Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 646 PM EST Fri Feb 25 2022 Valid 12Z Tue Mar 01 2022 - 12Z Sat Mar 05 2022 ...Overview... A relatively mild pattern is forecast for much of Alaska next week, as southerly flow dominates in between an elongated and reinforced trough across the Kamchatka Peninsula/western Aleutians/Bering Sea and ridging with an axis over northwestern Canada that should build over Mainland Alaska by mid next week. A couple of surface lows should move into the northeast Pacific/Gulf of Alaska while shortwaves rounding the western trough sends a couple of organized surface lows towards the Aleutians. Above average temperatures and periods of light to moderate coastal precipitation are expected with this pattern. ...Guidance/Predictability Assessment... Recent model and ensemble guidance continues to show fairly good agreement on the large scale pattern described above, but struggle with the smaller scale details, especially later in the period. There remain some timing issues with a surface low into the far southern Panhandle, with the UKMET notably slower/south than the rest of the guidance (the 00z ECMWF was slower too, but the 12z run sped up somewhat). For days 4-5, the WPC progs were comprised using a non-UKMET deterministic model blend. Meanwhile, a main upper level low will meander near the Kamchatka Peninsula through much of next week as various shortwaves/upper lows rotate across the western/central Aleutians and into the Bering Sea. Models show good agreement that the first should reach the Aleutians by around next Tuesday, weakening by Thursday. The next system, with model guidance suggesting it should be stronger than the first, will cross the Aleutians on Thursday as it sends a frontal system towards the western Mainland and Alaskan Peninsula. This second system exhibits a fair amount of uncertainty regarding both strength as track. The 00z and 12z ECMWF are notable outliers with this system as they were much faster and farther south with the main energy. Both the GFS and CMC (along with the ensemble means) suggest the system tracks in a more northerly direction across the Aleutians and into the Bering Sea next Friday-Saturday. Given the considerable run to run variations in this system, even compared to previous days, this suggests the evolution of this storm remains highly uncertain. It seems pertinent to lean heavily on the ensemble means later in the period. As such, the WPC blend used increasing percentages of the ensemble means days 6-8, though some inclusion of deterministic models (mainly the GFS) was maintained just for a little added system definition. ...Weather/Hazard Highlights... Moist southerly flow is forecast to keep rain and snow chances in the forecast particularly across coastal areas of the Aleutians and Alaska Peninsula. As the second and stronger of the two surface lows approaches the region by mid-week, a southerly fetch of moisture should increase precipitation chances from the far eastern Aleutians and into the AKPEN and Kenai Peninsula. Moderate to locally heavy precipitation is possible, but of course is highly dependent on timing and strength of the system. A period of gusty winds may accompany this low as well. Some light rain/mountain snow may reach into far western Alaska later next week, but otherwise much of the Mainland should remain dry underneath of a building upper ridge. Above average temperatures will dominate much of Mainland Alaska through next week, both for daytime highs and overnight lows. The highest anomalies are forecast over the northern and western parts of the mainland later in the week, with lows up to 30-40 degrees above normal and highs 20-30 degrees above normal. The exception to this will be across the Panhandle and southeastern Mainland where near to slightly below average temps are expected. Santorelli Hazards: - Heavy precipitation across portions of mainland Alaska, Thu-Fri, Mar 3-Mar 4. 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