Frost/Freeze in Lower Columbia Basin, Oregon

The ASOS KHRI recorded temperatures at or below 32 degrees for approximately 12 hours ending at 0935 PDT. The Umatilla RAWS recorded temperatures at or below 32 degrees for approximately 9 hours ending 0829 PDT. The mesonet station CW1075 Boardman recorded temperatures at or below 32 degrees for approximately 7 hours ending 0930 PDT. The mesonet station CW2444 Echo recorded temperatures at or below 32 degrees for approximately 14 hours ending 0930 PDT. Most stations in the zone recorded morning low temperatures below 28 degrees.

Increasing northerly flow reinforced by a cold arctic airmass behind a shortwave trough passage starting October 26th lead to temperatures region-wide dropping well below normal. Overnight temperatures across the lower elevations in the intermountain Pacific Northwest were able to cool well below freezing across much the region for much of the overnight period. This lead to all lower elevation zones experiencing their end of season freeze by the morning of October 28th.