Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
279 FXUS65 KSLC 282148 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 348 PM MDT Tue May 28 2024 .SYNOPSIS...A cold front will move through the region Wednesday. Scattered showers and thunderstorms associated with the front will bring a threat of lightning and gusty winds. Temperatures behind the front drop to below normal, but by Friday onward temperatures areawide return to near to above normal. Largely dry conditions are also anticipated to settle in following Wednesday`s frontal passage. && .SHORT TERM (Through 12Z/6AM Thursday)...Afternoon synoptic analysis shows mid/upper level ridge axis beginning to shift east in response to amplifying troughing into the PacNW. This has allowed for some weak energy to advect through overhead, which in combination with diurnal destabilization and mostly mid-level moisture is resulting in isolated convection. Mostly have seen convection tend to favor initiating off high terrain before drifting northeastward, but have seen a bit of general initiation over portions of western Toole and Box Elder County. With dry subcloud layers, SPC mesoanalysis highlights the bulk of the forecast region with DCAPE values at or above 1000 J/kg. As a result, any convection that matures sufficiently will be capable of gusty and erratic outflow winds as a primary threat in addition to lightning. So far today have generally seen max gusts in the 35-50 mph range, but wouldn`t entirely rule out a gust 50+ mph from anything more robust. While a few showers may linger into the evening, should see activity wane with loss of daytime heating. Wednesday continues to look like the more interesting day overall in regards to convective potential. Model guidance continues to show good consensus in a cold frontal boundary advancing into the region as the aforementioned PacNW trough continues to deepen and shift inland. Some minor differences are noted in exact timing, but rough timeline has the front entering N UT and SW WY by late morning to early afternoon, with the front continuing southward through the afternoon hours, eventually making it into S UT by late evening (though likely becoming more diffuse by then). Sufficient moisture feed ahead of the front (ensemble mean PWATs ~100-150% of normal) in combination with extra synoptic support and convergence along the front should result in scattered convective development accordingly as the front moves into the area. That said, CAM guidance ranges from very isolated (HRRR) to more widespread scattered (high res NAM), with reality probably somewhere more in the middle. CAMs do also suggest convective potential becomes less likely as the front drops further into S UT. While exact timing will influence the degree of destabilization, HREF mean SBCAPE builds to ~300-1000 J/kg late morning/early afternoon ahead of the front, and mean deep layer shear remains in the 20-40 kt range or so. This combination will be more favorable to allow stronger and more organized convection, as well as potential for better shear/cold pool balance. As a result, will have a threat of strong gusty winds with tomorrow`s convection, as well as potentially some small hail. Once again anticipate convection to further wane in the evening as instability decreases and the front continues to lose definition. Aside from convection, cooling H7 temperatures behind the baroclinic zone will result in much cooler overnight lows, with more marked decreases the northern half of the forecast region particularly. .LONG TERM (After 12Z/6AM Thursday), Issued 404 AM MDT...Thursday will begin a modest temperature drop in the wake of a cold front Wednesday. But for the end of May, temperatures are forecast to be very seasonal and very pleasant. The weather pattern headed into and through the weekend look to bring rather mild conditions to the region. Warming temperatures are forecast as southwest flow arrives by Saturday with high temperatures near the triple digit marker in St. George and in southeast Utah. High pressure is not expected to leave the region anytime in this long term forecast. In fact, there`s little variance in ensemble models until next week, where the question becomes, just how high will temperatures climb with a building ridge? && .AVIATION...KSLC...Isolated showers capable of gusty, erratic outflow winds are likely through around 06Z. Light southeast winds will prevail with mostly clear conditions once showers taper off through around 16Z. A cold front will transition winds to northwest around 16Z, with gusts around 20 knots through the afternoon. Clouds will increase, with isolated to scattered showers and thunderstorms from roughly 20-00Z. Gusty, erratic outflow winds are likely with showers and thunderstorms. .REST OF UTAH AND SOUTHWEST WYOMING...Isolated showers for southwest Wyoming and northern Utah capable of gusty, erratic outflow winds will last through around 06Z. Mostly clear conditions with light winds are likely after. A cold front will track into northwest Utah around 12Z, sweeping across southwest Wyoming and northern Utah through the morning and southern Utah through the afternoon and evening. Isolated to scattered showers and thunderstorms are likely from roughly 20-03Z, with southwest Wyoming and northern Utah most likely to get gusty, erratic outflow winds. && .FIRE WEATHER...A cold frontal boundary will move southward through Utah on Wednesday. The front will likely move through northern Utah late morning on into the afternoon hours, and central Utah thereafter from the afternoon into the early evening hours. Moisture appears sufficient to produce some isolated to scattered convection along the front, and with fairly high cloud bases, anticipate convection to carry a threat of gusty and erratic outflow winds in addition to sporadic lightning. The front will begin to lose definition as it moves into southern Utah, and convective threat looks lower accordingly. Colder temperatures set in behind the front, with below normal temperatures on Thursday (excluding southern Utah). Temperatures quickly rebound by Friday on into the weekend, moving back above normal. Drier conditions also appear likely as a ridge dominated pattern is generally favored to develop at this time. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && $$ SHORT TERM...Warthen LONG TERM...NDeSmet AVIATION...Wilson FIRE WEATHER...Warthen For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity