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NOUS45 KPIH 120113
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Public Information Statement
National Weather Service Pocatello ID
713 PM MDT Tue Jun 11 2024

...NWS STORM SURVEY CONFIRMS DAMAGING THUNDERSTORM OUTFLOW WINDS OF
60 MPH AND A WET MICROBURST WITH WINDS OF 65 TO 80 MPH IN EASTERN
JEFFERSON COUNTY, IDAHO ON FRIDAY, JUNE 7, 2024...

The National Weather Service in Pocatello conducted a storm damage
survey in eastern Jefferson County, Idaho on Saturday, June 8, 2024
to investigate reports, photos, and videos of significant damage
that occurred in association with a thunderstorm during the
afternoon of Friday, June 7, 2024.

SURVEY START: The survey began in Roberts just off of I-15, finding
no obvious damage. Working eastward, the first signs of organized
downed leaf litter/twigs was found in the N 3300 E corridor near and
south of ID-48, just west of Menan and Lewisville, suggesting
stronger sub-severe winds had occurred in this area. All litter and
twigs were strewn to the south of their parent trees and vegetation.
A slight increase in the size and coverage of downed leaf litter,
twigs, and small branches was noted eastward across the Menan,
Midway, Lewisville, and Barlow corridor, but the survey still did
not locate any significant wind damage (although there were public
reports of one tree uprooted in Menan and small tree limbs down in
Lewisville, and Rocky Mountain Power reported wind-related power
outages across these areas).

MAIN CORRIDOR OF DAMAGE: As the survey continued east, a corridor of
significant wind damage was noted stretching from just northwest of
Annis, southeast between Rigby and Lorenzo, ending between North
Yellowstone Highway and the Labelle community. The most significant
damage stretched as far west as N 3700 E, as far north as the Snake
River, as far south as the northern edge of Rigby proper near E 400
N, and as far east as just west of N 4200 E. Within this corridor,
an estimated 50 to 100 trees were either snapped off or uprooted,
multiple trees fell on top of or through homes with varying degrees
of damage, the roofs of several barns and outbuildings were damaged
or blown off, at least a dozen vehicles were significantly damaged
and approximately 20 sheep were killed due to falling trees, power
poles were damaged, multiple roads were blocked, and power outages
were widespread. Some highlights working northwest to southeast down
this corridor...a livestock outbuilding constructed of wooden beams,
wooden poles, and sheet metal was found destroyed along N 3800 E
south of E 800 N just north of Annis, along with multiple trees and
large tree limbs down in the area. Damage is this area was all
laying to the south or southeast, although one large tree limb was
observed to be laying to the northeast not far from the outbuilding,
and the outbuilding itself largely collapsed to the east. A very
large tree was down along E Menan Lorenzo Highway just east of
Annis, and a tree was snapped off at Annis Little Butte Cemetery,
both also laying southeast. The public also reported 4 trees snapped
off and down at the intersection of E 700 N and N 3700 E, with
several pieces of siding removed from a residence and small twigs
and branches impaled into the siding on one side of the residence.
Further southeast, two very large trees were uprooted and laying to
the southeast along N 3950 E just north of Long Island Canal, one
measured at 4 feet in diameter, one measured at 3.5 feet in
diameter, along with 1 power pole down. At least 7 additional trees
were down along Long Island Canal, and a local farmer reported that
approximately 20 sheep were killed due to falling trees in this
area. The survey observed other trees down in the distance on
inaccessible private property at several locations in the area. The
most severe damage of the event was found next along E 600 N between
N 3950 E and N 4062 E, about half way between Lorenzo and Rigby.
Speaking with residents and repair crews from Rocky Mountain Power,
as well as assessing damage visually: 10 power poles were down,
numerous power pole cross arms were broken, and at least 15 large
trees were down...some snapped at various heights and some
uprooted...in this area. Debris covered roads and yards. One large
tree fell through the bedroom of a residence and another split a
mobile home into two sections, with no injuries in either case. All
damage was laying to the east or southeast. Multiple roads in this
area were blocked. Crossing over US-20...an area of significant tree
damage was found at the intersection of N Yellowstone Highway and E
550 N where at least 4 large trees measured at 3 to 4 feet in
diameter were uprooted and down across Yellowstone Highway with
multiple other smaller trees and wires down across the area. All
damage in this area was observed to be laying again to the
southeast, or to the east-southeast. Other public reports from this
area were generally comprised of trees down, including on homes and
vehicles, with multiple vehicles damaged at a wedding at The
Millhouse Venue. Little to no damage was located by the survey
heading north of this corridor across the Snake River along the
Menan Buttes, and damage southward across the City of Rigby
generally decreased to just downed leaf litter, twigs, and small
tree branches.

SURVEY END: Continuing east, the survey found additional large tree
limbs down as far as Labelle along with significant downed leaf
litter and twigs in residential yards, all strewn to the southeast
or east, but damage decreased quickly further south and east of
Labelle. Some downed leaf litter was still evident as far southeast
as the area of ID-48 and 4500 E, which is where the survey concluded
as no larger downed tree limbs or other damage was found southeast
of Labelle.

FINDINGS: The damage from this severe thunderstorm is believed to
have come from two sources or components. First, an outflow boundary
was visible on doppler radar emanating from the south side of the
thunderstorm moving south-southeast, and a couple of the first
reports of small tree limbs down and power outages received by NWS
Pocatello came in timed with this outflow boundary. In addition,
video received via social media showed very strong winds occurring
ahead of the storm itself with no active rainfall. Thus, some damage
across the area was likely due to thunderstorm outflow winds
estimated at 60 MPH. However, multiple videos were also received
showing large trees actively falling during heavy rainfall, and one
resident interviewed during the survey described a "white wall of
water and wind" overtaking his residence which produced the damage
along N 3950 E including the two large uprooted trees on his
property. In addition, damage was strewn to the south out west
toward Menan and Lewisville, then largely to the southeast down the
main damage corridor, and then east-southeast on the eastern edges
of this corridor east of US-20. In addition, the one tree limb
laying to the northeast north of Annis was near the northern edge of
the main damage corridor. While not perfect by textbook standards,
this all suggests a slightly divergent wind damage pattern. Thus,
much of the damage across the area was likely due to a wet
microburst with winds estimated at 65 to 80 MPH. Winds across the
impacted area usually originate out of the southwest, so it should
be noted here that both the outflow and microburst winds were from a
direction abnormal for the area (north and northwest), which likely
exacerbated the degree of damage as the trees are not "hardened"
against winds from these directions. The overall body of damage
reports, photos, and videos received via social media also support
the above findings. Finally, evidence collected during the survey
and via other reports, photos, and videos does not support occurrence
of a tornado. One resident interviewed suggested that the trees
downed along Long Island Canal had actually fallen northward and had
been moved prior to the arrival of the survey team, but additional
corroborating evidence and damage indicators suggesting a tornado
were not found, no photos or videos were received by NWS Pocatello
showing rotation or anything that resembled a tornado, and no
resident accounts of the storm included descriptions of tornadic
activity. All damage is estimated to have occurred between 530 PM
(northwest) and 600 PM (southeast). No injuries or fatalities were
reported.

ACKNOWLEDGEMENTS: The National Weather Service in Pocatello would
like to thank Jefferson County Emergency Management for coordination
on storm impacts and locations to survey, the residents interviewed
during the survey for their time, valuable accounts of the event,
and for granting access to private property, and the public for
submitting hundreds of extremely valuable reports, photos, and
videos of the damage via the US National Weather Service Pocatello
Idaho Facebook page. Regardless of whether you have attended SKYWARN
Spotter Training or not, we would like to remind all residents of
southeast Idaho that any reports and photos of tornadoes, hail, wind
damage, and flooding during or after any weather event play an
extremely valuable role in our warning operations to protect life
and property and for post-storm verification, and are always
encouraged and appreciated as long as they can be obtained safely.

$$

KSmith