Overview

June was generally warmer than average (except along the coast) with roughly equal numbers of stations with above- and below-average precipitation. A major heat waves in the fourth week brought record-setting daily temperatures to many locations, but the heat wave was short-lived and conditions soon returned to normal.

Table 1 is a summary of monthly averages and totals at selected stations throughout the state. Table 2 lists daily temperatures and precipitation for most of the locations listed in Table 1. In Table 3, monthly and seasonal precipitation totals throughout the state are listed.

Basin Summary

Here is a summary of water indicators at the end of the month, by river basin:

n.a. Not available
(1) Percent of normal June precipitation, from NOAA Cooperative sites
(2) Percent of normal seasonal precipitation (since Oct. 1), from NOAA Cooperative sites
(3) Percent of normal seasonal precipitation, from Natural Resources Conservation Service (NRCS) SNOTEL sites
(4) Percent of normal June stream flow, from U.S. Geological Survey (USGS)
(5) Percent of normal seasonal stream flow (since Oct. 1), from USGS
(6) Surface Water Supply Index, from NRCS (-4 = very dry, 0 = normal, +4 = very wet)

Forecasts

The Climate Prediction Center forecast for July-September (see maps below) suggests a higher-than-average chance of above-normal temperatures. Precipitation odds slightly favor drier than normal conditions in most of Oregon. Oregon Climate Service predicts average temperatures and precipitation during those months.

ENSO Outlook
Australian Bureau of Meteorology, July, 2006

Summary: A persistence of neutral ENSO conditions

The overall ENSO status remains neutral. Generally weak trends have been observed in the main Pacific climate indicators during the past few weeks, and the potential for an El Niño event to develop this year is still relatively low.

The main concern remains the Southern Oscillation Index (SOI), which is hovering around the -10 mark, indicating a general weakness in the Pacific Walker Circulation. There has also been some weakening in the Trade Winds in the last week, so this situation will be monitored closely for any sustained trends. However, ocean temperatures are only marginally above average, both on and below the surface, so there is only a slight risk that the Pacific will warm to levels high enough for an El Niño event to develop.

Most of the ENSO prediction models surveyed at the end of June showed a continuation of neutral conditions, although on the warm side of normal. Some updated model runs since then indicate an increased likelihood of the Pacific warming to El Niño levels. However, a sustained warming beginning in July or August would be unusual, given that ENSO events typically begin to evolve between March and June.

A Major Storm in Central Oregon, June 12, 2006
George H. Taylor

During spring and summer, Willamette Valley residents often catch a glimpse of big cumulonimbus, or “thunderclouds,” over the Cascades in the afternoon. As warm air rises to pass over the Cascades, it cools and condenses, forming clouds. The condensation also releases “latent heat.”

Latent heat is the heat energy required to change a substance from one state to another. Evaporation uses or consumes heat, which is why you feel cooler when water evaporates on your skin (heat is taken from your body during the evaporation process). “Latent heat of condensation” is energy released when water vapor condenses to form liquid droplets. During condensation, massive amounts of latent heat are released, and this process drives the development and growth of thunderstorms.

Sometimes the thunderstorms that form over the Cascades stay in place and dump rain over the mountains (and start fires). Last Monday (June 12) a hum-dinger formed over the Willamette Pass area and moved northeastward, away from the mountains – and toward Bend.

The National Weather Service issued three severe thunderstorm warnings between 11:30 a.m. and 3 p.m. that day, but pinpointing the storm cells was difficult. The Bend area is near the edge of the radar coverage from all three Oregon Doppler radars (which are near Ashland, Portland, and Pendleton) and thus rain and hail don’t show up well on any of the radars (I have long advocated a central Oregon radar for this very reason).

As the storm moved over Sunriver, it dumped heavy rain and dime-sized hail, according to Corvallis resident Steve Sparkes, who told me the clouds were “absolutely black.” The storm’s intensity grew as it moved toward Bend.

Rain became more and more intense. In Bend, rain was so heavy that several underpasses filled with water, forcing drivers to abandon their stalled cars. Sizable hail broke windows, ruined roofs, dented cars, sent people running for cover and harmed livestock, according to area residents and emergency officials. The largest hail was reported near Prineville, where some of the hail exceeded 2 inches in diameter. At least one fire was started by lightning.

Erin Foote Marlowe of the Bend Bulletin interviewed several central Oregon residents about their experiences. The quotes below are from Erin’s article in the Bulletin.

Don Braem, a Bend resident since 1995, agreed it was the worst storm, and hail, he's ever seen in the area. "I was on my way driving into town and I saw this big wall of white coming toward me," Braem said. "All of a sudden - bam! - it just hit the top of the car. I was thinking my windshield was going to break." The hail broke windows in a greenhouse in Braem's neighborhood and hurt horses, he said.

When Kyle Buehner arrived at his house on Ward Road Monday afternoon, he said it looked like a disaster area. Vehicles were dented from hail, windows were broken, and branches, leaves and pine needles covered the driveway. "It was crazy," Buehner said. He estimated the storm did several thousand dollars worth of damage. He counted 10 windows that were broken. One side of his snowmobile trailer received so much damage, "it looked like a great big golf ball, like a thousand hammers hit it," he said. His truck also received extensive hail damage and some of the juniper trees were completely stripped of branches.

The storm trapped people in cars, houses and under the awnings of area businesses, such as Costco, where dozens of people took refuge. "Everybody was afraid to go out," said Larry Vlodica, a manager at Costco. "This was the hardest rain I have seen since we opened this building in 1993."

Bend Public Works Director Ken Fuller said the storm caused major flooding at underpasses in Bend. Traffic was diverted from underpasses on Greenwood and Franklin avenues and Third Street for several hours Monday, Fuller said, as crews pumped out several feet of water. The city wants better drainage systems at the underpasses but hasn't been able to justify the expense, Fuller said. "It's just those big thunderstorms that are getting us," he said. "We have some ideas, but they are a matter of prioritizing dollars."

A few power outages were reported in the region. Pacific Power spokesman Dave Kvamme said 731 customers in the Prineville area were without power for several hours Monday. Multiple lines were down in the area, probably caused by falling branches, he said.

Mike Vescio, office manager with the National Weather Service in Pendleton, said the storm formed about 10 to 15 miles southwest of Bend and made its way through four counties (Deschutes, Jefferson, Crook and Wheeler) before petering out in Morrow County.

When people think of severe thunderstorms, Oregon doesn’t usually come to mind. But every now and then we get a truly memorable storm. I was in Sunriver in July 1995 when a similarly-intense storm occurred. Now we can add “June 2006” to our list of significant historical storms. If I ever update “The Oregon Weather Book” (1999) I’ll add this event to the list of big, damaging storms.

Mike Sumpter, in van, steers his vehicle while it is towed out of the water
Monday afternoon on Third Street in Bend.
Photo by: Melissa Jansson / The Bulletin