Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 630 PM EDT Wed Jul 21 2021 Valid 12Z Sun Jul 25 2021 - 12Z Thu Jul 29 2021 ...Guidance/Predictability Evaluation... The synoptic pattern during the period is forecast to undergo a change from the stagnant cutoff upper low in the Gulf of Alaska (gradually filling in) to more pronounced upper troughing developing over the Bering Sea extending into the Aleutians. This pattern shows average to above average clustering with the latest model guidance including the deterministic ECMWF/GFS/CMC/UKMET. The main uncertainties lie with the potential development of stronger surface low late in the period. The deterministic solutions show varying scenarios but confidence is increasing that a deeper low will approach the Bering Sea late in the period. This could result in some unsettled weather for the Aleutians and western mainland region but details are murky at this point. For this cycle, the days 4-5 blend were comprised of the 12Z ECMWF/GFS/CMC/UKMET while given the increasing model spread for days 6-8, a heavier blend of the ECENS/GEFS was used while the deterministic ECMWF was included as well. ...Weather/Threats Highlights... The main precipitation and unsettled weather will be focused across the Aleutians and western mainland throughout the period as a series of low pressure systems impact the region. The systems for this weekend and early next don't appear to be too significant and hazardous at this time but late in the forecast period (Tuesday/Wednesday next week), a potential deeper/stronger low could drop into the Bering Sea and lead to higher waves and heavier precipitation. Otherwise, generally below normal temperatures are expected across the mainland through the period, particularly in the Far North. Taylor Hazards: No significant hazards are expected over Alaska during this forecast period. 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