Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 613 PM EST Sun Feb 27 2022 Valid 12Z Thu Mar 03 2022 - 12Z Mon Mar 07 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 (Thursday-Monday). An upper level ridge is expected to build over eastern Alaska and western Canada by Friday and into next weekend, keeping above normal temperatures in the forecast. ...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 Thursday into Friday (day 4-5), a surface low is forecast to lift across the eastern Aleutians and towards the eastern Bering or western Mainland. The past couple of runs of the ECMWF were farther south and east with the low than the rest of the guidance, but the 12z run today came into much better agreement. The ECMWF and the UKMET are both a little farther east/closer to the West coast with the system but a general model blend (between the 12z GFS/ECMWF/CMC/UKMET) seemed to provide a good middle ground solution. By Sunday/day 7, models bring the next low pressure system towards the Aleutians. There are some significant differences in timing and strength of this system as it possibly crosses into the Bering Sea and impacts the west coast again. The GFS is a little bit faster with the energy, while the ECMWF is slower and keeps the low center still south of the Aleutians by the end of the period Monday/day 8. The WPC forecast days 7 and 8 leaned more towards the ensemble means which creates a good middle ground position (although considerably weaker in strength). Some inclusion of the GFS and ECMWF were maintained though just for a little system definition. The 12z CMC was much farther south, even from the ECMWF, with the surface low and also had much weaker ridging over the mainland as well, so it was not included in the blend after day 6. ...Weather/Hazard Highlights... Southerly flow from the Gulf of Alaska will advect moisture northward and thus keep rain and snow chances in the forecast from the Aleutians to the Alaska Peninsula, as a low pressure system lifts northward and then enters the Bering Sea. Periods of moderate to locally heavy rain/snow are possible, along with gusty winds, and the locations of the heaviest QPF will be dependent on the low track. Some at least light rain/mountain snow will likely reach across western Alaska later next week and again next weekend with the next surface low. Central and eastern portions of the Interior should remain dry through the period underneath a building upper ridge. Above average temperatures will dominate much of Mainland Alaska through the period, both for daytime highs and overnight lows. The highest anomalies are forecast over the northern and western parts of the mainland later in the week and into the weekend. The exception to this will be across the Panhandle and southeastern Mainland where near average temps are expected owing to more onshore flow. 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