Alaska Extended Forecast Discussion National Weather Service College Park MD 737 PM EDT Sat May 10 2025 Valid 12Z Wed 14 May 2025 - 12Z Sun 18 May 2025 ...Overview... An upper low will be present over the Bering Sea as the extended period begins midweek, and troughing should maintain itself through late week into next weekend while the mean upper low sinks south and weakens. Rounds of weak upper ridging are likely to the trough's east. Around Wednesday a shortwave and surface low rounding the base of the trough could lead to enhanced precipitation and winds to the Alaska Peninsula and Kodiak Island, with moderate precipitation expanding into Southeast Alaska Thursday-Friday. ...Guidance Evaluation and Preferences... Model guidance at the start of the extended period is agreeable with the larger scale features of the pattern, including the Bering Sea upper low and an upper ridge from the Gulf into the Mainland. Smaller scale features such as the shortwaves south of the upper low are more questionable with the details. At least models agree on a surface low just south of the Alaska Peninsula on Wednesday, but there is increasing spread on the low track northwest or northeast by Thursday. Models vary with the low's interactions with other Bering and northern Pacific lows along with differences in the energy distribution within the upper trough, including variability on shortwaves tracking east into the Gulf, and these discrepancies persist into late week and the weekend. It is also difficult to determine any outliers in this pattern. Models all seem to show the general idea of a surface low south of the Alaska Peninsula tracking northeastward next weekend, along with a low ejecting from the Kamchatka Peninsula into the western Bering, and the details will continue to be refined with time. In the end, the WPC forecast was based on a multi-model mostly deterministic blend slightly favoring the ECMWF early in the period, with a gradual increase in ensemble means to just over half by Days 7-8 to mitigate the individual model differences. ...Weather/Hazards Highlights... A surface low supported by a shortwave aloft will direct moisture into the Alaska Peninsula and Kodiak Island vicinity on Wednesday, leading to moderate to locally heavy precipitation. Windy conditions are also possible for these areas and Cook Inlet. The precipitation and winds should be below any hazard thresholds though. By Thursday, precipitation is forecast to spread into Southeast Alaska for some moderate amounts into Friday. Rounds of surface low pressure/frontal systems in the Gulf could maintain unsettled weather with precipitation chances all across the southern coast from the Aleutians to Southeast through the period, but amounts should not be very heavy. By the weekend, light precipitation may also expand farther north into the Interior as the upper trough/low reorients and moist inflow reaches farther inland. Meanwhile, Arctic high pressure will maintain cool northeasterly flow across the North Slope and banking up into the Brooks Range. Temperatures will be cooler than average, with highs in the 20s. Downsloping from the Brooks Range southward and periods of ridging aloft should lead to clearer skies for the Yukon Flats to central and eastern parts of the Interior. Warmer than average temperatures are forecast for the western Interior as highs reach the 50s and 60s. The southern third or so of Alaska should generally be warmer than average for lows but near to below average for highs in the moist and cloudy pattern there. Tate 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