Area Forecast Discussion

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Today through Tuesday night)...

It is a rather complex weather set-up today with a pattern that look more reminiscent of Fall than Spring over Southern Alaska. A strong low in the Bering Sea is anchoring a series of upper level shortwaves that will move through Southcentral the next few days. This will keep persistent moist, west-to-southwest flow aloft over the area with periods of precipitation (mostly rain at lower elevations) as the shortwaves move through. In addition, strong southeasterly winds will develop today through Turnagain Arm and bend into the Anchorage Bowl so a wet and blustery day is expected. The south to southeast winds are also expected through the other typical gaps such as the Knik River Valley and along the Copper River.

Snow is expected for areas close to the Alaska Range where the higher elevations and upslope will keep the precipitation mostly snow. There is a winter weather advisory out for portions of both the Parks highway (from Chulitna north) and Richardson Highway (from Paxson north) through Monday afternoon for expected snow accumulation of anywhere from 4 to 10 inches. However, the big snow winner may very well be Hatcher Pass where one to two feet of snow is possible in this classic pattern for heavy snow in Hatcher Pass.

There is a high surf advisory in Kachemak Bay as the southwesterly winds increase this afternoon and bring in higher waves that could impact the Homer Spit. This high surf advisory runs this afternoon into Monday morning's high tide cycle.

For Monday and Tuesday, expect cloudy conditions with showers mainly along the mountains as a little more zonal flow sets in, and various weak upper level shortwaves transit the area. A weak surface low may develop near Prince William Sound Monday night, which will lead to enhanced precipitation for the Valdez and Cordova areas. However, this system will be weak and quick- moving, so impacts will be limited.

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

A strong 970 mb low continues to take up real estate in the western Bering Sea this morning as it continues to weaken through today. Its front also continues pushing inland of mainland Southwest Alaska this morning. Steady snow this morning across the Kuskokwim Valley and along the Western Alaska Range will become more showery in nature as cold air moves in from the southwest off of the Bering Sea. Meanwhile, locations such as Bethel and Kipnuk changed over to rain late last night. Precipitation this afternoon could mix with or change back over to snow as the cold air aloft previously mentioned moves back in from the southwest. Off and on rain/snow shower mix will continue across mainland Southwest through Monday. Most accumulation will occur along the Western Alaska Range due to westerly upslope flow enhancement with little additional accumulation elsewhere.

Another strong system will begin taking shape in the North Pacific late tonight and Monday. Upper level energy moving from west to east south of the Kamchatka Peninsula will interact with a cold airmass moving south out of Kamchatka on Monday and cause a developing surface low to intensify and deepen further. There is reasonable agreement between guidance that the developing low will slow its eastward progression down and potentially even stall between Amchitka and Adak Monday night into Tuesday as a strong ridge develops to the east. While the system slows down or stalls Monday night into Tuesday, it will wrap in more cold air from Russia and become a deep system by Tuesday night. The potential is there for another sub-970mb low in the south-central Bering Sea by Tuesday night.

This forecast package has the low mentioned above strengthening to storm-force by Tuesday afternoon with a corridor of 50 kt sustained northeast winds along the storm's northern periphery in the central Bering. Regardless of winds, this system looks to be quite wet as it will be accompanied by a tropical moisture tap. There is some uncertainty with where the initial best moisture surge for Monday morning into Monday afternoon. Current guidance has the best moisture and heaviest rain axis just to the west of Adak; this could change in future forecast packages, so stay tuned.

For Tuesday, a secondary and more widespread push of moisture lifts up from the North Pacific and impacts Adak/Atka, Nikolski/Unalaska/Akutan, and the Pribilof Islands with moderate to heavy rain. The moderate to heavy precipitation makes it to mainland Southwest Alaska by late Tuesday afternoon to early Tuesday evening. Precipitation may start as a period of snow along the Kuskokwim Delta/Kuskokwim Delta Coast Tuesday afternoon before changing to rain/snow mix and eventually rain through Tuesday night. The tropical moisture tap shifts eastward from Unalaska/Nikolski/Akutan to over the Alaska Peninsula Tuesday night into Wednesday morning. Moderate to heavy rain at times is looking likely from False Pass eastward to Chignik Tuesday night into Wednesday morning. However, this moisture axis does not look to hang around long as it continues eastward to Kodiak Island by late Wednesday morning. Stay tuned for further forecast updates regarding the development of the next unseasonably strong Bering low for next week.

.LONG TERM FORECAST (Days 4 through 7: Wednesday through Saturday)...

A transition toward cooler and more unsettled conditions is expected across much of Alaska through the upcoming week. A pattern dropping south from the north will usher in colder air along with periodic snow showers, particularly across the interior and the Alaska Range.

By early to mid next week, attention shifts to Southcentral and Southeast Alaska as a developing system draws in a deeper surge of moisture. This will likely bring several days of mixed precipitation, including rain at lower elevations and snow at higher elevations. The heaviest snowfall appears most likely across the Alaska Range and through higher elevation passes, accompanied by increasing winds.

A strong North Pacific low continues to be monitored. While current guidance keeps this system south of the state, any northward shift toward the Gulf of Alaska could introduce another round of impactful weather late next week.

LM

AVIATION

PANC...A frontal system moving into Southcentral will lead to breezy and rainy conditions for much of the TAF period today into tonight. Generally MVFR ceilings and visibility are expected as precipitation begins at the terminal early this morning. There could still be a rain-snow mix at the very onset in the early morning, but temperatures will otherwise be warm enough for rain for the rest of the day. Gusty southeast winds will continue to pick up ahead of the front through this afternoon, with peak gusts around 30 kt with potential for 35 kt anticipated during the early to mid afternoon.

Conditions will likely improve to VFR as the front passes through this evening around 03 to 06Z as rain ends and ceilings rise. Gusty winds will turn more out of the south at about the same time, with 20 to 30 kt gusts expected to persist overnight tonight into early Monday morning.