Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 326 PM EDT Sun Jul 15 2018 Valid 12Z Thu Jul 19 2018 - 12Z Mon Jul 23 2018 ...Guidance and Predictability Assessment... Model and ensemble forecast spread becomes increasingly problematic days 4-7 and overall offers larger than normal continuity change with the timing and amplitude of embeedded systems. This is especially evident over higher latitudes as systems show some potential to dig into the mainland from the arctic. The 00 UTC GFS/ECMWF/NAEFS ensemble means provide max clustering and continuity and their composite was used as the primary starting point for the WPC medium range product suite. ...Weather Highlights and Hazards... A closed low spinning over the Arctic well to the north of the state is expected to force height falls and a wavy/cooling surface front southeastward across the Chukchi Sea and Bering Strait to the North Slope/northern interior. This front and support may linger over the next week and offer some opportunity for scattered precipitation over the region. However, the models are quite varied with shortwave impulse/trough emphasis in a pattern with above normal uncertainty. Meanwhile, an amplified/slowed system progression now evident underneath starts with a lead system cresting the southeastern Alaskan panhandle Thursday along with some early period cooling and precipitation. Upstream, mid-upper level trough energy should support a slowed/organized surface low and frontal system approach to fuel widespread precipittaion across southwest and southern Alaska Thursday into the weekend. Additional shortwave energy slated to dig behind this feature may renew focus down across the Aleutians next weekend, but predictability is low. Schichtel 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