Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 728 PM EDT Sat May 25 2024 Valid 12Z Wed May 29 2024 - 12Z Sun Jun 02 2024 ...Overview... A couple of rounds of upper lows and surface low pressure systems will track across the Bering Sea and Aleutians into the northeast Pacific for the latter half of next week into next weekend, spreading some precipitation to the Southern Coast of Alaska. Upper ridging to the north and east should promote mild to warm temperatures over the Interior with some lighter convective showers. ...Guidance Evaluation and Preferences... Model guidance is fortunately rather agreeable with the larger scale systems. An upper low and an associated surface low will be located over the eastern Aleutians to Alaska Peninsula as the period begins Wednesday and is likely to meander there for a bit, but then looks to get kicked east into the northeast Pacific later Thursday into Friday. Just some minor spread is seen in the models with this system. Upstream, another upper low is forecast to eject from Kamchatka by Thursday and continue east across the Aleutians or vicinity for late week. This potentially deeper upper low should also have a stronger surface low with it near the western Aleutians, but looks to weaken somewhat as it moves east. These upper and surface lows do have more spread in the guidance compared to the first feature, but still within reason for the medium range. GFS runs show the eastward track faster by Friday-Saturday compared to the ECMWF and CMC. Ensemble means are faster than the EC/CMC, but seem like they may be merging the second low system from the Bering and the first northern Pacific system. The timing of the low track will make a difference with if/when the related energy merges with the northern Pacific low, and the details of this interaction will have to be resolved in future forecasts. Meanwhile, a generally ridgy pattern should be in place to the north across much of the Mainland. With this in mind, the WPC blend used a blend of the deterministic 12Z GFS, ECMWF, and CMC early in the period when that guidance clustered well. As typical, increased the proportion of ensemble means as the period progressed, reaching half the blend by Days 7-8 given the increasing uncertainty. ...Weather/Hazards Highlights... No significant weather hazards are forecast through the period with rain amounts generally remaining light to modest overall. The Southern Coast of the state--across the Alaska Peninsula to the Kenai Peninsula and Prince William Sound to the Panhandle--can expect some precipitation chances given the favorable troughing and expected low tracks, but nothing too heavy. Farther north into the Interior, some convective showers yielding light amounts are possible as well, with most shower coverage in the afternoons/evenings. 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 in the 60s to low 70s from midweek into the weekend, generally around 5-15 degrees above average. The North Slope is likely to be closer to average, with highs just above the freezing mark in the Arctic Coast communities. For the southern coast, temperatures at least for highs are forecast to stay below normal given the troughing and active pattern in place, 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