The start of the Fall season 2021 will introduce a quite significant temperature change across southern Canada and the northwestern United States, well coinciding with the official calendar dates.
The first significant cold event will also deliver some fresh snow with a notable accumulation across the High Plains and the northern Rockies.Measurable snow (4-7 inches) seems possible across parts of Idaho, Montana and Wyoming (precisely across the higher Wyoming, over the Yellowstone area). Some snow is also likely to accumulate across the higher mountains in Colorado. Also farther north, across the higher terrain of British Columbia and southwestern Alberta in Canada, measurable snow is likely. Up to 10 inches, possibly even a tad more is possible there.
A significant temperature drop is expected for the Northern Rockies and High Plains across Idaho, Montana, and Wyoming.Changing temperatures from nearly 20°C above normal on Saturday to around 10°C below normal on Monday morning, about 36 hours later. A strong cold front will bring much colder temperatures, so Monday and Tuesday morning are forecast to result in the first frost of the Fall Season 2021. Precisely across Wyoming, interior higher Colorado, Montana, Idaho and northern Utah. The lowest morning temperatures could dip into the upper 20s, possibly into the mid-20s°F in some parts of the region. That’s about 40°F lower than Saturday’s forecast High temperature.
Graphics provided by wxcharts.com