Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 545 PM EST Sun Feb 23 2020 Valid 12Z Thu Feb 27 2020 - 12Z Mon Mar 02 2020 After getting a better handle on the large scale flow pattern across Alaska during the extended period, guidance continues to struggle with some of the details of individual systems. An upper-level high should gradually weaken across the northern Bering Sea by late in the week. This setup will allow for increasing influence from arctic shortwave energy across much of mainland Alaska, with another round of very cold temperatures likely. Farther south, a very active North Pacific storm track will persist across the Aleutians, with the potential for a deep surface low to move into the southern Bering Sea by next weekend. By day 4 (Thu) a low pressure system is forecast to cross the Gulf of Alaska, bringing potentially heavy precipitation to portions of southern mainland Alaska and the Alaska Panhandle. Guidance shows some consensus that a second wave of low pressure along the trailing portion of this front could move across the far southeastern Gulf of Alaska on Fri, bringing a continuation of precipitation for Southeast Alaska north of the low track. Farther west, models show the potential for a couple low pressure system to affect the Aleutians later in the week, one Thu night-Fri (models show a fairly large degree of spread with this one) and another one (the stronger of the two) Fri night-Sat. Opted to lean toward the UKMET/ensemble means with the leading low, which showed an initially stronger system eventually becoming absorbed in the broader frontal zone before the second low approaches. For the Fri night-Sat system, model differences were a bit less, but solutions did show a fair degree of variability on the timing and track of the system. Ensemble means showed low pressure shifting east toward southern mainland Alaska by early next week, and this was reflected on the day 8 surface prog. In general, the UKMET was weighted relatively heavily along with some use of ECENS/GEFS ensemble means during days 4-5. During days 6-8 (Sat-Mon), due to increasing variability and spread among deterministic guidance, leaned much closer to ensemble means, along with some limited use of the ECMWF, which was reasonably well-centered within the ensemble spread later in the forecast period. 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 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