Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 607 PM EST Sun Feb 09 2025 Valid 12Z Thu Feb 13 2025 - 12Z Mon Feb 17 2025 ...Guidance Evaluation and Preferences... Model and ensemble guidance is well clustered in the day 4 (Thursday) to day 6 (Saturday) time frame with seemingly overall above normal predictability despite non-traditional flow transition. The general pattern features a building upper-level inverted trough extending from east to west across the mainland, a strong Arctic high to the north, and a low pressure system over the northeast Pacific approaching the Gulf of Alaska. The system looks to remain on a more southerly track given the strong upper-level trough entrenched over the mainland. The updated WPC forecast used a composite blend of the 12Z ECMWF/CMC/GFS, with a small preference given to the ECMWF/CMC due to a bit better overlap between the solutions overall over the forecast area. A small contribution of the ECens mean was included day 6 to help smooth out increasing smaller scale wave details with the system entering the Gulf. Then, deterministic and mean guidance shows the strong Arctic high begin to shift northward in tandem with the inverted upper-level trough late next weekend into early the following week, allowing an upper-ridge to build in over the Gulf of Alaska/southwest Alaska as a second system over the northeastern Pacific approaches. This may at least briefly bring back the recent pattern featuring southerly flow/storm track over the eastern Aleutians/Alaska Peninsula with the upper-ridge to the east and the second northeastern Pacific system turning northward into the Bering Sea. The 12Z GFS was a bit of an outlier in terms of maintaining this system northward into the Bering Sea, though even in this case mean upper-level troughing was still apparent. The GFS also maintained a more southerly position for the inverted trough over the mainland. Thus, the latter part of the updated WPC forecast featured an increasing contribution from the ECens/GEFS mean days 7-8 as a replacement for the GFS given the noted differences compared to the ECMWF/CMC. ...Weather/Hazards Highlights... Amplified upper-level flow for Alaska and vicinity will hold through midweek as highlighted by mean upper troughing from the North Pacific into the Bering Sea and downstream upper ridging from the eastern Gulf of Alaska poleward through the Mainland and the Arctic Ocean. Then, in a pattern change, ample and unsettling upper trough energy and height falls will increasingly work over the Interior and North Slope from high latitudes and Canada to undercut and split the Mainland ridge into later next week and weekend. An Arctic front on the leading edge of strengthening high pressure will push down across the Mainland, interacting with moist southerly flow preceding the approach of a northeastern Pacific/Gulf system and focus some precipitation along the southern coast. Some heavier precipitation looks to be possible in vicinity of the Kenai Peninsula. An increase in precipitation is also likely for Southeast ahead of the approaching system. Periodic wavey flow in the Interior could bring some light snow showers, though precipitation chances overall will be limited with moisture focused south of the front. A tightening pressure gradient between the strengthening Arctic high to the north and low pressure system over the Gulf could bring some gusty winds particularly for the North Slope and possibly in gap flow along the Southeast. A transition back towards a similar pattern to midweek with southerly flow focused over the Aleutians/Alaska Peninsula may bring a return of precipitation chances to these regions late weekend/early the following week as a ridge builds northward over the Gulf/southwest AK and another low pressure system over the northeastern Pacific approaches from the south-southwest. The Arctic front pushing towards the western and southern coasts will usher in a period of colder, below average temperatures late next week/early weekend for most of the state outside of the Aleutians, southwest Alaska, and portions of the southern coast. Daytime high temperatures will generally range in the negative single digits for the North Slope and eastern Interior, the single digits for the central Interior and Alaska Range vicinity, and the teens for the western coast. The Southeast, which has seen a period of below average temperatures compared to the rest of the state, will remain below average with highs in the 20s and 30s. A slight warming trend should begin by early the following week as the air mass begins to moderate. Temperatures south of the front will be in the 30s for the southwest and southern coast, with 40s into the Aleutians. Putnam 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