAFC
Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 532 AM AKST Mon Mar 8 2021
ANALYSIS AND UPPER LEVELS.
In the upper levels, a positively tilted trough with a broad low near the Kamchatka Peninsula extends its axis from the western Bering and south across the western Aleutians. The associated baroclinic front is moving east towards the AKPEN and into Southwest AK. WV/IR imagery shows an impressive deep fetch of warm, moist air lifting north from the Pacific. Radar indicates precipitation ahead of the front moving into Norton Sound and the Kuskowim Bay Coast. Ahead of this front, a high amplitude ridge is setting up nicely over the Southern Mainland with its axis extending from the Arctic Ocean to the North Pacific. Downstream of the ridge, a vertically stacked low continues rotating over the eastern Gulf, with latest ASCAT pass (scatterometer wind) capturing small craft winds south of Prince William Sound to the central and eastern Gulf. The nighttime microphysics shows low stratus/fog north of the Alaska Range and a some high clouds passing overhead. Otherwise, conditions are relatively quite across Southcentral. One interesting feature is some suspended glacial silt captured on satellite overnight drifting southward from the Copper River Delta thanks to gusty winds from a healthy north-south pressure gradient persisting since yesterday.
Model guidance are in relatively decent agreement with the synoptic features and are still on track with the active weather pattern for the Bering/Aleutians and Southern Mainland for this week. However, latest model solutions are still struggling to resolve the development, strength, and movement, of a triple point low forming along a frontal boundary near Kodiak Island, and the resultant weather over the Southcentral coast. The other minor discrepancies, although not too impactful, are the multiple meso- lows forming over the Bering on Tuesday in the wake of the aforementioned Kamchatka low.
AVIATION. PANC . VFR conditions with patchy fog this morning. A chance of intermittent MVFR vis possible through late morning. Light northerly winds will continue. Clouds will increase overnight but remain VFR.
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 to 3: Today through Wednesday Night) .
Conditions will remain clear and dry across Southcentral through the overnight hours and into early morning Tuesday. Outflow winds continue this morning, but are on the downward trend from Seward to Whittier. Winds are still gusty for Valdez and the Copper River Delta, but are expected to diminish through the day as the pressure gradient relaxes and the winds aloft shift more southerly as the upper-level ridge moves over the region.
As the ridge shifts east, the upper-level trough upstream over the Bering will also shift east. At the surface, a frontal system that is currently draped over the eastern Bering will move over Southwest Alaska. By late Monday, the front will begin to weaken as it makes its way toward the Alaska Range. The front, however, is tapping into a deep fetch of moisture from the north Pacific. This will allow precipitation to overspread Kodiak Island by late Monday evening, pushing north over the southern Kenai Peninsula, Cook Inlet, and the Susitna Valley by early Tuesday morning. For Kodiak, the precipitation should be mainly in the form of rain. For Homer and Seward, precipitation will likely start as snow before changing to rain. Farther inland, enough colder air should remain in place for the precipitation to stay all snow. By Tuesday afternoon, some light snow should make it to the Anchorage Bowl; however, it does appear that a cross-barrier flow will develop as a newly formed triple point low tracks along the eastern Kenai Peninsula. This flow would allow for some downsloping and limit precipitation chances for places like Anchorage and Palmer Tuesday afternoon through Wednesday morning before the low lifts into Prince William Sound as the upper-level flow shifts more northerly.
Right now, it looks like areas north and west of Willow in the Susitna Valley could see up to a foot of snow through late Wednesday. Hatcher Pass will could also see up to 18 inches of snow. Upwards of a foot of snow could also fall within Portage Valley and Turnagain Pass. The higher elevations around Prince William Sound and the eastern Kenai Peninsula, though, look to see the largest snow accumulations with this system.
The current forecast comes with a caveat, though, and it is this: There are still quite a bit of detail to be ironed out with this system, as models have yet to reach any consensus as to the strength and track of the aforementioned low. For example, the 6z GFS differs greatly from its previous run and has a much deeper low entering the northern Gulf. While there would still be a period of downsloping with this system, the winds aloft shift northerly sooner than the NAM and GEM. Thus, Anchorage and Palmer could see a second round of snow develop sooner than advertised by the NAM and GEM. In addition, while all models have the low eventually entering Prince William Sound, the stronger GFS solution would likely keep the bulk of the snow from Whittier to Cordova, with the extended northerly flow also bringing more snow into Turnagain Pass. The NAM continues to advertise a weaker low drifting slightly more into western Prince William Sound by late Wednesday into Thursday. This solution would favor the development of a snow band over Anchorage and allow for higher snow totals than the GFS is suggesting. The NAM is also indicating the potential for higher snow amounts along the Anchorage Hillside as the flow turns northwesterly with cold air advection and moisture lingering over the area. Nonetheless, given a blend of the two models mentioned, it looks right now like 2 to 4 inches of snow is possible for the Mat Valley, the potential for up to 6 inches of snow for Anchorage with higher amounts for the Hillside, and 6 to 8 inches of snow for the western Kenai Peninsula.
This system begins to weaken by THursday, but may stall out over the Prince William Sound with snow showers continuing across much of Southcentral.
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2: Today through Tuesday night) .
The long-awaited front from the Bering brought rain/snow mix since last night into early this morning along the Kuskokwim Delta Coast, and blowing snow conditions there as well. The front maintains a west to east track, which will bring increased snowfall over the region with heavier amounts along the Kuskokwim Delta Coast and Bristol Bay today. Warm temperatures combined with deep southerly winds mixing ahead of the front will yield to mostly rain over portions of AKPEN this morning, then transitioning to snow later in the afternoon. Meanwhile, snow remains in the forecast for Bristol Bay through the lower Kuskokwim Valleys through tonight. A few isolated surface troughs from the Bering Sea combined with cold air advection reaching -16 to -22 degrees Celsius at 850 mb could bring increased sky coverage and light snow along the Y-K Delta on Tuesday and Tuesday night. For now, will continue monitoring this situation closely before making new updates for POP and QPF.
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2: Today through Tuesday night) .
Water vapor shows a good amount of moisture across the Bering and Aleutians except a narrow pocket of subsident dry air trailing eastward toward Dutch Harbor this morning. A few surface troughs over the Bering combined with cold air advection will produce scattered to numerous light snow through the forecast period. An upper-level trough from western Aleutians could potentially increase the chance of expanding the freezing spray coverage on Tuesday and Tuesday night. In the meantime, freezing spray will be mainly focused over the west and north of Pribilof Islands today through Tuesday.
MARINE (Days 3 through 5: Wednesday through Friday).
Bering: A series of troughs with locally up to small craft winds will cross the Bering from west to east on Wed, with small craft or lower westerlies expected away from the troughs. Westerly winds could locally be as high as gales on the south side of each trough, but confidence for the track and timing of each wave is low at this time. Seas on Wed up to 10 feet. Another front will approach the western Bering by Thu, with southerly gales spreading into the western Bering Thu morning into early Fri. Seas building to up to 20 ft across the western Bering by Thu and Fri. A North Pacific low may approach the southern Bering and Central Aleutians on Fri, but track and timing for this next low remains uncertain. Expect potential for winds to increase to high gales to possibly low storms over parts of the central to western Bering for Fri, however exact timing and track of enhanced winds will depend on the low track.
Gulf of Alaska: A low will move into the central Gulf and then into or just south of the Prince William Sound on Wednesday. Widespread westerly small craft to gale force winds will spread across the central and southern Gulf south of the low center through Thu. Seas building from 10 to 15 feet from Wed to Thu. The low center will dive south towards the southern Gulf on Fri with small craft to gale force winds continuing and becoming northwesterly over the western gulf through Fri. Seas building to 20 feet in the western Gulf on Fri.
.LONG TERM FORECAST (Days 4 through 7: Thursday through Sunday) .
The large scale pattern from long term guidance remains in decent agreement for the Bering, Gulf and mainland AK, but some discrepancies do emerge across mainly the Bering by Saturday.
A longwave trough is likely to become the dominant influence over the mainland by Thursday and Friday this week, and the preceding warm spell over Southcentral early in the week will likely be cut short as a cold, Arctic air mass spills in from the northwest. This pattern will favor much colder and drier than average conditions over mainland AK from Wednesday to Friday, with offshore flow and the potential for stronger outflow winds for the typical spots near the North Gulf Coast from Thursday to Saturday. Longwave ridging will develop into the eastern Bering, while low pressure and troughing will persist in the northern and western Bering. Models diverge with the handling of a stronger shortwave rounding the base of this trough, with varying degrees of northeast progression of the wave depicted by operational models on Friday and Saturday. Despite the uncertainty, this will generally favor active and stormy conditions over the western Bering with multiple rounds of rain/snow and stronger southerly winds.
By Sunday, model agreement continues to lessen with global models trying to progress the western trough towards the Southwest/AKPEN while the longwave ridge moves farther east into the mainland with the Arctic air beginning to retreat up into the Yukon. This could lead to a warming trend beginning over mainland AK with the potential for another frontal system to move up the AKPEN into southcentral. However, the progress of this next system and related warming will greatly depend on how quickly the upstream ridging and surface high pressure associated with the cold air mass erode or advect east. This is a dynamic models can be overly optimistic about, especially looking this far out in time, so the cold and dry pattern for Southcentral could still linger on for longer into next week.
AFC WATCHES/WARNINGS/ADVISORIES. PUBLIC . Winter Weather Advisory 155,161. MARINE . Gale Warnings 155 160 165 180 181. Heavy Freezing Spray Warning 185 411. FIRE WEATHER . NONE.
SYNOPSIS AND MODEL DISCUSSION . MF/TM SOUTHCENTRAL ALASKA . TM SOUTHWEST ALASKA/BERING SEA/ALEUTIANS . CB MARINE/LONG TERM . AS
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