Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 338 PM EDT Fri Apr 12 2019 Valid 12Z Tue Apr 16 2019 - 12Z Sat Apr 20 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/expand 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 smaller-scale features generally decreases as a function of time. Therefore, a deterministic blend very early in the extended to one comprised mostly of ensemble means later in the period is the preference at this time. The ECMWF/GFS have shown some consensus for a couple runs with respect to a surface low pressure system expected to move north into the Gulf of Alaska Tue night-Wed night, and then pushing inland on Thu. This front could bring a round of heavy precipitation to portions of the Alaska Panhandle as it moves inland. With increased ensemble spread by later next week, confidence is low in the specific timing and structure of any low pressure systems moving south of the Aleutians/Alaska Peninsula and perhaps entering the Gulf during that time. Farther north, while models agree that upper ridging should expand east across the Bering Sea, solutions differ as to whether it also expands into the Arctic Ocean north of Alaska, which plays a significant role in whether arctic shortwave energy is able to dive south into Alaska by later next week. Thus, while confidence is good in the broad large scale pattern, confidence by later next week is actually quite poor when it comes to the specifics of individual systems/features. 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, Wed-Fri, Apr 17-Apr 19. 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