Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 434 PM EDT Fri May 19 2023 Valid 12Z Tue May 23 2023 - 12Z Sat May 27 2023 ...Synoptic Overview and Guidance Evaluation... Ridging across mainland AK will slowly erode as disturbances round a persistent deep layer cyclone in the southern Bering Sea. The 12Z model guidance suite is initially in decent synoptic scale agreement across the Alaska domain with some minor differences in features. To deal with the small discrepancies, used a blend of the 12z UKMET, 12z Canadian, 12z GFS, and 12z ECMWF for fronts, pressures, and wind early on before blending in some 00z ECMWF and 12z NAEFS ensemble mean thereafter. QPF was an even blend of the 19z NBM, 12z ECMWF, 12z GFS, and 12z Canadian. The remainder of the grids were the 19z NBM with some 12z ECMWF thrown into the mix. Overall, this kept reasonable continuity. ...Sensible Weather and Potential Hazards... A large, slow moving upper low will produce precipitation from the Alaskan Peninsula and the southern mainland coastline to the upper Alaskan Panhandle on May 22nd and May 23rd, with the areas most likely to witness the heavier rainfall totals stretching from the eastern Aleutians and the Alaskan Peninsula to Kodiak Island and Katmai National Park. Precipitation will primarily be in the form of rain, but the higher terrain of Katmai National Park and Katmai Wilderness could receive heavy snow. High water levels due to ice jams and snow melt in both the Yukon and Kuskokwim rivers still pose a threat for additional flooding into next week. Above average spring temperatures will continue for the central/eastern Interior as an upper-level ridge remains in place over northern Alaska into next week. This prolonged period of abnormally mild temperatures is expected to cause additional snowmelt and subsequent rises in water levels that could still be high enough in spots to cause localized flooding. Roth/Russell Hazards: - Heavy precipitation across portions of mainland Alaska, Mon-Tue, May 22-May 23. 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