Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 658 PM EST Sat Feb 10 2024 Valid 12Z Wed Feb 14 2024 - 12Z Sun Feb 18 2024 ...Heavy precipitation and strong wind potential for the Alaska Peninsula into the southwestern mainland could continue into midweek... ...Overview... The large-scale upper pattern over Alaska will consist of an amplified ridge and embedded high meandering over the Yukon/Southeast Alaska from midweek to next weekend. Mean troughing will be in place farther west from the western Bering to the Aleutians. The storm track of shortwaves and low pressure/frontal systems should thus be directed across western Alaska on the interface of the trough/ridge. Mean southerly flow will also produce well above average temperatures across most of the state. ...Guidance Evaluation and Preferences... Model guidance is generally 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. In general the ECMWF and CMC seemed to be the best clustered with the ensemble means with several of these features, as opposed to the displaced GFS runs that did not even match well with the GEFS mean. There is a general tendency for the upper ridge axis to pivot to negatively tilted late week into the weekend. Deterministic models become quite variable with flow over the Arctic Ocean, causing questions in how far north the ridge expands or is suppressed by energy there. Ensemble mean guidance at least provided a more agreeable middle ground with the extent of the ridge. Meanwhile there are some questions with upper and surface lows coming eastward across the Aleutians by late week/weekend. GFS runs remain off but the ECMWF/CMC are quite slow with these lows compared to the better clustered ensemble means. Thus the WPC forecast used a deterministic blend of models early in the period, favoring the ECMWF and to a lesser extent the CMC. Incorporated the ensemble means as the forecast progressed, reaching half Day 7 and more Day 8 given the increasing spread. ...Weather/Hazards Highlights... As the period begins Wednesday, low pressure and frontal systems from the Alaska Peninsula north into the western mainland and moist southerly flow will help to produce moderate to possibly heavy precipitation lasting into the latter part of the week. The heaviest totals should be across the Alaska Peninsula into the favored terrain north of Bristol Bay, with lesser amounts extending farther east toward the Kenai Peninsula and west into the Aleutians, as well as northward over the western mainland. Precipitation types may be varied in some areas. Mostly rain and snow are forecast but some freezing rain is possible where cold air is trapped at the surface and could be hazardous if freezing rain falls on snow. Localized areas where this could occur are yet to be determined. Gusty southerly winds are also possible. The northward and then northwestward expansion of the upper ridge will gradually turn the deep-layer south-southeasterly flow across western Alaska to more from the east-southeast by late next week into the weekend. This gradual counterclockwise turning of the prevailing deep-layer flow will gradually cut off the moisture and result in a gradual lessening threat of heavy precipitation along the southern periphery of Alaska by next weekend. 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 Wednesday. Gradual moderation is likely by next weekend but temperatures should still be above average in most places. 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