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Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
540 FXUS65 KSLC 121033 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 433 AM MDT Wed Jun 12 2024 .SYNOPSIS...Very hot temperatures will build into the region through Thursday, with the potential for the Wasatch Front to breach the century mark. An upper level low may bring cooler temperatures and precipitation by Friday. && .SHORT TERM (THROUGH 00Z SATURDAY)...High pressure will continue building into the area today and tomorrow ahead of an upper low that is continuing to meander off the Baja/SoCal coast. The airmass will continue to trend warmer today under the ridge, with H7 temperatures this afternoon forecast to range from around +15C across far northern Utah to +19C across east-central/southeast Utah. These H7 temperatures will then warm very slightly across the far north tomorrow while cooling a bit from the southwest. Combined with mostly sunny skies today, the warm airmass will lead to hot temperatures with afternoon maxes of 9-18 degrees above climatological normals across the forecast area. Tomorrow, midlevel moisture will start to increase, with increasing clouds from around the spine of Utah through the eastern valleys. This may result in temperatures being slightly cooler in those areas, while northern valleys remain hot (slightly hotter than today), especially as increasing southwest flow aids in mixing. Excessive Heat Warnings and Heat Advisories remain in place with no changes planned with this package. The airmass will remain relatively dry today. Still, PWATs of around 0.7 inches are in place across northern Utah. This will coincide with an axis of higher instability this afternoon where CAMS are indicating a few showers (and perhaps a thunderstorm or two with the stronger showers) will develop this afternoon and evening. Tomorrow, with the midlevel moisture moving in from the south, isolated to widely scattered high-based showers will be possible across the southern mountains through the east-central valleys. Cannot rule out a thunderstorm, but instability looks to be rather weak tomorrow. Otherwise, main threat will be gusty microburst winds given the dry low levels. The upper low will eject across southeast Utah on Friday while trending weaker. Moisture will continue to increase, but latest models suggest the bulk of the moisture may be farther east. As such, expect mainly high-based showers to continue across portions of southern/eastern Utah tomorrow night through Friday, with a somewhat greater potential for measurable (but not necessarily heavy) rain on Friday. Temperatures will start trending cooler again, but will remain slightly above climatological normals across the south and around 6-12 degrees above normal across the north. .LONG TERM (After 00Z Saturday/6PM Friday)...Sensible weather through much of the long-term period will be influenced by a broad trough initially setting up over the PacNW. Over the weekend, zonal flow will persist as the trough inches closer. Highs across northern areas will cool by a few degrees each day, influenced by the approaching trough, while highs in southern UT remain largely unchanged. Westerly winds across southern UT will begin to increase on Sunday as a strong shortwave trough begins to push southward and eastward. Current ensemble mean wind gusts range from 30-45mph across southern UT on Sunday and Monday afternoons; combined with critical RH <15%, this is certainly something to monitor for any fire weather concerns, especially given some fuels approaching critical. This shortwave trough will bring a strong cold front across portions of the northern Great Basin, with some question as to how far south it reaches. Current ensemble guidance is trending even cooler across UT and southwest WY, with 70% of members favoring a deeper trough. Around 40% of members have 700-mb temperatures dropping below 0C, which would be below the climatological 10th percentile for mid-June at SLC! For additional comparison, today and tomorrow could see 700- mb temperatures up to +16C. All that said, keep in mind that there is plenty of uncertainty, with a 25th-75th spread of -2C to +6C by Tuesday morning. So, what does this mean at the surface? In short, below-normal surface temperatures are looking increasingly likely. And finally, regarding any precipitation chances...despite some increasing mid-level moisture behind the frontal passage, precipitation is unlikely as the air mass will still be quite dry. && .AVIATION...KSLC...Southeasterly winds around 7-12kts will continue until a transition to northwesterly around 18-19z. VFR conditions will prevail. .REST OF UTAH AND SOUTHWEST WYOMING...Light, diurnally-driven winds will prevail overnight, with increasing southwesterly winds up to 25kts developing after 17z across central and southern UT. A few isolated showers are possible over the Uinta Mtns after 20z, with a 10% chance of reaching the vicinity of KHCR between 20-23z. && .FIRE WEATHER...High pressure will continue to build into the area through tomorrow, allowing the warming trend to continue, with very hot temperatures expected today and tomorrow. A few isolated showers and thunderstorms will be possible across portions of northern Utah this afternoon and evening, otherwise the lower levels remain dry with low surface humidities. Midlevel moisture starts to increase across southern and eastern Utah tomorrow ahead of a low pressure system moving into the desert southwest. This could bring increased high-based shower activity across the southern Utah mountains through the east-central valleys tomorrow, with an outside chance of dry thunderstorms. Gusty microburst winds will be possible even without the presence of thunderstorms. The airmass will moisten a bit more on Friday as the storm ejects across southeast Utah, bringing a potential for measurable rain and perhaps localized wetting rain. General southwest winds will increase today and tomorrow ahead of the approaching weather system. These winds, combined with low humidities will result in marginally critical fire weather conditions today and isolated/low-end critical fire weather conditions tomorrow across portions of southern Utah. Models are then hinting at an increased potential for critical fire weather conditions early next week, most likely Sunday and/or Monday, ahead of the next storm system. This storm system could potentially bring a strong but relatively dry cold front into the area next week. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Heat Advisory from 11 AM this morning to 6 AM MDT Friday for UTZ101-102-104>106. Excessive Heat Warning from 11 AM this morning to 10 PM MDT Thursday for UTZ131. WY...None. && $$ Cheng/Cunningham For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity