Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 648 PM EST Sun Feb 11 2024 Valid 12Z Thu Feb 15 2024 - 12Z Mon Feb 19 2024 ...Overview... The large-scale upper pattern over Alaska late this week will consist of an amplified ridge and embedded high meandering over the Yukon/Southeast Alaska, gradually relaxing into early next week. Mean troughing will be in place farther west from the western Bering Sea to the Aleutians, with heights lowering further by next weekend as an upper low comes overhead and supports a Bering Sea surface low/frontal system. Mean southerly flow will also produce well above average temperatures across most of the state, especially during the latter part of this week. ...Guidance Evaluation and Preferences... Model guidance is reasonably agreeable on the synoptic scale, at least with the persistent amplified ridge aloft. There is more variability with shortwaves and surface lows/fronts that track across the Bering Sea and western Alaska as well as the northern Pacific in this pattern, even early in the period. The ensemble means fortunately remain generally well clustered. But deterministic models have waffled quite a bit with their performance. In today's 12Z models, the ECMWF seemed to be an outlier in bringing energy and a surface low northward across the Alaska Peninsula into Bristol Bay Friday-Saturday, not matching the ensemble means or other deterministic guidance. The older 00Z ECMWF seemed more in line. By the weekend into early next week, there is quite a bit model variability with an upper low and its surface reflection coming eastward atop the Aleutians and potentially slowing. The CMC does not close off the upper low quite as much and thus does not allow it to go as far east as other guidance. Meanwhile GFS runs extend energy farther southeast and show a surface low tracking over/just south of the Aleutians by Monday, unlike other models/ensembles that keep the low north. Interestingly the 12Z ECMWF seemed reasonable with this upper and surface low. Once again the ensemble means seemed like the best way to lean toward for the forecast. These differences to the west also affect the potential to weaken the ridge to the east but perhaps break off a mid-upper high just northwest of the mainland, which does not show good consensus yet. Arctic flow differences also contribute to the disagreements there. The WPC forecast incorporated some GEFS and EC ensemble means even for the early part of the forecast given the deterministic model spread. The rest of the model blend was composed of the 06Z/12Z GFS, 12Z CMC, and 00Z ECMWF considering the issues with the 12Z ECMWF. Gradually increased the weighting of the ensemble means to half Day 7 and more Day 8 as spread increased. ...Weather/Hazards Highlights... The bulk of precipitation during the period should focus across the Alaska Peninsula into the favored terrain north of Bristol Bay, as well as Kodiak Island and the southern Kenai Peninsula. Mean southeasterly flow (easterly and convergent at the surface) with Pacific moisture will support this precipitation. Precipitation types may be varied in some areas, but mostly rain and snow are expected. Multi-day precipitation totals could be several inches in terms of liquid equivalent in localized areas favored by upslope flow in this pattern. In general though, the precipitation amounts should be lower and less widespread compared to earlier this week. Gusty winds are possible at times from the Aleutians to southern Alaska. Into late this week, some precipitation looks to stretch north across the western mainland, but chances for precipitation there will gradually lessen by the weekend as the upper ridge expands over that region. The eastern half of the Mainland and into Southeast Alaska should be quite dry through the period underneath the upper ridge. The ridgy pattern will also favor above normal temperatures across a majority of the state. The greatest anomalies should set up in western to northern parts of the mainland and could be more than 30 degrees milder than normal. Above freezing temperatures are possible well into the southwestern mainland especially on Thursday. Gradual cooling is likely by next weekend but temperatures should still be above average in most places, perhaps reaching around normal for eastern parts of Interior Alaska by Monday. Near normal temperatures are forecast for the Panhandle though as cooler surface high pressure is in place. 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