Area Forecast Discussion

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: This afternoon through Monday afternoon)...

Key Messages:

* Stormy weather continues through late tonight, then a transition towards widespread showery conditions through the weekend. By Monday, another front pushes into Southcentral.

* High Wind Warning remains in effect for Cordova through 1 AM tonight. Winds will continue decreasing for all but Prince William Sound through the remainder of this evening.

* Winter Weather Advisories remain in effect for Thompson Pass through 10 PM, and for Northern Susitna Valley (including Broad Pass) through 1 AM.

* Convective snow showers this weekend could lead to periods of reduced visibilities in heavy snow, especially for higher elevation roadways during the colder early morning or evening hours. Our primary area of concern is the Seward Highway from Primrose north to Turnagain Pass, though confidence is low with the timing of showers.

Discussion:

As mentioned in this morning's discussion, this frontal system (associated with the remnants of former Typhoon Champi) has over-performed expectations from yesterday. Here are some of the peak gusts that were observed over the past 24 hours: 79 mph in Potter Valley (Anchorage), 73 mph in Glen Alps, 70 mph in Eagle River, 69 mph in Palmer, 69 mph at Ted Stevens Airport, 67 mph in Rabbit Creek (Anchorage), and 66 mph in Abbott Loop (Anchorage). Precipitation amounts were about what was forecast, with 24 hour rain totals of 3.30 inches in Seward, 2.62 inches at Cordova Airport, and some measurements of as high as 4 to 5 inches at higher elevation sites around Prince William Sound. Satellite and radar imagery show the front gradually exiting eastward this afternoon, with conditions forecast to improve from west to east through late tonight. The High Wind Warning for Cordova was extended to 1 AM tonight as the barrier jet is forecast to stall for longer over the region, while the Winter Weather Advisory for Northern Susitna Valley was extended to account for additional moderate snow as weaker shortwaves move in behind the front.

Looking ahead to this weekend, the main story will be widespread convective showers as an upper level longwave trough and its associated low move over Southcentral. The colder air and bountiful vorticity associated with this feature will drive robust showers, with the potential for periods of heavy snow (especially in training showers) along higher elevation roadways around Prince William Sound. Given all the various shortwaves rotating around this upper low, it'll be difficult to hone in on the exact timing and placement of showers. Still, use caution and be aware of the potential for sudden visibility reductions in heavier showers if you'll be traveling along the Seward Highway this weekend. The other thing to watch for with this showery weather pattern will be the potential for lightning in especially robust convection.

-KC

.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days 1 through 3)...

Key Messages:

* Wind Advisory in effect for Unalaska/Nikolski through 10 AM AKDT Saturday morning

* Cold air from the north moves in behind the strong Bering low as it moves into the Gulf of Alaska for this weekend.

* Pattern remains active across the Bering and Aleutians this weekend and into the new work week. Low tracks look to be a little more southerly than this past week.

The strong Bering low is currently located in the Western Bering Sea. This low will continue south and east and over the Alaska Peninsula (AKPEN) by this evening. Rain will continue across the Aleutians, AKPEN, and Southwest and become more showery in nature for this weekend with cold air moving in. Overall, the forecast remains largely on track. The coastal flood advisory that was out until Saturday morning was cancelled. There will be higher water levels at the Saturday morning tide, but winds have diminished significantly and the next tide will be lower than the Friday morning tide.

For Saturday, a push of cold air moves into Southwest and the AKPEN from the north and west. Temperatures will only make it to the 30s and low 40s across the area, with the warmer temperatures along the AKPEN and Bristol Bay coast. Rain showers will also change over to rain/snow mix across the Kuskokwim Delta and Coast Saturday and Saturday night.

Flow switches back to the south and southeast for Sunday ahead of the next storm system moving across the Bering. Initially, on Saturday, a North Pacific low tracks south of Kamchatka as its gale-force front moves across Shemya and the western Bering Saturday evening. The gale-force front spreads gusty southeasterly winds to Adak/Atka Saturday night through Sunday morning before making its way to the Pribilof Islands, Unalaska/Nikolski, and the southern AKPEN by Sunday afternoon and evening. Light to moderate rain will also accompany this front on its eastern journey across the Bering this weekend. Behind the front, strong winds are expected to wrap cooler air into the low. Gale force winds are expected at this time to switch from southeasterly with southwesterly. Stronger gusts above 55 kt will be possible. There is a potential for storm force sustained winds or stronger Sunday (30 to 40 percent).

The front and its gusty easterly to east-southeasterly winds eventually make it to the coastal Southwest by Monday morning, along with rain. Right now, this set up does not look conducive for a coastal flooding threat along the Kuskokwim Delta Coast, due in part to the more offshore/easterly component to the wind. Continue to monitor the forecast for updates as the active weather pattern continues to unfold.

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

The weather pattern will remain active through the long term as a broad trough with numerous shortwaves remains over the Bering Sea and far northern Pacific. Due to the abundance of shortwaves and interactions along a broad baroclinic zone, models are struggling to reach a consensus on the track of each respective storm/shortwave as they move from the Chain into the Gulf. As such, forecast confidence for the timing of strong winds and/or rain remains low. Given then abundance of warm air from the current system, and another warm and wet system on Tuesday, rain remains the main precipitation type for most populated areas throughout the southern Mainland and Aleutians. Modeled snow levels are forecast to be between 1500 and 2500 ft, but due to the large spread in storm track there is a large variation in which areas may be cold enough to get snow. Overall, the forecast remains noisy, but warmer than normal temperatures and areas of rain will continue. In comparison to the current weather, impacts such as wind and rain are more likely to be over the Aleutians, Kodiak, the Alaska Peninsula and the Kenai Peninsula.

AVIATION

PANC...A strong southeasterly Turnagain Arm wind will persist over the terminal through early Saturday morning with gusts of 25 to 40 mph, through around midnight. While wind are expected to continue to slowly weaken through the overnight hours into Saturday morning, occasional gusts to around 25 kt are likely to remain over the terminal through Saturday morning.

Rain showers with MVFR ceilings are possible through this evening with MVFR visibilities in heavier showers. The precipitation will likely taper off by around midnight. However, another round of scattered showers is likely by early Saturday morning. While VFR conditions are expected to prevail during this time, any heavier showers could result in brief periods of MVFR ceilings and visibilities.