This past weekend, we saw our first few forest fires of the season, thanks to ideal fire weather conditions. Both fires are relatively near each other, in the Bull Mountains and Tobacco Roots, between Butte and Bozeman. Transport wind has been from the southwest, so the smoke plume has impacted air quality and visibility in the Helena Valley and Great Falls. However, both locations remain GOOD
A strong ridge of high pressure is responsible for the heat and fire weather that we have experienced for the past few days. Relative humidities have actually been quite a bit higher than we are used to east of the Divide, but strong heating in the afternoons has brought relative humidities below 10% in some places of southwest Montana, with strong winds mixing down to the surface. Such conditions this afternoon have allowed the existing fires to fire up again, with a visible smoke plume seen on satellite (below). Red Flag Warnings are in effect until 9:00 PM for much of the southern half of the state. Across northern Montana, relative humidities have been and will likely stay fairly high. A slight chance for severe storms is in place off the Rocky Mountain Front and across the east.
Tonight, inversions will trap smoke and pull it closer to the surface around Helena, White Sulphur Springs, Great Falls, and the surrounding areas, with air quality becoming MODERATE
by morning. Tomorrow, a low pressure system will finally make its way to the Northern Rockies to help ease some of the heat. Rain and some storms will pass across northwest Montana, including the northern Rocky Mountain Front, starting tomorrow morning. Unfortunately for the drier parts of the state, rain looks less likely anywhere else. A cold front will pass throughout the afternoon, so we will see strong winds again. Transport winds will switch from the south/southwest to the west by Wednesday, and fire concerns will greatly diminish by then.
There are two active wildfires between Butte and Bozeman, and smoke from these fires is impacting locations to the northeast, such as Helena, White Sulphur Springs, Great Falls, and beyond. Low relative humidity and strong winds this afternoon have prompted Red Flag Warnings for much of the southern half of Montana through 9:00 tonight. Smoke will continue to blow over the aforementioned locations this evening, with air quality becoming MODERATE
. Overnight inversions will trap the smoke until a cold front passes and transport wind shifts after Tuesday afternoon.