Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 753 PM EDT Thu Jun 01 2023 Valid 12Z Mon Jun 05 2023 - 12Z Fri Jun 09 2023 ...A stalled deep layer low will bring heavy rain and high winds to the Alaska Peninsula/Southcentral next week... ...Overview/Guidance Evaluation/Preferences... The main feature of note for Alaska's weather next week will be a consolidating upper low (and its surface low reflection) stalling over the eastern Aleutians or so in a blocky pattern. Model guidance for the Monday-Tuesday period varies on timing of the bulk of the energy coming in from the west across the Bering Sea that combines with energy initially sitting near the same area. Yesterday's guidance indicated a slower trend for the combination of these energies compared to the day before, but this slower trend has continued even more so in some recent guidance (looks more like the UKMET from yesterday/Tue that was thought to be a slow outlier). The non-NCEP guidance including the CMC and EC ensemble means especially slowed this energy down while the GFS and GEFS mean continued to be farther east and faster. The 12Z CMC and UKMET were a bit better of a middle ground than the comparatively slow ECMWF (though its older 00Z run was even slower than the 12Z) and the fast GFS. But an even blend of those 12Z ECMWF/CMC/UKMET/GFS models served to create a compromise position. Some ensemble means were added to the blend for the latter part of the forecast period to mitigate any smaller scale differences in the models. But with models agreeable on the eventual position of the upper low, model consensus seemed to be overall better for the latter half of next week compared to the earlier part of the week. East of the Bristol Bay/Eastern Aleutians/Alaska Peninsula low, there may be a bout of ridging across Southeast Alaska around Tuesday-Wednesday after an initial low moves out Monday. Then recent guidance mostly indicates the influence of the main upper low may win out and push this ridge into western Canada by later next week. But upper ridging looks more likely to stay in place through much of the week across the northern Mainland as the ridge axis stretches northwest. The blend described above worked well for these aspects of the forecast too. ...Sensible Weather and Potential Hazards... The heaviest precipitation amounts next week will be from the Alaska Peninsula into Southcentral Alaska and the Kenai Peninsula, as the strengthening deep layer cyclone over the Aleutians brings increasing moisture in the form of an atmospheric river channeling moisture from what is currently Tropical Storm Mawar in the western Pacific. Precipitation is likely to begin early next week and last for multiple days, accumulating to several inches in Southcentral Alaska. Mainly rain is likely though some precipitation could be snow in the highest elevations. Strong winds could also be a threat ahead of the lows especially over marine and adjacent areas, with favored gap wind areas increasing wind speed. Some rain may spread into Southeast Alaska with time, while the northern half of the state could also see increasing precipitation chances by the latter half of next week. A warming trend is in store for areas north of the Alaska Range next week after a cool period in the short range, as the upper troughing over the northern Mainland lifts out and warm front moves north. Temperatures should generally warm to above average on Monday and beyond in the lower elevations, though the higher elevations of the Brooks Range may take longer to moderate. Afternoon highs will likely rise into the 70s for lower elevations of the Interior for Monday-Friday, with lows perhaps staying in the low 50s by midweek. However, the upper low and the coincident rain and cloudiness chances could keep high temperatures down below normal along the southern coastal regions. Southeast Alaska may warm somewhat around Tuesday-Wednesday, but could cool again by late next week depending on whether the upper low's influence extends that far east. Tate Hazards: - Heavy rain across portions of mainland Alaska, Mon-Tue, Jun 5-Jun 6. - High winds across portions of mainland Alaska and the Aleutians, Mon, Jun 5. 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