Area Forecast Discussion

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

A broad, upper-level trough extends along the Al-Can border south over the eastern Gulf of Alaska. The shortwave embedded within this trough responsible for the showers and thunderstorms across Southcentral yesterday is still slowly meandering east toward the Copper River Basin this morning. It is this feature, combining with a vorticity lobe advecting westward from the Yukon and elongating over the region, that will be the catalyst, providing the instability and lift, for another round of showers and thunderstorms this afternoon and evening.

The best chance for showers and widely scattered thunderstorms will be near this feature, over the Copper River Basin. Given the weak flow aloft, the bulk of the activity will develop along the foothills surrounding the periphery of the basin. Any showers and thunderstorms that do develop will likely be slow moving or remain nearly stationary, resulting in wetting rains wherever heaver showers develop.

Farther west, linger low-level moisture and a west-northwesterly flow aloft may also result in a few scattered and isolated thunderstorms around the westward facing foothills of the Talkeetnas and Kenai Mountains.

This feature will be slow to exit, finally lifting northward over the Alaska Range by Friday evening. Thus, showers and isolated thunderstorms remain in the forecast for Friday afternoon and evening. Given the increasing southerly flow, however, the focus for showers and thunderstorm for Friday will shift slightly to the northern half of the Copper River Basin.

By late Friday, focus will also shift to Kodiak Island and the southern Gulf where a strong gale-force front will move over the area. 1 to 2" of rain, along with east winds approaching 40 mph, are likely for the eastern half of Kodiak Island through Saturday. The front then moves quickly to the Southcentral coast by Saturday morning with steady rain and gusty winds for Prince William Sound and the eastern Kenai Peninsula. Some rain will also move across interior Southcentral Saturday morning as the upper- level wave associated with the surface front moves inland. Any rain, however, is expected to be light. As this front begins to break down late Saturday, a second upper-level wave moving from the North Pacific into the southeastern Gulf will spin up a second strong surface low and front. This low looks to move toward Kennedy Entrance by Sunday morning with its front more rain and wind to the Southcentral coast for Sunday.

- TM

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

A pattern of persistence over Southwest Alaska and the Bering will make for a repetitive weather regime through the remainder of the week across the region. Temperatures in the Southwest interior continue to be warmer than previously expected, and with clear skies expected again today and Friday, the warmer trend will persist. However, along the coast and over the vast majority of the Bering Sea, ridging continues to promote a very large swath of low stratus clouds and fog over the area. The lowest ceilings and fog have been most prominent in the overnight and early morning hours, lifting to a low stratus in the afternoons. The large bank of fog is expected to steadily recede westward into Friday afternoon as a low pressure system approaches the Southern Alaska Peninsula, promoting offshore easterly winds.

Ample surface heating over the Southwest Alaska interior will continue to promote afternoon convective activity, with isolated wet thunderstorms possible this, and Friday afternoon. Similarly isolated thunderstorms are possible Saturday, however will likely be consolidated to northern extent of the Lower Kuskokwim Valley. Drier and hotter conditions over the interior of Southwest will continue to be a forecast focus today and tomorrow. This is fringing on ideal fire weather conditions, however the strength and scale of winds Friday and Saturday remain a borderline case.

A new low pressure system is poised to approach the southern Alaska Peninsula by Friday afternoon. This system's rainfall and movement in the overall air column may bring a reprieve in the fog over the area, but replace it with continued low stratus and light rain. Easterly gale-force winds are expected to establish over the southern side of the Peninsula, including for communities such as Sand Point, persisting into Saturday morning.

-CL

LONG TERM FORECAST (Days 4 through 7: Sunday through Wednesday)

Showers are expected for Southwest Alaska and the eastern Aleutians through Tuesday from a Gulf low. An upper level ridge over the eastern Gulf will remain nearly stationary before moving eastward by Monday. These two systems are important to note as it blocks an originating Pacific Low from going into the eastern Gulf. The combination of the anticyclonic flow aloft from the ridge and cyclonic flow from the low pressure system will enhance southerly flow ushering in warm and moist air into the northern and western Gulf coast. This is expected to bring precipitation to Southcentral Alaska, the Alaska Peninsula, and Kodiak Island. There is high confidence that there will be periods of heavy rain for Eastern Kenai Peninsula and Prince William Sound Saturday into Sunday. Lingering showers are possible Monday through Tuesday as the southerly enhanced flow shuts off. A weak upper level low over Kamchatka will move over the Aleutians Tuesday through Wednesday, generating showers.

-SS

AVIATION

PANC...VFR conditions are expected to prevail through the period, although ceilings falling to or slightly below 5,000ft cannot be ruled out for later today as showers redevelop in the vicinity of the terminal. Light southerly winds this morning are expected to become more westerly by around noon today. A brief period of fog or low stratus is possible both early this morning and again Friday morning. This is due to an area of low stratus and fog lingering over Cook Inlet and moving northward toward the terminal during the overnight hours.