Thunderstorms in Grant county on Sunday, May 20 produced heavy rain and small hail. One storm produced a funnel cloud as observed by a member of the public.
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The episode as NWS PDT wrote it up.
Thunderstorms in Grant county on Sunday, May 20 produced heavy rain and small hail. One storm produced a funnel cloud as observed by a member of the public.
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 Pendleton, OR wrote its last area forecast discussion before the first event at May 20, 9:10 AM PST, 1 hour 20 minutes earlier.
Area Forecast Discussion...Updated National Weather Service Pendleton OR 1010 AM PDT Sun May 20 2018 Updated Aviation Discussion .SHORT TERM...Today and tonight...A moist southerly flow over the region in advance of an approaching upper level trough. Remnants of convection from California and Nevada is being lifted north across eastern Oregon this morning by the approaching trough producing showers. The trough will add some additional instability to the atmosphere this afternoon providing a chance of thunderstorms across central to northeast Oregon that will linger into the evening. The trough will be in the process of splitting with the southern portion heading into California creating a closed low. The northern portion of the trough will slowly move into the area overnight for some lingering showers mainly over the far eastern mountains. && .AVIATION...18Z TAFs...Generally VFR conditions are expected through the period with cigs 050-080 over much of the region. Scattered showers and isolated thunderstorms possible through early evening near all sites except DLS/YKM - the bulk of any heavier activity will stay confined to the mountains. Drier conditions are expected Monday in subsidence behind a departing trough. Peck && .PREV DISCUSSION... /issued 459 AM PDT Sun May 20 2018/ SHORT TERM...Today through Tuesday night...A trough of low pressure continues to approach the WA/OR coast, with a weak impulse riding north across eastern OR bringing scattered to numerous showers early this morning. This cluster of showers will move north to extreme NE OR and SE WA in the next 2-3 hours, decreasing in coverage as it moves northward. For later today and tonight, the trough will move onshore later this morning, stretching out this afternoon, and beginning to split tonight. Increasing moisture in southerly flow aloft, along with a shortwave rotating around the trough, will result in a high coverage of showers from central OR to the eastern mountains by this afternoon, slowly decreasing tonight as the trough begins to split. With sufficient instability, will retain isolated to scattered thunderstorms for the higher precip coverage areas. Deep layer shear is not very strong, so do not expect organized strong/severe storms. With rather weak steering flow, some of the storms could produce brief heavy downpours. Clouds and precip will hold temperatures down somewhat for today, with highs in the upper 60s to mid 70s for the lower elevations. Near to slightly above normal low temperatures can be expected tonight. The trough will continue to split Monday, with the latest models showing it cutting off across the southern Great Basin late Monday or Monday night, with ridging building off the WA/OR coast. Precip coverage will decrease, but enough mid level moisture and instability will pool for low chances of mainly afternoon showers and thunderstorms for the eastern mountains. Temperatures will warm to above normal Monday, with rather warm highs in the upper 80s to around 90 Tuesday for the lower elevations. LONG TERM...Wednesday through Sunday...Warm and unsettled weather will continue through the long term period. On Wednesday an upper low will be centered over Idaho and Montana and instability and moisture circulating around the low will create a slight chance of showers over central Oregon and the mountains in the morning becoming a chance of showers and a slight chance of thunderstorms in the afternoon. The lower elevations will have a slight chance of showers though the Columbia Basin will be mostly dry. Rain amounts in the wetter locations in the mountains will be up to two tenths of an inch though most locations will be under a tenth of an inch. Wednesday night a strong closed low will approach the central California coast and develop a transitory ridge over the area through Thursday night though a southwest flow will keep a chance of showers and a slight chance of afternoon and evening thunderstorms over central Oregon and the eastern Oregon mountains. Models have some differences Friday through Sunday but generally have the closed low drifting northwest and coming ashore Saturday night and through our area Sunday. This will keep generally unstable conditions under a south to southwest flow. This will keep a chance of showers and a slight chance of afternoon thunderstorms over central Oregon and the mountains while the lower elevations will have a slight chance of showers. Temperatures will remain well above normal with highs in the mid 80s to lower 90s and in the 70s and lower 80s in the mountains Wednesday through Saturday. Sunday cools to the upper 70s to lower 80s with mid 60s to mid 70s in the mountains. && .PRELIMINARY POINT TEMPS/POPS... PDT 70 53 77 53 / 60 30 10 10 ALW 72 53 79 54 / 60 30 10 10 PSC 75 55 82 56 / 20 10 10 0 YKM 77 52 83 53 / 20 10 0 0 HRI 74 54 81 53 / 40 20 10 0 ELN 74 49 80 50 / 20 10 0 0 RDM 68 39 76 43 / 40 20 10 0 LGD 67 49 72 48 / 70 60 20 10 GCD 65 49 73 48 / 70 60 20 10 DLS 75 52 83 54 / 20 10 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && 91/74/74
The Pendleton radar (KPDT), 169 km away, was scanning. The volume nearest the first event began at 18:32 UTC.
1 funnel cloud. Local standard time, as filed.
From southbound Highway 395, north of Seneca, a member of the public observed a brief funnel cloud from a thunderstorm. The funnel cloud lasted approximately 3 to 4 minutes. Heavy rain and pea sized hail also occurred.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2018Every state in 2018This day in weather historyWarnings in Oregon, May 2018
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: 754838.