An incoming low pressure system created conditions favorable for thunderstorms on this day. Some of the storms became severe with large hail.
Every event with a place to put it. Tap one for its entry below.
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 MFR wrote it up.
An incoming low pressure system created conditions favorable for thunderstorms on this day. Some of the storms became severe with large hail.
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 Medford, OR wrote its last area forecast discussion before the first event at May 30, 7:34 AM PST, 3 hours 6 minutes earlier.
Area Forecast Discussion
National Weather Service Medford OR
834 AM PDT Sat May 30 2020
.DISCUSSION...So far this morning the forecast appears on track.
Two areas of impactful weather are anticipated. The first will be
heavy showers, with embedded thunderstorms likely from the
Cascades west. Rain rates in the common showers are expected to be
around 0.2"/hr. The embedded convective elements could increase
these rates in excess of 2"/hr for brief periods of time; as storm
motion is faster paced. The rain rates in these convective
elements will be enough to cause ponding along roadways, localized
urban flooding and decreased visibility for drivers.
The previous shift also noted the appearance of back building.
Backbuilding is a common pattern that can lead to flooding and is
likely to cause rapid rises in creeks and small streams. Areas of
backbuilding can currently be observed over Del Norte county in N.
California, at an area of diffluence. This region will shift
north and eastward through the morning, as the low tracks towards
Mt. Shasta.
Also of concern is the risk for severe thunderstorms in northeast
Klamath county and northwest Lake county. SPC has placed this
region in a slight risk for severe. This threat will be mainly in
the morning, with storms developing after noon having a lower
probability of being severe. The main threat with these fast
moving storms will be strong winds in excess of 50mph. A reminder
that these winds are not tied to the immediate storm, outflow can
travel long distances with much reduction in wind speeds. There
is a hail threat, but lapse rates still do not appear favorable.
Only the shear EBWD around 60 kt and most unstable CAPE around
1500-2000 J/kg. Hail is anticipated to generally be subsevere
between pea and nickle sized, but severe hail 1" (quarter sized)
is possible. -Miles
&&
.AVIATION...For the 30/12Z TAF Cycle...Showers and thunderstorms are
ongoing over most locations west of the Cascades this morning.
Shower and storm activity will be on the increase during the morning
hours as the low approaches the Pacific Northwest. Some storms may
produce strong wind gusts and outflows. Outside of storm activity,
MVFR ceilings with pockets of IFR ceilings will prevail this morning
along the coast with VFR ceilings to the east.
MVFR will likely prevail for most of the afternoon as showers and
storms increase in coverage. These lower ceilings will probably
continue into the evening hours, although pockets of clearing are
possible overnight.
-Smith
&&
.MARINE...Updated 830 AM PDT Saturday 30 May 2020...High and steep
seas will continue through this morning. Conditions will improve
later today as a low moves through the area. As the low moves in,
look for showers and the chance for thunderstorms with gusty winds
and heavy rain. Gusty north winds and steep to very steep seas will
return Sunday and persist through much of next week. Keene
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 8 PM PDT this evening for ORZ030-031.
CA...Wind Advisory until 8 PM PDT this evening for CAZ085.
Pacific Coastal Waters...Small Craft Advisory until 11 AM PDT this morning for
PZZ350-356-370-376.
Hazardous Seas Warning until 11 AM PDT this morning for PZZ376.Special Weather Statement National Weather Service Medford OR 1012 AM PDT Sat May 30 2020 CAZ080-081-083-ORZ026-028-301800- North Central and Southeast Siskiyou County CA- Central Siskiyou County CA-Western Siskiyou County CA- Siskiyou Mountains and Southern Oregon Cascades OR-Jackson County OR- 1012 AM PDT Sat May 30 2020 ...SIGNIFICANT WEATHER ADVISORY FOR NORTH CENTRAL SISKIYOU... SOUTHWESTERN JACKSON AND SOUTHEASTERN JOSEPHINE COUNTIES UNTIL 1100 AM PDT... At 1011 AM PDT, Doppler radar was tracking a strong thunderstorm near Hornbrook, or 12 miles northeast of Yreka, moving northwest at 30 mph. Winds in excess of 40 mph will be possible with this storm. Locations impacted include... Pilot Rock, I 5 Siskiyou Summit, Mount Ashland Snow Park, Kennedy Meadows, McKee Bridge Recreation Site, Woodrat Mountain, Grouse Gap Snow Park, Cantrall Buckley County Park, Squaw Lakes Recreation Site, Hilt, Hornbrook and Ruch. This includes the following highways... Highway 96 in California near mile marker 95, and between mile markers 101 and 105. Highway 238 in Oregon between mile markers 22 and 31. Interstate 5 in Oregon between mile markers 1 and 4. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. Persons in campgrounds should consider seeking sturdy shelter until this storm passes. && LAT...LON 4189 12232 4175 12247 4212 12324 4233 12302 TIME...MOT...LOC 1711Z 126DEG 41KT 4186 12246 MCB
Special Weather Statement National Weather Service Medford OR 1050 AM PDT Sat May 30 2020 CAZ081-083-084-ORZ026-028-301830- North Central and Southeast Siskiyou County CA- Central Siskiyou County CA- Northeast Siskiyou and Northwest Modoc Counties CA- Siskiyou Mountains and Southern Oregon Cascades OR-Jackson County OR- 1050 AM PDT Sat May 30 2020 ...SIGNIFICANT WEATHER ADVISORY FOR NORTH CENTRAL SISKIYOU... SOUTHEASTERN JACKSON AND SOUTHWESTERN KLAMATH COUNTIES UNTIL 1130 AM PDT... At 1047 AM PDT, Doppler radar was tracking a strong thunderstorm near Juanita Lake Campground, or 22 miles east of Yreka, moving northwest at 35 mph. Pea size hail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Pilot Rock, I 5 Siskiyou Summit, Mount Ashland Snow Park, Howard Prairie, Juanita Lake Campground, Emigrant Lake, Hyatt Lake Campground, Siskiyou Summit, Camp Creek At Iron Gate Lake, Copco Lake and Howard Prairie Recreation Area. This includes the following highways... Highway 66 in Oregon between mile markers 4 and 29. Interstate 5 in Oregon between mile markers 1 and 12. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. Lightning is not currently observed with this storm, but should be anticipated. && LAT...LON 4183 12205 4171 12223 4210 12275 4231 12240 TIME...MOT...LOC 1747Z 139DEG 30KT 4184 12221 MCB
Special Weather Statement National Weather Service Medford OR 1110 AM PDT Sat May 30 2020 ORZ026-028-301900- Siskiyou Mountains and Southern Oregon Cascades OR-Jackson County OR- 1110 AM PDT Sat May 30 2020 ...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL JACKSON COUNTY UNTIL NOON PDT... At 1109 AM PDT, Doppler radar was tracking a strong thunderstorm near Fish Lake, or 16 miles northeast of Ashland, moving northwest at 25 mph. Half inch hail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Shady Cove, Butte Falls, Willow Lake, Lost Creek Lake, Dodge Bridge Jackson County Park, Casey State Park, Fish Lake, Joseph Stewart State Park, Rogue Elk Park and Trail. This includes the following highways... Lake of the Woods Highway 140 in Oregon between mile markers 6 and 28. Highway 234 in Oregon between mile markers 16 and 17. Highway 62 in Oregon between mile markers 12 and 34. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. && LAT...LON 4236 12233 4227 12252 4259 12293 4275 12266 TIME...MOT...LOC 1809Z 141DEG 23KT 4237 12248 SK
The Medford radar (KMAX), 126 km away, was scanning. The volume nearest the first event began at 18:42 UTC.
2 hail. Local standard time, as filed.
Large hail damaged vehicles. This occurred at milepost 8 on the Silver Lake Highway (Oregon 31).
A member of the public reported 1.75 inch hail. It hailed for approximately 15 minutes, with the hail damaging vehicles. Minor street flooding and mudslides in town.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2020Every state in 2020This day in weather historyWarnings in Oregon, May 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: 884162, 884161.