Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 704 PM EDT Thu Aug 3 2023 Valid 12Z Mon Aug 7 2023 - 12Z Fri Aug 11 2023 ***Very warm temperatures likely over parts of central/eastern Mainland Alaska early next week*** ...Synoptic Overview... An overall blocky upper flow pattern is expected to be in place across the Alaska domain through about midweek, with an anomalously strong upper ridge axis situated 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, followed by a gradual cooling trend. Meanwhile, a strong storm system over the Bering Sea will be slowly weakening going into the first half of the week, and a couple of slow moving but weaker disturbances over the Gulf will likely stay south of the southern Alaska coast, but comes close enough to provide a moist onshore flow with 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 upper ridge over northwestern Canada. Looking ahead to the middle of next week, the guidance becomes a bit more varied across the North Pacific with shortwave energy crossing south of the Aleutians and how it affects the next Gulf low that develops. There has been a trend for a quicker surface low progression compared to this time yesterday. By the end of the week, the CMC becomes displace to the south of the model consensus with the core of the upper low over the eastern Aleutians, where the other guidance supports this being over the Bering Sea. The GFS is slightly stronger with the second Gulf low for the Thursday-Friday time period. Taking these factors into account, the WPC front/pressures forecast is primarily derived from a nearly multi-deterministic model blend through Tuesday, and then less of the GFS and CMC by Wednesday and beyond, and increasing use of the ensemble means to about 40% by next Friday. ...Weather/Hazards Highlights... The high latitude upper ridge over the eastern mainland into the Yukon will support well above normal temperatures, especially over the northeastern quadrant of the state, likely peaking this weekend with Monday being the warmest day of this forecast period. Daytime highs may reach the mid to upper 80s over parts of the Yukon Flats, while the North Slope could see readings rise into the 75-80 degree range. Temperatures are forecast to moderate a little from west to east through the week as the ridge axis slowly breaks down, with highs mainly in the 60s and 70s across most of the mainland by next Friday. Low temperatures should generally be above normal nearly statewide with the greatest anomalies over the North Slope and a few scattered areas farther south. In terms of precipitation, 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. Some localized totals of 2-4 inches are possible across the windward terrain near the coast. Rainfall chances also increase across the southeast Panhandle region to close out the week. Hamrick Hazards: - Heavy rain across portions of southern Alaska, Sun, Aug 6. - Hazardous heat across portions of the North Slope of Alaska, Sun, Aug 6. - Hazardous heat across portions of eastern interior Alaska, Sun-Mon, Aug 6-Aug 7. 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