![National Oceanic and Atmospheric Administration](/build/images/header/noaa.d87e0251.png)
![National Weather Service](/build/images/header/nws.4e6585d8.png)
![United States Department of Commerce](/build/images/header/doc.b38ba91a.png)
Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
826 FXUS65 KSLC 042140 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 340 PM MDT Thu Jul 4 2024 .SYNOPSIS...High pressure will gradually shift eastward over the next seven days, bringing increasingly warm temperatures first to southern Utah this weekend...and then northern and central Utah Tuesday. A few disturbances passing well to the east will help to increase winds across the eastern valleys Saturday and Sunday. && .SHORT TERM (Through 12Z Sunday)...It`s going to get quiet hot, however, that is covered well in the long term forecast discussion. For the immediate short term, afternoon upper air and satellite analysis indicates a strong, broad upper level ridge off the California Coast. A longwave trough is currently centered across the northern High Plains. Most of Utah is under northwest flow. This northwest flow will continue to bring weak fronts through northern and eastern Utah over the weekend. The main impact will be an increase in gusty winds across eastern Utah...bringing the potential for critical fire weather conditions Saturday to the San Rafael Swell and the western Uinta Basin. By Sunday morning, the upper level ridge will be centered near the central Sierras...and the heat will be on for southern Utah. .LONG TERM (After 12Z Sunday), Issued 418 AM MDT...Main theme of the long term portion of the forecast will be very hot and dry conditions. Global deterministic and ensemble forecast systems are in excellent agreement in their relative depictions of the presence of an unseasonably strong high pressure ridge into the region. While there remain some minor strength and positioning differences among the model solution space, this doesn`t take away from the fact that temperatures may approach record values in the Sunday through Tuesday timeframe across Utah. By Sunday, EFI values and anomaly plots suggest the most likely location for unseasonably hot temperatures reside across SW Utah, with this extreme heat then expanding into northern valleys by Tuesday and persisting through the end of the workweek, coincident with the center of the ridge migrating overhead. Existing Excessive Heat Warnings will likely need to be expanded in both geographical extent and temporal extent as we get closer to the event. There is some uncertainty as to how far out to extend these at this juncture, as temps may ease ever so slightly across southwest Utah by mid-week, but still remaining above normal. So, how hot are temperatures likely to get? In St. George, temperatures will reach or exceed 110F each day from Saturday through at least Thursday (with lows in the upper 70s to around 80F), with a 10% chance of tying the State`s all-time record high of 117F on Sunday, per latest NBM probabilities. Thus, forecast temperatures in terms of magnitude through the period have some potential to rival the extreme heat wave of early to mid July 2021. Excessively hot temperatures will also overspread Zion NP and the Glen Canyon area where warnings are in effect. Farther north, the hottest days are most likely to begin on Tuesday and persist through the workweek, where high temperatures are forecast to meet or exceed 100F. Here, latest NBM advertises nearly a 30% chance of tying SLC`s all-time record high of 107F by Thursday or Friday of next week. Day- to-day variations in temperature trend as well as the magnitude of the temperatures can be explained by the subtle differences in the strength and positioning of the ridge through this time. The bottom line is that the cumulative effects of this excessive heat will place significant stress on people and pets, particularly those without adequate cooling and those that spend significant time outdoors, which adds to the vulnerability. Avoid strenuous outdoor activities during the hottest time of the day, drink plenty of water and limit exposure to the sun. Towards the end of the workweek, an increasing portion of the model solution space advertises an increase in PWAT across the region, with this moisture originating from the western Mexican coastal region and the Gulf of California. Latest consensus advects this moisture to the north and into the Great Basin in the Thursday- Sunday timeframe next week. The trajectory of this moisture plume will ultimately be dictated by the position of the ridge by this time, which ensemble means generally suggesting the vicinity of the Four Corners region. It`s too early to conclude whether this moisture will be limited to the mid-levels (tending to favor dry lighting assuming sufficient instability) or will be manifest in an increase in sensible low-level moisture all the way through the precipitation-bearing layer, which would be more supportive of more widespread rains. Either way, moisture does appear sufficient to begin to support at least low-end probability for precipitation across high-terrain areas of southern Utah as early as next Thursday/Friday, with the potential gradually increasing with time. Uncertainty does exist surrounding the timing and extent of any moisture, which will dictate where and when precipitation chances will appear in the forecast as we approach this period of time. && .AVIATION...KSLC...No significant weather expected at the terminal. VFR conditions persist with clear to mostly clear skies. NW winds anticipated to shift SSE ~04-06Z this evening, and back to NW ~16- 18Z Friday. Some periods of more light and variable flow possible near times of diurnal wind shifts. .REST OF UTAH AND SOUTHWEST WYOMING...In general, no significant weather is expected at area terminals through the TAF period, with VFR conditions and clear to mostly clear skies persisting. Only noted exception is a small potential for any terminals downwind of area fires to experience brief VIS drops due to smoke plume advecting through. Otherwise, anticipate winds to follow a fairly typical diurnal pattern. && .FIRE WEATHER...A strong upper level ridge will gradually shift eastward through the next 7 days. A mean trough remains across the northern High Plains, with occasional disturbances shifting south into the High Plains. Eastern Utah will remain close enough to this stronger northwest flow to allow for periods of critical fire weather conditions for the eastern valleys Saturday and Sunday. Meanwhile, as the upper level ridge shifts east, very hot temperatures will build into southern Utah Sunday...gradually shifting north through the remainder of the state for Tuesday. This long duration heat wave will bring near record temperatures, single digit daytime RHs for many locations, and very poor overnight recoveries. Current models suggest this extended heat wave may last through the next weekend...and beyond...though mid- level moisture may begin to increase across portions of southern and eastern Utah as early as next Thursday. While this may bring a slight improvement to humidities...there is also the potential for an increased threat of dry lightning. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Red Flag Warning until 9 PM MDT this evening for UTZ482-489. Fire Weather Watch from Saturday afternoon through Saturday evening for UTZ482-489. Excessive Heat Warning from 9 AM Sunday to 9 PM MDT Tuesday for UTZ123-124-131. WY...None. && $$ Kruse/Warthen/ADeSmet For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity