Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 621 PM EDT Mon Apr 26 2021 Valid 12Z Fri Apr 30 2021 - 12Z Tue May 4 2021 ...Weather Pattern and Model Guidance... The forecast period begins on Friday with a closed and elongated upper low over western Alaska, a weakening trough over the Gulf, and a large low passing south of the central/western Aleutians. The upper low/trough lingers over the Alaska mainland going into next weekend, followed by potential upper level ridging early next week. Meanwhile, the Aleutian low should continue slowly eastward near 45-50 degrees north and reach the northern Gulf by next Monday, albeit a little weaker by this time. The 12Z deterministic guidance agrees well on the overall synoptic scale pattern through next weekend, and is an improvement compared to the past couple of days. In terms of differences, the 12Z ECMWF is faster with the Bering Sea/Gulf system by Monday compared to the GFS/CMC solutions, and the ECMWF is slightly ahead of the 12Z EC mean. Similar to yesterday, the greatest uncertainty resides across the Bering Sea and eastern Siberia regarding a separate shortwave pivoting around the upper trough over western Alaska, and how that eventually evolves. The WPC forecast leaned toward a blend of the 12Z ECMWF/CMC/GFS/UKMET for the Friday through Sunday time period, and then more of the EC/GEFS means beyond that. ...Sensible Weather... Temperatures are expected to be on the cool side for much of the western half of Alaska under the influence of the upper level trough and mostly cloudy skies, and near to slightly above normal for portions of the North Slope and the eastern Interior. In terms of precipitation, there will be two main rounds, with the first round on Friday/Saturday associated with the weakening disturbance from the northern Gulf region. The second round will likely affect locations from the Alaska Peninsula to the southeast Panhandle as the next storm system approaches from the Aleutians. Hamrick Hazards: - Heavy precipitation across portions of the Alaska Panhandle, Thu-Fri, Apr 29-Apr 30. 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