Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 755 PM EDT Fri Oct 23 2020 Valid 12Z Tue Oct 27 2020 - 12Z Sat Oct 31 2020 ...Guidance/Predictability Assessment... The forecast period begins on Tuesday with a lingering surface low over the northern Gulf of Alaska, and a surface high building over the Interior by the middle to end of the week. Deterministic guidance indicates reasonable mass field agreement through Wednesday, and then normal levels of model spread become apparent. This holds true with the next and stronger storm system to pass south of the Aleutians, with the CMC and GEFS mean closer to the Alaska mainland, in contrast to the GFS/ECMWF that are a bit slower and farther offshore. By the end of the forecast period next Saturday, a third system may approach the western Aleutians, with surprisingly better model agreement regarding location of the surface low, and greater model spread over the Gulf region. The WPC fronts and pressures forecast was primarily derived from the 12Z GFS/ECWMF/EC mean, and with time increasing the weighting of EC mean along with some of the NAEFS mean. ...Weather/Threats Highlights.. Heavier rain and mountain snow is expected across the southeast panhandle and portions of the southeastern Mainland on Tuesday as the surface low over the northern Gulf meanders slowly and gradually weakens, with onshore flow to the east of the low. Some snow showers will also be possible across the Arctic Coast region as a couple of disturbances pass north of the region. Very little in the way of snow is expected for the Interior as high pressure will govern the overall weather pattern. The coldest temperatures are expected to be across the east-central portion of the state, especially for the latter half of the forecast period where some sub-zero high temperatures will be possible. Depending on the track of the Aleutian storm system towards the middle to end of next week, strong winds may materialize across this region, although confidence in this remains limited for now. Hamrick Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Mon, Oct 26. 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