995 FXUS65 KSLC 012138 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 338 PM MDT Sun Jun 1 2025 .SYNOPSIS...An active pattern will continue through the week. There is a heightened threat of flash flooding across portions of southern Utah Monday and again Wednesday. && .DISCUSSION...Feels more like July across the Beehive State than the first day of June. Temperatures have surged into the mid-90s across portions of the Wasatch Front. As of about 310 PM, KSLC has hit 94F, typing the record for the date. Widespread convection has developed across portions of western and southern Utah. Early afternoon upper air and satellite analysis indicates a cut- off upper level low with a semi-tropical moisture tap crossing into northern Baja California. An upper level trough is crossing the PACNW, with yet another upper level low slowly cutting off on the south side of the trough near northern California. The first upper level low will gradually shift across the Desert Southwest over the next 24 hours or so before weakening and lifting northeast into the central Rockies. As mentioned earlier, convection is developing in advance of this low across much of western and southern Utah. Given 50-60 degree dewpoint depressions across western Utah, the most significant threat with the convection today will be gusty and erratic microburst winds. Several CAMS suggest wind gusts up to about 55 mph will shift through portions of the Wasatch Front as part of a mature cluster of convection between 5 and 8 PM. As moisture advection continues in earnest across southern Utah overnight, the threat will shift toward more of a flash flood concern for Monday afternoon and evening. The initial band of precipitation will shift into southern Utah Monday morning. While earlier runs over the last few days suggested this band of precipitation would shift well into Utah and perhaps disrupt any later convective potential, the bulk of the CAMS/high resolution models have shifted away from this solution. HREF SBCAPE values increase to near 500-1000 J/kg across portions of eastern and southern Utah by Monday afternoon. With deep layer shear around 10-15kts, the main focus of any convection in the deformation axis of the upper level low will be heavy rain. NAEFS PW anomalies reach the max for 12Z in the relative climatology by Monday morning. This combined with storm motion less than 10-15 kts and down drainage trajectories will support a conditional threat of flash flooding...as long as the instability is sufficient for convection (this is increasingly likely). CAMs suggest convection will develop across the southern mountains and then shift down the instability axis across the lower terrain of Utah later afternoon into the evening Monday. HREF 1 hour rainfall rates exceed 1"/hour in several of the members, with the heaviest focus between Zion National Park and western portions of the Grand Staircase (including Buckskin Gulch/Paria Canyon). Given this, upgraded the flash flood potential to probable for Snow Canyon, Zion National Park, and portions of the Grand Staircase. While confidence is not high enough for a flood watch, those with outdoor plans in slot canyons, normally dry washes, slickrock areas, etc across southern Utah should consider a plan B for Monday. As the next upper level low approaches the region, Tuesday looks to be a break in widespread convection across southern Utah, with coverage expected to be more isolated to scattered. Noteably, while the main moisture tap will be interrupted, PWs will still remain above the 90th percentile along the Utah/Arizona border. Any thunderstorms will be capable of heavy rain. The next cut-off upper level low will cross the Desert Southwest through the day Wednesday. With PW anomalies creeping back up into the 97-99th percentile across southern Utah, continued slow storm motion and sufficient instability, Wednesday afternoon and evening look to be another period of heightened flash flood threat. The Weather Prediction Center has added portions of southern Utah to a marginal risk for excessive rainfall Wednesday (in addition to the area for Monday). This is another to consider a backup plan to outdoor plans that include slot canyons, etc. While temperatures will cool considerably in this active pattern after today, a reminder to be heat safe. Carry sufficient water (0.5L to 1L per hour per person) and follow heat guidelines. Heat can be deadly. There have been over a dozen rescues in the last few days due to inadequately hydrated or prepared hikers. Be safe out there! && .AVIATION...KSLC...Light northwest winds will prevail through at least 00Z. Scattered showers and thunderstorms will track in after 00Z and influence winds. Although there will be little or no precipitation, gusty, erratic outflow winds could gust to around 40 knots. Showers and thunderstorms along with gusty, erratic outflow winds will diminish around 06Z. Light southeast winds will prevail into early Monday, but northwest winds will build in by 12Z. Clouds will decrease through the day. .REST OF UTAH AND SOUTHWEST WYOMING...Scattered showers and thunderstorms for much of southern and western Utah will be capable of gusty, erratic outflow winds through the evening. These will track into the urban corridor of northern Utah after 00Z, also capable of gusty, erratic outflow winds. Showers and thunderstorms will taper off for much of Utah around 06Z, although showers will continue for southern Utah into Monday. Showers and thunderstorms for southern Utah will bring localized heavy rain and gusty, erratic outflow winds after 20Z Monday. && .FIRE WEATHER...An active pattern will continue to evolve across the region. High-based showers and thunderstorms will bring the threat of microbursts across mainly western and northern Utah this afternoon and evening. As an upper level low shifts across the Desert Southwest through Monday, deep moisture will build into southern Utah. Depending on the degree of cloud cover...there is a conditional threat of thunderstorms with very heavy rain, particularly south and east of a line from Parowan to Loa. Tuesday has trended toward less convective coverage. The next upper level low will cross the Desert Southwest Wednesday into Thursday, bringing another round of thunderstorms to southern utah with the threat of heavy rain. The active pattern will continue through the remainder of the week. Expect deep mixing (largely 80th+ percentile across the state) to shift toward more typical mixing around the 50th percentile for Monday. Mixing will largely remain in the 50-70th percentile until Saturday, when deeper mixing is once again forecast. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && $$ Kruse/Wilson For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity