Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 647 PM EDT Sun Mar 29 2020 Valid 12Z Thu Apr 02 2020 - 12Z Mon Apr 06 2020 A relatively progressive weather pattern appears set to evolve across Alaska and the North Pacific during the extended forecast period. A strong upper-level jet along the northern periphery of a building upper-level ridge axis near the date line and along the southern periphery of a broad region of cyclonic flow across eastern Siberia will result in an increasingly active storm track across the Bering Sea. A leading frontal system should bring precipitation and gusty winds to the Alaska Peninsula on Thu (day 4), while surface high pressure weakens and retreats across the Interior. Deterministic solutions showed quite a bit of variability and inconsistency throughout the extended forecast period, making it difficult to prefer a single model solution for the forecast across Alaska and surrounding waters. The ECMWF was a bit of an outlier in terms of its intensity for a wave of low pressure across the Bering Sea on Thu. With the next, much stronger low pressure system expected to enter the Bering Sea Fri-Sat, the GFS becomes an outlier in terms of track, which is much farther south than almost all other guidance as well as ensemble means. The one solution that seems to be somewhat reasonable across the board is the 12Z UKMET, which was weaker (like the GFS) with the leading Bering low, but then much closer to the ECMWF and overall consensus with the track of the more intense low pressure system in the Bering Fri-Sat. Thus, opted to lean heavily on the UKMET early in the forecast period (days 4-5). The Fri-Sat Bering Sea system is forecast to weaken as it approaches western mainland Alaska on Sun. The system should bring the potential for a round of precipitation to the Aleutians and western mainland Alaska through next weekend, with the potential for gusty winds near the coast. The overall pattern looks to persist, with the potential for another significant low pressure system to enter the Bering Sea late Sun into Mon. Model/ensemble spread gets quite large by days 7-8 (Sun-Mon), with the ECENS mean almost entirely out of phase with the GEFS/CMCE means. The ECMWF/ECENS were substantially slower with this system than other guidance. Given the fairly progressive pattern, and a somewhat more consistent solution in the GEFS, opted to lean heavily toward the GEFS (and to some degree the NAEFS) by late in the forecast period. Given the large degree of spread, forecast confidence by days 7-8 was well below average. Ryan 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 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