Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 737 PM EDT Fri Jul 31 2020 Valid 12Z Tue Aug 04 2020 - 12Z Sat Aug 08 2020 ...Guidance Evaluation... The WPC Alaskan medium range product suite was primarily derived from a composite blend of now well clustered guidance from the 12 UTC GFS/ECMWF, 12 UTC GEFS/ECMWF ensemble means and the 19 UTC National Blend of Models Tuesday-Thursday. Convergence of these guidance pieces toward a more common solution bolsters forecast confidence for this period. Quickly transitioned to a blend of the now compatible 12 UTC GEFS/ECMWF ensemble means days 7-8 (next Friday/Saturday) amid fast growing forecast spread. The 12 UTC ECMWF ensemble mean has trended toward the GEFS for most features. However, flow evolution/system development at high latitude over the Arctic Ocean is quite uncertain and the ensemble mean blend dilutes most features amid uncertainty. ...Weather Highlights/Threats and Predictability... Energy with a deepened surface low under a supporting closed upper low/trough will transfer downstream into the Northern Gulf of Alaska Tuesday and gradually fill through Wednesday, but enhanced wrapping moisture, wind and rain should spread earnestly into southern/southeast Alaska. This storm will also present a maritime hazard over the Gulf of Alaska. Upstream, guidance has really come together compared to yesterday in depiction of a second deep surface low and closed upper low/trough on the heels of the lead system that is expected to develop and work into the Southern Bering Sea/Aleutians early-midweek. This low progresses into Bristol Bay and the Alaskan Peninsula/Southwest Alaska Thursday, then emerges into the again unsettled northern Gulf of Alaska waters next Friday and Saturday. This system also offers potential for enhanced wind/waves/rains along the track and downstream into southern/southeast Alaska. Schichtel 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: - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Mon-Tue, Aug 3-Aug 4. 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