Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 744 PM EDT Thu May 23 2024 Valid 12Z Mon May 27 2024 - 12Z Fri May 31 2024 ...Overview... An upper low over the northeastern Pacific early next week will spin down as it slowly moves east. Meanwhile models suggest that another upper low will track meander near the Bering Strait early to midweek. As the week progresses, troughing/energy are likely to spill east into the Bering Sea and Aleutians but with low confidence in the details. ...Guidance Evaluation and Preferences... Model guidance is agreeable with the large upper low and associated surface low over the northeast Pacific gradually drifting east while weakening early through midweek. Meanwhile, models continue to indicate an upper low near the Bering Strait and vicinity as the period begins, but guidance has shifted from a southward track of the low that they showed a day ago to more of a meandering slow westward track into midweek, so trended the forecast that direction. While models are generally agreeable in the low's existence, GFS runs are centered farther northeast with it compared to the more agreeable non-NCEP models. The low's track is also dependent on upstream features; model spread increases upstream as larger scale upper troughing/possible closed lows and vorticity maxima track from the Kamchatka Peninsula eastward across the Bering Sea/Aleutians/Northern Pacific. Fortunately there was some better agreement than a day ago as models generally show a first upper low tracking east across the Aleutians around Tuesday-Wednesday, though still with spread in timing, strength, and track. especially as it moves into the northeastern Pacific late week. Another upper low could reach the western Aleutians by Thursday or Friday. Given all the spread in individual members, ensemble means seem to be having problems resolving the individual systems. Overall, rounds of troughing are likely for the western part of the forecast domain but finer details will have to be resolved in future forecasts. The WPC forecast used a model blend favoring the ECMWF and CMC early in the forecast. Gradually progressed to include more ensemble means to half by Days 7-8 amid the increasing spread and uncertainty. ...Weather/Hazards Highlights... Rain amounts should be modest through the period overall. Southern parts of the Panhandle may see a relative maximum as the northeast Pacific upper low directs moisture there. Light to moderate lower elevation rain and higher elevation snow is forecast in the southeastern quadrant of the Mainland to the Alaska Range in particular, with some light amounts farther west, and by midweek farther north into the Interior. Energies and possible lows/frontal systems pushing through the Aleutians to Alaska Peninsula could lead to periodic precipitation as well. River flooding is a possibility in a couple of spots as ice breaks up--see the Alaska-Pacific River Forecast Center for details. Interior Alaska is likely to see the mildest temperatures across the state, with highs generally in the 60s to low 70s as the week progresses with a warming trend. The Brooks Range to North Slope should also see temperatures warm with time, from around to above the freezing mark for highs in the Arctic Coast communities. For the southern coast, temperatures at least for highs are forecast to stay below normal, with 40s and 50s for the most part. 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