Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 645 PM EST Wed Feb 08 2023 Valid 12Z Sun Feb 12 2023 - 12Z Thu Feb 16 2023 ...High winds may affect the Alaska Peninsula/Kodiak Island/Kenai Peninsula Sunday-Monday and the Aleutians Monday-Tuesday... ...Overview... An upper trough pattern will be in place atop much of Alaska through much of next week. Early in the week, a trough/low over western Alaska looks to spill shortwave energy into a Gulf of Alaska surface low that will produce ample precipitation from Southcentral to the Panhandle. On the backside of the low, high winds look to be possible around the Alaska Peninsula/Kodiak Island/Cook Inlet with northwesterly flow for Sunday-Monday. Meanwhile around Monday through midweek, an upper trough/low is forecast to track through the northern Pacific, likely phasing with the northern stream trough. This pattern should lead to much below average temperatures especially for western Alaska, and could produce potentially strong low pressure at the surface, which could affect parts of Alaska with high winds and precipitation. This appears most likely for the Aleutians but may spread into the southern coast as well dependent on the eventual storm track. ...Model Guidance/Predictability Assessment... Despite some smaller scale differences in shortwave energies, 12Z model guidance is generally agreeable regarding the pattern at the start of the period, consisting of a fairly weak upper low centered near the Seward Peninsula while energy stemming from the low spills farther southeast. This supports a surface low in the Gulf of Alaska that shows good agreement. Thus the early part of the period was based on a majority deterministic blend of the 12Z GFS/ECMWF/CMC and minority of the EC ensemble mean. Upstream, the upper low and a possibly strong surface low counterpart coming through the Pacific early-mid next week have some spread in the models/ensembles in terms of track and timing. While over the past couple of days there have mainly been latitudinal differences with the low, some timing issues have arisen as well. The 12Z UKMET and the 06Z GFS were on the fast side of the spread with the low timing, and were not favored. The 06Z GFS also appeared too far south. But most other guidance, specifically the 12Z ECMWF and GFS and CMC as well as the EC/CMC means indicate reasonably good agreement in terms of the low track considering the forecast lead time. They take the surface low south of the Aleutians but likely close enough to affect the Aleutians with winds and precipitation and across the northern Pacific and perhaps as far north as the Gulf of Alaska. GEFS guidance has been less consistent, with ample spread in the ensemble member lows leading to a very weak surface pattern at times and looking flatter aloft too. The 12Z GEFS mean seemed to capture the pattern a little better though. The WPC forecast tempered the forecast blend with increasing amounts of ensemble mean guidance--primarily the better defined EC mean--by days 7-8 to about half to minimize individual model differences. ...Weather/Hazard Highlights... The storm track during the period will tend to focus the most active weather from the Aleutians through the southern coast and Panhandle. A surface low present in the Gulf of Alaska is forecast to direct a fetch of Pacific moisture from Southcentral Alaska and into the Panhandle early in the week. Locally moderate to heavy precipitation is possible especially in the Panhandle, but currently expect amounts at most locations to stay below hazardous thresholds on a daily basis. The northwesterly flow behind the surface lows could create strong gap winds that could be hazardous across portions of the Alaska Peninsula, Kodiak Island, and into the Kenai Peninsula across the Cook Inlet. Precipitation activity is forecast to lighten across the southern mainland into the Panhandle by Monday, but is likely to become more active across the Aleutians by Monday and shifting gradually into Southcentral Alaska and the Panhandle Tuesday-Thursday as a result of upper troughing and surface low pressure tracking eastward through the northern Pacific. Exact precipitation amounts and winds will vary dependent on the eventual low track, but the majority of guidance continues to suggest enhanced winds in the Aleutians at least, as well as precipitation across southern Alaska. Additionally, light snow is possible across the western/southern mainland early next week as the upper trough develops. While Alaska sees generally a mix of above/below normal temperatures for the weekend, the upper trough developing over the western/southern mainland will likely lead to a return of below normal readings early next week, first spreading into the southwestern part of the state and then eastward through much of next week. But the southwestern mainland should keep the greatest anomalies in temperatures and are likely to be 20-30F below average in terms of lows and highs, perhaps locally even lower. Tate Hazards: - High winds across portions of mainland Alaska, Sun-Mon, Feb 12-Feb 13. - High winds across portions of the Aleutians, Mon-Tue, Feb 13-Feb 14. - Much below normal temperatures across portions of mainland Alaska, Sun-Wed, Feb 12-Feb 15. 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