Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 602 PM EST Wed Feb 12 2020 Valid 12Z Sun Feb 16 2020 - 12Z Thu Feb 20 2020 An active upper-level jet across the North Pacific will cause a series of relatively deep low pressure systems to progress near the Aleutians and into the Gulf of Alaska or across southern mainland Alaska during the extended forecast period. Clustering of deterministic solutions and ensemble members was perhaps a bit better than average through the period, despite a fair degree of variability on timing/intensity among deterministic solutions. A weakening low pressure system across the Gulf of Alaska on day 4 (Sun) showed relatively good consensus among the guidance. Farther west, a significant low pressure system appears likely to pass near the Aleutians into the southern Bering Sea Sun-Mon, and into southern mainland Alaska by Tue. The ECMWF/CMC showed the best consensus with ensemble means surrounding this system, while the GFS persisted in taking a fairly strong leading low pressure area north along the western mainland coast Mon (an idea with relatively little ensemble support). Guidance shows general consensus that another similar deep low pressure system is likely to pass near the Aleutians by the middle of next week, with above average ensemble clustering given the time range under consideration. Farther north, the arctic influence across the North Slope and northern portions of the interior looks to persist into at least the middle of next week, although some slight moderation of cold temperatures across the interior is possible with southerly mid/upper-level flow early next week before the region once again falls under the influence of arctic flow by the middle of next week. Heavy snow is expected across southern mainland Alaska and perhaps portions of the interior Sun night into Tue as the deep low pressure system traverses the region. Heavy precipitation will also be possible across much of the Panhandle in association with this system. The next low pressure system toward the middle of next week will bring another round of widespread precipitation from the Aleutians east across southern mainland and Southeast Alaska, with heavy precipitation possible for some areas. Additionally, the arctic air mass across the interior and the North Slope will hold strong through much of the forecast period, with high/low temperatures 10 to 20 deg F below average for many areas. Ryan Additional 3-7 Day Hazard information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Tue-Wed, Feb 18-Feb 19. - Heavy snow across portions of mainland Alaska, Sun-Tue, Feb 16-Feb 18. - Much below normal temperatures for parts of mainland Alaska, Sat-Wed, Feb 15-Feb 19. WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can also be found at: https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html