A 24-hour rainstorm from Tuesday night through Wednesday soaked the Walla Walla Valley and broke rainfall records around the lower Columbia Basin.
Walla Walla was walloped with 1.76 inches of rain at the official weather station at the Walla Walla Regional Airport, shattering the previous May 20 record of 0.92 inches set back in 1960.
The all-time record for Walla Walla is 3.64 inches on July 23, 1992, according to the National Weather Service.
Around the region, Pasco received a half-inch of rain in 24 hours — a record. Pendleton took in 1.11 inches of rain in 24 hours — another record for May 20. Pasco’s previous record was 0.42 inches in 1962. Pendleton’s previous record of 0.79 inches dated back to 1894.
Flooding over roadways was reported on Birch Creek in Pilot Rock, Ore., and McKay Creek in Pendleton after the Oregon Bureau of Reclamation released excess flows from McKay Reservoir.
Major flooding in Walla Walla and Columbia counties was not reported as of Thursday morning when the weather service lifted flood warnings.
Weather service meteorologist Joe Solomon said the region was lucky this time.
“Had this occurred two months earlier, we could’ve had a repeat of February again,” Solomon said. “But luckily the snow melt wasn’t there.”
Solomon said this weather pattern happens from time to time in the Inland Northwest.
He calls it a “wraparound,” where a weather system moves in from the Pacific Ocean but then stalls over Idaho before its tail whips around from Western Montana and North Idaho and back down through Eastern Washington.
The wraparound storm then slowly moves up to the base of the Blue Mountains where an up-slope effect causes excess moisture to dump out.
“We knew this would happen to an extent,” Solomon said. “We knew there would be quite a bit of precipitation and some potential there for some flooding warnings. ... The models aren’t perfect — they don’t always capture the severe extent of things.”
The weather service issued a flood watch Tuesday afternoon and upgraded it to a flood warning by Wednesday morning. That warning was lifted today at 9 a.m.
Solomon said waters on local rivers and creeks peaked early Thursday morning after midnight and waters would continue to recede over the weekend.
He added that most of the moisture would not have an effect on local farm fields as most of it would run off rather quickly.
“That much water moving that fast is not effective at soaking into the ground,” Solomon said.
According to data from the National Weather Service, in 24 hours Touchet and Lowden were soaked with 1.62 inches, the Waitsburg area got 2.19 inches and Milton-Freewater fielded 1.63 inches. Elsewhere, Prescott had 1.06 inches, Athena had a staggering 3.03 inches, Weston Mountain had 2.91 inches and the highest total in the lower Columbia Basin was near Ukiah, Ore., with 4 inches of precipitation.
One weather station just south of Walla Walla High School measured 1.95 inches of rain.
The Blue Mountains received the brunt of the storm with the Meacham area between Pendleton and Baker City netting 2.82 inches of rain in 24 hours, a record. Tollgate had about 1.8 inches of precipitation in 24 hours, according to the data.
According to the data, the storm was technically 48 hours in length, but the majority of it took place in the 36 hours from Tuesday around 11 p.m. through this morning. Rainfall records are usually numerated by 24-hour totals.
Solomon said a warming trend is in the forecast with a chance of some more minimal rain today and tonight and temperatures climbing back up into the 70s and 80s by next week.
“Next week, it looks like it’s back to summer or late spring weather,” Solomon said.