Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 740 PM EDT Thu Jul 14 2022 Valid 12Z Mon Jul 18 2022 - 12Z Fri Jul 22 2022 ...Overview... A persistent and anomalously deep (for this time of year) upper low will be in place just north of eastern Siberia toward the Chukchi Sea and meander there through next week, spreading a general troughing pattern across the bulk of Alaska along with cool temperatures. One energetic shortwave and surface low pressure system along with their associated rainfall are expected to track quickly across the southeastern mainland Monday. Then additional rounds of energy south of the low along with a cold front crossing the mainland, as well as meandering and reforming surface fronts affecting the northern tier, will keep a cool and wet pattern in place over the state through much of next week. ...Guidance/Predictability Assessment... While model guidance is quite agreeable with the existence of the upper low and the general theme of spreading troughing across Alaska, the details are more nebulous, particularly with the center of the upper low and some typical differences in shortwaves rounding the low. The initial strong shortwave over southeastern Alaska Monday still shows some slight variability among the guidance but generally within reason. Regarding the larger scale upper low, the ECMWF and the UKMET dive it southward toward the southwestern mainland compared to the GFS/CMC runs by around midweek, affecting surface low placement as well. Meanwhile the 12Z GFS and especially the 12Z CMC start to split off a separate low fartherĀsouth of the main one by next Thursday. Did not favor the phased and south deterministic ECMWF solution since ensembles (especially the ensemble means) did not favor it. Splitting energy like the GFS and CMC indicate for the latter part of the week seems possible but confidence is low at this point. The WPC forecast favored the GFS runs as a good middle ground through the forecast period, with some components of the ECMWF/CMC/UKMET early, and phasing the ECMWF and UKMET out in favor of the EC ensemble mean by around day 6, for a nod toward the farther southeast solutions but less extreme than the deterministic EC. Increased the proportions of the GEFS and EC ensemble means to 70 percent by the end of the period given the increasing model differences. ...Weather/Hazard Highlights... Enhanced rainfall may linger into Monday across southeastern Alaska and into the Panhandle as the southern shortwave and surface low move across the region with moisture streaming in. After that, chances for precipitation continue across the state (from the Aleutians into the Mainland and Panhandle at times) with rounds of energy aloft and frontal systems in place that could focus the moisture. Confidence in the details is low, but current forecasts show that Southcentral Alaska could see enhanced rain amounts around midweek. Precipitation may be in the form of snow in northwestern and north-central Alaska, especially in higher elevations. Given the proximity of the northern upper low spilling troughing into the state next week, expect temperatures to be well below normal in most areas, especially in terms of highs. Low temperatures are forecast to cool as well Monday-Friday for western Alaska and the northern two-thirds of the state, starting in the northwest and spreading inland as the trough encroaches. Chilly lows in the 30s are possible for parts of the Brooks Range and North Slope. Tate Hazards: - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Sun, Jul 17. - Much below normal temperatures across portions of mainland Alaska, Mon-Tue, Jul 18-Jul 19. Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook 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