The Treasure Valley will remain warm and smoky through Wednesday before a welcome pattern change arrives Thursday, bringing cooler temperatures, increased precipitation chances, and potential flash flooding concerns for the central Idaho mountains through the weekend.
Smoke and heat may decrease a bit in Scott Dorval's video forecast
Smoke and Air Quality Update
Wildfire smoke will continue to be a significant concern through at least Wednesday. In addition to smoke from local fires, westerly transport winds are bringing smoke from numerous large fires burning in central and southern Oregon across the region. While afternoon mixing conditions have improved slightly, nighttime surface-based temperature inversions will continue to cap mixing and allow smoke to settle thickly into valley locations overnight. The Treasure Valley will see patchy to widespread smoke impacts through Wednesday morning before conditions gradually improve.
Residents with respiratory conditions, the elderly, children, and others sensitive to smoke should continue to limit outdoor activities during the morning hours and keep windows and doors closed. Check AirNow.gov or the Idaho Department of Environmental Quality for real-time air quality conditions.
Warm and Dry Through Wednesday with Isolated Storm Chances
Temperatures will remain above normal through Wednesday, with the Treasure Valley seeing highs near 96 degrees Tuesday and 92 degrees Wednesday. A slight 10 to 15 percent chance of isolated thunderstorms will exist near the southern Idaho border Tuesday and again Wednesday afternoon as monsoon moisture lingers near the Nevada-Idaho border. Any storms that develop will be high-based with lightning on dry fuels being the primary concern.
Major Pattern Change Arrives Thursday
The most significant weather story of the week is the pattern change arriving Thursday. A weak upper-level trough will move into the Pacific Northwest late Wednesday, shifting the high pressure that has dominated the region eastward by Thursday. Monsoonal moisture will advect into the region from the south, bringing increased chances of showers and thunderstorms beginning Thursday and peaking Friday and Saturday.
Temperatures will drop 4 to 6 degrees below normal Thursday through Sunday, with Treasure Valley highs falling to the mid to upper 80s. This will be a welcome relief after the prolonged stretch of dangerous heat.
Precipitation Threat: Flash Flood Risk for Central Idaho Mountains
The central Idaho mountains will see the highest potential for accumulating precipitation, with a 40 to 60 percent chance of showers and thunderstorms forecast Friday and Saturday. Heavy rainfall in these regions will bring a flash flood threat, especially over steep and rocky terrain and recent burn scars. Anyone planning to be in the mountains Friday through the weekend should be aware of this threat and have an evacuation plan.
The Treasure Valley will see lower precipitation chances, with a 20 to 30 percent chance of showers Thursday night through Friday. While significant rainfall is not expected in the valley, any precipitation will be welcome after the prolonged dry and hot stretch.
Weekend Outdoor Recreation
The pattern change will make for a much more comfortable weekend outdoors compared to recent weeks. Temperatures in the mid to upper 80s Saturday and Sunday will be much more manageable, though smoke may still linger into the weekend. Those heading into the central Idaho mountains should be aware of the flash flood threat Friday and Saturday and monitor conditions closely. Check the National Weather Service Boise at weather.gov/boi for the latest forecasts and any flash flood watches or warnings.
Looking Ahead
Moisture will taper off late Sunday into Monday as a ridge builds back over the Intermountain West, bringing a return to warm and mostly dry conditions early next week.
Tonight
Patchy smoke before 10pm. Mostly clear, with a low around 60. Light wind.
Tuesday
Patchy smoke after 7am. Sunny and hot, with a high near 96. Light wind.
Tuesday Night
Patchy smoke. Partly cloudy, with a low around 62. Light wind.
Wednesday
Areas of smoke before 7am. Mostly sunny and not as hot, with a high near 92. Light wind.
Wednesday Night
Partly cloudy, with a low around 62. Light wind.
Thursday
A 20 percent chance of showers after noon. Mostly cloudy & cooler, with a high near 86.
Thursday Night
A 30 percent chance of showers, mainly after midnight. Mostly cloudy, with a low around 60.
Friday
A 30 percent chance of showers before noon. Mostly sunny & comfortable, with a high near 87.
Friday Night
A 20 percent chance of showers after midnight. Partly cloudy, with a low around 60.
Saturday
Mostly sunny, with a high near 89.
Saturday Night
A 20 percent chance of showers and thunderstorms. Partly cloudy, with a low around 60.
Sunday
Mostly sunny and a little hotter, with a high near 91.
Sunday Night
Partly cloudy, with a low around 61.
Monday
Partly sunny, with a high near 88.
