A series of thunderstorms from a slow moving upper trough brought heavy rain and localized flooding to the Magic Valley.
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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 BOI wrote it up.
A series of thunderstorms from a slow moving upper trough brought heavy rain and localized flooding to the Magic Valley.
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 Boise, ID wrote its last area forecast discussion before the first event at Aug 18, 1:08 PM MST, 1 hour 52 minutes earlier.
Area Forecast Discussion National Weather Service Boise ID 208 PM MDT Sun Aug 18 2024 .SHORT TERM...Tonight through Tuesday night...Isolated thunderstorms are expected to develop by 3 PM MDT today along the Idaho/Nevada border due to increased instability, moisture, and shear ahead of an approaching embedded shortwave. The most favorable conditions for storms are expected east of a line from Mountain Home to Banner Summit through the evening. Surface- Based CAPE values around 300 J/KG and 0-6 KM shear near 40 KTS suggest organized storm development is likely across southern Twin Falls County and the Western Magic Valley, with a 30% chance of occurrence. Stronger storms or clusters may produce outflow winds up to 50 MPH, blowing dust, and brief heavy rain. There’s a 20% chance that this activity could shift into the central Idaho Mountains later, mainly south of Banner Summit. For Monday, the weather pattern remains largely unchanged with an upper-level low to the west and a ridge over the Four Corners region. Temperatures will stay in the upper 80s to low 90s in the valley. However, monsoonal moisture is expected to reach further north, bringing a slight 20% chance of thunderstorms from the western Magic Valley to eastern Valley County Monday afternoon and evening. By Tuesday, the upper-level ridge is forecasted to shift further east, leading to slightly lower temperatures in the upper 80s and pushing monsoon moisture out of the forecast area. However, increasing Pacific moisture and dynamics could provide a slight 15% chance of thunderstorms over the higher terrain of Baker County in southeast Oregon Tuesday afternoon. Smoke may return to the valleys in the mornings as early as Monday, with light diurnal winds expected. The latest HRRR model shows less smoke than previous runs, but recent fires, particularly the Middle Fork Complex fires in the Boise mountains, have been very active, trapping smoke in the mountain valleys. There’s at least a 30% chance of a smoky commute in the Treasure Valley on Monday and Tuesday mornings. .LONG TERM...Wednesday through Sunday...As a weak longwave trough continues to influence the Pacific Northwest on Wednesday, a stronger, closed upper low will move south along the coast of southwestern Canada, reaching the Pacific Northwest by late Thursday. The weakening initial low will pass to the north, leaving only a slight chance of showers and thunderstorms over the higher terrain of Baker County. Otherwise, conditions should remain dry with temperatures slightly below normal. By Thursday, as the new upper low moves south along the coast from Washington to Oregon, moisture is expected to spread farther south and east into eastern Oregon, bringing a chance of precipitation to most of Baker County, far northwest Malheur County, and much of Harney County. The low will reach northern California on Friday, leading to at least a slight chance of showers and thunderstorms across most of the area. Deterministic models are now in better agreement, showing the low center moving through the forecast area between Saturday and Sunday. Ensemble models largely support this, with 62% of members predicting the low will pass through on Saturday and 29% on Sunday. The extended forecast currently favors the majority ensemble solution, suggesting the low will move through Saturday into early Sunday. As a result, the chance of precipitation increases and extends across the entire area. By Sunday, the low should be moving northeast, leaving only the northern higher terrain with a significant chance of showers and thunderstorms worth mentioning in the forecast.. && .AVIATION...VFR, except localized MVFR/IFR and mountain obscuration in the Idaho mtns due to wildfire smoke. Thunderstorms near KTWF/KJER, producing outflow winds up to 35-45 kt 18/21z to 19/03z. Surface winds: Variable 5-15 kt. Winds aloft at 10kft MSL: generally S 15-35 kt. KBOI...VFR. Light smoke/haze may return Monday morning (30% chance). Surface winds: NW 5-10 kt becoming light variable by 08z && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.twitter.com/NWSBoise SHORT TERM...JDS LONG TERM....JDS AVIATION.....JDS
Special Weather Statement
National Weather Service Boise ID
315 PM MDT Sun Aug 18 2024
IDZ016-030-182200-
Southern Twin Falls County ID-Western Magic Valley ID-
315 PM MDT Sun Aug 18 2024
...A STRONG THUNDERSTORM WILL IMPACT SOUTH CENTRAL TWIN FALLS COUNTY
THROUGH 400 PM MDT...
At 314 PM MDT, Doppler radar was tracking a strong thunderstorm over
Rogerson, or 15 miles north of Jackpot, moving northeast at 20 mph.
HAZARD...Wind gusts up to 50 mph and penny size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
This strong thunderstorm will be near...
Rogerson around 320 PM MDT.
Hollister around 340 PM MDT.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4217 11475 4253 11460 4242 11428 4240 11429
4210 11452
TIME...MOT...LOC 2114Z 203DEG 16KT 4221 11460
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH
BWSpecial Weather Statement
National Weather Service Boise ID
326 PM MDT Sun Aug 18 2024
IDZ016-182200-
Western Magic Valley ID-
326 PM MDT Sun Aug 18 2024
...A STRONG THUNDERSTORM WILL IMPACT CENTRAL TWIN FALLS AND
SOUTHWESTERN JEROME COUNTIES THROUGH 400 PM MDT...
At 326 PM MDT, Doppler radar was tracking a strong thunderstorm over
Filer, or near Twin Falls, moving northeast at 10 mph.
HAZARD...Wind gusts up to 50 mph and penny size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
This strong thunderstorm will be near...
Twin Falls and Filer around 330 PM MDT.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 4242 11451 4252 11472 4278 11460 4264 11427
TIME...MOT...LOC 2126Z 210DEG 7KT 4254 11457
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH
BWThe national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
Twin Falls County Sheriff dispatch office reported flooding near a construction zone on mile marker 70 on eastbound Interstate 84. This impacted construction activities and slowed traffic in the area.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2024Every state in 2024This day in weather historyWarnings in Idaho, August 2024
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: 1206097.