A strong upper level ridge of high pressure and a surface thermal trough brought several days of record high temperatures across the PacNW, with many locations in the lower and higher elevations experiencing extreme heat risk during this event. The multiple days of extreme heat risk has been attributed to several fatalities across the region.
Every event with a place to put it; 5 filed by county or forecast zone are drawn at its center, in a lighter ring. 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 PDT wrote it up.
A strong upper level ridge of high pressure and a surface thermal trough brought several days of record high temperatures across the PacNW, with many locations in the lower and higher elevations experiencing extreme heat risk during this event. The multiple days of extreme heat risk has been attributed to several fatalities across the region.
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 Jun 30, 7:14 PM PST, 4 hours 46 minutes earlier.
Area Forecast Discussion
National Weather Service Pendleton OR
814 PM PDT Wed Jun 30 2021
.UPDATE...Thunderstorms have formed this afternoon and evening
over much of the southern forecast area with high bases and little
rainfall. This was due to the hot and dry conditions at the
surface with increased mid level moisture, which resulted in
increased instability. Thunderstorms are beginning to weaken and
radar echoes are showing cells becoming more stratified around the
remaining cells. The storms are moving from southeast to northwest
around the southwest side of the departing high pressure system
that brought record heat to the region during the past week. West
to east pressure gradients have developed across eastern OR/WA and
over the Cascades which resulted in breezy to windy conditions
this past afternoon and this evening, though the winds are showing
signs of diminishing now. The strongest winds are currently through
the Cascade gaps, passes and the eastern Columbia River Gorge. A
Red Flag Warning is currently in effect until midnight PDT tonight
for these thunderstorms with abundant lightning and very dry
fuels/hot temperatures. Am waiting for a few more hours to see if
these storms are going to continue through later into the night
or end after sunset.
The upper high pressure system will continue to move off to the
northeast and be replaced by a southwest flow aloft as an upper
trough along the coast tries to move into the PacNW on Thursday.
This will continue to increase moisture and instability on
Thursday, which will result in more afternoon and evening
thunderstorms. There is a Fire Weather Watch in effect for
Thursday for this, and am waiting for a new model run or two to
gain enough confidence on whether Thursday's storms will be
enough to warrant an upgrade of the Fire Weather Watch to a
warning or not. An Excessive Heat Warning remains in effect
through Sunday, which may be able to be downgraded to a Heat
Advisory as temperatures do not appear that they will become as
hot as previously expected through Sunday. Also, a Red Flag
Warning will remain in effect through 10 PM Thursday for the
Eastern Columbia River Gorge and the Lower Columbia Basin fire
zones for wind and low relative humidity. Otherwise current
forecast looks good. 88
&&
.AVIATION...06Z TAFS...VFR conditions will prevail at all
terminals through the next 24 hours. There may be a few passing
thunderstorms this evening near KBDN and KRDM, otherwise there
will just be mid and high cloud cover at all terminals due to
decaying thunderstorms. West to northwest winds will occasionally
increase to as high as 15 to 25 kts with higher gusts this
evening, especially at KDLS, KRDM, and KBDN, before diminishing
late tonight for a while before sunrise. 88
&&
.PREV DISCUSSION... /issued 408 PM PDT Wed Jun 30 2021/
SHORT TERM...Tonight through Friday...Lingering high pressure
aloft over the region will continue to bring very hot temperatures
across the Basin, Gorge, and adjacent valleys this late
afternoon, while everywhere else will see temperatures 5 to 10
degrees cooler than yesterday. Satellite this afternoon still
showing stratus over portions of the western half of OR/WA this
afternoon while breezy westerly winds have picked up through the
Cascade gaps and the Gorge. This is a good sign that the marine
push has developed, and will provide a little relief to areas
along the east slopes of the Cascades. This marine push will
continue into Thursday afternoon as cross Cascade pressure
gradients stay tightened. Though temperatures will be slightly
lower and a weak marine airmass will push east, relative
humidities will still be near to critically low enough that with
the increased westerly winds a Red Flag Warning is in effect for
the eastern Columbia Gorge and portions of the Columbia Basin.
As the upper level ridge continues east and north through
tomorrow, southerly flow aloft and at the surface will push a
monsoonal airmass with increasing instability north into central
and eastern OR today and tomorrow. This will increase chances of
isolated to scattered thunderstorm chances in these areas this
afternoon, and so a Red Flag Warning has also been issued across
central and eastern OR mountains through this evening.
The upper level ridge of high pressure will continue to break down
with a zonal flow developing over the PacNW Friday. A series of
weak shortwaves will pass north of the forecast area Friday, which
will help to keep the ridge from building back over the region.
That said, the only impacts to the forecast area will be in
Wallowa county, where a slight chance of showers and thunder are
expected in the afternoon. Otherwise, cross Cascade surface
gradients will begin to relax Friday, with winds becoming locally
breezy across the Gorge, Basin, and through the Cascade gaps.
Temperatures by Friday afternoon will also be in the 95 to 105
range, but with lows still in the mid 60s to lower 70s the
excessive heat warning will still be in effect, though this may
need to be downgraded to an advisory as we get into the weekend.
Lawhorn/82
LONG TERM...Saturday through Wednesday...Models relatively
consistent in depicting hot and dry weather through the holiday
weekend. High temps across the forecast area will remain above to
slightly above average, with the lower Basin likely seeing daytime
highs at or around the triple digits through the middle of next
week. Other areas will begin to tick down into the low to mid 90s,
with 80s in the mountains. Synoptic pattern remains relatively
stagnant through the period with light zonal flow aloft. Models
depict a weak system off the California coast that may usher in some
moist SW flow into the area, however guidance has scaled back on
precip threat in the eastern mountains over the weekend, with both
ensembles and deterministic models showing limited moisture
associated with this system.
Ensembles then begin to converge on some shortwave impacting the
forecast area the middle of next week. Large differences in timing
of this system are evident, especially between the deterministic GFS
and ECMWF. That being said, guidance not yielding much of any precip
thus far, however should this system verify, could see another
chance of mountain showers and thunderstorms, as well as increased
breeziness that could exacerbate fire weather conditions. Temps
could also cool further towards seasonal averages for early July.
For the holiday weekend, however, weather looks to be quiet,
although some caution should be exercised when celebrating
Independence Day, as RHs will still be very low due to the severity
of this recent heat wave. 74
FIRE WEATHER...Red Flag warnings are in effect for the Lower
Columbia Basin and the eastern Columbia River Gorge for low RH
and breezy westerly winds for this afternoon/evening as well as
for tomorrow afternoon/evening. Though conditions will be low end
criteria, with the recent heat wave and the upcoming holiday
weekend, a warning was warranted. Red Flag warnings have also been
issued for the central and eastern mountains for this afternoon
and evening as isolated to scattered thunderstorm chances will be
on the increase. For tomorrow afternoon, a watch is still in
effect for possible increasing thunderstorm chances across the
eastern mountains. Lawhorn/82
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 67 99 63 101 / 10 10 10 0
ALW 73 102 67 103 / 10 10 10 0
PSC 73 103 68 103 / 0 0 10 0
YKM 71 100 63 101 / 0 0 10 0
HRI 72 103 64 104 / 10 0 10 0
ELN 69 91 62 95 / 0 0 10 0
RDM 56 96 55 98 / 10 0 10 0
LGD 65 97 62 97 / 20 20 20 10
GCD 66 99 64 100 / 30 20 30 10
DLS 70 91 64 99 / 0 0 10 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning until 8 PM PDT Sunday for ORZ041-044-049-
050-502-503-505>511.
Red Flag Warning until 10 PM PDT Thursday for ORZ639-641.
Red Flag Warning until midnight PDT tonight for ORZ640-642-644-
645.
Fire Weather Watch from Thursday morning through Thursday
evening for ORZ642-644-645.
WA...Excessive Heat Warning until 8 PM PDT Sunday for WAZ024-026>030-
520-521.
Red Flag Warning until 10 PM PDT Thursday for WAZ639-641.
&&
SHORT TERM...88
LONG TERM....74
AVIATION...88The national radar mosaic for the moment the first event began.
5 excessive heat. Local standard time, as filed.
The Roberts Butte RAWS recorded consecutive daily high temperatures over 95 degrees from June 27th through July 1st, with many daily high temperatures even meeting or exceeding 100 degrees during the period.
The Eden RAWS recorded consecutive daily high temperatures over 95 degrees from June 27th through July 1st, with many daily high temperatures meeting or exceeding 100 degrees during the period.
Calculated heat risk at the Milton Freewater, OR GHCN station recorded consecutive days between June 25th through July 1st of temperatures that met or exceeded excessive heat warning criteria.
Calculated heat risk values at the Boardman, OR GHCN station recorded consecutive days between June 26th through July 1st of temperatures that met or exceeded excessive heat warning criteria.
Calculated heat risk values at a GHCN in La Grande, OR recorded consecutive days between June 29th through July 2nd of temperatures that met or exceeded excessive heat warning criteria.
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, July 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: 977218, 977219, 977221, 977223, 977226.