Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 658 PM EST Fri Feb 09 2024 Valid 12Z Tue Feb 13 2024 - 12Z Sat Feb 17 2024 ...Heavy precipitation and strong wind potential early next week for the Alaska Peninsula into the southwestern mainland... ...Overview with guidance evaluation and preferences... Model guidance since yesterday has not shown too much deviation from the overall synoptic pattern evolution theme forecast for the vicinity of Alaska for much of next week. Tuesday should begin with a sheared occluded cyclone skirting just off the west coast of Alaska midst an upper-level ridge extending and expanding northward from the Gulf of Alaska across the mainland and into the Arctic Ocean. The continued northward expansion of the ridge will likely shear the occluded low further apart while pushing it northward into the Arctic Ocean through midweek. The latest ECMWF solution was the slowest guidance regarding the forward motion of the low while the GFS was the fastest, and the CMC somewhere in between. Their ensemble means follow the same theme. On the other hand, the latest ECMWF was the fastest and most aggressive guidance in amplifying and pushing the ridge through eastern mainland Alaska and Yukon Territories toward the Arctic Ocean through mid- and late next week. The deterministic guidance shows quite a chaotic solution over the Arctic Ocean late next week in contrast with a much more agreeable solution for an inverted trough over this area. It appears that given the increasingly amplified upper-level pattern, the more aggressive ECMWF solution is preferred. The northward and then northwestward expansion of the upper ridge will gradually turn the deep-layer south-southeasterly flow across western Alaska early next week to more from the east-southeast by late next week. This gradual counterclockwise turning of the prevailing deep-layer flow will gradually cut off the moist southerly flow directed from the northern Pacific early next week, resulting in a gradual lessening threat of heavy precipitation along the southern periphery of Alaska through next week. ...Weather/Hazards Highlights... Despite some continued model uncertainties with the northward motion of the occluded low just off the west coast of Alaska early next week, a period of heavy precipitation and strong winds can be expected near the southern coastline of the Alaska Peninsula possibly extending northward into portions of the southwestern mainland. Thus today's Days 3-7 Hazards Chart depicts heavy precipitation areas for Tuesday the 13th over the eastern Alaska Peninsula and in favored terrain north of Bristol Bay, with these locations seeing the best overlap of hazardous precipitation potential among the varied guidance possibilities. Wind strength in relation to hazardous criteria will be more sensitive to surface details where the largest threat of high winds should be closer to the coast as depicted on the map. Lesser precipitation amounts should extend farther east toward the Kenai Peninsula and west into the Aleutians, as well as northward over the western mainland. The forecast remains on track for increasing dominance of mid-latitude Pacific low pressure by the latter half of the week, which combined with northwestern Canada into Arctic high pressure, should turn winds through a deep layer of the troposphere more easterly over the Alaska Peninsula and surrounding areas by midweek. This flow will likely maintain some precipitation enhancement by wind-facing terrain but with lighter totals. Expect locations from Prince William Sound through the Panhandle and northward through the eastern mainland to be relatively dry next week. The forecast pattern will favor above normal temperatures over a majority of the state with the highest anomalies over western and northern areas during the first part of next week. High pressure becoming established over northwestern Canada should promote colder/below normal readings over portions of the Panhandle along with some pockets of near to somewhat below normal readings over the eastern mainland. The rest of the mainland should see warm anomalies gradually become less pronounced later in the week as Pacific influence decreases. Nevertheless, the upper ridge may prove to be stronger and tougher to break, thereby maintaining the warmth over northern Alaska into next weekend. Kong/Rausch 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