A strong low pressure system swept across the Pacific Northwest initiating severe convection across parts of Southwest Idaho.
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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 strong low pressure system swept across the Pacific Northwest initiating severe convection across parts of Southwest Idaho.
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 Apr 30, 8:01 AM MST, 5 hours 14 minutes earlier.
Area Forecast Discussion National Weather Service Boise ID 901 AM MDT Thu Apr 30 2020 .DISCUSSION...Atmosphere is already unstable as seen by early morning thunderstorms near McCall and Sun Valley. Radar at 8 AM MDT showed scattered showers in Idaho mainly east of McCall - Mountain Home - Owyhee/NV. No echoes is eastern Oregon this morning. Weather should stay quiet until midday. Pacific cold front will move across eastern Oregon around noon PDT, i.e., a little later than previous forecast. Thunderstorms will develop along the front as it moves east into the more unstable air over Idaho this afternoon. Thunderstorms will become strong in western Idaho near the front especially between about 2 PM and 5 PM MDT. SPC again has our area in a marginal risk of severe thunderstorms. The area now covers all of southern Idaho, western Wyoming, southwest Montana, and a small part of Malheur County/OR, i.e., a little east of where SPC had it yesterday. Again, this is a marginal risk, but even that doesn't occur often in our area. Front will exit east early this evening and showers and storms will end. Patchy fog toward morning then dry Friday. No updates. && .AVIATION...VFR. Showers and thunderstorms will become more widespread this afternoon. Periods of MVFR in stronger thunderstorms along with small hail this afternoon. Showers tapering off this evening. Surface winds: generally northwest 10-20 kt with gusts 20- 30 kt, except gusts to 35-50 kt possible near thunderstorms. Winds aloft at 10k ft MSL west to southwest 25-40 kt. Weekend Outlook...Showers and thunderstorms through the weekend. Breezy northwest winds along with a threat of gusty outflow winds from thunderstorms. && ,PREV DISCUSSION... SHORT TERM...Today through Friday night...The atmosphere will remain somewhat unstable through the morning, allowing for continued showers and isolated thunderstorm activity. A cold front will pass through the region today, across SE Oregon mid-morning and entering SW Idaho around noon. Supported by steep lapse rates and cold temperatures aloft, this feature will cause rapid destabilization and provide enough lift for thunderstorm redevelopment across the region this afternoon. The highest instability will set up over southern Idaho, in which storms will form over higher elevations and propagate eastward. Models are consistently hinting at strong storms initiating over the Owyhees and moving into the Snake River Plain, though exact locations and timing remain uncertain. Ample shear will allow for long-track storms capable of producing small hail and outflows up to 50-55 mph. The SPC has issued a marginal risk for severe thunderstorms across SW Idaho and may increase the risk as more data comes in this morning. Showers and thunderstorms will dissipate in the evening while clearing will allow for cooling and patchy valley fog. A chance for showers over higher elevations remains for Friday afternoon, though some showers across higher elevations will linger through Friday. LONG TERM...Saturday through Thursday...Models continue to be in good overall agreement through the extended. The next strong cold front will enter the Pacific Northwest Saturday morning and move across the forecast area through Sunday. Breezy conditions are expected ahead of the cold front along with a threat of showers and thunderstorms over a majority of the region. A secondary wave will push through Sunday and Monday, but little in the way of instability. Therefore removed the thunderstorm threat for that time period but showers are expected. That system will kick eastward Monday, but a threat of lingering showers will continue across the eastern portions of Idaho's central mountains. Well above normal temperatures expected Saturday then dropping below normal Sunday and Monday. The upper ridge will rebuild for the middle of next week and bring well above normal temperatures to all zones. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && www.weather.gov/Boise www.facebook.com/NWSBoise www.twitter.com/NWSBoise DISCUSSION...LC AVIATION.....ST PREV SHORT TERM...AL PREV LONG TERM....CR
The Boise radar (KCBX), 12 km away, was scanning. The volume nearest the first event began at 20:11 UTC.
3 thunderstorm wind, 1 flash flood, 1 hail. Local standard time, as filed.
Streets were flooded due to heavy rain from thunderstorms and stranded cars which lead to road closures in Southeast Boise.
A trained spotter in Oreana reported large hail measuring 1.75 inches.
The ASOS at Boise recorded a wind gust of 61 MPH with numerous reports of wind damage across the Treasure Valley.
The ITD mesonet site at Hammett Hill recorded a wind gust of 63 MPH with reports of wind damage around the area.
The ITD mesonet site north of Gooding recorded a wind gust of 64 MPH with reports of wind damage around the area.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2020Every state in 2020This day in weather historyWarnings in Idaho, April 2020
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: 879902, 879907, 879904, 879905, 879906.