Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 750 PM EDT Sun May 26 2024 Valid 12Z Thu May 30 2024 - 12Z Mon Jun 03 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 this 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 Thursday before it is 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 into the western Bering Sea 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. The 12Z GFS and 12Z UKMET were on the fast side in bringing the lows across the Aleutians into the northern Pacific before Saturday rather than on Saturday like the 12Z ECMWF/CMC and 06Z GFS. The ensemble means were closer to the latter cluster, so preferred an in between solution but on the slower side. Additional energy tracking in from the west looks to consolidate in the northeastern Pacific early next week and possibly deepen the surface low. To the north and east of the storm track, a generally ridgy pattern aloft should be in place across much of the Mainland through the week. Model guidance does show some possibility of Arctic energy diving southwest toward or into the northwestern Mainland by next weekend or early next week. GFS runs indicate this lobe of vorticity making it the farthest south but this remains uncertain. Given these considerations, the WPC forecast used a blend of the deterministic guidance early in the period, but preferring the 06Z GFS to the 12Z GFS. As typical, increased the proportion of ensemble means as the period progressed, reaching half the blend by Day 7 and just over half Day 8 given the increasing uncertainty. ...Weather/Hazards Highlights... No significant weather hazards are forecast through the period with rain amounts generally remaining 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. Some localized heavier totals in typically favored areas of terrain are possible, but heavy amounts should not be widespread. Farther north into the Interior, some convective showers yielding light to modest 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 late this week into early next week, 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