Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 641 PM EST Wed Jan 10 2024 Valid 12Z Sun Jan 14 2024 - 12Z Thu Jan 18 2024 ...Stormy conditions for southwestern Alaska... ...Overview... An active and windy pattern expected as multiple low pressure systems move through the region. One particular low will follow a more southerly track across the Alaska Peninsula to Kodiak Island for some enhanced winds and precipitation over the weekend. The upper ridge will promote milder than normal temperatures across most areas, with the exception of the eastern Interior and Southeast Alaska where continental flow ahead of a trough will bring in cold air. The upper ridge will likely break down early next week, with increased precipitation chances along the southern coast into Southeast Alaska, and potentially into portions of the Interior as well. ...Guidance Evaluation/Preferences... The latest guidance for the extended period begins in fairly good agreement with a well-clustered low tracking from the Yukon across the North Slope/Brooks Range to the Chuckchi Sea for Days 4-5. Meanwhile another low pressure system will be tracking near Bristol Bay/Aleutians/AK Pen- clustering with this feature is fair with typical spread. The ECWMF/GFS/CMC were generally the best models with both of these features. Beyond Day 5 model spread increased however there is consensus for ridging to continue spreading west over the Aleutians while and inverted trough shifts north/east across the North Pacific/Gulf of Alaska. Upstream over the Bering Sea, there is general agreement in bringing the upper-level trough over the Bering Sea eastward along the southern coast and over the Gulf of Alaska, helping to break down the interior Mainland ridge from the west. The ECMWF as well as the ensemble means agree that mean ridging will build in over the Aleutians following the departure of the upper-level trough to the east. Given this depiction, it was the preferred guidance. The latest WPC forecast had an initial starting point of the ECWMF/GFS/CMC/EC ensemble mean through Day 4. Day 5 and beyond the GEFS means was included and the weighting of the ECWMF/EC ensemble mean were kept higher than the other guidance. This helped maintained continuity while trending toward a slight more amplified pattern. ...Weather/Hazards Highlights... Moderate to heavy rain will likely linger into Saturday across the Alaska Peninsula and into southwestern portions of the Mainland. The amplified pattern will keep winds rather gusty with a tight surface pressure gradient focused along western portions of the Mainland, as well along the North Slope. The strongest gusts are expected Friday across portions of the Alaska Peninsula into southwestern Alaska as the low pressure system passes through, and along eastern portions of the North Slope Saturday into Sunday as the northern portion of the interior ridge breaks down. The combination of snow, particularly away from the coast and into higher elevations, as well as the gusty winds could lead to some blizzard conditions. Despite some disagreement with respect to timing in the guidance, the upper trough/surface low are expected to continue eastward along the southern coast of Southcentral Saturday and eventually towards Southeast by Sunday, with some areas of heavy precipitation possible, but not particularly anomalous for this time of year. Initially dry conditions will prevail for the eastern portions of the Interior with the upper ridge in place, however the approach of the upper trough/low pressure system over the Alaska Peninsula/southwest and along the southern coast may allow for at least some moisture/precipitation to spread inland into western and central portions of the Interior. Another system upstream over the Bering Sea will also potentially bring an additional round of precipitation to the western coast and Interior early next week. The western two-thirds of the Mainland will see milder than average temperatures, with the highest anomalies across northern and western portions of the Mainland. Above normal temperatures will expand eastward into the weekend. Initially, eastern Interior and portions of the Panhandle will be running below average as the noted inverted trough over the Yukon expands into eastern portions of the state; however will trend back to near normal by the middle of the extended period. With the potential pattern change into early next week, temperatures across the Mainland are likely to cool closer to normal as well. Campbell 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