Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 621 PM EDT Mon May 15 2023 Valid 12Z Fri May 19 2023 - 12Z Tue May 23 2023 ...Spring warming to advance Interior snowmelt runoff and river ice breakup and flooding threats this week... ...Guidance Evaluation/Predictability Assessment... The 12 UTC GFS/ECMWF/Canadian and GEFS/ECMWF/NAEFS/Canadian ensemble mean solutions seem much better clustered for Friday into Saturday. A composite model blend was preferred for this time period. Forecast spread then increases significantly in the models and ensembles. The rest of the WPC medium range progs and product suite was then mainly derived from the ECMWF ensemble mean, and to a lesser extent the 12 UTC ECMWF for Sunday-next Tuesday to maintain best possible WPC product continuity despite a pattern with below average forecast 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 warm and dry pattern over Southeast Alaska into later this week under an upper ridge. Upper ridging and warmer temperatures are also forecast farther north across the Interior this week that will broadly increase the rate of snowmelt runoff and river ice breakup that are expected to lead to flooding threats. Please refer to ongoing advisories and watch/warnings from your local weather offices for impacts, details and needed actions. Slow pattern translation and the digging of eastern Bering Sea upper trough/low energies will force deepened short range surface low pressure systems from coastal western/southwestern Alaska back down through the Aleutians late week along with some lingering showers. Meanwhile, this pattern will also support a main rotation of organizing maritime systems to settle from the northern Pacific to across the Gulf of Alaska. These will linger and offer renewed sweeping precipitation chances for the full Alaskan southern to southeastern tier late week into next week, albeit dependent on low positioning that remains highly uncertain in the models and ensembles. Schichtel Hazards: - Flooding possible across portions of mainland Alaska, Thu-Mon, May 18-May 22. 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