Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 357 PM EDT Tue Mar 19 2019 Valid 12Z Sat Mar 23 2019 - 12Z Wed Mar 27 2019 Upper ridging over northwestern Canada at the end of the week will only briefly relax next Monday before again building over the eastern interior into the Yukon. This favors continued/renewed troughing in the Bering Sea with a split flow south of the Gulf of Alaska. The models/ensembles were in good agreement through much of the period but showed a large shift in the forecast for next Mon/Tue near the central Aleutians. Instead of maintaining a singular frontal passage, the models/ensembles now forecast a significant surface wave to develop off Asia and deepen into the Bering Sea, potentially into the 950s mb. The ensemble means were closer to 980mb and opted to depict a 970s mb low for now given the large change in continuity, lead time (6 days), and the spread among the models in location/timing (and even depth per the 12Z Canadian). Such a deep system (winds at least 30-40kts) would bring a wind/wave threat to the open Bering Sea waters and western coastal areas. This system is forecast to lift north-northeastward, blocked from moving inland too much from the ridge downstream, focusing precipitation west of 155W (multi-inch totals). Southerly flow would bring in well above average temperatures, possibly near record highs, to much of the interior and especially North Slope. By next Tue/Wed, ensembles show no discernible system behind that front but troughing would maintain cold air aloft over the Aleutians/Bering and eventually into western Alaska. Fracasso Bullet points from the WPC Days 3-7 Hazards chart can be found at: https://www.wpc.ncep.noaa.gov/threats/threats.php - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Fri-Mon, Mar 22-Mar 25. - Heavy precipitation across portions of mainland Alaska and the Aleutians, Mon-Tue, Mar 25-Mar 26. - High winds across portions of mainland Alaska and the Aleutians, Fri, Mar 22. - High winds across portions of the Aleutians, Mon, Mar 25. - High significant wave heights for coastal portions of mainland Alaska, Fri, Mar 22. 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