Area Forecast Discussion
Issued by NWS Salt Lake City, UT
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Issued by NWS Salt Lake City, UT
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-- Discussion containing changed information from previous version are highlighted. --290 FXUS65 KSLC 202149 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 349 PM MDT Thu Jun 20 2024 .SYNOPSIS...-- Changed Discussion --Deep moisture will spread into eastern Utah through Friday, bringing the threat of showers and thunderstorms capable of producing heavy rain. Drier conditions are expected over the weekend and into early next week with increasingly hot temperatures, though enough low level moisture is expected to linger across southern Utah to support isolated showers and thunderstorms through early next week.-- End Changed Discussion --&& .SHORT TERM (Through 12Z/6AM Saturday)...-- Changed Discussion --Moisture is on the increase this afternoon over eastern Utah with satellite derived PWs predominately in the 0.7 to 0.8 inch range. Showers and thunderstorms have sprouted over southeast Utah, but so far heave primarily stayed east of the CWA. Any storms that develop through the early evening will have the potential to produce gusty microburst winds given the high based nature of the moisture. Elsewhere across the area, seeing generally dry conditions with maxes in excess of 5F warmer than values observed yesterday, about 5F above seasonal normals. Moisture will continue to spread into eastern Utah through Friday morning, with values topping out in the 1.0 to 1.2 inch range over eastern Utah, in excess of the 90th percentile for moisture this time of year. Convective development will be aided by shortwave energy from a weakening trough moving across the area, also providing good jet support and notable shear. Thus, a greater than usual potential persists for storms that will produce heavy rain capable of flash flooding, and a Flash Flood Watch remains in effect tomorrow afternoon and into the early evening for much of eastern Utah. Some concern of developing cloud cover limiting convective development, as sometimes happens with an airmass this moist. However, if such clouds fail to develop or erode, storms will become fairly widespread and could result in dangerous conditions for outdoor activities in eastern Utah. .LONG TERM (After 12Z/6AM Saturday), Issued 416 AM MDT...Saturday looks to have at least some potential to be another interesting day across portions of the area. Similar to Friday`s setup, forecast region will be positioned on the NW periphery of a strong ridge extending throughout the southern Plains, though the northern stream trough influence will be lessened as it exits. Still, southern and eastern Utah in particular will see continued favored moisture content with elevated PWAT values (around 125-200% of normal) in addition to enhanced upper level jet flow overhead. While less than that of Friday, this jet flow should still yield marginal deep layer shear around 20-30 kts or so. Provided any lingering cloud debris from Friday has cleared, modest destabilization (MUCAPE ~250-750 J/kg) should also occur. Given the departure of the northern stream trough, a little less trigger mechanism is noted, but combination of terrain and weak PVA should yield some scattered convective development by the afternoon, albeit likely with lesser of an areal extent. Given the aforementioned ingredients, the ECMWF Extreme Forecast Index (EFI) continues to also highlight southern to eastern Utah in shading depicting anomalous CAPE-Shear values, further supporting at least some potential for more mature and strong convection. Additionally, given the moisture profile, any mature convection should be able to efficiently produce rainfall, so those recreating in rain sensitive areas (slickrock areas, slot canyons, dry washes, etc.) should remain weather aware. Elsewhere, dry conditions are expected, with increasingly hot weather as H7 temps continue upwards. Sunday onward into midweek, anomalous moisture lingers especially across southern and eastern Utah leading to continued daily chances of isolated to scattered convection, and the nearby strong ridge continues to yield very warm temperatures. By Sunday, northern Utah warms sufficiently that the urban corridor in particular will see heat approaching potentially dangerous levels (upper 90s to low 100s across much of Wasatch Front). Opting to hold off at least one more set of guidance given it is still a few days out, but it appears increasingly likely some sort of heat related headlines may be needed for a portion of the region. The following several days show similar levels of heat to maybe ever so slightly cooler, though spread in guidance also increases a bit. For the southern half of Utah, conditions will gradually warm day to day moving into the middle of the week, with increasing potential for heat related risk accordingly. By Wednesday, current suite of guidance shows widespread upper 90s on into the 100s, with current NBM giving ~25% chance to hit or exceed 110 at KSGU. Given the prior mentioned lingering moisture and limited daily convective potential, these high marks will have some potential to be modulated by whatever does manage to develop. In any case, suffice to say the heat is very much back as we move into astronomical summer. Looking Thursday onward a little beyond the coverage of this forecast package, guidance shows increasing consensus on a trough deepening southward from the PacNW. Less consensus is noted on the eventual evolution including how quickly it advances inland and how deep it remains when it does. While some guidance shows any trough influence could come as early as Thursday, ensemble membership increases by Friday, with only a limited number of members showing little to no influence. Still, this looks to be the next window to see the heat abated a bit, at least across the northern half of the forecast region or so.-- End Changed Discussion --&& .AVIATION...-- Changed Discussion --KSLC...Northwest winds will transition to southeast around 05Z. Mostly clear conditions or scattered clouds will prevail overnight. South winds will increase around 15Z, with gusts around 20 knots through around 19Z. A transition to northwest winds is likely around 20Z. Mostly cloudy conditions are likely, with around a 20% chance for a shower or thunderstorm from 18-03Z. .REST OF UTAH AND SOUTHWEST WYOMING...Mostly cloudy to overcast conditions will build into eastern Utah, with isolated to scattered showers capable of gusty, erratic outflow winds after 12Z. Showers and thunderstorms capable of heavy rain are likely from around 18- 03Z. Almost all showers and thunderstorms will be in the eastern half of Utah. Southwest winds will gust around 25 knots throughout southwest Wyoming and southern Utah from around 15-03Z.-- End Changed Discussion --&& .FIRE WEATHER...-- Changed Discussion --Moisture is starting to increase over southeastern Utah this afternoon, resulting in some development of showers and thunderstorms. The moisture will peak Friday, with values quite unseasonably high. An approaching trough will provide additional instability, so showers and storms will be fairly widespread over eastern Utah by Friday afternoon. Any storms that develop will be capable of producing heavy rainfall along with gusty and erratic winds. The trough will move east of the area on Saturday, allowing high pressure to rebuild. This will bring a drying trend, but a few showers will remain possible over the weekend over the higher terrain of southern Utah. With the ridge building over the weekend, temperatures will steadily warm, particularly over northern Utah.-- End Changed Discussion --&& .SLC WATCHES/WARNINGS/ADVISORIES... UT...Flood Watch from Friday afternoon through Friday evening for UTZ113-120-121-128>131. WY...None. && $$ SHORT TERM/FIRE WEATHER...Traphagan LONG TERM...Warthen AVIATION...Wilson For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity