Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 704 PM EDT Tue Mar 15 2022 Valid 12Z Sat Mar 19 2022 - 12Z Wed Mar 23 2022 ...Overview... The most notable feature over Alaska for the medium range period will be an upper low with possibly multiple centroids at times meandering in the Gulf of Alaska. Initial energy near the Alaska Peninsula combined with an active storm track across the northeastern Pacific will serve to redevelop and reinforce mean low pressure across the Gulf through early next week. A series of low pressure systems will bring a sustained period of unsettled weather through the Panhandle and occasionally up into the southern coast for much of the period. By late period, another low near the Kamchatka Peninsula will swing a cold front through the Aleutians, but a blocky upper ridge setting up near/over Mainland Alaska will probably keep the low from much eastward progression. ...Guidance/Predictability Assessment... On the large scale, the models show fairly good agreement with the pattern, but still present quite a bit of uncertainty at the surface regarding details of low pressure systems in the Gulf and how said systems interact with each other. This shows plenty of differences in strength and position of the lows, which has implications for hazards along coastal regions. Given the small scale nature of these details, it will likely take at least a couple of days to resolve these. Felt it best to use a general model compromise between the 12z runs of the GFS, ECMWF, CMC, and UKMET which seemed to offer a good middle ground and compromise between the possible solutions. By early next week, troughing should begin to amplify more over the Mainland, with a compact embedded low in the Gulf. Prior runs of the ECMWF took this low by mid next week farther east into western North America than the GFS or CMC, but the 12z run today adjusted back westward more in line and usable. Upper ridging building over the Bering Sea will keep another low near the Kamchatka Peninsula from much progression eastward, though the ECMWF is a little bit more aggressive/farther east with the cold front through the Bering/Aleutians which pushes the blocky upper high more into the northern Mainland. The greatest outlier solution is the 12z GFS which breaks off a deep surface low from the main low, sending it south of the Aleutians by days 7-8. This is unsupported by any of the other deterministic solutions. For days 7 and 8, the WPC blend trended towards the ensemble means, with smaller contributions from the ECMWF and CMC for added system definition. ...Weather/Hazard Highlights... Precipitation through the period is expected to focus along southern parts of Alaska given the northern Pacific storm track. South-central Alaska to the Panhandle in particular should see rounds of enhanced precipitation, with varying intensity depending on location of the surface lows and the orientation of the upper trough/low. While precipitation does not appear to be very intense, recent heavy rain/snow across the area could make it more sensitive to additional impacts, and amounts may pick up by early next week. In addition, brisk winds are expected with the approach of a surface low into Saturday with some gusty winds possible across the Panhandle. On the other side of the lows, periods of breezy northerly winds are expected over the Aleutians, along with some chances of snow showers. Snow is also possible for the eastern mainland over the weekend. With plenty of troughing aloft, colder than average temperatures are forecast across the majority of Alaska through the period. The greatest anomalies (10-20 below average) are expected initially across western/southwest Alaska, with a gradual eastward progression into central Alaska this weekend and early next week. Across the North Slope and southeast Alaska, temperatures should average closer to normal. Morning lows, however, may actually be above normal for these same regions through the period, with interior Alaska min temperatures closer to normal. Santorelli 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