Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 635 PM EDT Mon Jul 13 2020 Valid 12Z Fri Jul 17 2020 - 12Z Tue Jul 21 2020 ...Overview and Weather/Hazard Highlights... The flow pattern across the North Pacific is forecast to become gradually more amplified during the extended forecast period, with an upper trough strengthening from the Bering Sea south across the Aleutians, and an eastern Pacific ridge attempting to make some headway northward into the Gulf of Alaska. The amplifying flow will allow for increasing potential for arctic upper-level energy to move southward, with an arctic upper low expected to affect the North Slope this weekend, and another upper low forecast to dig south into the western Bering Sea Sun-Mon. The primary impact of the system affecting the North Slope will be on temperatures, with colder temperatures spreading across the region, and highs forecast to be 10-20 deg below average. Through time, cooler temperatures are forecast to spread farther south across much of mainland Alaska by by early next week. In the meantime, a low pressure/frontal system is forecast to move east across the Alaska Peninsula Fri as it weakens, with another frontal wave following quickly behind it by Sat. These systems will keep rounds of showers in the picture from the Aleutians east into southern mainland Alaska from late this week into the weekend, with some potential for gusty winds at the coast. Shower activity may also be enhanced by Fri-Sat across portions of the Interior as moisture interacts with a weak stationary front. One additional aspect of this pattern will be persistent onshore flow across Southeast Alaska (on the northern periphery of the upper-level ridge), with widespread showers this weekend and into early next week. ...Guidance/Predictability Assessment... Model/ensemble consensus showed some improvement over recent days. The 12Z ECMWF/CMC seemed to be the deterministic solutions most well-centered within the overall consensus through much of the extended forecast period. Thus, these solutions were heavily weighted in the WPC forecast initially on day 4 (Fri). After that, a gradual trend toward heavier weight on ensemble means (ECENS/NAEFS) was shown through time, with ensembles comprising a majority of the forecast by days 6-8 (Sun-Tue). Ensemble consensus in terms of the large scale flow pattern across Alaska and the North Pacific was relatively good through day 8, with little in the way of significant pattern changes indicated. Thus, forecast confidence was average to slightly above average. Ryan Additional 3-7 Day Hazard information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php Hazards: No significant hazards are expected over Alaska during this forecast period. 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