Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 657 PM EDT Thu Apr 16 2020 Valid 12Z Mon Apr 20 2020 - 12Z Fri Apr 24 2020 ...Overview and Guidance Evaluation... Forecast uncertainty remains an issue from the Aleutians southward for early to middle of next week as a double-barrel low pressure system rotates in the vicinity. Nevertheless, the model spread has decreased since yesterday as the ECMWF slows down considerably while the GFS and the CMC speed up and weaken the system toward the middle of next week. The ensemble means have also come into much better agreement with each other, placing a cyclone center south of the central Aleutians next Tuesday into Wednesday. The WPC pressure fields were derived using a consensus of the 00Z EC mean and the 12Z NAEFS together with the 12Z ECMWF and the 06Z and 12Z GFS. More of the ensemble means were used for the longer range period, splitting between the 00Z EC mean and the 12Z NAEFS. This results in a cyclone moving quite slowly eastward to a position south of the Alaska Peninsula by next Friday. Models are much more agreeable for other areas of Alaska. The stationary ridge over Alaska should gradually weaken with time while the arctic air farther north is forecast to edge closer toward Alaska and then slide off to the east. ...Weather/Threats Highlights... A good chance of precipitation should be across the southern to central Alaska due to remnant moisture associated with a dissipating front moving into the western mainland early next week. The wavy front persisting across the northern mainland for most of the period will also provide a precipitation focus. It appears that the large scale pattern evolution should promote a drier trend over much of the inland section while moisture will tend to hover across the southern coasts as an occluded cyclone approaches from south of the Aleutians. A lead wave on the triple-point could bring a higher chance of precipitation into southern and southeastern Alaska on Wednesday. Forecast uncertainty continues to prelude more specific details for the latter part of next week but lingering precipitation appears the most probable scenario along the southern coastlines. 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. As broad cyclonic flow edges southward from the Arctic and then slides off to the east, there is a general cooling trend for much of Alaska toward the end of next week. Kong 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, Mon-Wed, Apr 20-Apr 22. - Heavy precipitation across portions of mainland Alaska, Sun, Apr 19. - Much above normal temperatures across portions of mainland Alaska, Sun-Mon, Apr 19-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