Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 327 PM EDT Mon Jul 15 2019 Valid 12Z Fri Jul 19 2019 - 12Z Tue Jul 23 2019 Upper pattern will feature an upper low in the Arctic Ocean and flat ridging over the Aleutians with lingering troughing just south of the Gulf of Alaska. The models/ensembles show good agreement along 50N with possible weak surface wave development along a wavy stationary boundary. The GFS has been most aggressive with such surface waves but has backed off over recent days. This should stay south of the Panhandle but some runs do track the low and lift the front northward. Much more spread exists out of northeastern Russian into northwestern/interior Alaska. The ensembles have been somewhat split on timing of the breakdown/evolution of the flow near the New Siberian Islands (~140E) and how quickly that moves eastward through the Bering Strait. This influences the weather over the North Slope as weaker surface waves may precede more significant frontal passage. However, consensus does not exist at this point and even it if did the lack of continuity yields lower than average confidence. As such, a blend of the 12Z GFS and 00Z ECMWF with the 00Z NAEFS mean and ECMWF ensemble mean proved to be a good starting point for the first few days before a transition to nearly all ensemble guidance was necessary. The 00Z ECMWF was off in timing compared to most ensemble members out of the Bering and through the interior to render it less useful (but not implausible). 12Z GFS was a bit too deep given the uncertainty. Cooler than average temperatures are forecast for much of the northern half of the state due to the reinforced troughing. Near to slightly above average temperatures are forecast for Southcentral especially away from the higher PoPs. The Panhandle may eventually see a drier pattern but the lingering upper trough may maintain a daily chance of at least light rain. More substantial rain is forecast for the Brooks Range westward toward the Chukchi Sea over a multi-day period. Fracasso 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 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