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Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
532 FXUS65 KSLC 292114 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 314 PM MDT Sat Jun 29 2024 .SYNOPSIS...High pressure will bring hot and dry conditions through the remainder of the weekend. Increasing southwest winds will bring the potential for critical fire weather conditions into Monday across western Utah. A cold front will cross the region early next week bringing a cooldown for the midweek period. && .SHORT TERM (Through 12Z/6AM Monday)...Southwesterly flow resides across the Great Basin region this afternoon, sandwiched between an upper trough along the Pacific Coast, and an elongated subtropical ridge axis extending into the Desert Southwest. Lingering moisture remains across eastern Utah, and has supported isolated convection from the Manti-Skyline area northward into the western Uintas. This convection should quickly diminish with the loss of daytime heating. Further south, an additional plume of moisture noted across central/southern Arizona eastward into New Mexico. Meanwhile, much drier air resides across western Utah where afternoon RH values are running in the single digits, and temperatures in the mid to upper 90s including KSLC. This hot and dry airmass will remain across western Utah through Sunday, allowing KSLC to make a run at the 100F mark. The moisture plume across the Desert Southwest will spread into eastern Utah, bringing an increase in convective coverage as compared to today, and have increased PoPs across these areas. By Sunday evening a dry frontal boundary will push into far northwest Utah, crossing the Wasatch Front during the evening hours. .LONG TERM (After 12Z/6AM Monday), issued 314 AM Saturday...A bit of a cooldown is our weather headline for the first of July, which is not the headline you would anticipate. This cooldown won`t impact all of our area, but the northern 2/3rds of Utah will feel the impacts. The set up here is a fairly broad and far reaching trough of low pressure across the western US, tracking very slowly eastward through mid- week. There isn`t a forecast model that doesn`t support this solution so there is quite good confidence in these cooler conditions. The trough moves so slow in fact that conditions Monday compared to Tuesday are quite similar, or even cooler. Conditions are mainly expected to be dry across the region, in all areas except far southeastern Utah where some moisture may reside. A slight risk for showers and thunderstorms will exist in areas like Lake Powell/Glen Canyon where lift is supportive ahead of the trough. If forecast confidence wavers any, it will be in the mid-week time frame when the low exits and strong high pressure begins to build in from the west. The transition period timing does differ between forecast models with the GFS bringing in the high by Wednesday while the ECMWF waits until later in the week. Friday and into the weekend, temperatures become a tough forecast. Consensus is for high pressure to be parked somewhere over the western US. However, it will make a difference which areas feels the heat the most based on where it does situate itself. Essentially, there`s a 50/50 split amongst ensemble models favoring hotter temperatures or favoring cooler temperatures in our area. The hotter temperatures would arrive under high pressure centered directly over our area, favored mostly by the GFS, whereas favored cooler temperatures are noted by northwest flow associated with an area of low pressure to our north. The range for possible temperatures outcomes widens Friday and Saturday, which is no surprise looking at this uncertainty. && .AVIATION...KSLC...No precipitation and clear to mostly clear skies expected at the terminal. Enhanced southerly drainage flow anticipated overnight into Sunday morning with a few gusts possible. Gusts pick up and southerly winds are then maintained through the day Sunday. .REST OF UTAH AND SOUTHWEST WYOMING...Isolated diurnal convection possible across eastern Utah through Saturday evening, with some redevelopment possible Sunday afternoon. Otherwise, anticipate mostly clear to partly cloudy skies and VFR conditions. After following a somewhat typical diurnal pattern overnight, enhanced south to southwesterly winds and gusts expected through the day Sunday. && .FIRE WEATHER...A hot southwesterly flow will reside across the region through the remainder of the weekend. Across western Utah, the airmass will remain very dry, with daytime RH values in the 5 to 10% range. This combined with gusty afternoon winds will result in critical fire weather conditions across west central and southwest Utah Sunday, and have upgraded to a Red Flag Warning across these areas. Further east, the next surge of monsoon moisture across Arizona will spread across the eastern half of Utah Sunday afternoon, resulting in elevated daytime RH along with isolated to scattered showers and thunderstorms. Given the elevated RH values, have dropped the Fire Weather Watch for Sunday across zone 498. A cold front will push into northern Utah late Sunday, then slowly cross central and southern Utah late Monday through Monday night. Ahead of this front, hot dry and breezy conditions will persist across central and southern Utah, where the Red Flag Warning will remain in effect through Monday evening. RH is a bit more marginal across the eastern half of the state Monday, thus have held onto the Fire Weather Watch for zone 498 for now. A cooler but dry airmass will follow the front for Tuesday, along with daytime northwest winds. A gradual warming trend will follow for the remainder of the week. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Red Flag Warning from noon Sunday to 9 PM MDT Monday for UTZ492- 495>497. Fire Weather Watch from Monday afternoon through Monday evening for UTZ498. WY...None. && $$ Seaman/Warthen/NDeSmet For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity