Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 708 PM EDT Tue Jul 25 2023 Valid 12Z Sat Jul 29 2023 - 12Z Wed Aug 02 2023 ...Heavy rain possible across portions of southwest Alaska late this week into the weekend... ...Pattern overview with Guidance Evaluation/Preferences and Predictability Assessment... The overall upper pattern over Alaska should remain rather blocky through next week as a strong upper high/ridge sets up over the Mainland, with a deep upper low breaking off and sliding into the Gulf and another system (or two) in the Bering Sea. Models show good agreement on the synoptic set up, with lingering differences in the details, particularly later in the period as upper troughing moves into the Bering. The 12z CMC was an early outlier as it maintains a secondary and compact closed low (in addition to the one moving into the Gulf) over parts of the Mainland resulting on overall weaker ridging. This also allows additional energy from the Bering Sea around the middle of next week to edge farther east and into parts of far western Alaska. There is no support from any of the other deterministic or ensemble mean guidance on this scenario and so the 12z CMC was excluded from the WPC blend for today. For today's forecast, used a blend of the 12z GFS/ECMWF/UKMET the first half of the period, and increased to 50% ensemble means by the second half as there were timing and placement differences with a couple of surface lows near the far western Aleutians. ...Weather/Hazards Highlights... Deep southerly flow into western Alaska associated with the cutoff upper low moving across the Peninsula and into the Gulf early in the period will result in an ongoing threat for heavy rainfall across parts of southwest Alaska through at least Saturday. Showers may linger into Sunday, but should be lighter in nature farther to the east and north, depending on the overall strength of the upper ridge. Showers should begin to move into the Aleutians Sunday onward as the next few systems move into the region. The persistent upper ridging over the Mainland should keep temperatures across northern and eastern well above normal. Daytime highs across the eastern Interior could be well into the 80s, to near 90 in some locations this weekend, with some moderation thereafter. Southeast Alaska/the Panhandle region will be quiet and warm through the period. Santorelli 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 - Heavy rain across portions of southwestern Alaska, Fri-Sat, Jul 28-Jul 29. - Hazardous heat across portions of mainland Alaska, Fri, Jul 28. 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