On May 11th, afternoon instability increased across southwest Idaho as an upper-level trough moved over the region. This allowed for thunderstorms to develop in the early afternoon.
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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.
On May 11th, afternoon instability increased across southwest Idaho as an upper-level trough moved over the region. This allowed for thunderstorms to develop in the early afternoon. The boundary layer was dry with an inverted-V sounding observed.
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 May 11, 8:55 AM MST, 3 hours 50 minutes earlier.
Area Forecast Discussion
National Weather Service Boise ID
955 AM MDT Sun May 11 2025
.DISCUSSION...Showers and thunderstorms are exiting the western
Magic Valley this morning, otherwise dry and relatively mild
conditions persist. Morning satellite imagery (water vapor and
visible) shows a dry slot and accompanying area of clear skies
passing through SE Oregon and entering SW Idaho. Showers and
thunderstorms will redevelop this afternoon across the higher
terrain of SE Oregon and w-central Idaho. The focus for stronger
storms will again be across s-central Idaho, from the ID/NV border
into the eastern Boise Mountains through early evening. Wind gusts
to 60 mph will be the main threat with hail also possible. The other
area of focus will be across Baker County along a cold front that
advances into SE Oregon this evening. Colder air aloft could make
small hail more likely from storms in this area. Otherwise a breezy
and warm day across the region with winds becoming gusty this
afternoon out of the southwest. Current forecast is on track.
&&
.AVIATION...Mainly VFR. Scattered showers and isolated thunderstorms
will develop this afternoon across S-central ID and NE OR, including
near the Magic Valley terminals and KBKE. Activity will persist
tonight across NE OR and W-central ID. Small hail and outflow gusts
up to 60 mph are possible in storms near the Magic Valley. Surface
winds: SW 10-25 kt with gusts 30-45 kt this afternoon. Strongest
winds along ridges and near NV border. Areas of blowing dust may
reduce visibility. Surface winds becoming SW-NW 5-15 kt by Mon/06Z.
Winds aloft at 10kft MSL: SW 30-45 kt.
KBOI...VFR under mid to high clouds. A 10% chance of showers and
thunderstorms this afternoon. Light surface winds this morning,
becoming S-SW 12-20 kt with gusts up to 30 kt this afternoon,
shifting to W-NW around Mon/03Z this evening.
&&
.PREV DISCUSSION...
SHORT TERM...Today through Tuesday night...An upper-level low
approaching the Pacific Northwest today will continue to provide
favorable conditions for showers and thunderstorms. The main concern
remains the threat of strong wind gusts this afternoon and evening,
particularly across the Western Magic Valley, Camas Prairie, and
Eastern Boise Mountains. Early this morning, radar showed mostly
virga across southwest Idaho with a few lightning strikes observed
in Owyhee County. This activity appears to be tied to a weak
embedded shortwave rotating northeast through the area and should
diminish shortly after sunrise as the wave exits.
Another round of thunderstorms is expected to develop this afternoon
and evening. Overall setup remains similar to Saturday, with deeply
mixed boundary layers and a strong low-level jet supporting the
potential for sporadic severe wind gusts—mainly from Twin Falls
County through the Camas Prairie. Storms are expected to initiate
around 2 PM and move quickly northeast. There is a 5% chance of
gusts reaching 60 mph. Further west, dynamics and moisture increase
significantly across central and northeast Oregon by early evening.
While high-res guidance keeps the strongest instability and shear
north and west of Harney and Baker Counties, a few storms could
drift east into these areas after 6 PM—especially if the upper low
progresses slightly farther east than currently forecast. The
strongest storms will be capable of gusty outflow winds and possibly
small hail.
Strong southwesterly flow aloft (35–50 kt at 10kft MSL) will mix to
the surface starting late morning, leading to widespread windy
conditions through the evening. Winds will be strongest across
southeast Oregon and southwest Idaho south of the Snake Plain, where
gusts of 40–50 mph are expected. Blowing dust will be possible,
particularly along Hwy 95 and Hwy 51. A Wind Advisory remains in
effect for Harney, Malheur, and Owyhee Counties this afternoon and
evening.
On Monday, the upper trough axis pushes inland, bringing an
increasing chance for showers from west to east. Baker and Harney
Counties will see the highest PoPs (60–80%), with lower
probabilities farther east across southwest Idaho due to trough
elongation. Modest instability may support a few thunderstorms over
southeast Oregon Monday afternoon. Winds will remain breezy with
gusts of 20–30 mph. Shower chances linger across higher terrain
Monday night (20–30%) as the upper trough slides into eastern
Oregon. Highs will cool to just below normal. By Tuesday, the upper
trough moves overhead, bringing a 30–50% chance of showers and
thunderstorms. Tuesday looks to be the coolest day of the week, with
valley highs running roughly 10 degrees below normal.
LONG TERM...Wednesday through Sunday...An upper low will exit the
area on Wednesday, and a shortwave on the backside of the trough
will allow for a 20-30% chance of precipitation that afternoon
alongside some breezy NW winds. Lingering instability Wednesday
afternoon could pop up a few thunderstorms in the eastern periphery
of our CWA. With snow levels still 6000-7000 ft MSL light snow
accumulations are possible on higher peaks.
Weak upper level ridging will bring slightly warmer and drier
conditions on Thursday. After the brief break, a weak trough Friday
will lead into another active period. 30% precipitation chances over
higher terrain on Friday increase to 40-60% area wide Saturday
afternoon as deep Alaskan low moves in. This will cool temps after
the brief ridge on Thursday, keeping temps near to a few degrees
below normal through most of the long term.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Wind Advisory from noon today to midnight MDT tonight IDZ015-
029.
OR...Wind Advisory from noon MDT /11 AM PDT/ today to midnight MDT
/11 PM PDT/ tonight ORZ061-063.
&&
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DISCUSSION...DG
AVIATION.....ST
SHORT TERM...JDS
LONG TERM....JMThe Pocatello radar (KSFX), 145 km away, was scanning. The volume nearest the first event began at 19:43 UTC.
5 thunderstorm wind. Local standard time, as filed.
Mesonet station 3251 D4 - Hansen Bridge recorded a wind gust of 79 MPH as a thunderstorm passed over.
Twin Falls airport ASOS measured a wind gust of 61MPH as a thunderstorm passed over.
Mesonet station TT087 Saylor Creek measured a wind gust of 63MPH.
Mesonet station SLDMT 9.8 NW Soldier (UUNET) measured a wind gust of 64MPH as a thunderstorm passed over.
Mesonet station TGFI1 Trail Gulch measured a wind gust of 58MPH.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2025Every state in 2025This day in weather historyWarnings in Idaho, May 2025
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: 1251765, 1251766, 1251767, 1251768, 1251769.