Issue Date: Thursday, June 7, 2018
Issue Time: 10:25AM MDT
Summary:
A cold front moved through the northeast corner of the state Wednesday morning helping shift winds and slightly moisten the lower levels of the atmosphere a bit under the otherwise strong, dry ridge. The front eventually stalled out over the Palmer Divide by late morning. By mid-afternoon, a Denver cyclone had formed east of the Urban Corridor. Strong easterly winds on the north side helped increase dew points into the mid and upper 50Fs over the Northeast Plains. On its east side, a line of convergence and a passing shortwave helped trigger numerous severe thunderstorms over the Northeast Plains. Outflow boundaries from these storms helped provide additional lift for more thunderstorm development in the moist, high CAPE environment.
The severe thunderstorms over the Northeast Plains produced large hail and gusty winds. The largest hail stone was reported in Logan County where the 4 inch diameter stone (softball size) blew out the windshield of a trained spotter – yikes! Gusts between 55-60 mph were also commonplace under these storms. An areal flood advisory was issued for northern Logan and Sedgwick Counties around 8PM for a nearly stationary thunderstorm along a boundary. 1-hour rain rates were estimated at 2 inches with totals just above 2.5 inches. The boundary slowly sagged south and more thunderstorms developed along the line (to the west) producing very heavy rainfall that trigged two more areal flood advisories. The town of Yuma reported 1.69 inches of rainfall and street flooding. Radar estimates were over 4 inches in the area, and a CoCoRaHS station recorded 2.76 inches just north of town. If estimates are correct, that’s about a 1 in 200 year storm for this area. Storms eventually moved out of the state by 2AM.
Over the Front Range and Urban Corridor, storms began to fire over the higher terrains by 3PM and continued into the evening. Due to the lack of moisture, these storms were high-based and produced little rainfall. However, multiple rounds of pulse-like convection was able to produce 24-hour rainfall amounts up to 0.3 inches over Fool Creek outside of Winter Park at a SNOTEL site. An evening thunderstorm rolled off the mountains into Denver around 8PM and produced gusty winds. A mesonet station in Ken Caryl reported a gust of 58 mph. Total rainfall amounts were under 0.2 inches.
For rainfall estimates over your area, scroll down to the State Precipitation Map below.
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Note: We have identified a possible underestimation in QPE over the southwest part of the state. We are working to on this issue, and will provide an update as soon as possible.
