A strong system brought strong winds with damage, highway closures and gusts up to 70 mph to the Snake River Plain and Arco desert.
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The episode as NWS PIH wrote it up.
A strong system brought strong winds with damage, highway closures and gusts up to 70 mph to the Snake River Plain and Arco desert.
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 Apr 8, 2:22 AM MST, 8 hours 38 minutes earlier.
Area Forecast Discussion National Weather Service Pocatello ID 322 AM MDT Thu Apr 8 2021 ...WIND EVENT TODAY WILL CREATE DIFFICULT DRIVING FOR HIGH PROFILE VEHICLES AND MAY LEAD TO AREAS OF SIGNIFICANT BLOWING DUST... .SHORT TERM...TODAY THROUGH SATURDAY NIGHT... OVERVIEW: A compact shortwave trough is forecast to drop SE across the nrn Rockies today, with it's base shifting right across the CWA this afternoon/eve. A tightening pressure gradient in the base of the trough, coupled with a 60-70kt 500mb mid-level jet riding down the back side of the trough into it's base, will set the stage for strong/gusty sfc winds for much of the CWA and will be our focus today. While the best chance of precip will reside further north under the main body of the trough, isolated light/low impact rain/snow showers remain possible across the Central Mntns north of Ketchum/Mackay eastward across the Upper Snake north of Idaho Falls and into the ern highlands. Best window for this activity based on the HREF ensemble consensus is 1 PM to 9 PM, perhaps lingering until midnight east of Idaho Falls, but QPF amounts should be very light only supporting up to 1" or so of snow accum where snow can manage to stick. High temps will top out in the upper 40s to upper 50s, near to slightly below climatological norms for early April. WINDS: Expectations for today's wind event have not changed at all. A strengthening 700mb flow will result in a slow increase in sfc winds over the course of this AM. This will be felt first at upper slopes/peaks above the weakening nocturnal inversion, with a more muted response at valley floors at first. Expect a rapid increase in low-elevation sfc winds between 10 AM and noon as the inversion breaks and mixing increases. This afternoon, strong dry-adiabatic low-level sfc-700mb lapse rates of 8.5 to 10.0 degC/km as projected by NAMNest/GFS soundings (maximized up the Magic Valley/Snake Plain corridor) will support strong/efficient mixing with 700mb flow increasing to 40-45kts. HREF mean cloud cover remains pretty limited for most areas, further supporting good destabilization and mixing. We again used a composite blend of 100% NBM everywhere, coupled with 95% ADJMET (NAM MOS) and 80% ADJMAV (GFS MOS) in the Magic Valley/Snake Plain, for the wind forecast, yielding W-SW winds of 25- 35 MPH gusting 45-55 MPH up the ern Magic Valley/Snake Plain corridor into the adjacent highlands to the south/east, and W winds of 15-25 MPH gusting to 45 MPH elsewhere across the CWA. An isolated gust or two over 60 MPH will be possible. The MAV guidance continues to run at the high end of the guidance envelope (10-15kts higher than the MET) and seems to be an outlier compared to nearly all other guidance, so while we're excited about strong mixing, we're not biting off on those values. Manual adjustments were made to bump up speeds/gusts along the I-84 corridor north of Sweetzer Summit which benefits from downsloping off the terrain west of the interstate and often overperforms, and to light up mntn peaks (which of course intrude further into the stronger flow aloft). Anytime we can achieve low-level lapse rates of 9.0 C/km or better, it becomes very likely the atmosphere will be capable of mixing down 100% of the 700mb flow, and our forecast above does this nicely. We don't get to say this often, but confidence in the overall wind forecast and timing today is very high. Our forecast leans closer to the 10m HREF ensemble max for both speeds/gusts, but given the dry environment/lapse rates, we are comfortable with this. The ECMWF EFI continues to light up at 0.7-0.9 suggesting this is an unusual event compared to the past 5-week M-climate period, and every single EC ensemble member continues to exceed 40 MPH gusts for Burley, Pocatello, and Idaho Falls (with many members exceeding 50 MPH for both Pocatello and Idaho Falls). Winds should start trending down around 8-10 PM, but may remain quite breezy especially across the srn highlands through midnight. This remains a SOLID advisory-level event, and the going WIND ADVISORY remains unchanged this AM. PRIMARY IMPACT CONCERNS: Difficult driving for high-profile vehicles is a given today, especially on north-south and NW/SE oriented highways where crosswinds will set up. This is a common hazard for our advisory events. The BIG potentially high-impact but very low- confidence wildcard in the forecast remains BLOWING DUST. While areas like Idaho Falls/Rexburg exceeded 0.25" QPF and Pocatello exceeded 0.50" Mon/Tue, most of the rest of the Magic Valley/Snake Plain came in at less than 0.10" (driest as you head SW toward Burley/Twin Falls), and we're in the middle of about a 48-hour-long opportunity to dry out. Widespread plowing is in progress in agricultural areas. IF sfc soils can adequately dry, the potential remains for SIGNIFICANT blowing dust in the advisory area resulting in pockets of visibility near zero and highway closures. Normal trouble spots like I-15 between Idaho Falls and Hamer, I-15 in the Fort Hall area, and I-86 between American Falls and Arbon Valley would be prime candidates. We honestly don't have a great way to monitor soil moisture trends, so our confidence in this hazard will remain low until we can start "now-casting" based on webcams and see how soils are responding today, but we urge everyone to remain very cognizant of this potential hazard. Continue to generously broadbush blowing dust in the forecast grids up the Snake Plain corridor. If you encounter low visibility, slow down, turn on headlights, and use road lines to help guide you. If pulling over, pull off the road as far as possible in a safe location. LESSER IMPACT CONCERNS: Given the sub-warning wind speeds/gusts currently forecast, a lack of leaves on the trees, and a climatologically "normal" wind direction from the WSW, any tree damage and power outages should remain very isolated and be less of a concern with this event. While they can't be ruled out, these impacts don't usually become widespread at these speeds. Loose outdoor objects may blow around, and should be secured by late AM. FRIDAY AND SATURDAY: Another break between systems is forecast Fri as a shortwave-style "tongue" of high pressure ridging slides across the nrn Rockies, bringing plenty of sunshine and highs nudging a few degrees warmer compared to today. Forecast confidence is high. Sat, we repeat everything all over again as yet another shortwave trough drops across the nrn Rockies bringing a few light/low-impact rain/snow showers to mtn areas north of the Snake Plain and another round of potentially advisory-level winds/blowing dust. Didn't get as cute with this forecast yet with the focus on today's system, but did run a similar NBM/MAV/MET composite blend to capture the wind gradient in the terrain while lighting up the Magic Valley/Snake Plain corridor where the MAV/MET performs well. At a glance, 700mb flow looks SLIGHTLY stronger compared to today's event, but low- level lapse rates may be a bit weaker, so we'll see how all the applicable parameters trend. Soils will be drier by Sat, so it's possible the blowing dust threat will be higher. It will be interested to see how today unfolds with respect to calibrating our expectations and confidence for Sat. - KSmith .LONG TERM...SUNDAY THROUGH NEXT THURSDAY... Consensus has come together with keeping East Idaho under the influence of weak troughing Sunday behind main low and wind event Saturday. Reinforcing shortwave drops through BC/Alberta Canada through the panhandle early in the week, though there are differences in timing and depth between GFS, ECMWF and ensemble means. Even the clusters are struggling with difference scenarios. Regardless, the deterministic solutions are not generating much precipitation or wind over East Idaho with this feature, and the blend has followed this trend. The upper low does appear to close off and wobble around the northern Great Basin/East Idaho for the remainder of the forecast period. There isn't a lot of support for this yet in the clusters, though it is making an appearance. The blend appears to favor weaker trough influence on the eastern borders and drier conditions for the rest of the area. - DMH && .AVIATION... Winds look to be the main impact today with speeds picking up shortly after sunrise and remaining strong through the day. All terminals should expect gusts over 25kts, but the Snake Plain terminals KBYI/KPIH/KIDA will see the worst with gusts exceeding 40kts through the afternoon. Blowing dust may be an issue, especially with spring agricultural activity starting in many areas. However, given recent precipitation, there is not enough confidence to put BLDU and restricted visibilities in the terminals yet. We may see a few showers across northern higher terrain, which may include KDIJ so will keep VCSH for the afternoon and evening. Gradient turns northwest after sunset with winds remaining breezy but significantly less windy. High pressure returns for Friday with continued VFR conditions and less wind. - DMH && .PIH WATCHES/WARNINGS/ADVISORIES... Wind Advisory from 10 AM this morning to 10 PM MDT this evening for IDZ051>058-062. &&
The national radar mosaic for the moment the first event began.
4 high wind. Local standard time, as filed.
A 72 mph wind gust was measured 6 miles northwest of Atomic City at the ITD RWIS weather station at the INL Puzzle site. Several gusts of over 60 mph were recorded including 69 mph at Craters of the Moon and 67 mph at Rover.
A peak wind gust of 68 mph was measured at the Idaho Falls Airport ASOS site. Interstate 15 was closed in both directions from Idaho Falls/US 20 north to Idaho route 33 due to zero visibility in blowing dust. A sheet metal shed was destroyed and blown into a road in Ammon . A large tree was uprooted in Rigby. An Idaho Falls business had part of their roof peeled off. The Idaho Falls fire department reported a tree down on their station near the intersection of 8th St and S Holmes. A power pole was snapped off north of Osgood blocking W 113th north . A sports field light pole snapped off at Sandcreek Middle School in Ammon . A large pine tree was uprooted crushing a pickup truck in Idaho Falls. A power pole was snapped off in Rexburg.
A 62 mph wind gust was recorded at the Dead Man Canyon mesonet site.
The Pocatello ASOS recorded a wind gust of 62 mph. Other sites also recorded over 60 mph. Interstate 15 near Fort Hall had reduced visibility due to blowing dust and a semi tractor trailer blew over. A large highway sign also blew over near Blackfoot. Idaho route 39 had zero visibility between Aberdeen and American Falls around 530 PM.
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, April 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: 953601, 953604, 953605, 953608.