Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 725 PM EDT Sat May 13 2023 Valid 12Z Wed May 17 2023 - 12Z Sun May 21 2023 ...Spring warming to advance eastern to central Interior snowmelt runoff and river ice breakup threats into next week... ...Guidance Evaluation/Predictability Assessment... The 12 UTC GFS/ECMWF converged on a solution near the middle of the full envelope of GEFS/ECMWF ensemble solutions for early to mid-later next week. A composite blend of these models and ensembles was preferred for this time period. Even so, forecast spread remains problematic, but especially heading into next weekend when a switch to a blend of these ensemble means is recommended. This overall forecast strategy maintains reasonably good WPC product continuity despite a pattern still generally with overall below average forecast predictability. The blending of compatible guidance tends to mitigate small-mid scale system variances consistent with predictability. Applied manual edits to ensure sufficient surface low pressure center depths and wind speeds as supported aloft, but otherwise muted by the blending process and forecast spread. ...Overview and Weather/Hazard Highlights... Expect a warming/drying trend over Southeast Alaska next week with ridging at the surface and aloft settling over the region. Upper ridging and warmer temperatures are also forecast farther north into the eastern to central Interior by early next next week that will broadly increase the rate of snowmelt runoff and river ice breakup and lead to flooding threats. Slow pattern translation and uncertain splitting of supporting Bering Sea/Aleutians upper trough energies will also act to bring low pressure systems into mid-later next week to western/southwestern Alaska where enhanced precipitation and winds are locally expected. The channeled poleward feed of moisture on the western periphery of the amplified downstream upper ridge may prove efficient, especially for favored coastal terrain, but also to support a period favorable for scattered precipitation into the Interior as system and upper trough/impule energies work inland. Meanwhile, modest frontal advances and lead triple point developments will work into the northwestern/northern Gulf of Alaska through next midweek to tap the deepened moisture to fuel moderate precipittaion chances from the Alaska Peninsula and Kodiak Island to Southcentral with a potential Kenai Peninsula and vicinity focus. This pattern should also then allow additional organized maritime systems to rotate up across the Gulf of Alaska from the northern Pacific and linger and offer renewed precipitation chances for the Alaskan southern to southeastern coastal tier into late week/next weekend. Schichtel 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