Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
997 FXUS65 KSLC 251028 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 428 AM MDT Tue Jun 25 2024 .SYNOPSIS...Hot and dry conditions will continue across northern Utah while showers and thunderstorms continue to be a threat across southern Utah. By Wednesday, the threat of showers and thunderstorms will spread across the state. Another round of strong thunderstorms is expected Thursday afternoon and evening. && .SHORT TERM (Through 12Z Thursday)...While late June is climatologically one of the driest part of the years for Utah, the last few days have been anything but typical. Morning upper air and satellite analysis indicates a broad upper level ridge remains in place across the southern Plains/southern Rockies. An atypically strong upper level trough is approaching the Pacific Northwest. PWs remain quite elevated, averaging around 1-1.25" across the lower valleys of southern Utah, around 0.50-0.75 across the remainder of southern Utah. Much of southern and eastern Utah will see SBCAPE values approaching 500-750 J/kg by this afternoon. With deep layer shear less than 20 kts and relatively slow storm motions, the most significant threat will again be flash flooding with any thunderstorms that form across southern and eastern Utah this afternoon and evening. Guidance suggests an MCV related to convection currently in northern Mexico/farther southern Arizona will rotate north around the upper level ridge and may bring the threat of nocturnal convection to Utah by tonight. Per usual, models are having a difficult time resolving this feature. By Wednesday, the upper level trough will be crossing the Pacific Northwest. This will help to substantially increase deep layer shear across much of the Utah and also help to push a relatively moist airmass northward. Expect widespread showers and thunderstorms to develop by Wednesday afternoon and evening, with the continued threat of heavy rain...and potentially small hail and gusty winds. Hot temperature are again expected across northern Utah this afternoon and evening. Overnight lows have trended cooler than previously expected...but kept going heat products given temperatures will once again approach the century mark across the Wasatch Front. .LONG TERM (After 12Z Thursday)...A progressive pattern will develop for the long term period as the ridge of high pressure responsible for the recent heat will shift east into the southern CONUS. Ample moisture will only be in place on Thursday as the first trough pushes through to our north. A dry airmass will be ushered in behind the aforementioned trough. This airmass will help to cool temperatures briefly, but the dry conditions will persist through the remainder of the period. This dry airmass will pair with windy conditions as another trough moves into the region this weekend resulting in favorable fire weather conditions. The approaching trough on Thursday will pair with PWATs (~1.2" for KSLC) approaching climatological maxes for this time of year. Forecasted CAPE values near 1000 J/kg and bulk shear >50kts will create an atmosphere conducive for strong to severe thunderstorms across the CWA. The limiting factor, however, will be how much precipitation and cloud cover will be lingering across the region from the previous days convective activity. A lot of the hi-res guidance does keep precipitation ongoing Wednesday night into the morning on Thursday. If these showers are able to dissipate early enough then the atmosphere could become primed for strong thunderstorm development as the axis of the trough passes through Utah and SW Wyoming. In addition to the threat of severe weather, flash flooding will also be a concern across flood prone regions such as dry washes, slot canyons and burn scars. This precipitation will quickly shift east and out of the CWA late on Thursday as drier and cooler air advects in behind the frontal passage. Friday`s high temperatures will be the coolest of the long term period with near normal temperatures. Shortwave ridging will temporarily build back into the area on Saturday leading to high temperatures returning to ~5 degrees above normal. Similar temperatures on Sunday along with increasing southwesterly flow ahead of our next trough will lead to gusty winds developing across most of the CWA. The dry airmass will be characterized by minimum relative humidity values <15% for the afternoon on Sunday. The trough axis will push east of us on Monday with temperatures the remainder of the period returning to near normal and winds weakening slightly, but staying elevated. && .AVIATION...KSLC...VFR conditions will persist for the KSLC terminal. Skies will be mostly clear with light diurnally driven winds. .REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will persist for the airspace throughout the period. Expect dry conditions with light and variable winds across the northern two thirds of the airspace with scattered afternoon convection developing for the southern third. These storms will be capable of producing gusty and erratic winds. && .FIRE WEATHER...Another day of anomalously high moisture across the south, with dry and hot conditions across the north. By Wednesday, an upper level trough will be crossing into the Pacific Northwest. This increase in flow combined with several subtle disturbances rotating through Utah will support more widespread convection and increasing humidities through the state. By Thursday, a dry slot will start nosing into western Utah while widespread convection continues across the remainder of the state. This may bring at least localized critical fire weather conditions to portions of western Utah. A cold front will cross the state late Thursday into Friday. A much drier airmass will build into the state Friday, with the threat of critical fire weather conditions in locations where fuels are conducive. This threat may extend through the weekend. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Excessive Heat Warning until 11 PM MDT this evening for UTZ101- 104>106-116. Heat Advisory until 11 PM MDT this evening for UTZ102-103-107- 118-119. WY...None. && $$ Kruse/Mahan For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity