Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 540 PM EST Sun Dec 15 2019 Valid 12Z Thu Dec 19 2019 - 12Z Mon Dec 23 2019 ...Below average temperatures expected across the Alaska Interior and portions of the North Slope later this week... A blend of the ECMWF/GFS was preferred as a forecast starting point during days 4-5 (Thu-Fri). These solutions were relatively agreeable with respect to low pressure moving east across the Gulf of Alaska during that time frame. Farther west, model consensus has improved with respect to a relatively deep low entering the western Bering Sea on day 4, and the aforementioned blend should resolve this system favorably. Farther north, upper ridging across the arctic is forecast to migrate toward Siberia during the early extended period, allowing arctic shortwave energy to carve out lower heights across the North Slope and the Interior, with many solutions continuing to show an upper low developing across the North Slope by Fri. Solutions continue to show a fair degree of run-to-run variability with this chaotic arctic flow, however, and it may take some time for this to be resolved favorably by the guidance. By days 6-8 (Sat-Mon), deterministic solutions show another wave of low pressure developing along an active North Pacific frontal zone, perhaps nearing the Aleutians by Sat night-Sun. While models agree on the potential for this system, solutions vary widely on the track, timing, and intensity (although a number of solutions suggest the potential for a deep system). Spread among ensemble members suggests that uncertainty with this system is even higher than would be indicated by spread among the deterministic solutions - thus confidence in the forecast specifics surrounding this system is low. Given increased spread during days 6-8, went heavily toward ECENS/GEFS ensemble means during that time frame. This pattern should favor persistent wet conditions across the Panhandle/Southeast Alaska from the middle of the week onward. Precipitation should become more widespread across the Aleutians by next weekend, with the potential for gusty winds if some of the deeper deterministic solutions were to verify (confidence is low at this time, however). Farther north, the growing arctic influence will result in dropping temperatures later this week, with a period of well-below average temperatures expected across the Interior and portions of the North Slope away from the coast. Max temperatures as much as 20 deg F below average are forecast by mid to late this week. Relatively dry conditions should prevail across these regions, however. Ryan Additional 3-7 Day Hazard information can be found on the WPC medium range hazards 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