Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
191 FXUS65 KSLC 190958 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 358 AM MDT Thu Sep 19 2024 .SYNOPSIS...Stable conditions remain in place across the region with temperatures returning to near, or slightly below, normal on Thursday. Dry conditions prevail until Friday/ Saturday as an upper low moves across southern Utah and brings showers and thunderstorms to southern Utah. Dry, seasonable conditions are then expected for next week. && .SHORT TERM (Through 12Z/6AM Sunday)...Early Thursday morning, a closed low was located off of the Southern California coast, with a modest northwest/southeast oriented ridge axis in place across Utah and southwest Wyoming. Deterministic and ensemble solutions are in good agreement regarding the large-scale pattern evolution through the first half of the weekend, bringing the low eastward through Southern California on Friday, across northern Arizona Friday night, and finally through southern Utah Saturday into Saturday night. Initial instances of precipitation are expected to develop across southwest Utah on Friday evening, before showery conditions overspread much of southern and central Utah on Saturday. Mid-level cyclonic flow around the low will tend to add a southeasterly orographic enhancement component to the precipitation field on Saturday, tending to favor those eastern slopes of the central and southern mountains and up into Castle Country. The low is expected to undergo strengthening with a noticeable TROWAL developing across Colorado by Saturday night, with an increasingly organized trend in the QPF fields across Colorado during this time. Most likely, healthy precipitation associated with this phase of the low will occur east of the forecast area, although ensemble max QPF does approach 3/4" of an inch across eastern portions of the Uinta Basin, suggesting a low- end chance that some of the healthier moisture could wrap back into this area. Otherwise, highest precipitation appears that it will be confined largely to the terrain of central/eastern Utah, particularly those areas that perform will in moist, easterly/southeasterly flow. Either way, for those planning to recreate across southern/central Utah on Saturday, be prepared for cool, damp and less than ideal conditions. With the low tracking across southern Utah, a period of easterly mid-level winds will develop Friday night through Saturday morning across northern Utah and southwest Wyoming, leading to the potential for enhanced canyon winds. An examination of the 700mb winds, thermal gradient and pressure gradient reveals that these parameters all fall short of typical values that would be associated with a downslope wind event. Currently, ensemble max wind gusts during this period max out in the 25-35 mph range, with less than a 10% chance for gusts to reach 58 mph. Thus, this event can be best described as an enhanced canyon wind event as currently presented by the model solution space. .LONG TERM (After 12Z/6AM Sunday)...Beautiful weather is in store for the long-term period, with near-normal temperatures and mostly clear skies. In the wake of a closed low, shortwave ridging will build across the area on Sunday, producing drier conditions and temperatures hovering around normal. Monday will largely be the same, though a passing shortwave trough sliding across northeastern UT/southwestern WY will result in partly to mostly cloudy skies, with a few isolated showers over the Uinta Mountains. There are still a handful of ensemble members that favor a stronger shortwave, which could bring light showers to more of the area, though this chance is fairly low (15% chance). Heading into midweek, a ridge will likely build across the area, raising temperatures to just above normal. Model guidance hints at another developing trough possibly late in the week, but there is still a wide range of potential solutions. && .AVIATION...KSLC...Winds will remain southeasterly through the morning, becoming light and variable at times. Winds will then transition to northwesterly around 17-18z. VFR conditions will prevail with mostly clear skies. .REST OF UTAH AND SOUTHWEST WYOMING...Largely light, diurnally- driven winds will prevail, with VFR conditions persisting. && .FIRE WEATHER...Cool, stable conditions will remain in place Friday across the area, with good overnight recovery, with the exception of the southeast portion of Utah. An area of low pressure is then expected to track into northern Arizona Friday, and across southeast Utah on Saturday. This will bring showers and a few thunderstorms to southwest Utah late Friday, with this activity expected to spread across much of southern, southeast and central Utah on Saturday. The low is then expected to exit the area on Sunday, with cool temperatures in its wake. Overnight recovery will improve for central, southern and southeastern areas this weekend thanks to the presence of the low. As we head into next week, dry conditions are expected, along with near normal temperatures for late September. At this time, no days with critical fire weather conditions are expected, although RH is expected to steadily dry out, especially southern areas. Overnight recovery is expected to be largely good for northern areas through the week, and modest for southern areas. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && $$ ADeSmet/Cunningham For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity