Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 516 PM EDT Sun Apr 23 2023 Valid 12Z Thu Apr 27 2023 - 12Z Mon May 01 2023 ...Heavy rainfall expected late week into this weekend across south-central Alaska... ...Overview... An upper low will drop southwest through the Bering Sea allowing ridging aloft to build across central and eastern AK. A persistent wet pattern is expected across Southcentral Alaska to the southeastern mainland which should pick up in intensity mid next week and continue into the weekend before possibly fading, with rounds of rain also possible for the Aleutians/Alaska Peninsula and the Panhandle. ...Guidance Evaluation/Predictability Assessment... The model guidance was in reasonable agreement into next weekend. A blend of the deterministic guidance was used from Tuesday into Thursday for the pressures, winds, and 500 hPa height pattern. To deal with uncertainty in details of the forecast, increased the use of the 12z NAEFS and 00z ECMWF ensemble mean for the above fields to 40%. This generally maintained good continuity. The remainder of the grids were mostly based on the 19z NBM, with some 12z ECMWF included. ...Weather/Hazard Highlights... Starting mid-week, as the mid to upper cyclone retrogrades and drops slowly through the Bering Sea, the mean flow will become more southerly into south-central AK and bring onshore low as well as a low pressure system on later on Wednesday which will support heavy rainfall particularly across Southcentral Alaska late next week into next weekend and modify the cold air mass inland. Local liquid equivalent precipitation amounts in the 5-10" range in orographically favored spots remain forecast. The remainder of southern AK should remain wet as assorted cyclones impact the AK Panhandle and Peninsula. The various low pressure systems should lead to periods of gales, with the possibility of storm force gusts, across portions of the Gulf of AK and Bering Sea. The northern coast of AK also has the threat of gales late week into the weekend as the pressure gradient tightens over the region. Roth 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