textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Discussion:

Several key features in place today that will come into play over the next several days. Currently, high pressure remains over the Bering Sea with another stout ridge entrenched over much of the western Canadian Territories. Various low pressure systems are positioned around and in between these areas of high pressure. Several shortwaves have been transiting across the Bering Strait and northern Alaska, helping to give a bit of lift to afternoon convection over the past several days. A weak trough remains stalled over the Central Chugach this morning but will lift north through the Copper River Basin today. This feature will help drive another round of scattered shower and thunderstorm activity from the foothills of the Talkeetna Mountains through the basin to the Alaska Range. Much like previous days, the overall steering flow remains relatively weak so any convective shower will result in some brief heavy downpours. The nearly saturated marine layer across Kennedy Entrance and Cook Inlet has resulted in the redevelopment of widespread low stratus and fog that has advected as far north as Willow and Palmer overnight. This area of low clouds and fog will likely linger through mid morning before slowly eroding.

Further south, a low moving up from the North Pacific into the southwestern Gulf will bring gale force winds as the front lifts across the Gulf. Gusty east to northeast winds are expected for Kodiak Island with periods of moderate to heavy rainfall from Friday afternoon through late Saturday. The heaviest rainfall will accompany the front as it quickly lifts through resulting in a general 1-2 inches for many locations across Kodiak Island, though some isolated 2-3 inches are possible especially for areas of enhanced upslope flow. This low will track to the south of Kodiak Island before stalling and weakening near Sand Point.

For interior locations, southeasterly gap winds will precede the front as a coastal ridge builds, resulting in a tightening of the surface pressure gradient between it and a trough over interior Alaska. Expect gusts 30 to 40 mph for Turnagain Arm, West Anchorage, and Palmer from late this afternoon through late tonight.

The eastern Kenai Peninsula and northern Gulf coast will also widespread rainfall as the front lifts through. Another low will quickly move up along the eastern periphery of the aforementioned low...quickly deepening before it lifts towards the eastern Kenai Peninsula and weakens. This low will bring a modest surge of moisture north with another round of moderate to heavy rainfall for the northern Gulf and Prince William Sound.

- PP/TM

LONG TERM FORECAST (Days 4 through 7/Monday through Thursday)

Starting early next week, there will be an upper level trough over mainland Alaska and the Gulf of Alaska/Kodiak Island, with a ridge upstream over the Bering Sea/Aleutians. This will be the tail end of wet and windy weather across much of southern AK and bordering coastal waters, with showers and clouds lingering across much of the region. As we continue through the week, the high amplitude trough will exit eastward to Canada, leaving a weak flow regime with weak embedded features. The subtropical jetstream over the North Pacific will also weaken through the week, with a noted absence of strong storm systems. Thus, the pattern looks very "summer-like", with daily afternoon/evening showers and thunderstorms over southern AK driven by surface heating and resulting instability and generally light winds across much of the Aleutian, Gulf and southern AK coastal waters. While the week will start out cloudy, expect increasing sunshine and warming temperatures through the week. High pressure will remain centered across the southern Bering and Aleutians, so widespread low clouds and fog will be common.

-SEB

AVIATION

PANC...A light up-inlet flow will persist this morning, allowing another marine stratus layer to return over the Terminal through around noon. Expect LIFR or IFR conditions through mid-morning due to both the low stratus and areas of fog moving in and out of the terminal. Similar to yesterday, IFR to MVFR conditions may persist through late morning or around noon before the marine layer retreats back over Cook Inlet and VFR conditions prevail. Once the marine layer advects back over the inlet, VFR conditions are expected through Saturday. Another reason for the improved cigs and vis later today will be the development of a southeasterly Turnagain Arm wind that is expected to clip West Anchorage and the terminal by late afternoon or early evening. Wind gusts of 30 to 40 mph are possible this evening before the the pressure gradient shifts and the Turnagain Arm bends away from the terminal and down Cook Inlet, likely between 1 AM and 3 AM. LLWS will be possible early Saturday morning as the surface winds become northerly while winds aloft remain southeasterly. The southeasterly winds off Turnagain Arm are expected to move back over the terminal Saturday afternoon.