Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 659 PM EST Sun Dec 20 2020 Valid 12Z Thu Dec 24 2020 - 12Z Mon Dec 28 2020 ...Guidance and Uncertainty Assessment... Overall, the model guidance is in fairly decent agreement once again. However, the 06Z/12Z runs of the GFS were running about 6 to 12 hours faster than the clustered deeper 12Z ECWMF/CMC solutions, especially with the initial system over the eastern Gulf and the next wave behind it. Given the spread in timing and amplitude, the evolutions are similar. A general blend of the 06Z GFS and 12Z GFS/CMC/ECWMF was the preferred starting point while incorporating the 00Z ECWMF ensembles and GEFS means by mid-period and increasing weight by the end of the forecast. This compromise keep a general trough-iness over the Gulf of Alaska with ridging over Canada. There are decent model signals that a couple of weaker cyclones will edge closer towards the Alaska Panhandle during the Christmas holiday, but uncertainty regarding their speeds of motion and intensities remain high. By next weekend, global model ensemble means continue to show decent agreement that the next large-scale cyclone will be moving into the Aleutians. ...Weather/Hazards Highlights... The southwest and southern portions of the state will be have been impacted with heavy precipitation and high winds just prior to the start of the extended period; the heavy precipitation will shift to the Panhandle Wednesday. The chance of heavy rain should generally decrease during the Christmas holiday along the entire stretch of the southern coastal sections, but a couple of smaller scale cyclones could bring periods of enhanced precipitation near the Alaska Peninsula and Alaska Panhandle. Another large cyclone is expected to track across the Aleutians ushering in high winds and more precipitation - gale to storm force winds and periods of heavy precipitation appear likely. Under the ridge, milder than average temperatures will overspread much of the Mainland and continue through the holiday before cooling down by the weekend. Campbell 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