Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 616 PM EST Mon Feb 28 2022 Valid 12Z Fri Mar 04 2022 - 12Z Tue Mar 08 2022 ...Pattern Overview... Multiple storm systems are forecast to traverse the North Pacific and impact the Aleutians, portions of the western mainland, and the southern Coast during the extended range period (Friday-Tuesday). The first will bring a storm system to southwest Alaska, and southerly flow ahead of this combined with another low will bring possibly heavy precipitation to parts of the southern coast and Panhandle. Mean troughing over the Aleutians will facilitate several low pressure areas rotating through the base of the trough. Weak troughing replaces upper ridging briefly this weekend, with the upper ridge building back in by early next week and above normal temperatures prevalent. ...Guidance/Predictability Assessment... The guidance overall shows reasonable synoptic scale agreement on the main weather features, however continue to exhibit a ton of run to run variability in the details which leads to a low confidence forecast, especially the second half of the period. On Friday-Saturday (day 4-5), a surface low is forecast to lift across the eastern Aleutians, into the Bering Sea, and skirt the west coast of Alaska. The past couple of days models have shown some placement differences, but today they seem to better converge on a surface low center a little closer to the mainland. The next low into the Gulf this weekend also shows decent agreement on placement, but the 12z CMC was notably slower/south of the consensus. The greatest forecast concerns during this period seem to surround various low pressure systems in and near the Aleutians. Models are struggling with placement/track of the first low... the UKMET and CMC both are displaced north of the Aleutians on Sunday, while the ECMWF/GFS and ensemble means support something farther south. After Sunday, things get pretty chaotic across the region as this low should weaken in favor of the next one in line entering the region early next week, and another possible low (which gets washed out by the ensemble means) lifting northward towards the Peninsula. Amongst the deterministic guidance, there is a lot of uncertainty in the details and timing of these systems. The WPC forecast leaned mostly on the deterministic solutions days 4-5 (with more weighting on the GFS/ECMWF) which allowed for a good middle ground placement on the Bering low and the Gulf low. After day 5, increasing ensemble mean weighting was included to help mitigate the late period uncertainty. Did continue to include some smaller amounts of the GFS/ECMWF for added system definition. ...Weather/Hazard Highlights... Low pressure lifting across the eastern Aleutians into the Bering Sea will bring light to moderate precipitation to parts of the AK Peninsula and southwest Alaska, along with a period of gusty winds into Friday. Southerly flow ahead of this system and combined with another low lifting towards the Gulf into this weekend will also keep precipitation in the forecast from the Southern Coast to northern Panhandle region with moderate to heavy precipitation possible, but dependent on exact low track. A parade of lows rotating through the base of the mean Aleutians trough will likely keep conditions generally unsettled into early next week from the Aleutians to the Peninsula. Elsewhere, most of interior central/eastern Alaska should remain mostly dry through the period besides some light precipitation associated with weak troughing this weekend. Above average temperatures should prevail across much of Alaska into early next week, both for daytime highs and overnight lows. The warmest anomalies are expected to be over the northern and western parts of the state where daytime highs 10-20 degrees (and locally higher) are possible. The exception to this will be across the Panhandle and southeastern Mainland where near or below average temps are expected due to increased onshore flow and periods of upper level troughing. Santorelli Hazards: - Heavy precipitation across portions of southern mainland Alaska, Thu-Fri, Mar 3-Mar 4. - Heavy precipitation across portions of the Alaska Panhandle and southeast mainland Alaska, Sat, Mar 5. - High winds across portions of southwest mainland Alaska and the Aleutians, Fri, Mar 4. 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