textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Key Messages:

- Winter Weather Advisories remain in effect for snow from Anchorage Hillside, across the Northern and Western Copper River Basin and Thompson Pass.

- Temperatures trend colder for the latter half of the week in the wake of this storm system.

Discussion:

An upper level low is currently moving over Southcentral Alaska. Snowfall over Southcentral is tapering off as colder and drier air filters into the region from the northwest. However, steady light snowfall will persist in the Copper River Basin at least through Wednesday morning. By Wednesday afternoon, snowfall will end across Southcentral. As the surface low in Prince William Sound slowly moves eastward over the next couple of days, gusty northeast gap winds set up around Kodiak Island. Gap winds will also persist in Resurrection Bay, Passage Canal, and Valdez through Thursday.

Overnight lows across the bulk of Southcentral will be much colder over the next few days, dipping into the teens and 20s in most spots for early tomorrow and Thursday morning, and into the single digits for portions of the Copper River Valley by Wednesday night/Thursday morning if skies remain clear. Fog may form across Anchorage, the Mat-Su, and the Kenai Peninsula due to moist ground and clearing skies. Cool and dry conditions persist through Friday as an upper ridge encroaches into Southcentral from the west. Looking ahead, a front looks to move into Southcentral from the west on Saturday, likely bringing rainfall to Kodiak Island. Southerly flow with this front may bring warmer temperatures along with it, warming even inland temperatures to the 40s.

-JAR/TM

LONG TERM FORECAST (Days 4 through 7: Saturday through Tuesday)

Key Messages:

* A series of strong storms move across the Bering Sea and into Alaska through the weekend, bringing strong winds and heavy precipitation.

* Confidence is low to medium with regards to impacts, strong onshore winds and elevated coastal water levels concerns for Southwest Alaska, mainly Friday and Saturday and again on Monday.

Discussion:

The biggest story in the long-term forecast continues to focus on a strong low transiting from the Kamchatka Peninsula to Alaska. Ensembles continue to be in relatively good agreement with this storm, with seemingly higher-than-average forecast confidence given that this feature is 3 to 6 days out. Good run-to-run consistency among deterministic global models is also contributing to higher-than-average forecast confidence. The areas of highest agreement with this feature are for gale to storm force sustained winds along the front as it moves across the Aleutian Chain, the Southwest Alaska coastline, and the Alaska Peninsula. These onshore winds are raising concerns for coastal impacts (including high surf and perhaps even minor coastal flooding) for south- facing portions of the Western coast. A high wind watch has been issued for portions of the Southwest coast and for the Cold Bay area as the front passes. We are closely monitoring this storm as it transitions from the long term forecast to the short term. Southcentral should be spared the worst of the winds with this storm, as the front will very likely be weakening by the time it exits Southwest Alaska.

In addition to winds, there will also be plenty of moisture along the front, which will bring periods of moderate to heavy precipitation to the Aleutians, Alaska Peninsula, and Southwest Alaska. Given the strong winds associated with the front, precipitation totals will depend on not on the duration of the front over the area, but also its interaction with terrain features including orographic lift and areas of downsloping that would reduce precipitation totals. While warm air advection will likely keep precipitation mostly rain for the majority of Southwest Alaska, colder air lingering in Southcentral could mean that lower elevation areas may see snow.

After this Bering low moves north and the front weakens, southwesterly flow dominates the Bering Sea with embedded surface lows that will continue to keep weather active with at least periods of gale force winds across the Bering. However, resolving these features are less clear through early next week.

The front could continue into Southcentral, bringing precipitation to the region this weekend. Low confidence on the forecast amounts as models vary with its progression eastward. Otherwise high pressure begins to builds across the area Sunday until midweek.

AVIATION

PANC...While steady precipitation has come to an end for the terminal, about a 20 to 40 percent chance of rain/snow showers lingers through the rest of the afternoon and evening as weak upper level waves move through. Ceilings will likely be predominantly VFR, except for periods of MVFR ceilings as showers move through. Southerly winds turn clockwise through the afternoon and evening, becoming northerly at around 10 kt close to midnight tonight.