Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
926 FXUS65 KSLC 162139 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 339 PM MDT Sun Jun 16 2024 .SYNOPSIS...A strong cold front will cross the region Monday, bringing a much colder airmass to the area for Tuesday. Temperatures will quickly moderate midweek, with another period of very hot temperatures by Sunday. && .SHORT TERM (Through 00Z Wednesday)...The Beehive State is in for a bit of a roller coaster ride, with the next 7 days including the threat of freezing conditions in the Wasatch Back...to near 100 again by next Sunday across the Wasatch Front. So we`ll be running the gamut here over the next week. Afternoon upper air and satellite analysis indicates a longwave trough is shifting south and east into the Pacific Northwest. This trough is associated with an anomalously cold airmass...around the lowest in the EPS climatology for this time of year. The associated cold front will approach the Utah/Idaho border Monday morning, blasting through the state and reaching southern Utah by the first half of Monday night. While the global models have been relatively dry with the frontal passage, CAMS nearly universally depict convection during the afternoon and evening associated with the strongest forcing, mainly near and north Salt Lake City. Given the dry subcloud environment, suspect a line of high-based convection with microbursts mixing down stronger winds will be the predominant mode during the afternoon and evening. Something to monitor going forward. Guidance still suggesting winds are likely to remain below wind advisory criteria in most locations, with gusts to 45 mph or so for an hour to two hours. It should be noted however that the latest run of the HRRR has become quite bullish with wind gusts with the front Monday evening into MOnday night, with widespread gusts in excess of 60 mph across Washington County and perhaps downsloping into Castle Country and the western Uinta Basin. HREF probabilities for the Black Ridge Canyon area are approaching 100% for gusts over 55 mph. It should be noted that the high res guidance notoriously overforecasts strong winds in this area...but future shifts will need to monitor for a potential High Wind Watch. For the SR-10 corridor in Castle Country...without jet support...winds have a difficult time shifting off the terrain. This will be another area to monitor for future shifts. As far as the very cold temperatures, guidance continues to show high probabilities of freezing temperatures across the Wasatch Back...and thus have issued a Freeze Watch for Monday night into Tuesday morning. Patchy frost will be possible across the Wasatch Back, Cache Valley, Sanpete Valley and Rush Valley. Highs on Tuesday will be well below average across much of the region. .LONG TERM (After 00Z Wednesday), Issued 403 AM MDT... In the wake of Monday`s frontal passage, a much cooler and more stable airmass will temporarily reside across the forecast area. Clearing skies Monday night along with this much colder airmass will allow min temps to fall near freezing across portions of the Wasatch Back and potentially the Cache Valley as well, and Freeze headlines may be needed if this trend holds. Max temperatures Tuesday afternoon will run nearly 15F below climo across northern Utah, where highs will struggle to reach the 70F mark across the northern valleys. Further south temperatures will run closer to 10F below climo, with upper 80s to low 90s across the lower elevations of southern Utah. A mean trough axis will remain situated to the west of the forecast area throughout the middle to latter portion of next week, leaving the forecast area under a mild and dry southerly flow aloft. Max temperatures will quickly rebound to near climo Wednesday, then continue to trend a few degrees warmer each day from Thursday into next weekend. Additionally, moisture being pulled into the southern and central Rockies may gradually spread west during the latter portion of next week, allowing for a small chance for showers and thunderstorms mainly over the far eastern CWA. && .AVIATION...KSLC...NW winds expected to linger into the evening, flipping SE between ~05Z-07Z Mon. SE winds then persist, with an early switch back NW ~13Z-15Z Mon as a cold front gradually sinks through the region. Tightening gradient will result in increasingly gusty NW winds throughout the daytime, generally in the 25kt to 35kt range. Winds will gradually relax late Monday evening into the overnight hours, with NW direction favored to persist. Precipitation chances low (around 20%), but best chance noted from ~21z Mon to ~03Z Tue. Given high-based nature, any convection would be capable of further gusty and erratic outflow winds. .REST OF UTAH AND SOUTHWEST WYOMING...Winds expected to lighten up and largely follow a diurnally normal pattern overnight. From Mon morning on through the afternoon, a cold front will sink southward through N UT and SW WY terminals, reaching S UT terminals by later Mon evening. At northern terminals, NW winds become favored following frontal passage, and gusty conditions set in during the daytime hours (generally in the 25kt to 35kt range). Additionally, a low chance (around 20%) of high-based convection is noted at northern terminals during the afternoon. At southern terminals, gusty SW prefrontal winds develop during the day, with at least some potential noted for patchy smoke related haze to advect in from fires in the SW CONUS. Winds at southern terminals flip N to NW abruptly later Mon evening following frontal passage. && .FIRE WEATHER...Critical fire weather conditions continue across southern Utah this afternoon, with multiple sites seeing winds in excess of 30 mph with humidities at or below 15%. Expect another night of poor recoveries across southern Utah. A strong cold front will cross the state Monday into Monday night. Ahead of this front, expect gusty southerly winds across southern Utah with very low humidities. The front will bring an abrupt change in wind direction to the north to northwest...remaining strong and gusty for several hours behind the front. While temperatures will be considerably cooler in many locations Tuesday, humidities will not rebound much across southern Utah. Another round of critical fire weather conditions is possible Thursday into Friday across southern Utah as southwest flow increases ahead of the next system. Mid-level moisture may increase by Friday, spreading west from the Gulf of Mexico, which may bring lightning to areas that have been very dry for a considerable period of time across southern Utah. Something to watch moving forward. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Freeze Watch from Monday evening through Tuesday morning for UTZ108. Red Flag Warning until 9 PM MDT Monday for UTZ495-496. Red Flag Warning until 3 AM MDT Tuesday for UTZ498. Red Flag Warning until midnight MDT Monday night for UTZ497. WY...None. && $$ Kruse/Warthen/Seaman For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity