Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 654 PM EST Tue Feb 07 2023 Valid 12Z Sat Feb 11 2023 - 12Z Wed Feb 15 2023 ...Overview... This weekend, upper troughing looks to be atop western Alaska, spilling shortwave energy into a couple of Gulf of Alaska surface lows 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. Into the first half of next week, an upper trough/low is forecast to track through the northern Pacific and could produce potentially strong low pressure at the surface, which may affect the Aleutians, but with a lot of uncertainty in the latitude of the storm track. ...Model Guidance/Predictability Assessment... Model guidance shows general agreement at the start of the period Saturday with a weak upper low centered near the Seward Peninsula. Meanwhile a surface wave could be present over the Alaska Peninsula or so, as favored by the GFS/CMC and their ensemble guidance, while the 00Z EC ensemble centers a low farther west. Another surface low farther southwest appears in the GFS and CMC runs, while the ECMWF indicated a low in between these two possible features. Aloft, shortwave differences still abound as they stem from the upper low and spill toward the southeast. Regardless of these initial differences, by Sunday the surface lows seem to merge near the Gulf of Alaska and may deepen a bit, leading to the aforementioned potential for precipitation and winds. The WPC forecast overall preferred a two low solution (less of the ECMWF/ECens solutions) but still incorporated some, especially since overall they seemed to share a common pattern farther north. Thus the early part of the period was based on a majority deterministic blend of the 12Z GFS/ECMWF/CMC and minority of the ensemble means from the EC and GEFS. As has been true in recent days, the upper trough/low and a possibly strong surface low counterpart coming through the Pacific early-mid next week show fairly good agreement in the timing of the track eastward, but with less agreement on the latitude. While the 12Z GFS and ECMWF happened to agree somewhat well on a surface low track south of the Aleutians (but possibly close enough to affect the Aleutians) across the northern Pacific, ensemble member low plots have significant spread. While hopefully the GFS/ECMWF agreement is not just a fluke, did temper the forecast blend with increasing amounts of ensemble mean guidance by days 7-8 to about half. Primarily the ECens mean was used for greater definition of the upper and surface features compared to the relatively flat/weak GEFS mean (an indicator of model spread within the GEFS). ...Weather/Hazard Highlights... The most likely storm track during the period will tend to focus the most active weather from the Aleutians through the southern coast and Panhandle. Over the weekend, an initial low pressure system and another reinforcing it will be present in the Gulf of Alaska, directing a fetch of Pacific moisture from the Alaska Peninsula and Southcentral Alaska and especially into the Panhandle. Locally moderate to heavy precipitation is possible, but currently expect amounts at most locations to stay below hazardous thresholds on a daily basis. Multi-day totals could be meaningful though, especially over the Panhandle. 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 may become more active across the Aleutians by Monday and shifting into Southcentral Alaska Tuesday-Wednesday. Precipitation amounts and winds will vary dependent on the eventual low track, but the majority of guidance suggests at least some enhancement of winds and precipitation in those areas. Additionally, light snow is possible across the western/southern mainland this weekend into 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. Tate Hazards: - High winds across portions of mainland Alaska, Sun-Mon, Feb 12-Feb 13. 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