Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 604 PM EDT Thu May 11 2023 Valid 12Z Mon May 15 2023 - 12Z Fri May 19 2023 ...Spring warming to advance eastern/central Interior snowmelt runoff and river ice breakup threats next week†...Guidance Evaluation/Predictability Assessment... The 12 UTC GFS has trended more in line with recent runs of the ECMWF as well as recent ensembles and WPC continuity for early-mid next week. A composite blend seems to offer a good forecast starting point. The 12 UTC Canadian/UKMET show less run to run consistency and seem outlier progressive guidance given overall applified larger scale flow. Forecast spread and uncertainty further increase mid-later next week. Accordingly, prefer a quick transition to the reasonably more compatible 12 UTC GEFS/ECMWF ensemble means. Prefer composite blends to mitigate, consistent with predictability, smaller scale variances. 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... A lingering Gulf of Alaska/northern Pacific deep layered low will steadily lose influence by early next week. Expect a warming/drying trend over Southeast Alaska with ridging at the surface and aloft settling over the region through next week. Upper ridging and warmer temperatures are also forecast to build farther north into the Interior and North Slope by next week, which could broadly increase the rate of snowmelt runoff and river ice breakup and eventually lead to potential flooding threats, especially over eastern/central portions of the Interior. To the West, the slow advance and uncertain splitting of supporting upper trough energies will meanwhile act to bring additional low pressure systems across the Bering Sea and with leading triple point development into the northwestern Gulf of Alaska. This combination will spread moderate rains and some enhanced winds from the Aleutians and the Alaska Peninsula to coastal Southcentral, but also well northward, especially across western Alaska. Guidance does not show excessive amounts, but has trended upward, especially for the Kenai Peninsula and vicinity. The northward feed of moisture and Gulf system energies in a channeled conduit into the mainland between the Bering system and the building downstream upper ridge may prove more efficient, especially for favored coastal terrain. Expect some showers will also be scattered across the Interior next week as well and on the increase next week as upper trough/impulse energies work ever inland. Schichtel Hazards: - Much above normal temperatures across east/central Interior Alaska, Sun-Tue, May 14-May 16. 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