Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
138 FXUS65 KSLC 081002 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 402 AM MDT Wed Oct 8 2025 .SYNOPSIS...Another day of dry and calm conditions continue today ahead of a surge of tropical moisture from the south on Thursday. Wet conditions persist Thursday through the weekend with flash flooding possible across southern UT, particularly on Friday and Saturday. Following this active stretch, a cold front will push through bringing cooler and drier conditions to the forecast area with mountain snow across higher elevations. && .DISCUSSION...Key Messages: * Generally dry conditions persist today with gusty winds across the majority of the state ahead of an approaching system. * Tropical moisture from Hurricane Priscilla begins to push up from the south on Thursday resulting in widespread chances for rain across southern UT. * Chances for rain become increasingly widespread across nearly the entirety of the forecast area Friday and Saturday as moisture continues to surge north. * Chances for flash flooding exist Thursday through Saturday with a particular emphasis on southern UT where higher quality moisture exists. Additionally, Friday and Saturday appear to possess the highest threat for flash flooding across southern UT as well. Ridging aloft persists today ahead of an approaching trough from the Pacific NW. Generally dry conditions are expected to persist as large-scale subsidence aloft persists across the forecast area, though enhanced southwest flow aloft looks to develop in the afternoon hours with the approaching trough to our northwest. As a result, winds are expected to mix to the surface with gusty winds ranging from 20-30mph developing across southern UT, central UT, higher elevations of northern UT, and southwest WY. Most lower elevations are expected to decouple from the boundary layer following sunset with gusts subsiding as a result, though higher elevations should continue gusting throughout the evening hours into Thursday morning. In the early morning hours on Thursday, PoPs begin to see an increase as moisture associated with Hurricane Priscilla begins to move north into the state. While Priscilla remains well to our south, moisture aloft is expected to advect northeast toward the forecast area as the pressure gradient tightens aloft with the approaching trough from the Pacific NW. This stream of moisture is expected to persist through at least Sunday, continually increasing in quality as Priscilla eventually phases into the mean flow with more robust moisture arriving to the forecast area on Friday and Saturday. PWATs with this system certainly raise eyebrows given guidance indicates a PWAT anomaly across the majority of UT and SW WY around 0.5" above normal for this time of year. If that wasn`t enough, guidance also indicates that PWAT anomalies across Washington county and areas adjacent to Lake Powell range from 0.75" up to 1" above normal. For Thursday, the WPC currently has a Marginal Risk (level 1 of 4) of flash flooding outlined across southern UT and the entirety of eastern UT. Regarding Friday and Saturday, moisture quality looks to increase with increasingly favorable ascent as the upper trough continues to move east. Assuming cloud cover isn`t overly persistent allowing instability to build somewhat, some storms may be longer-lived and with deeper moisture in place, may result in an increased flash flooding threat compared to Thursday, particularly across southern UT. Additionally, moisture will continue surging north with increasingly favorable ascent across the entirety of the forecast area increasing PoPs across northern UT and SW WY. At this time, it appears that the strongest signal for heavy rainfall through the duration of this event appears to be across southwestern UT where the most favorable overlap of deep moisture and favorable dynamics overlap. On Friday, the WPC has a Marginal Risk (level 1 of 4) encompassing central UT with the majority of southern UT now outlined in a Slight Risk (2 of 4) of flash flooding. On Saturday, the WPC has expanded the Marginal Risk (1 of 4) to include the majority of UT and SW WY with a Slight Risk (level 2 of 4) encompassing southeast UT. This appears to be evolving into a pretty impressive rainfall event for the forecast area, particularly across southern UT. With this impressive parameter space, it is worth noting that the flash flooding threat appears somewhat concerning for slot canyons, recent burn scars, dry washes, and slickrock areas. If you are planning on venturing out to flood prone areas in southern UT, be sure to keep up to date with recent forecasts and remain situationally aware. Remember, turn around, don`t drown! On Sunday, a cold front looks to sweep across the forecast area as the trough begins to depart to our east. Lingering mid-upper level moisture with snow levels decreasing in the wake of the cold front will result in snowfall across higher elevations, particularly above ~7500ft. Chances for rain continue into early next week as long- range guidance indicates another upper trough will slide down toward the Pacific NW keeping conditions unsettled across the forecast area through the foreseeable future. && .AVIATION...KSLC...The SLC terminal will see VFR conditions throughout the day with mostly clear skies. Southeast winds are expected to shift to the northwest between 20Z and 22Z. .REST OF UTAH AND SOUTHWEST WYOMING...The entirety of the airspace will see VFR conditions and mostly clear skies throughout the day. Winds will be generally light and terrain driven this morning, with some increase in southerly winds during the afternoon hours. && .FIRE WEATHER...Dry conditions are expected to persist across UT through the remainder of today, though gusty winds ranging from 20-30mph out of the south appear possible ahead of an approaching storm system. Conditions begin to deteriorate early Thursday morning as tropical moisture begins to push up from the south increasing humidities and chances for rain, primarily across southern UT. A wet trend will persist through the weekend providing multiple chances for a wetting rain across the majority of the state. Conditions look to clear out on Sunday as a cold front sweeps through the area bringing cooler and drier air to the state via northwest flow. Additionally, snow appears possible on Sunday across higher elevations as snow levels drop following the passage of the cold front. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && $$ PUBLIC...Worster AVIATION...Traphagan FIRE WEATHER...Worster For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity