Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 710 PM EDT Fri May 05 2023 Valid 12Z Tue May 09 2023 - 12Z Sat May 13 2023 ...Large Gulf of Alaska Storm pattern all next week... ...Overview... The weather pattern next week will be highlighted by a resurgent and large/deep layered low pressure mean position expected to settle over the Gulf of Alaska from early-mid next week into next weekend as stalled by a potent upper ridge in Canada. This will present a maritime hazard and also with enhanced onshore precipitation and wind chances within the multifaceted storm period, with the highest precipitation totals likely to spread from the Alaskan Peninsula, Kodiak Island and Southcentral Alaska during the regular workweek with low proximity to Southeast Alaska heading into and through the following weekend and impulses wrap moisture around the maritime low. ...Guidance Evaluation/Predictability Assessment... There is above normal forecast confidence and continuity for much of this forecast period in a pattern highlighted by a main and reforming multi-day Gulf of Alaska storm. The 12 UTC ECMWF/UKMET/Canadian solutions seem best clustered Days 4-6. The models and ensemble means remain compatible Days 7/8, but GFS/GEFS solutions continue a recent trend of raising heights too much for the mainland over time and were discounted during the WPC/Alaska forecaster collaboration process. This solution favors an overall slightly cooler pattern for the Interior/North Slope than a full guidance consensus to consider for rate of river ice breakup, but still limited precipitation. Overall, prefer a blend at these longer time periods with strong weighting of the ECMWF ensemble mean given steadily growing forecast spread, but also ample ECMWF/Canadian model input that still offer some embedded system validity. ...Weather/Hazard Highlights... A pattern favoring reformation, deepening and settling of low pressure systems into the Gulf of Alaska should lead to a broad area of rainfall along with brisk to strong wrapping/gap winds from the Alaska Peninsula and Kodiak Island into Southcentral Alaska to include likely higher elevation snow and coastal rain, periodically lasting for much of next week. Some easterly component of the flow would provide precipitation enhancement especially along favored terrain of the Kenai Peninsula, Kodiak Island and the Alaska Peninsula. Farther east, periods of deeper moisture influx to fuel enhanced precipitation chances should increase across Southeast Alaska late next week into next weekend, enhanced as potent systems lift/wrap on the eastern periphery of the main low centroid position. This pattern favors below normal maximum daily temperatures across the southern coast of Alaska, but minimum daily values should range closer to normal. Schichtel Hazards: - Heavy precipitation across the Alaskan Peninsula, Kodiak Island and Southcentral Alaska, Mon-Wed, May 8-May 10. - Heavy precipitation across Southeast Alaska, Thu-Fri, May 11-May 12. 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