An elongated trough drew in enough elevated CAPE for a few storms to pop up in eastern Oregon. Very strong lapse rates (≥ 8-9.5 C/km) mixed down strong momentum from roughly 4-5 km AGL, producing downed trees and measured gusts to 65 mph. ProbSevere v3 (PSv3) showed rapid increases in the probability of severe at around 00:20 UTC and 00:50 UTC (Figures 1 and 2).
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| Figure 1: ProbSevere v3, MRMS MergedReflectivity, and NWS severe weather warnings for a storm in eastern Oregon. |
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| Figure 2: Time series of PSv3 probabilities for the eastern Oregon storm |
The increasing MESH (up to around 1"), composite reflectivity (up to 63 dBZ), and ENI lightning (up to 10 fl/min) contributed to the first rapid rise in the probability of severe. A very strong satellite growth rate at 00:46 led to the next jump, up from 49% to 67%. One can see the cooling cloud tops in the GOES-18 visible/IR sandwich imagery that preceded 3 of the 4 severe wind reports (the first wind report was recorded at 00:41 UTC).
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| Figure 3: GOES-18 10.3-µm brightness temperature and 0.64-µm reflectance for the storm in eastern Oregon. |
In this example, the probability of severe hail seemed to be the strongest value; however, wind was the only hazard reported. While PSv3 generally has improved discernment among severe weather hazards, this would be a good case to look into to see if we can better incorporate model predictors in PWv3 that take into account the mixing of momentum very high in the atmosphere down to the surface, which is relatively common in the western U.S.