Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 401 PM EDT Thu Apr 11 2019 Valid 12Z Mon Apr 15 2019 - 12Z Fri Apr 19 2019 The long wave pattern across Alaska is not expected to change significantly during the extended forecast period. Upper-level ridging is expected to persist from extreme eastern Russia into the western Bering Sea. Downstream of the upper ridge, the pattern will favor a persistent mean trough across the north central Pacific, centered generally south of the Alaska Peninsula. This mean trough will be reinforced through the forecast period by a number of smaller scale shortwaves traversing the broader cyclonic flow. With the large scale pattern fairly stable, with broad consensus among the guidance, predictability of these smaller-scale features generally decreases as a function of time. Therefore, a relatively simple transition from a heavily deterministic blend early in the extended to one comprised mostly of ensemble means later in the period is the preference at this time. The ECMWF/GFS/CMC showed relatively good consensus and clustering with ensemble members with respect to a surface low initially over the Gulf of Alaska on Mon, with only modestly higher spread for a second low entering the Gulf late Tue. After Tue, ensemble means suggest another surface low crossing the Gulf late Wed/Thu, with the associated frontal system pushing inland by late Thu/Fri. This front could bring a round of more widespread/heavy precipitation to portions of the Alaska Panhandle as it moves inland. With increased ensemble spread by that time, however, the timing and structure of any low pressure systems crossing the Gulf by mid to late next week are certainly subject to change in future model cycles. Farther north, arctic shortwave energy sliding around the eastern periphery of the upper ridge will areas from the North Slope to the Bering Coast through the period, with one such wave diving southeast Mon-Tue showing good consensus in the guidance, and perhaps another by the middle of next week (albeit with much more uncertainty in the guidance). Ryan Bullet points from the WPC Days 3-7 Hazards chart can be found at: https://www.wpc.ncep.noaa.gov/threats/threats.php - Heavy rain across portions of the Alaska Panhandle, Thu, Apr 18. 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