Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 549 PM EST Fri Feb 21 2020 Valid 12Z Tue Feb 25 2020 - 12Z Sat Feb 29 2020 After quite a bit of variability among guidance over the last few days on the expected evolution of the large scale flow across Alaska next week, spread among model guidance seems to have reduced somewhat. Some important differences remain, however, even at the larger scales, and the specific details of individual systems continue to be quite murky at best. A relatively weak upper-level ridge axis across Southeast Alaska and western Canada is expected to quickly erode by the middle to end of next week, while a closed upper-level high, separated from the main ridge, should gradually weaken across the northern Bering Sea. This setup will allow for increasing influence from arctic flow across much of mainland Alaska, with another round of very cold temperatures looking likely. Farther south a very active North Pacific storm track will plague the Aleutians and the Gulf of Alaska with frequent low pressure systems spaced 24-36 hours apart. A relatively deep area of low pressure is forecast to move northeast across the Gulf of Alaska Tue-Wed. Models had quite a bit of spread on the timing and exact track of this low. The UKMET was the solution most well-situated in the center of ensemble member spread (and was also relatively close to forecast continuity), this the UKMET was weighted heavily in the forecast during days 4-5. By day 6 (Thu) another similar low pressure system is forecast to enter the Gulf of Alaska, with spread a bit higher than the first - warranting an increase in weighting of ensemble means (ECENS and GEFS). Both of these systems are expected to bring potentially heavy precipitation to portions of southern mainland Alaska and the Alaska Panhandle. Farther west, models show the potential for a couple significant low pressure system to affect the Aleutians later next week (Thu night through Sat). Due to high variability and spread among deterministic guidance, leaned much closer to ensemble means by later next week, along with some use of the ECMWF, which was reasonably well-centered within the ensemble spread. Ryan 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 Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Tue-Thu, Feb 25-Feb 27. 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