A ridge of high pressure was situated over the inland Northwest from 7/28-7/31, resulting in many record high temperatures.
Every event with a place to put it; 4 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 ridge of high pressure was situated over the inland Northwest from 7/28-7/31, resulting in many record high temperatures.
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 Jul 28, 9:37 AM PST, 1 hour 23 minutes earlier.
Area Forecast Discussion
National Weather Service Pendleton OR
1037 AM PDT Tue Jul 28 2020
...UPDATED AVIATION DISCUSSION...
&&
.AVIATION...18Z TAFs...Generally VFR conditions expected today
though isolated storms are possible for KBDN and KRDM. Now, some
convective debris lingers around 100-150kft from near Blue Mtns of
WA/OR and eastward. Expecting Cu field to develop soon in
elevated terrain and some of these will become Cb and storms
later. Storms are likely to focus in southern Blue Mtns of OR in
vicinity of KGCD but VCTS still looks likely for KBDN, and
possibly KRDM. VFR conditions and relatively light winds expected
elsewhere except KDLS where typically gustiness is expected
through the afternoon. Also seeing some localized temporary
haziness around portions of US-97 and KPSC. 76
&&
.PREV DISCUSSION... /issued 830 AM PDT Tue Jul 28 2020/
SHORT TERM...Today and tonight...A ridge of high pressure will
continue over the region providing very hot temperatures thus heat
advisories continue. Some monsoon moisture continues across eastern
Oregon which will lead to some isolated to scattered thunderstorms
mainly over central and northeast Oregon but could clip southeast
Washington too. A weak marine push this afternoon will usher in some
slightly cooler air and locally breezy conditions along the east
slopes of the Cascades.
PREV DISCUSSION... /issued 259 AM PDT Tue Jul 28 2020/
SHORT TERM...Today through Thursday...Satellite and radar
currently showing some remnant clouds from convective activity
yesterday afternoon has pushed into the Columbia Basin this early
morning. With a relatively stable airmass over the basin, this
activity will continue to clear through the morning.
Through the week, the synoptic pattern over the region will be
dominated by an upper level ridge of high pressure that will
maintain well above normal temperatures, especially in the lower
elevations. A heat advisory is currently in effect for most of the
Columbia Basin and surrounding valleys through Thursday, while the
Kittitas valley and lower elevations across north/central OR will
be under the heat advisory Wednesday and Thursday. Expect high
temperatures to get will into the low to mid 100s each afternoon
in the lower elevations, and 90s in the higher elevations.
Flow aloft will begin to turn more southwesterly today over the
region, pushing some mid-level moisture further across eastern and
northeastern OR. Increasing mid-level moisture and a weak impulse
passing over the region will aid in thunderstorm development
across the mountains in central and northeastern OR this
afternoon. An isolated storm over the Blue Mountain foothills is
not ruled out for later this evening. Breezy conditions associated
with a weak marine push will develop across portions of the
Columbia Gorge/Basin as well as in the Kittitas Valley this
afternoon. Wednesday, flow will begin to turn more southerly in
response to a deepening upper level trough off the coast. A fairly
weak impulse will pass over eastern OR through the afternoon, but
convective activity will be limited over the northeastern
mountains and short lived. Overnight Wednesday into Thursday, a
stronger impulse will swing around the trough over western OR into
central WA. With the timing of this system, there is potential
for thunderstorm development overnight across the forecast area.
The rest of Thursday will be fairly quiet as storm activity will
be well north of the forecast area. Lawhorn/82
LONG TERM...Friday through Monday...Friday looks to be the last
of the really hot days, and the heat advisory may have to be
extended. The upper level ridge is still in place over the 4
corners, although the axis is probably a bit further east than on
Thursday.
An area of low pressure off the British Columbia coast and its
associated trough will be approaching the coast on Friday.
However, the strong high will impede its progress. By Saturday,
the low moves into British Columbia and there is enough eastward
movement of the trough that heights lower and temperatures will
finally decrease, and bring an end to the heat. Guidance is split
on thunder chances over the eastern Oregon mountains later Friday,
will leave out for now, but there could be some low chances added in
later. Otherwise, it appears the trough will move in mainly dry and
that dry weather will continue through the extended period.
As the trough advances later Friday into Saturday, there could be a
period of gusty winds. Another low will approach British Columbia
on Monday and reinforce the trough/southwesterly flow ahead of it,
but have little impact on our sensible weather.
Friday will see high temps 100 to 104 across the Columbia Basin and
Foothills and mid to upper 90s elsewhere. Saturday's highs will be
cooler, with highs mainly from the upper 80s to mid 90s. Highs on
Sunday and Monday will be similar to Saturday, all within a degree
or two of each other.
FIRE WEATHER...Red Flag warnings will continue for zones across
central and northeast OR through this evening. An impulse moving
across the region and increasing mid-level moisture across central
and eastern OR will aid in the development of isolated
thunderstorms over higher elevations this afternoon and evening.
Thunderstorm activity will be weaker tomorrow afternoon, however
an overnight shortwave passage could trigger isolated
thunderstorms moving across the northern forecast area. An
extension of the red flag warnings may be considered for this
activity. Winds will be locally breezy across the Columbia
Gorge/Basin and along the east slopes of the Cascades this
afternoon.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 100 68 101 69 / 10 10 0 10
ALW 101 67 102 69 / 10 10 0 10
PSC 103 67 103 69 / 0 0 0 10
YKM 100 63 101 71 / 0 0 0 10
HRI 103 69 105 68 / 0 0 0 10
ELN 96 64 100 67 / 0 0 0 10
RDM 96 57 100 58 / 20 10 0 0
LGD 93 61 96 65 / 20 30 10 20
GCD 94 62 99 65 / 20 30 20 20
DLS 97 72 103 72 / 0 0 0 10
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory until 8 PM PDT Thursday for ORZ041-044-507.
Red Flag Warning until 10 PM PDT this evening for ORZ640-642.
Heat Advisory from noon Wednesday to 8 PM PDT Thursday for
ORZ505-508-510-511.
Red Flag Warning until 10 PM PDT this evening for ORZ644-645.
WA...Heat Advisory until 8 PM PDT Thursday for WAZ024-027>029-521.
Heat Advisory from noon Wednesday to 8 PM PDT Thursday for
WAZ026.
&&
91/76/76The national radar mosaic for the moment the first event began.
5 heat. Local standard time, as filed.
Temperatures peaked at 108 degrees on 7/30 at KALW ASOS.
Temperatures peaked at 113 degrees on 7/30 at Richland, WA.
Temperatures peaked at 105 degrees on 7/30 at KYKM ASOS.
Heat peaked on 7/31 with a temperature of 99 degrees at Easton.
High temperature peaked at 108 degrees on the afternoon of Jul 30 at KDLS.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2020Every state in 2020This day in weather historyWarnings in Washington, July 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: 902607, 902610, 902612, 902669, 902671.