Roy Junior High School, UT Hourly Weather Updates

Key Messages

• Flash flood threat continues today, especially for southwest Utah and the southern/central mountains including recent burn scars and normally dry washes, slot canyons, and slick rock areas.
• Much drier conditions will build into the region this weekend into early next week, along with temperatures returning to near to slightly above normal by late in the week. Elevated to locally critical fire weather conditions will occur across mostly lower-elevation portions of central and southern Utah from Tuesday onward.

Discussion

, Issued 1053 AM MDT Fri Aug 14 2026... A Mesoscale Convective System associated with a SSW to NNE oriented upper-level jet is currently moving through southwest Utah as of this writing. This is bringing a number of morning Flash Flood Warnings to various sensitive areas including Zion National Park. This MCS is moving into an environment in central Utah with 500-1000 J/Kg of MUCAPE per the SPC Mesoanalysis, along with 25kts of bulk shear (closer to 50kts near the jet nose itself). Combined with an existing pool of PWATs near an inch and surface dewpoints in the mid to upper 50s, this MCS is efficiently wringing out rainfall. A Flood Watch for flash flooding continues through midnight for southwest Utah and the southern/central mountains (the latter largely due to recent burn scars).

Moving forward through today, looking at CAMs the RAP/HRRR have the best handle on the MCS location and intensity; they advance it northward along the I-15 corridor and mountains to the east of I-15 through at least Millard County, thus suggesting a threat to the Cottonwood and Widemouth 2 burn scars in addition to other recent burn scars. Beyond central Utah, CAM confidence breaks down in terms of how well it holds together tracking farther north. For what it`s worth, the RAP has the best handle on the current location and is depicting the MCS holding together all the way through the Wasatch Front / Wasatch Back and up to the UT/ID border, reaching the southern/central Wasatch front around 2-4pm and up to the northern Wasatch Front and Cache Valley by 6pm. Will continue to monitor this MCS through the afternoon.

In the wake of today`s jet/shortwave, much drier air moves into the region overnight into tomorrow along with synoptic subsidence. PWATs dropping closer to a half inch. CAMs depict isolated convective initiation in the typical terrain-focused areas, though one thing to watch for based on past experience is monsoonal moisture tends to hold on a little longer than models expect, so would not be surprised if convective initiation is more widespread than currently shown. In that case, would expect initiation in any areas favored by southwest flow, depending on the degree of overall subsidence.

Expect a similar trend of isolated to scattered convection Sunday along with temperatures warming around 5 degrees as heights build over the Central Rockies. A generally dry westerly flow aloft then sets in for Monday through next week, bringing drier and warmer conditions. Any drying/warming can bring a return of elevated fire weather concerns, depending on whether any weak shortwave troughs can bring elevated winds as well. As of now this appears unlikely, so the chance of critical fire weather conditions is isolated over pockets of mainly central and southern Utah.

The next round of monsoonal moisture is highly uncertain from looking at various ensembles. The general theme is many members slowly bring monsoonal moisture back into the area lake next week and on through August, though there is little agreement on timing.

Aviation

...KSLC...VFR conditions are expected to prevail through the TAF period. There exists a 30% chance that one more round of showers and thunderstorms may impact the terminal until about 02-03z, with gusty outflow winds to 35 kts and brief heavy rainfall dropping cigs to MVFR. Aside from any erratic storm outflow, southerly winds will likely dominate through the evening, though a 30% chance of northerly outflow winds from storms to the north may impact the terminal between 06-09z.

REST OF UTAH AND SOUTHWEST WYOMING...Thunderstorms are expected to wane around sunset, with a 30% chance of persisting at SGU into late evening. Otherwise light diurnal winds will dominate through the TAF period.

Fire Weather

, Issued 1147 AM MDT Fri Aug 14 2026... One more day of widespread showers and thunderstorms is in store today as this monsoon surge comes to an end by tonight. High pressure will then shift eastward, with Utah transitioning to a dry southwest to westerly flow aloft through at least midweek. Minimum humidities are currently forecast to fall near critical levels for most valley and lower-elevation locations by early next week. Higher elevations and areas near the Utah/Idaho border are currently expected to remain above critical RH levels, though drying as well.

A system crossing to the north may bump winds enough on Tuesday and Wednesday to bring elevated to locally critical fire weather conditions to portions of central and southern Utah each afternoon and evening. Again, this threat is mostly for the lower elevations.

While some models suggest another monsoon surge by late next week into the following weekend, there is considerable uncertainty as to the timing of when this next round arrives. For now, the forecast has trended mostly dry for next week, other than an isolated afternoon shower/thunderstorm over the higher terrain of northern Utah.

Watches / Warnings / Advisories

/WARNINGS/ADVISORIES... UT...Flood Watch until midnight MDT tonight for UTZ116-117-122>129.

WY...None.