Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 657 PM EST Fri Jan 14 2022 Valid 12Z Tue Jan 18 2022 - 12Z Sat Jan 22 2022 ...Overview... Today's guidance generally shows an eventual transition toward a pattern that is warmer, and across the far southern mainland/Panhandle wetter as well, by late next week as upper ridging becomes more prominent from near the British Columbia coast northwest into the mainland. However there is considerable uncertainty over some of the specifics of this trend in light of very poor model agreement/continuity in recent days for upper flow details over and near the mainland. Meanwhile over the North Pacific there is a general consensus for an axis of relatively low heights aloft and low pressure at the surface. At least a couple individual individual features within this area will tend to maintain breezy and somewhat unsettled conditions along the Aleutians. ...Guidance/Uncertainty Assessment... Operational runs of the GFS/ECMWF/CMC in the past couple days or so have been all over the place with respect to what becomes of upper trough/low energy currently expected to be near the northwest coast of the mainland as of the start of the period early Tuesday. This suggests below average confidence in any specific solution until guidance can improve its clustering and maintain some run-to-run continuity. Early in the period there is a signal from latest models that some energy within the initial feature may shear eastward while a combination of remaining/additional energy may reinforce the trough and form another upper low over or near the northwestern mainland. The past two ECMWF runs and 12Z CMC (jumping well south of its 00Z run) are most aggressive in bringing a deep upper low into the west-central mainland. The 12Z UKMET is not quite as deep or southeast while the 00Z/06Z/12Z GFS runs pull the energy farther west into the Bering Sea. In contrast the ensemble means show mere troughing over the northwestern mainland after early Tuesday. Interestingly the ECMWF mean has been steadily trending toward lower heights within this trough, or at least delaying how much heights rise on the northern periphery of the upper ridge that builds in from the southeast late in the week, while the GEFS mean has been fairly steady with a stronger ridge extending into the mainland. Overall preference was to start with a blend of operational guidance (GFS represented by the 06Z run since its overall pattern fit better with consensus than the 12Z version) Tuesday into early Wednesday and then start incorporating 12Z GEFS/00Z ECens input so that days 7-8 Friday-Saturday consisted of 60 percent total ensemble weight. Versus yesterday's continuity, the resulting forecast yields a deeper trough/upper low over the northwestern mainland into Thursday but not to the depth and southeastward position of the ECMWF/CMC. Then the feature retrogrades into the Bering Sea in a manner hinted at by the means. The new 12Z ECMWF mean still shows more modest troughing over the northwestern mainland while the 18Z GFS now shows a deep upper low wobbling just south of the Bering Strait after midweek--somewhat east of where the prior GFS runs positioned their features. The aforementioned blend provides reasonable continuity for a system that may track toward or south of the Alaska Peninsula and possibly into or near the Gulf of Alaska around Wednesday-Thursday. GFS/CMC runs show the farthest north/west track for the parent low, with the intermediate blend having the support in principle from the less defined ensemble means. Farther west, an initial system south of the Aleutians should retrograde out of the picture after Tuesday while another system tracking south of it reaches closer to the Aleutians late in the week. There is still quite a bit of spread for specifics of the latter system, favoring the model/mean blend approach. ...Weather/Hazard Highlights... Depending on specifics of the leading North Pacific system, some moisture may reach the Alaska Peninsula already by Tuesday or so. With somewhat less sensitivity to details there should be an increase of precipitation across the southern coast and Panhandle by late in the week as the associated front reaches the area and then flow ahead of an upstream Pacific system brings additional moisture into the region. Amounts could be moderate to heavy over some areas while wind speeds may pick up as well. Elsewhere, portions of the Interior may see light snow in the vicinity of a front draped across the area while North Pacific systems will produce periods of brisk to strong winds and some precipitation along the Aleutians. Currently expect the North Slope and Seward Peninsula to see below normal temperatures for most of the period while above normal readings prevail farther south. In general anomalies for min temperatures should be somewhat warmer than those for max readings. Most areas should see a noticeable warming trend toward Friday or Saturday with the best potential for highest anomalies over Southcentral. The forecast over parts of the central/western mainland is uncertain, with potential for colder readings if the deeper and southeastward side of the guidance spread for the upper trough/low over the northwestern mainland ends up gaining more credibility. Rausch Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Fri, Jan 21. - High winds across portions of the Alaska Panhandle and mainland Alaska, Fri, Jan 21. 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