Continued push of monsoonal moisture into Idaho caused continued flooding into the first couple of days of August.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS PIH wrote it up.
Continued push of monsoonal moisture into Idaho caused continued flooding into the first couple of days of August.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Pocatello, ID wrote its last area forecast discussion before the first event at Aug 1, 12:56 PM MST, 3 hours 4 minutes earlier.
Area Forecast Discussion National Weather Service Pocatello ID 156 PM MDT Sun Aug 1 2021 .SHORT TERM...Tonight through Tuesday. An area of low pressure extending from Washington through eastern Oregon is working with monsoonal moisture over the region to produce scattered to numerous showers and thunderstorms once again this afternoon. Considerable mid level stratus held back temperatures this morning but there are indications that may be eroding away somewhat. So convection chances for southeast Idaho this afternoon still looks good. Precipitable water values are around 1.25 inches meaning that heavy rain and localized flooding is once again possible this afternoon and evening. A flood watch remains in effect for the southern highlands and central mountains where the best chances for thunderstorms exist. On Monday the low pressure moves east through the Idaho panhandle into western Montana. This will shift the focus for thunderstorms from central and western Idaho into eastern Idaho. Morning cloud cover and debris from overnight convection may hinder development. But models continue to show thunderstorms firing by mid afternoon. Heavy rain once again remains likely under these storms. So have expanded the flood watch to include the Challis/Mackay/Arco zones along with the upper Snake highlands. Still think the potential for flooding in the Snake Plain is low because of the flatter terrain. Although street flooding and ponding of fields is possible and bench areas are vulnerable as well. There is light at the end of the tunnel with models drying us out nicely for Tuesday. Hanging onto a low chance for showers and thunderstorms in the afternoon. With all the moisture around, a random pop up storm is certainly still possible. 13 .LONG TERM...Wednesday through Sunday. The ridge is slipping east Wednesday, allowing for some isolated showers and thunderstorms across western areas to develop. Another bigger round of showers and storms is expected Thursday. These storms have less moisture to work from, so heavy rainfall won't be a widespread risk...but not necessarily zero. The storm track remains just north of us through the weekend. We may see storms near the Montana border, but the bigger story likely will be gusty winds across most of eastern Idaho. Keyes && .AVIATION...Showers and thunderstorms will persist through tomorrow. Right now, we are carrying VCTS/VCSH for most periods. Expect VFR unless a stronger storm passes over a particular airport. Heavy rain has been dropping conditions to MVFR/IFR the past couple of days and would expect nothing different. Some storms will produce gusts over 30kts and small hail as well. Keyes && .FIRE WEATHER...More widespread showers and thunderstorms with heavy rain will continue through tomorrow. With very deep monsoon moisture in place, very heavy rain at times will be the main risk...creating the potential for flooding and debris flows. Stronger storms may also produce gusts over 35 mph and small hail. High pressure builds across Idaho Tuesday and Wednesday, bringing a much drier pattern. HOWEVER, it does appear that we may not be storm free those days. Tuesday, lingering showers and storms are possible generally east of I-15 with more spotty development across 422, 427 and 476. On Wednesday, eastern areas look dry, but isolated showers and storms are possible across the central mountains...and 427. Expect a mix of wet and dry. As another low passes through central Idaho and into Montana Thursday, another round of showers and storms is expected and stronger winds outside of those storms in general. The next low passes to our north over the weekend. We may see a few storms along the Montana border, but the bigger issue may end up being widespread gusty winds. Keyes && .PIH WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Monday evening for IDZ056>064-069- 071>074. Flash Flood Watch from Monday afternoon through Monday evening for IDZ065>068-070. &&
Special Weather Statement National Weather Service Pocatello ID 455 PM MDT Sun Aug 1 2021 IDZ051-052-068-074-075-012345- Arco/Mud Lake Desert ID-Shoshone/Lava Beds ID- Wood River Foothills ID-Big Lost Highlands/Copper Basin ID- Lost River Valleys ID- 455 PM MDT Sun Aug 1 2021 ...SPECIAL WEATHER STATEMENT... At 454 PM MDT, Doppler radar was tracking a strong thunderstorm near Craters Of The Moon, or 18 miles east of Carey, moving north at 5 to 10 mph. Winds in excess of 30 mph and small hail will be possible with this storm. Locations impacted include... Craters Of The Moon. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 4322 11340 4322 11387 4360 11385 4352 11338 TIME...MOT...LOC 2254Z 185DEG 12KT 4334 11358 TW
The Boise radar (KCBX), 140 km away, was scanning. The volume nearest the first event began at 22:58 UTC.
6 flash flood. Local standard time, as filed.
Several inches of mud, rocks and debris moved across Baker Creek road that closed the road. The cause was heavy rain over a burn scar area.
Idaho Transportation Department reported multiple mudslides and rock falls along US 93 between Evans and McKim Creek roads.
Idaho Transportation Department reported a mudslide and running water across Idaho Route 75 between East Fork Rd and Malm Gulch Rd completely blocking the highway.
Idaho Transportation Department reported water running across Idaho Highwy 37 between Lawery Lane and Cow Canyon Road.
A NWS survey found evidence of an extensive mud slide along and across Highway 75 North of Clayton.
Heavy rains caused several rock and mud slides along Trail Creek Road for several days.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2021Every state in 2021This day in weather historyWarnings in Idaho, August 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 977491, 977489, 977493, 977494, 977513, 977529.