Alaska Heatwave
During mid-June 2025, National Weather Service (NWS) Fairbanks, AK, issued Heat Advisories for the first time over the Alaskan Interior, where above normal temperatures were expected over the region. The newly implemented advisory system for Alaska was a way to help better communicate heat impacts to the general public. An example of a heat advisory issued by NWS Fairbanks, AK, via social media, can be found below.
The prolonged summer heat lead to significant snowmelt and the reduction of existing snow cover over northern Alaska, that included the Brooks Mountain Range. JPSS polar-orbiting satellites observed the snowmelt over the course of two weeks, captured by the VIIRS GeoColor product at 750-m spatial resolution. The daytime animation below shows the reduction of the snow areal extent, while observing fires and smoke, in addition to multiple rounds of convection during the time period. Note, the daytime images were taken each day, between ~19-02Z. Refer to the blue rectangle within the animation.
VIIRS GeoColor observations over northern Alaska from 9-24 June 2025
Another way to view the rapid melting of snow is from the VIIRS Snowmelt RGB at 750-m spatial resolution. The RGB utilizes the VIIRS 1.24 um channel that is not available on GOES satellites, and is highly sensitive to snow properties, such as grain size and relative wetness. In a qualitative way, the VIIRS Snowmelt RGB observes wet/old snow (dark blue colors) over northern Alaska that could lead to increased snowmelt runoff and flood potential. Dry/new snow appears brighter (cyan colors) in the imagery; as the snow ages over time, the imagery reflectance will gradually decrease. Additionally, the RGB differentiates between liquid clouds (white), thick ice clouds (shades of cyan), thin ice clouds (bluish-white) and vegetation (brown/green colors). The VIIRS Snowmelt RGB image comparison below highlights the existing snow cover on 9 June 2025 and the remnant snow cover seen on 17 June 2025.
Comparison of the VIIRS Snowmelt RGB on 9 June and 17 June 2025
