Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 609 PM EST Fri Jan 01 2021 Valid 12Z Tue Jan 05 2021 - 12Z Sat Jan 09 2021 ...Overview and Guidance/Uncertainty Assessment... A relatively progressive flow pattern is expected across the region during the medium range period with a series of shortwaves moving across the northern Pacific while persistent/weak troughing resides over the eastern Bering/western mainland. Aloft, there was reasonable agreement with the latest deterministic/ensemble guidance for day 4/5. Beyond that, timing individual waves of low pressure was the greatest model differences, particularly by the middle of the period where a secondary area of low pressure undercutting the occluded low in the northern Pacific rapidly lifts toward the coast. The GFS was a southeasterly/fast outlier while the ECMWF/CMC showed fairly good agreement. By late in the period, there is increasing signal for a stronger low pressure to approach the Aleutians by day 8 which has decent support in the both the deterministic and ensemble data, however ahead of that system there is uncertainty in another low that could race ahead of it. The ECMWF/CMC advertise a deepening low approaching the coast while the GFS largely leaves it out. For now, the support was given toward the ECMWF/ECENS solution but maybe not as deep/strong in the WPC blend. There was some support in the latest NAEFS means as well, so the deterministic GFS was largely discounted for day 7/8. ...Weather/Hazards Highlights... The active storm track through the Gulf of Alaska will bring several waves of low pressure to the state, especially the southern coast and Panhandle where both heavy precipitation and significant waves are possible. Copious amounts of moisture with a strong low Monday night will bring heavy mountain snows and valley rains along the coast. Elsewhere, quieter conditions with below normal temperatures are expected early before a warming trend takes place with milder Pacific air moving in. The approach of the stronger storm system by the end of the period could pose hazards to the Aleutians, but it is just beyond the current forecast period. Taylor - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Tue-Thu, Jan 5-Jan 7. - Heavy precipitation across portions of the Alaska Panhandle, Tue-Wed, Jan 5-Jan 6. 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