Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 427 PM EST Sat Jan 13 2024 Valid 12Z Wed Jan 17 2024 - 12Z Sun Jan 21 2024 ...Guidance Evaluation/Preferences... Model and ensemble solutions seem well clustered overall through medium range time scales in a pattern with above normal predictability. A composite of the 12 UTC GFS/ECMWF/UKMET/Canadian valid for Wednesday to Friday seems to provide good detail while reasonably mitigating lingering flow embedded system differences consistent with individual predictability. Opted to once again switch to the more compatible 12 UTC GEFS/ECMWF ensemble means by next weekend amid slowly growing forecast spread. This necessitated the application of manual adjustments to better link precipitation, probabilities of precipitation and terrain/upslope winds and also to ensure sufficient surface system depth consistent with upper support, the later mainly for the main offshore low pressure systems. These adjustments were to offset inherent weakenging by the blending process. The signal in guidance remains impressive to re-develop blocky flow for Alaska and vicinity as anchored by a mighty closed upper ridge/high set to focus over the Bering Sea and vicinity. These types of features often prove slow to dislodge. WPC product continuity is good with this overall forecast plan. ...Weather/Hazards Highlights... It remains the case that the overall Alaska and vicinity flow pattern will continue to transition over the next few days as northern Pacific and Bering Sea systems more earnestly work through an ambient upper ridge now centered over mainland Alaska. In this flow, a dynamic Bering Sea system is slated to slam eastward and inland into western Alaska Tuesday, with full passage across the North Slope and Interior Wednesday. This should produce unsettled weather across the broad region to include gusty winds and locally enhanced and blowing snows. This will be followed by a post-frontal trend to colder temperatures through later next week. Periodic unsettled and locally snowy/gusty periods may redevelop later next week and weekend as energies digs sharply through the mainland and into the Gulf of Alaska to the lee of the upstream and amplified Bering Sea centered upper high/ridge that will anchor a slow to dislodge blocky flow pattern for Alaska and vicinity. The upper trough system energies offer some timing/strength challenges, but seem likely to periodically focus enhanced winds/tighter pressure gradient gap winds and snows through later next week and weekend from the North Slope/Brooks Range and central-eastern Interior southward through the Alaska Range/SouthCentral Alaska to the Gulf of Alaska and the Southeast as colder air settles in contrast to offshore low pressure gradients. Formation of these deep layered closed upper low/trough and slow meandering and redevelopments over the Gulf of Alaska next week/weekend will also maintain and focus protracted and widespread maritime wind/wave impacts offshore. Schichtel Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook 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