Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
872 FXUS65 KSLC 182131 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 331 PM MDT Tue Jun 18 2024 .SYNOPSIS...Temperatures will trend warmer across the area through Thursday before anomalous moisture spreads into eastern Utah late Thursday through Friday, bringing showers and thunderstorms. Drier conditions are expected over the weekend with hot temperatures. && .SHORT TERM (THROUGH 12Z THURSDAY)...A west-southwesterly flow aloft is in place this afternoon over Utah as a mean longwave trough remains over the western CONUS. Several embedded disturbances continue to ripple through the mean trough, but very little in the way of moisture is available (0.2 inches of PWAT) to generate any showers. Temperatures will continue to remain on the cool side tonight, though generally warmer compared to last night. Temperatures will be much noticeably warmer tomorrow, given H7 warm advection as the mean trough axis retrogrades to the West Coast. However, afternoon maxes are still expected to remain slightly below normal. .LONG TERM (After 12z/6AM Thursday), Issued 423 AM MDT... Ensemble guidance remains in great agreement on a trough remaining upstream of the forecast area through at least early Friday with a ridge building into the area Friday through the weekend. Past Sunday, models diverge a bit as there is some uncertainty on the depth of a trough progged to move through southern Canada. The depth of this trough will ultimately influence the temperature trends (mainly in the northern area) through next week. A trough upstream of the area during the latter portion of the week will continue to promote warm and dry southwesterly flow over the forecast area, allowing temperatures to warm back to above normal levels. To the east of the area over the southern Plains, an wave propagating to the west will interact with the upstream trough and bring an increase in lower level flow as well as initiating a moisture flux into the eastern Great Basin region. Increased flow in the lower levels will bring increasing surface winds during the afternoon on Thursday. The increase in flow will bring concerns of elevated fire weather conditions in eastern Utah before the near surface moisture arrives. At this time, no fire weather headlines have been issued as fuels are not currently over their critical thresholds in the zones of concern. Moisture continues to work into the area through the evening hours on Thursday, while the aforementioned trough begins shifting over the region. Isolated showers and thunderstorms over eastern Utah will be possible, and will carry the threat of dry lightning as the lower level moisture lags. Should expect to see an increase in shower activity through the overnight hours as upper level support for lift increases. Going into Friday, upper support and increasing moisture in the lower levels will act to destabilize the environment and bring an increasing threat of strong thunderstorms and flash flooding (model PWAT anomalies continue to push 200-250% of normal over eastern Utah). Will need to continue to assess the threat of flash flooding on Friday afternoon as models maintain abnormally moist conditions over eastern Utah. The one concern with this is whether or not the added dynamics from the trough will bring too much cloud cover to destabilize the environment to the potential that the models are suggesting. In general, if you`re planning a slot canyon trip, you might want to hold off until late in the weekend. A stout ridge builds back over the region late in the weekend, which will help to reinforce hot conditions areawide as well as provide a drier environment. Confidence is increasing that the Wasatch Front will be pushing temperatures to near 100 degrees and into the mid- to upper-100s for lower elevations in southern Utah by Sunday. Will need to continue to assess the need for heat related headlines by Sunday as overnight lows will provide minimal recovery from the heat. Thankfully for the northern portions of Utah and southwest Wyoming, the heat looks to be fairly short lived as an active storm track resumes to the north of the area, which should tamper down the strength of the high. There is still uncertainty on how much the high will be repressed by the northern stream, but in general we should expect a gradual cooling trend into the middle portion of the week across the northern half of the area. For the southern area, heat looks to be maintained unless we can develop a deeper trough into the CONUS (supported by ~30% of ensemble members). && .AVIATION...KSLC...Northwest winds are forecast to shift southeast around 04z this evening at light speeds. VFR conditions are forecast throughout the forecast period. .REST OF UTAH AND SOUTHWEST WYOMING...Calmer conditions are forecast today with lighter winds across the region. These conditions will persist into tomorrow morning. VFR conditions are expected for all sites with only some lingering high based clouds in southern Utah. && .FIRE WEATHER...Relatively benign weather is expected through Wednesday with dry conditions remaining in place while temperatures trend warmer. Southwest winds increase on Thursday while midlevel moisture starts to spread into southeast Utah. As the lower levels remain relatively dry on Thursday, the increasing winds will bring isolated or marginally critical fire weather conditions to portions of southern Utah where fuels have cured (latest guidance only indicates localized areas with greater than a 50% chance of reaching critical fire weather conditions). Additionally, there will be a threat of isolated dry lightning on Thursday. As the airmass continues to moisten across eastern Utah into Friday, humidities will increase. Precipitation chances will also increase across eastern Utah with a 40-60% chance of wetting rain. Thereafter, the airmass begins to quickly dry, although lingering low-level moisture may continue to bring a threat of showers and thunderstorms to portions of southern/eastern Utah on Saturday. Hot temperatures will settle into the area for the weekend into early next week. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && $$ Cheng/Webber/NDeSmet For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity