Increasing surface moisture and shortwave trough embedded in southwest flow aloft lead to the initiation of convection across portions of central OR in the early afternoon. The storms were strong enough to produce hail around an inch across Deschutes and Crook counties.
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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 PDT wrote it up.
Increasing surface moisture and shortwave trough embedded in southwest flow aloft lead to the initiation of convection across portions of central OR in the early afternoon. The storms were strong enough to produce hail around an inch across Deschutes and Crook counties.
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 Aug 2, 9:55 AM PST, 2 hours 35 minutes earlier.
Area Forecast Discussion
National Weather Service Pendleton OR
1055 AM PDT Mon Aug 2 2021
.Updated Aviation Discussion.
.SHORT TERM...Clearing skies across central Oregon, combined with
HREF-suggested MUCAPE values in the 500-1000 J/kg range, ample
surface dew points in the 40s and 50s, and a subtle shortwave
embedded in the SW flow aloft should allow convection to develop
this afternoon and evening across central Oregon. SPC has a
marginal risk out for the region for severe storms, primarily
concerned with the potential for isolated strong downdrafts.
Associated with the thunderstorm threat, a Red Flag Warning is in
effect this afternoon and evening across central Oregon.
Afternoon highs of 90 to just over 100 for the region, highest in
the Basin and adjacent lowlands. Haze and smoke will persist
through the period. 86
.AVIATION...18Z TAFS...VFR conditions across all sites, with the
exception of PSC which is and has been IFR since 11Z due to HZ
producing VSBY's of 1 1/2SM. This should slowly improve this
afternoon but will still hover between MVFR and IFR due to the 2SM
to 3SM VSBY's. PDT/YKM/ALW are expected to drop to MVFR this
afternoon as well for 4SM to 5SM VSBY's. There is also a potential
for isolated thunderstorms for RDM/BDN starting at 20Z. 75
&&
.PREV DISCUSSION... /issued 445 AM PDT Mon Aug 2 2021/
.SHORT TERM...Today through Tuesday...The plume of high
precipitable water air is gradually shifting to the north and east
of the area but a subtle shortwave trough embedded in the sw flow
aloft will help trigger a few thunderstorms in central Oregon by
early afternoon. This activity will then lift newd and weaken this
evening before ending. Forecast Soundings in central Oregon show
moderate instability and a deep mixed boundary layer so gusty
outflow winds will accompany the storms. SPC has the region in a
marginal risk for severe storms today. It will be hot today with
highs 90 to 100 in the lower elevations. A warm night is expected
tonight with lows 65-70 in the lower basins. This will set the stage
for an even warmer day Tuesday with highs in the lower 100s across
the Columbia Basin and adjacent lowlands. An excessive heat watch
will be issued for these areas for Tuesday (and Wednesday). Isolated
thunderstorms will be possible again Tuesday afternoon and evening
across the central and northeast mountains but forcing for upward
motion will be weak and there will be some capping. Haze and smoke
will be around from the area wildfires through the period. 78
Tuesday night into Wednesday, lingering precipitation is possible
across the John Day Highlands into the Blues, but only a slight
risk. High resolution models also show the haze/smoke across the
region beginning to subside, but some lingering across the Columbia
Basin and Yakima Valley region. For now, continue to show a retreat
of the reduced visibilities into Washington followed by a return
into northern Oregon Wednesday evening before the trough pushes
across our area.
Models are then diverging on precipitation chances for Wednesday,
with the ECMWF completely dry, the GFS light on its chances, and the
NAM a bit more excited. Based on earlier trends, it appears models
have dialed back on our expected rain chances for the forecast
region. The National Blend continues to give us at least a 20-30%
chance for the forecast region, so have elected to remain with this
solution for now.
.LONG TERM...Thursday through Monday...With a more progressive
weather pattern developing, the ensemble models are beginning to
have their differences. The ECMWF Ensemble Mean is faster pushing
the first upper level low/trough east Thursday evening and moves the
next low over central BC Friday afternoon resulting in slight
troughiness over WA. Meanwhile, the GFS Ensemble Mean is slower in
pushing the first low/trough east late Thursday night and digging
the next low deeper and farther south resulting in more troughiness
extending into northern Oregon Friday night. PWATs are a little
higher with the second system according to the ECMWF while the GFS
is a little drier. Despite these differences, there should be a good
chance of showers and thunderstorms Thursday and Thursday night. At
this time, the system over BC primarily affects WA, but a slight
chance of showers and thunderstorms will continue over the mountains
Friday and Saturday. Drier northwest flow is expected to develop in
its wake Sunday into Monday. Generally speaking, the Cluster 500 MB
Heights all show a trend more towards the ECMWF solution with
respect to the second low remaining over central/southern BC.
The minor differences in the Mean Ensembles become stark differences
in the deterministic models, especially with the second system
Friday into Saturday. The first low swings through Thursday into
Thursday night with the ECMWF faster and farther north while the GFS
moves it through northern CA and northern NV. If the GFS solution
pans out, it will primarily affect southern Oregon. There will be a
short-lived break between it and the next system over BC. Again,
the ECMWF is faster and farther north as the system swings through
southern BC Friday and Friday night. Meanwhile, the GFS swings it
through central WA late Friday afternoon into Saturday morning. With
these difference, will keep precipitation confined to the mountains.
As noted earlier, they both show dry, northwest flow builds in its
wake as an amplifying ridge builds over the eastern Pacific. Earle
.FIRE WEATHER...A red flag warning is in effect from noon until
11 pm for Oregon zones 610 611 and 640 for isolated to scattered
thunderstorms producing abundant lightning and gusty outflow
winds. Storms will develop by early afternoon and then move
northeastward through this evening. There will be some rain with
the storms but some of it will evaporate before reaching the
ground due to a dry sub cloud layer. 78
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 98 69 102 66 / 0 0 10 10
ALW 99 71 104 71 / 0 0 0 10
PSC 100 73 104 72 / 0 0 0 10
YKM 99 71 102 69 / 0 10 0 10
HRI 101 70 105 70 / 0 0 0 10
ELN 97 68 99 66 / 0 0 0 10
RDM 97 61 99 61 / 20 20 10 10
LGD 94 66 97 64 / 0 0 20 20
GCD 97 66 100 64 / 20 20 20 20
DLS 101 74 105 73 / 0 10 0 10
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Watch from Tuesday morning through Wednesday
evening for ORZ041-044-507-508.
Red Flag Warning from noon today to 11 PM PDT this evening for
ORZ610-611-640-642.
WA...Excessive Heat Watch from Tuesday morning through Wednesday
evening for WAZ024-026>029-521.
&&
SHORT TERM...91/86
LONG TERM....75
AVIATION...75The Portland,OR radar (KRTX), 238 km away, was scanning. The volume nearest the first event began at 20:29 UTC.
2 hail. Local standard time, as filed.
A report relayed by a local television station in Deschutes county of hail slightly larger than one inch southeast of Bend, OR.
A trained spotter in Crook county, OR reported quarter sized hail and that there had been damage to Aluminum siding.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2021Every state in 2021This day in weather historyWarnings in Oregon, August 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: 980145, 980152.