A ridge of high pressure built over the region accompanied by a near surface thermal trough which lead to a few lower elevation areas reaching critical heat risk thresholds while the mountain zones saw several days of high temperatures meet or exceeding 95 degrees.
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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.
A ridge of high pressure built over the region accompanied by a near surface thermal trough which lead to a few lower elevation areas reaching critical heat risk thresholds while the mountain zones saw several days of high temperatures meet or exceeding 95 degrees.
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 19, 8:47 PM PST, 3 hours 13 minutes earlier.
Area Forecast Discussion National Weather Service Pendleton OR 947 PM PDT Wed Jul 19 2023 Updated Aviation Discussion .UPDATE... Current forecast remains quiet and latest satellite imagery shows a generally clear sky across the Pacific Northwest. Only made minor changes to the forecast, mainly to adjust temperatures, based on the latest guidance and current observations. && .AVIATION... 06Z TAFS...VFR conditions with clear skies. Winds will be light (10 kt or less) and terrain driven...except for northwest 15G25kt Thursday afternoon and evening at KDLS...KRDM and KBDN as marine air pushes through the Cascade gaps. 78 && .PREV DISCUSSION... /issued 401 PM PDT Wed Jul 19 2023/ SHORT TERM...Today through Friday night...Concerns revolve around heat and fire weather the next 60 hours. The main highlights include: - Highs continuing to increase with temperatures 4 to 8 degrees warmer tomorrow, around 10 degrees above seasonable values Thursday. - Low category red/level 3 to orange/level 2 heat risk Thursday across the Yakima and Kittitas valleys, Lower Basin, into the foothills of the Northern Blues. - Increasingly breezy to locally windy Thursday and Friday outside of the eastern mountains and central OR mountains, especially across the eastern Gorge spilling into the far Lower Basin, Kittitas Valley, and gaps with the east slopes of the Cascades. - Enhanced fire weather to locally critical fire weather concerns Friday across the Kittitas valley, east slopes of the Northern OR Cascades, and the far western parts of the Lower Basin. Latest satellite imagery shows largely clear skies except for a few cu across the central OR mountains. Water vapor imagery depicts an amplifying upper ridge that extends from the Desert SW to British Columbia and a closed upper low west of Haida Gwaii. The large scale pattern through tomorrow Friday sees only a minor evolution as this upper ridge amplifies downstream of the upper trough and closed low in the eastern North Pacific. This upper ridge becomes shunted more east late Friday to extend more across the Northern Rockies as the low digs south to be more west of Vancouver Island. This sets the stage for a modest summer hot spell which is support by a modest uptick in 850 hPa temperatures Thursday, and also coincides with increasing southwesterly flow as a mid-level corridor of 35-40 kts winds move into eastern WA Friday. Somewhat of an innocuous MSLP develops Thursday with respect to a developing surface trough that then sharpens on Friday. This promotes an increased cross-Cascade gradient and will set the stage for increasing breezy conditions to locally windy conditions Thursday that increase and expand slightly eastward on Friday. 24-hr Daily Max Sustained Winds probs exceed 70% for 20 mph or greater across the eastern Gorge into parts of north central OR, Kittitas valley, and Cascade gaps. This probs see an uptick Friday for 20 mph or more max sustained winds spreading into Umatilla county and across more of the east slopes of the Cascades and farther along Kittitas valley. Of the two days, confidence in red flag is low (<30%) Thursday owing to the limited overlap of winds with low afternoon RH. More concerning is Friday with a better combination across the northern OR Cascades, Gorge into the Lower Basin, and Kittitas valley wherein there is some potential (30-50%) more for a RFW event. Meantime, expecting a modest heat spell for Mid July Thursday- Friday with departures from normal only 10 degrees or so, not very anomalous. This is seen with very low EFI values as well, even though chances for 100 degrees or more eclipse 75% across parts of the Lower Basin and the eastern Gorge. Lows are a limiting factor with the heat impact levels predominantly level 1/minor with lows generally in the mid 60s. As such, this setup preclude a need for a heat headline at this time based on the combination of modest HeatRisk (mentioned above), the short duration of this spell, time of year, and temperatures not being abnormal. LONG TERM...Saturday through Wednesday...The PacNW will find itself under a SW flow pattern for much of the period, as the region is wedged between a building ridge over the Four Corners area and a surface low over the Gulf of Alaska that will slowly cross over into Canada over the next week. Main impacts from this pattern will be a return to more seasonable temperatures, with widespread highs in the mid 80s to low 90s across our population centers, as well as continuously breezy conditions across our Cascade Gaps during the afternoon hours. While a particularly breezy day with advisory-level gusts is not borne out across guidance at this time, wind gust ensembles do key in on these gap winds spilling out into drier areas over the weekend , which could lead toward critical fire weather conditions with the recent heat causing RHs to crash down into the teens. EPS and NBM ensemble members suggest sustained winds around 20 mph in the Gorge with gusts in the mid 30s possible (30-40% confidence), with similar conditions around Kittitas. While RHs may remain a bit more elevated in the Gorge as cooler air filters in from west of the Cascades, these winds could easily spill over into the Oregon Basin and deeper into the Kittitas Valley, leading to Red Flag conditions. How prolonged these breezy winds and low RHs last remains in question, with forecast confidence hinging primarily on the former, but Saturday afternoon in particular is worth keeping an eye on. RHs will rebound later in the week as the prolonged SW flow aloft allows temps to decrease heading towards the midweek next week. As a result, conditions for critical fire weather concerns are concentrated mostly on this weekend. As the upper-level low pushes in more moisture as it advances onshore, could see some light orographic showers over the WA Cascades, however ensembles this far out are not keying in on much of a signal for precip, maybe only a 20% or so chance for the peaks in central WA. Otherwise, breezy conditions will continue to prevail across the Cascade Gaps as the rest of the forecast area sees relatively quiet and clear weather through the end of the period. Ensemble clusters then diverge a bit beyond the period, varying between a zonal flow pattern and more SW flow aloft. Evans/74 && .PRELIMINARY POINT TEMPS/POPS... PDT 63 99 62 97 / 0 0 0 0 ALW 64 102 67 101 / 0 0 0 0 PSC 62 103 68 102 / 0 0 0 0 YKM 64 100 63 98 / 0 0 0 0 HRI 64 103 67 101 / 0 0 0 0 ELN 60 99 64 95 / 0 0 0 0 RDM 55 95 54 95 / 0 0 0 0 LGD 58 99 60 98 / 0 0 0 0 GCD 58 99 59 100 / 0 0 0 0 DLS 64 98 65 95 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && UPDATE...77 SHORT TERM...80 LONG TERM....74 AVIATION...78
The national radar mosaic for the moment the first event began.
2 excessive heat. Local standard time, as filed.
Calculated heat risk values at the Hermiston Airport recorded temperatures that met or exceeded excessive heat warning criteria on July 20th. .
Calculated heat risk values at the The Pendleton GHCN recorded temperatures that met or exceeded excessive heat warning criteria on July 20th.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2023Every state in 2023This day in weather historyWarnings in Oregon, July 2023
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: 1122452, 1122455.