Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 444 PM EST Sun Dec 10 2023 Valid 12Z Thu Dec 14 2023 - 12Z Mon Dec 18 2023 ...Lingering Heavy Precipitation Pattern for Southeast Alaska into late week... ...Guidance Evaluation/Preferences... Guidance forecast spread is lower than normal Thursday and Friday. A 12 UTC GFS/ECMWF/UKMET/Canadian composite offers a good forecast basis/detail and maintains good WPC product continuity in flow with above normal predictability. Opted to then transition preference to the reasonably compatible 12 UTC GEFS/ECMWF ensemble means amid growing forecast spread and unresolved run to run model continuity issues. ...Weather/Hazards Highlights... An cooling and unsettling upper trough position should weaken but linger over the mainland while likely re-centering over western/northwestern Alaska later this week into the weekend as part of a pattern transition. This may lead to periods of light to locally enhanced snows and winds. Meanwhile, a main storm genesis pattern will persist just to the south of the state into later this week with the development and poleward track across the Gulf of Alaska with a continued series of complex and deepened low pressure/frontal systems. The systems will offer a maritime to coastal high wind/wave threat. Deepened moisture will feed inland by enhanced wind flow around these storms, with main focus over Southeast Alaska. Expect periodic surges of heavy precipitation in the form of coastal rains with potential runoff issues due to week long accumulation that will also be a factor for heavy inland/terrain/mountain snows. Upstream, amplified upper trough/closed low energies are expected to work steadily eastward through the Bering Sea and Aleutians Friday through next weekend as a leading/blocking upper ridge also shifts eastward and gradually weakens. This occurs as the northern portion of the initially amplified ridge splits off into a closed upper high over the Arctic Ocean to the northwest of the state. The advent of this transition would allow for less certain details of northern Pacific/Aleutians and Bering Sea traveling systems to bring new organized precipitation more eastward into these areas and then increasingly to the mainland next weekend into early next week. This looks to include a renewed conduit for downstream propagating systems energies to emerge back into the Gulf of Alaska. This emerging pattern would threaten potential for periodic and growing over time opportunities for some locally enhanced precipitation and winds from the Aleutians into Southwest Alaska into the Interior with growing southwesterly flow, but then especially the Alaskan southern tier. 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