Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 554 PM EDT Sat Oct 17 2020 Valid 12Z Wed Oct 21 2020 - 12Z Sun Oct 25 2020 ...Guidance/Predictability Assessment... Upper ridging is forecast to move into western coastal Alaska from the Bering Sea by midweek next week, blocking much of the Interior from significant precipitation until perhaps next weekend. The 12Z guidance showed decent agreement to start the period Wed-Thu though the 12Z GFS/ECMWF were closer to the ensemble means than the Canadian/UKMET. Differences remained with how to handle a northern central Pacific system next week with some trends to a bit farther south initial position Wed-Thu but then a farther north position next Fri-Sat. By that time, ensembles showed a large amount of east-west spread (GEFS west, ECMWF ensembles father east) as the surface low should move eastward just south of the Aleutians but then turn northeastward due to more ridging into the Gulf than previously forecast. In light of the recent uncertainty, trended to just the 00Z ECMWF ensemble mean for next weekend as it was between the quicker ECMWF and slower/west GFS and GEFS. This was only a bit to the northeast of the forecast yesterday. ...Weather/Threats Highlights.. Upper ridging will bring above normal temperatures to much of the western coastal area and Interior, especially over the North Slope, with dry conditions. Temperatures may be 10-15 degrees above normal along and north of the Brooks Range, and 5-10 degrees above normal north and west of the Alaska Range. Areas of eastern/southeastern Alaska and especially the Panhandle will see near to below normal temperatures as high pressure (around 1040mb) delivers easterly flow to the region. Rainfall will be confined to the Aleutians initially, then spreading across coastal Southcentral areas into southwestern Alaska as the Aleutian system moves along the island chain and perhaps toward Bristol Bay. It will be rather breezy over the southern Bering and Aleutians due to the tightening pressure gradient between mainland high pressure and the low pressure system. 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 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