Afternoon thunderstorms continued over Utah in the second half of August, with some producing flash flooding or large hail.
Every event with a place to put it. Tap one for its entry below.
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 SLC wrote it up.
Afternoon thunderstorms continued over Utah in the second half of August, with some producing flash flooding or large hail.
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 Salt Lake City, UT wrote its last area forecast discussion before the first event at Aug 20, 8:52 PM MST, 38 minutes earlier.
Area Forecast Discussion National Weather Service Salt Lake City UT 952 PM MDT Sun Aug 20 2017 .SYNOPSIS...Southerly flow aloft early this week will bring an increase in mid-level moisture, leading to an increase in shower and thunderstorm chances. Eclipse viewing on Monday will likely be hampered by clouds in southern Utah. && .DISCUSSION...A closed low remains in place off the southern California coast this evening while in the southerly flow aloft upstream of this low, moisture began to increase across southern Utah. PWATs made it to the 0.8-0.9 inch range across the far south by late this afternoon. Showers and thunderstorms developed along the higher terrain today as well some of the southern Utah valleys where instability was higher. Most of the activity across the north quickly tapered off with the loss of daytime heating, while across the south showers and thunderstorms have decreased in intensity. A few showers are expected to linger through the night across the south as moisture continues to spread northward. Similar conditions are expected tomorrow, except with a bit more coverage of storms across southern and central Utah given the increase in moisture. Much of northern Utah is expected to remain on the drier side and less convectively active as a result. Northern Utah will remain more promising for eclipse viewing tomorrow compared to southern Utah. Given the convection today and lingering showers expected overnight, southern Utah will likely be partly to mostly cloudy with areas of thicker clouds. Northern Utah is currently seeing little convective debris clouds and most of these are not expected to persist into tomorrow morning. However, a band of mid and high clouds is trailing an upper trough currently crossing the northern Rockies. This band of clouds, evident on satellite imagery across Oregon and central Idaho, is expected to be draped across northwest Utah tomorrow morning. However, these clouds will tend to thin as they continue to approach Utah. By eclipse time, expect these clouds should be sufficiently patchy and thin to allow for periods of unobstructed eclipse viewing. && .AVIATION...VFR conditions will continue through the TAF period at the KSLC terminal. Southeast winds will prevail through the night. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && Cheng For more information from NOAA's National Weather Service visit... http://weather.gov/saltlakecity For frequently asked questions about the Area Forecast Discussion visit... http://weather.gov/saltlakecity/general/afd_faqs.php
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
737 PM MDT SUN AUG 20 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0645 PM DEBRIS FLOW 5 S PAROWAN 37.76N 112.82W
08/20/2017 IRON UT 911 CALL CENTER
DEBRIS FLOW OFF OF THE BRIAN HEAD BURN SCAR BETWEEN MILE
MARKERS 2 AND 14 CLOSED STATE ROUTE 143 IN BOTH
DIRECTIONS.
&&
RGRAHAMThe Cedar City radar (KICX), 25 km away, was scanning. The volume nearest the first event began at 04:28 UTC.
1 flash flood, 1 hail. Local standard time, as filed.
Flash flooding along Parowan Creek spilled over onto Interstate 15, temporarily closing the right-hand lane of northbound Interstate 15.
Quarter-sized hail was reported across Herriman, with a picture of the hail also provided.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Utah in 2017Every state in 2017This day in weather historyWarnings in Utah, August 2017
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: 719020, 719003.