Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 632 PM EDT Tue Apr 14 2020 Valid 12Z Sat Apr 18 2020 - 12Z Wed Apr 22 2020 ...Overview and Guidance Evaluation... Models and ensemble means agree rather well that an upper-level ridge will remain stationary across Alaska through the medium-range period. In contrast, the most uncertain area in the forecast period continues to be from the Aleutians southward for early to the middle of next week where a cyclone should be in the vicinity. First of all, the spread of the cyclone center location between the GFS and ECMWF has increased in recent runs, with the GFS placing it over the central Aleutians but the ECMWF much farther east by next Wednesday. The CMC also shows a stronger low farther west comparable to the GFS solutions. On the other hand, the GEFS' cyclone center locations in recent runs exhibit a gradual eastward trend toward the 00Z EC mean center located farther to the east. This appears to indicate that the 00Z EC mean solution is more credible for the longer range. With the faster EC solutions, the ridge over Alaska becomes weaker in the longer range while the arctic air farther north is forecast to edge closer toward Alaska. Therefore, the WPC pressure fields were derived using a consensus of the 12Z ECMWF/12Z GFS/12Z GEFS trending increasingly toward the 00Z EC mean for the longer range period. ...Weather/Threats Highlights... Expect a broad area of precipitation to cross Alaska through the weekend, due to an initially strong low level flow ahead of a dissipating front moving into the western mainland and a weakening low pressure system over Aleutians/Bering Sea. The wavy front persisting across the northern mainland for most of the period will also provide a precipitation focus. Thus far there has not been a coherent signal for which areas should see highest totals during the period, with a number of regions potentially seeing significant enhancement at least on a localized basis. The large scale pattern evolution should promote a drier trend over much of the mainland early next week. Parts of the Aleutians/Alaska Peninsula could see meaningful precipitation/gusty winds depending on the precise surface evolution by the latter half of the period. The temperature forecast looks consistent, with above normal temperatures over most of the state during the period aside from the Panhandle and major valleys over the southern mainland where highs may be modestly below normal. Morning lows should tend to be farther above normal than daytime highs and the northern mainland will likely see the highest anomalies. Multi-day trends have been toward a later southward push of the northern mainland front but it should eventually drift south next week as broadening cyclonic flow aloft over the Arctic begins to have some influence over the northern part of the state. Kong/Rausch 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, Fri-Sun, Apr 17-Apr 19. - High winds across portions of mainland Alaska and the Aleutians, Fri, Apr 17. - Much above normal temperatures across portions of mainland Alaska, Fri-Mon, Apr 17-Apr 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