Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 620 PM EST Thu Feb 13 2020 Valid 12Z Mon Feb 17 2020 - 12Z Fri Feb 21 2020 An active upper-level jet across the North Pacific will bring a series of relatively deep low pressure systems across/near the Aleutians and into the Gulf of Alaska or southern mainland Alaska during the extended range period. The first of such lows moves from just north of the Aleutians on Monday to the western/southern Mainland by Tuesday. While the models agree that a significant storm system is possible, there remains fairly substancial disagreement on placement. The ECMWF/CMC remain the best clustered with the ensemble means, while the GFS shows multiple triple point lows, and a position well east/north of the better clustering of ensembles. As this low weakens over the mainland on Wednesday, models indicate a second potentially deep low to approach the Aleutians. Significant timing and intensity differences remain, but the ensemble means show good clustering on a track into the northern Gulf or southern coast by Friday. For this system, prefer a mostly ensemble mean blend by days 7 and 8. Heavy snowfall is expected across the southern mainland Alaska and perhaps into portions of the interior Monday and Tuesday with the first deep low pressure system, with heavy precipitation also working into the Panhandle region on Wednesday. The next low pressure system towards the middle of next week will bring another round of widespread precipitation from the Aleutians eastward into the southern mainland and Panhandle. Heavy precipitation may be possible for some locations. Additionally, an arctic air mass across the interior and North Slope regions will hold through at least the middle of next week, with high temperatures 10 to 20 degrees F below average to many. Some moderation of temperatures is possible by the end of next week across interior locations, but should remain below average across the North Slope. Santorelli 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-Thu, Feb 18-Feb 20. - Heavy snow across portions of southern Alaska, Sun-Tue, Feb 16-Feb 18. - Much below normal temperatures across portions of mainland Alaska, Sun-Mon, Feb 16-Feb 17 and Wed-Thu, Feb 19-Feb 20. 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