Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
887 FXUS65 KSLC 261005 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 405 AM MDT Sun May 26 2024 .SYNOPSIS...High pressure will gradually work its way into the area through the first half of the upcoming week. A substantial warming and drying trend will accompany this high, pushing temperatures 5 to 10 degrees above normal by Tuesday. A mostly dry cold front will push through the region late Wednesday through Thursday. && .SHORT TERM (Through 12Z/6AM Tuesday)...The shortwave trough which brought widespread showers and thunderstorms to much of the forecast area Saturday is moving into the central High Plains early this morning, leaving a stable and relatively cool airmass across the eastern Great Basin and Colorado Plateau region. Gradually rising heights and resulting warming aloft, coupled with airmass modification from a late May sun angle, will allow temperatures to rebound 5 to 8 degrees this afternoon. Despite this temps will remain slightly below climo, reaching the low 70s along the Wasatch Front and approaching 90 near St George. Mid level ridging will amplify across the Great Basin region on Memorial Day, allowing for an additional 5-8F degrees of warming and pushing temperatures a little above climo Monday afternoon. Upper 70s to low 80s will be common across northern and western valleys, while St George reaches the mid 90s. As the ridge axis shifts slightly east Monday afternoon, a weak shortwave trough crossing the Sierra Crest/Western Great Basin will spread just enough moisture into the area to support isolated high based convection the higher terrain late Monday afternoon. This threat will be greatest across the central and southern Utah terrain. Given the deeply mixed boundary layer in place any precip would be minimal, and the main threat would be microbust wind and a few lightning strikes. .LONG TERM (After 12Z/6AM Tuesday)...On Tuesday, deterministic and ensemble model solutions are well-clustered in their respective output, all showing the presence of modest deep-layer southwest flow across the region in the wake of a departing ridge, and downstream of an area of low pressure approaching the British Colombian coastline. Such a configuration is favorable for warm temperatures across the region, and that is indeed expected to be the case, with the warmest day of the year so far in store for Tuesday. Highs will surge into the upper 90s across Lower Washington County, and into the mid to upper 80s across the Wasatch Front. Modest moisture advection will combine with the influence of the approaching low to promote an isolated shower or thunderstorm or two, mainly across high terrain areas of northern Utah and SW Wyoming during the afternoon and early evening. Gusty microburst winds appear to be the main threat. Over the past several days worth of forecasts, the greatest source of uncertainty has been around the strength, track and timing evolution of the British Colombian low. While there still remain some lingering differences, model solution space appears to be converging on a solution that drops this low across the Northern Rockies in the Wednesday to Thursday timeframe, with the most likely solution suggesting the low and associated cold front will graze northern Utah and SW Wyoming in the process. There is a seasonably strong tight height and baroclinic zone associated with this low, so main impacts with it appear to be gusty westerly winds, especially on Wednesday and Thursday, when wind-prone locations such as SW Wyoming are in line for gusts in the 30-40 mph range during the afternoon and early evening hours. Additionally, a few showers and thunderstorms will once again develop, namely over higher terrain areas of northern Utah and SW Wyoming once again. After another warm day on Wednesday, temperatures will cool a few degrees in the wake of the front across northern areas Thursday and Friday. The above represents the current most likely solution. It`s worth mentioning that there remain some members that do not budge the ridge all all, and such an outcome would imply a continuation of warm and dry conditions through the week. Meanwhile, other members on the opposite end of the distribution drop a stronger low across Utah, suggesting greater coverage of cooler, unsettled conditions. Nonetheless, there is quite good consensus in the idea of a ridge building back across the area next weekend, with some modest strength and positioning differences. && .AVIATION...KSLC...VFR conditions expected through the period with occasional mid clouds early this morning, and a few afternoon cumulus building off of the terrain. In terms of winds, morning drainage (SSE) winds expected to become NW between 16Z and 18Z before returning to southerly between 04-05Z this evening. .REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions largely anticipated through the period, with isolated valley fog possible for those areas that receive late-evening rain and have since cleared up in the presence of light winds. Otherwise, mid cloud deck is expected to diminish this morning with a few cumulus building off of the terrain this afternoon. && .FIRE WEATHER...In the wake of Saturday`s storm system, high pressure will build into the region today, and further strengthen through the early portion of the upcoming week. This will result in a considerable warming and drying trend beginning today, and continuing through Tuesday. By Tuesday afternoon summer like conditions can be expected with max temperatures will run 5 to 10 degrees above normal, and afternoon humidity falling below 15 percent across much of the state. This warm and very dry airmass will remain in place through much of Wednesday, as gusty southwest winds develop ahead of an approaching cold front. These winds will likely gust in excess of 25 mph Wednesday afternoon over much of the region south of I-80. The combination of warm temperatures, very low humidity and gusty winds would meet critical fire weather conditions if fuels were sufficiently dry. A mostly dry cold front is forecast to push into northern Utah late Wednesday, then continue through central and eventually southern Utah Thursday. Currently little if any precipitation is expected with this front, with the main impacts being gusty northerly winds behind the front along with a cooling trend. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && $$ Seaman/ADeSmet For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity