Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 704 PM EDT Wed Aug 2 2023 Valid 12Z Sun Aug 6 2023 - 12Z Thu Aug 10 2023 ***Very warm temperatures likely over parts of central/eastern Mainland Alaska this weekend into early next week*** ...Synoptic Overview... An overall blocky upper flow pattern is expected to be in place across the Alaska domain through at least early next week, primarily owing to an anomalously strong upper ridge axis that builds northward across northwestern Canada and into the Arctic. This will support unusually warm conditions for much of the lower elevations of the eastern Interior and even across the North Slope region through Tuesday. The strong ridge axis will also limit the eastward progression of a strong storm system over the Bering Sea this weekend, and an upper low over the Gulf will likely stay south of the southern Alaska coast and weaken by Monday, while a second low tries to develop farther south by Tuesday-Wednesday. These low pressure systems will keep scattered showers in the forecast for western and southern portions of the state, and potentially heavy rain for the southern coastal mountain ranges. ...Guidance Evaluation/Preferences and Predictability Assessment... The 12Z model guidance suite has a good overall depiction of the Bering and Gulf lows, and especially the building upper ridge over eastern Alaska for the weekend. Looking ahead to early next week, the guidance becomes a bit more varied across the Gulf with shortwave energy south of the ridge axis and how it evolves south of the upper ridge axis. By the middle of the week, the CMC becomes stronger with a low crossing south of the Aleutians and the ECMWF has a stronger low over the Gulf region, while the GFS is stronger with an inland low over northeastern Alaska. Taking these factors into account, the WPC front/pressures forecast is primarily derived from a nearly multi-deterministic model blend through Monday, and then less of the GFS and CMC by Tuesday and beyond, and increasing use of the ensemble means to about 50% by next Thursday. ...Weather/Hazards Highlights... The amplifying upper ridge over the eastern mainland into western Canada will support well above normal temperatures, especially over the eastern Interior and North Slope regions and likely peaking Sunday. Of particular note, highs may reach the upper 80s and even near 90 degrees over parts of the eastern Interior, especially the Yukon Flats, while the North Slope could see readings rise into the lower 80s. Temperatures will likely moderate a little from west to east early next week depending on how much the ridge breaks down. Elsewhere, the southwestern mainland and the southern coast will likely see a trend toward slightly below normal highs. Low temperatures should be above normal nearly statewide with the greatest anomalies over the North Slope and a few scattered areas farther south. In terms of precipitation, the guidance continues to show a broad area of mainly light to occasional moderate rainfall during the weekend across the far western mainland as a band of deep-layer southerly flow sets up between the advancing eastern Bering Sea front and the upper ridge farther east, and some heavier thundershowers are possible over favored terrain. Onshore flow across the southern mainland coastal areas and also the Alaska Peninsula will favor rounds of moderate to occasionally heavy rainfall next week, and the trend has been for heavier rainfall totals compared to yesterday. Hamrick Hazards: -Hazardous heat across portions of eastern interior mainland Alaska, Sat-Mon, Aug 5-Aug 7. -Hazardous heat across portions of the North Slope of northern Alaska, Sun, Aug 6. 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