Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
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361 FXUS65 KSLC 241032 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 431 AM MDT Mon Aug 24 2026 .KEY MESSAGES, Issued 1151 AM MDT Sun Aug 23 2026... - There is a Marginal Risk (level 1/4) for excessive rainfall across most of the region through early next week. - Thunderstorms will continue to impact the higher terrain and adjacent valleys through Wednesday. Another round of more widespread thunderstorms is increasing in likelihood for Friday into early next weekend. && .DISCUSSION, Issued 1151 AM MDT Sun Aug 23 2026... Strong to severe convection will develop this afternoon and evening, with the highest probability of significant impacts (10% chance of wind gusts in excess of 70 mph) across northern Utah. A Slight Risk (level 2/5) for severe thunderstorms has been issued for this area by the Storm Prediction Center. Looking at the set-up, this morning`s 12Z sounding at KSLC already showed almost 1000 J/kg MUCAPE but with a fairly stout amount of convective inhibition. Latest guidance suggests this effective cap will erode by 20-21Z, allowing for robust convective development across northern Utah. Mean HREF SBCAPE indicates a broad area of values near to above around 1000-1500 J/kg across northern Utah coincident with deep layer shear around 25-30 kts. Weak surface convergence associated with a shortwave trough passing to the north may help to organize convection into a quasi-linear feature, though per typical in terrain, this is difficult to discern in model fields. The latest few HRRR runs do show a signature of an organized line of very strong outflow shifting across the west desert and into the Wasatch Front between 21Z and 01Z and then continuing to be quite strong into the Uinta County, WY area by 02-03Z. Peak wind gusts in these runs have increased to 55kts, but given the very steep lapse rates, relatively high instability for the Great Basin, modest deep layer shear and low LCLs, expect storms to be able to attain cold pool/shear balance. Saturday`s convective outflow peak was 80 mph near Grassey on I-80...cant rule out a repeat somewhere along this area of outflow winds this afternoon and evening. For areas south of I-70, the heavy rain threat continues. While HREF peak 1 hour rates have decreased over Saturday`s values, net available moisture has only decreased subtly. Expect any stronger thunderstorms, especially those tied to terrain features and/or training, to be capable of rainfall rates in excess of 0.50 inches per hour. Will need to monitor for flash flood threat across much of this area...especially for slot canyons, normally dry washes and recent burn scars. With the previously mentioned upper level trough passing to the east Monday, the best chance for strong outflow winds will shift to mainly the Utah/Idaho border region. Convection will become increasingly tied to the higher terrain and adjacent valleys through Wednesday...with only isolated convection expected Thursday as high pressure brings a drying trend to most locations. However...with the tropical eastern Pacific remaining quite active, at least a portion of ensemble members indicate the next trough approaching the Pacific Northwest will assist in shifting remnant tropical moisture into the Great Basin by Friday. This is something to watch moving forward. && .AVIATION, Issued 1025 PM MDT Sun Aug 23 2026... KSLC...Showers and isolated thunderstorms will persist into the overnight hours in the vicinity of KSLC, however the chance for lightning at the terminal will diminish below 10% after 06Z. Brief MVFR VIS can be expected should a heavier shower or thunderstorm move over the terminal. Winds will continue to be outflow driven through at least 06Z, varying in direction and speed, but will eventually become southeasterly/drainage by 09Z. Another round of showers and thunderstorms is expected around the general area Monday. REST OF UTAH AND SOUTHWEST WYOMING...Showers and thunderstorms will continue across northern Utah and southwest Wyoming into the overnight hours, gradually decreasing in coverage and intensity with time. Frequent lightning, gusty outflow winds to 30 kts, and periods of MVFR VIS within heavier rain will all be possible. VFR conditions will prevail across southern Utah. Another round of showers and thunderstorms will develop across the area Monday afternoon and evening potentially impacting all terminals. && .FIRE WEATHER...High pressure centered over the Four Corners region will remain fairly stationary throughout the week. Diurnal thunderstorms will continue through the week with a lull in activity during the second half of the week as slightly drier air moves into the region. However, models have trended away from a more significant drying trend as the high pressure remains more stationary. This will likely result in isolated convection centered over the higher terrain Wednesday-Friday. Southwesterly winds will start to increase towards the end of the week as an upper level low pressure moves into the PNW. This will coincide with lower relative humidity to create locally critical fire weather conditions. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && $$ PUBLIC... AVIATION... FIRE WEATHER...Mahan For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity