Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 730 PM EDT Wed May 31 2023 Valid 12Z Sun Jun 04 2023 - 12Z Thu Jun 08 2023 ...A stalled deep layer low will bring multiple days of heavy precipitation and perhaps strong winds to the Alaska Peninsula/Southcentral next week... ...Overview/Guidance Evaluation/Preferences... Early next week, an upper and surface low feature looks to move east across Southeast Alaska, with reasonably good model agreement. Farther north, another upper low centered just north of Alaska should continue to shift northeast away from the state early next week, with some minor variations in the position but within typical model spread for this lead time. But the main weather feature affecting Alaska through the period is ample energy over the Bering Sea and vicinity into much of next week. There is likely to be an initial stacked low near the eastern Aleutians Day 4/Sunday before additional energy and low pressure comes into the same region. There are some model differences in the evolution of the combination of these energies, with perhaps a slower trend to combine the two compared to yesterday's forecast and model guidance. Though within this slower trend, the 12Z UKMET did appear to be an outlier as it was even slower than other guidance. Preferred instead the more agreeable 12Z GFS/ECMWF/CMC and the ensemble means for the forecast. This worked well through much of the period and provided an average solution for some waffling model guidance with the positions of the upper and surface lows stalling with time. Gradually increased the proportion of ensemble means with lead time, but was able to maintain a majority deterministic blend through the period with the fairly good synoptic scale agreement. One area of uncertainty that will have to be monitored is the interface of this upper low and ridging farther east over western Canada, and which influence will win out to affect the pattern over Southeast Alaska. ...Sensible Weather and Potential Hazards... A round of light to moderate rain is likely to affect Southeast Alaska early next week coincident with the upper and surface lows moving through. Light to moderate rain (snow in higher elevations of the Brooks Range) could also be in store for parts of the western/central Mainland this weekend, followed by a drier trend for both regions around Tuesday before potentially renewed precipitation chances for midweek. Meanwhile the strengthening deep layer cyclone over the Aleutians into next week should bring increasing moisture flow onshore to the Aleutians first for some moderate rain amounts there, followed by increasing precipitation chances and amounts for the Alaska Peninsula eastward into Southcentral and the Kenai Peninsula. These areas are most likely to see heavy amounts of mainly rain, though with some snow possible in the highest elevations. Precipitation looks to begin Sunday with the heaviest amounts on Monday-Tuesday while some precipitation lasts into the middle of next week, and multi-day rain totals could be several inches for parts of Southcentral Alaska. High available moisture values will be likely as an atmospheric river transports moisture from what is currently Typhoon Mawar. Strong winds could also be a threat ahead of the lows especially over marine and adjacent areas. 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 near average Sunday and 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-Thursday, 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 as the period progresses, though this will depend on whether the influence of the upper ridge reaches that far west or if it remains farther east over Canada. Tate Hazards: - Heavy precipitation across portions of mainland Alaska, Mon-Tue, Jun 5-Jun 6. 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