Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 658 PM EST Sat Mar 12 2022 Valid 12Z Wed Mar 16 2022 - 12Z Sun Mar 20 2022 ...Overview... The most notable feature over Alaska for the period will be an upper low meandering slowly southeastward over the Alaska Peninsula midweek and eastward across the Gulf of Alaska by next weekend. The initially closed low will interact with an active storm track across the northeastern Pacific to support a series of surface low pressure systems and bring a sustained period of inclement weather through the Panhandle and occasionally up into the southern coasts for much of the week. ...Guidance/Predictability Assessment... Overall model guidance has rather good agreement for a medium range Alaska forecast throughout most of the period. The closed upper low appears well handled by the guidance especially through Wednesday-Thursday as it drifts from the southwest mainland to near Kodiak Island. Thus the WPC forecast was able to use a multi-model deterministic blend led by the 12Z ECMWF early on. By early Friday, the GFS/GEFS runs appeared a bit slower with the upper low as it moves into the Gulf compared to other models, but still with relatively small differences for Day 6. The 06Z GFS does seem to be against the consensus in its handling of the Gulf surface low (farther south) by Friday-Saturday, so did not prefer it there. However, farther west and along the northern Pacific storm track, the 06Z GFS looked better clustered with other guidance than the 12Z GFS with another upper/surface low south of the Aleutians during that timeframe. By next weekend, energy from the northern Pacific storm track and some spilling southward across the Bering and western mainland could both interact with the original upper low, and this leads to more spread in the details overall. But the general idea is there for the upper low to persist over the Gulf, which is shown by the agreeable ensemble means as well as the deterministic guidance though they vary with the specifics. The WPC forecast gradually transitioned a blend of about half GEFS/EC ensemble means and half operational models by Days 7-8, continuing to favor the ECMWF as the model closest to the means with placement of features, but giving some added depth to the systems. The results are similar to continuity. ...Weather/Hazard Highlights... Much of the mainland should see dry conditions during the period, though perhaps with increasing snow showers by next weekend in the eastern mainland, as precipitation is expected to focus along southern parts of Alaska given the northern Pacific storm track. The Panhandle in particular should see rounds of enhanced precipitation, with the heaviest amounts currently expected on Wednesday with the initial surface low. The precipitation will tend to linger through late next week across the Panhandle with rounds of increasing and decreasing intensity depending on location of surface lows, but with perhaps a gradual downward trend overall. While precipitation does not appear to be very intense, recent heavy rain/snow across the area could make it more sensitive to additional impacts. In addition, brisk winds are expected with the approach of the initial low with gusty winds possible for the Panhandle on Wednesday, and possibly again later in the week. On the other side of the lows, periods of breezy northerly winds are expected over the Aleutians. Colder than average temperatures especially in terms of highs are forecast for much of Alaska with troughing aloft, with highs 10-30F below normal for mid-March across the southwestern mainland and Alaska Peninsula on Wednesday, and again there and spreading east for Friday-Sunday as a reinforcing cold front comes through. The North Slope will be the main area that can expect near to above normal temperatures. Meanwhile, the Panhandle should see below normal highs through the period and a mix of above and below normal lows. Tate 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