Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
597 FXUS65 KSLC 221122 CCA AFDSLC Area Forecast Discussion...CORRECTED National Weather Service Salt Lake City UT 522 AM MDT Fri Aug 22 2025 .SYNOPSIS...With high pressure centered over the Four Corners, monsoon moisture will gradually spread northward into Utah and southwest Wyoming through early next week. This will bring increased coverage of showers and thunderstorms, the potential for flash flooding, and gradually less hot temperatures. && .SHORT TERM (Through 12Z/6AM Sunday)...High pressure is parked over the Four Corners this morning, as it will be for the next several days. The resultant southerly flow is bringing deep monsoonal moisture steadily northward, with satellite derived PW values currently in the 0.8 to 1.0 inch range over much of Utah and southwest Wyoming, and a bit higher over far southern Utah. Seeing some shower activity continue into the overnight hours over northeastern Utah in association with a passing weak shortwave. These showers will remain light through much of the remainder of the morning. In the moist airmass, will see additional convective development this afternoon, primarily focused over the higher terrain, particularly over central and southern Utah, with a bit of valley drift. There will be a better chance of wetting rains today but the moisture, particularly over northern portions of the forecast area, will be more in the mid to upper levels, with gusty and erratic winds the main threat with any storms that develop. Temperatures will remain on the hot side for this time of year, with highs expected to run up to 5F above seasonal normals. The increase in moisture will slow a bit tomorrow as the center of the low slides a bit west, resulting in light flow over the forecast area. Still, the existing moisture will be more than enough for additional convection, particularly for southern Utah. .LONG TERM (After 12Z/6AM Sunday)...Monsoonal moisture is expected to become especially pronounced across the entirety of Utah and southwest Wyoming on Sunday into early next week, with PWAT anomalies pushing 150-200% of normal areawide. As such, expect widespread coverage of showers and thunderstorms each day, with this amount of moisture in the column favorable for locally heavy rainfall under stronger cores. The Weather Prediction Center continues to carry a Marginal risk (level 1 of 4) for excessive rainfall across the entire forecast area through at least Tuesday. Those with outdoor plans should continue to monitor the forecast given the associated risk for flash flooding. Locations with greatest threats for flash flooding include slot canyons, normally dry washes, slickrock areas, recent burn scars, and urban areas. While moisture availability will be plentiful, the one factor that could impact afternoon convective development and evolution includes the potential for nocturnal convection. If any nocturnal convection occurs and skies remain sufficiently cloudy, we could see more stable atmospheric conditions develop. This would inhibit the development of convection into the afternoon, instead favoring a more stratiform precip regime. Will be something to monitor as we get closer. In addition to widespread precipitation, this pattern will bring a much-needed gradual cooling trend throughout the long term period. Temperatures begin near-average on Sunday, dropping to around 5-10F below seasonal averages by the end of the week. && .AVIATION...KSLC...VFR conditions to persist at KSLC through the period. Afternoon showers and thunderstorms are expected to develop after 18z, with a roughly 30% chance to impact the terminal through around 22z. Any storms that develop will be possible of producing gusty and erratic winds during this period. Otherwise, expect winds to remain generally light and diurnally driven. .REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions to continue for all regional terminals through the period. Winds remain generally light and diurnally driven. Afternoon showers and thunderstorms are expected to develop again today, with greatest coverage generally south of the I-80 corridor. Storms will be capable of producing gusty and erratic outflow winds through this evening. && .FIRE WEATHER...The state will stay under southerly flow over the next several days as high pressure parks itself over the Four Corners region. This will act to draw monsoonal moisture northward. The increase will be gradual at first, with a more pronounced surge late in the weekend. This will bring increasing relative humidity values, decreasing temperatures, and increased coverage of showers and thunderstorms. The moisture will initially be high based, with gusty and erratic winds remaining the main threat today before wetting rains become more likely this weekend. Model guidance continues to suggest that the moisture will peak by the middle of next week. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Extreme Heat Warning until 9 PM MDT this evening for UTZ123-124. WY...None. && $$ SHORT TERM/FIRE WEATHER...Traphagan LONG TERM/AVIATION...Whitlam For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity