Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 758 PM EDT Fri Aug 4 2023 Valid 12Z Tue Aug 8 2023 - 12Z Sat Aug 12 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 most of the week, 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. A stronger storm may approach the Alaska Peninsula by next weekend. ...Guidance Evaluation/Preferences and Predictability Assessment... Models and ensembles for the 12Z model cycle are in good overall synoptic scale agreement across the Alaska domain for the Tuesday and Wednesday time period, with some minor timing differences with shortwave energy crossing the north Pacific. Looking ahead to the end of the week, the deterministic guidance is indicating an intensifying surface low south of the Aleutians, with the CMC the strongest solution, and the GFS generally east of the better clustered CMC/ECMWF. The greatest degree of model spread exists over the Gulf region by the Friday-Saturday time period, and the best agreement over interior portions of Alaska. Taking these factors into account, the WPC front/pressures forecast is primarily derived from a nearly multi-deterministic model blend through Wednesday, and then slightly less of the GFS and CMC by Thursday and beyond, and increasing use of the ensemble means to about 40% by next Saturday. ...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 early in the week. Daytime highs may reach the middle 80s over parts of the Yukon Flats, while the North Slope could see readings rise into the 75-80 degree range away from the coast. 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 and Saturday. Low temperatures should generally be above normal across most of the state with the greatest anomalies over the North Slope. 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, with some localized totals of 2-4 inches possible across the windward terrain near the coast. Rainfall chances also increase across the southeast Panhandle region to close out the week, and more widespread rain and wind is possible going into next Saturday from the Alaska Peninsula to the southern mainland coast as a stronger low pressure system may approach the region from the southwest. Hamrick Hazards: - Hazardous heat across portions of eastern interior Alaska, Mon-Tue, Aug 7-Aug 8. 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