Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 156 PM EST Sun Dec 16 2018 Valid 12Z Thu Dec 20 2018 - 12Z Mon Dec 24 2018 Models remain very jumpy in a quasi-blocky pattern with several modest closed highs and lows in the high latitudes atop a roaring Pacific jet. End result is a parade of lows without a Grand Marshal and lots of detail uncertainty. Ensembles have at least been better, though naturally less-defined, at maintaining system progression from cycle to cycle so used their agreement as a basis. Main feature will be a slowly retrograding upper low from southwestern/western Alaska Thu/Fri into northeastern Russia next weekend. Again favored the 00Z ECMWF ensemble mean a bit over the GEFS mean as the former typically handles non-zonal flow better. The 00Z ECMWF and some of the 06Z/12Z GFS fit with the ensemble idea and used various weights of those models to form a starting point. Temperatures will slowly rise from below average to near or above average over much of the state (especially eastern areas of the interior) as heights build and lower level temperatures creep upwards. Western Alaska may stay below average under the upper trough until next week. Precipitation will be favored over Southcentral (especially southern/southeastern Kenai) eastward to the Panhandle given the storm track with modest amounts through the period. Ensembles focus most of the QPF into southern British Columbia near the triple point of any given system. Fracasso WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can be found at: http://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif http://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml http://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html