Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 614 PM EST Fri Jan 12 2024 Valid 12Z Tue Jan 16 2024 - 12Z Sat Jan 20 2024 ...Guidance Evaluation/Preferences... Guidance now seems in better agreement overall through medium range time scales, bolstering forecast confidence to a degree despite an apparent pattern transition and eventual blocky flow reformation that historically can offer forecast challenges. A composite of best clustered guidance the 12 UTC ECMWF/UKMET/Canadian Tuesday into Thursday seems to reasonably mitigate lingering flow embedded system differences consistent with individual predictability. The 12 UTC GFS has trended more in line, but has shown less than stellar run to run continuity recently. The 12 UTC GFS solution is less likely but still plausible given overall flow amplitude. Opted to switch to a composite of the compatible 12 UTC GEFS/NAEFS/ECMWF ensemble means at longer time frames to smooth less predictable smaller scale variances. Even so, am impressed with the strongly growing signal in guidance to re-develop blocky flow for Alaska and vicinity as anchored by a mighty closed upper ridge/high set to settle/focus over the Bering Sea by next midweek. These types of features often prove hard to dislodge. ...Weather/Hazards Highlights... The overall flow pattern will transition over the next few days as northern Pacific and Bering Sea systems crash through an ambient upper ridge now centered over mainland Alaska. In this flow by next midweek,a potent Bering Sea system is slated to slam eastward/inland across western Alaska and the North Slope/Interior. This should produce unsettled weather across the broad region Tuesday into Wednesday to include gusty winds and locally enhanced snows followed by a post-frontal trend to colder temperatures by later next week. Periodic unsettled/cold/snow potential is expected be reinforced into next weekend as energies dig into the region to the lee of an upstream and building/settling Bering Sea centered upper high/ridge that will anchor a renewed and slow to dislodge blocky flow pattern for Alaska and vicinity. Downstream, lead midweek upper trough/surface system energies offer some timing/strength challenges but seem likely to focus enhanced Gulf of Alaska to Southeast Alaska winds and precipitation Tuesday whose scenario could be periodically repeated in overall drier/cooler flow later next week through the North Slope and eastern Interior toward the Southeast and the Gulf of Alaska with additional digging and approach of dynamic shortwave energies. Eventual deep layered closed upper low/trough developent and slow meandering/retrogression over the Gulf seems intent to maintain and focus a protracted maritime to coastal impact into next weekend. 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