694 FXUS65 KSLC 281104 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 504 AM MDT Sun Apr 28 2024 .SYNOPSIS...Northwesterly flow will bring slightly below normal temperatures across the region today. Southwesterly flow will spread across the area Monday bringing a warming trend. A fast moving cold front will cross the area late Monday through Monday night, with a colder trough expected midweek. && .SHORT TERM (Through 12Z/6AM Tuesday)...In the wake of an upper low spinning over the central High Plains, a general northwesterly flow aloft prevails across the forecast area early this morning. A weak wave embedded within this flow has been driving a band of shallow convection across northern Utah, which has been weakening over the past hour or so as it crosses the Wasatch Crest. The remnants of this band should clear the CWA by sunrise, with lingering moisture coupled with daytime heating yielding isolated to scattered showers across mainly northern and central Utah this afternoon and early evening. With increased sunshine this afternoon and gradually rising heights, max temperatures will trend 5-8F warmer across the forecast area, reaching the low the low 60s along the Wasatch Front southward to Cedar City, and 70s across the lower elevations of southern Utah. Southwesterly flow will increase Monday yielding breezy to locally windy conditions across western Utah. Increased mixing coupled with warming aloft will allow max temps to trend up another 5-8F, with upper 60s along the Wasatch Front south to Cedar City, and low 80s around St George and Bullfrog. This increased flow is in advance of a shortwave trough which will dig through the northern Rockies Monday, pushing a cold front through northern Utah late Monday afternoon, then eventually into central Utah Monday evening. Model guidance has trended a little deeper with the parent shortwave with better jet support spreading across the forecast area with the passing baroclinic zone. This forcing will allow a broken band of precipitation to accompany the frontal boundary as it pushes south through the area. Minimal precip is expected in the northern valleys as this boundary pushes through, with up to 0.25" QPF across the northern mountains through late Monday evening. .LONG TERM (After 12Z/6AM Tuesday)...Guidance remains in good agreement that an active, progressive weather pattern will remain in place with low probability of high impact weather over the forecast area. Late Tuesday through Wednesday will feature a trough moving across at least a portion of the forecast area, bringing wetter and cooler weather. Thursday forward, there lies much more uncertainty in the evolution of the pattern, with solutions ranging from a cooler trough to a ridge that would bring warmer and drier weather. Tuesday will start out dry with near seasonal temperatures across the northern half of Utah and southwest Wyoming and above average (by about 5-7 degrees) across the southern half of Utah. Afternoon cloud development is expected across the northern half of the area as moisture lingers, and a few of those clouds will develop into a light shower (mostly over the northern mountains). Tuesday evening through Wednesday, a shortwave trough is expected to follow in the wake of the wave moving through on Monday. Ensemble guidance still seems to be fairly split with how deep this trough will become as it moves over the forecast area. While ~55% of guidance supports a shallower trough that would keep a cold front confined to the northern half of the area, the remaining 45% favor a deeper trough that would introduce a colder airmass to much of the region. From the deterministic guidance perspective, the guidance remains fairly split with a slight favoring toward the deeper trough. What this uncertainty means for the sensible weather will be a lower confidence forecast in the temperatures for both Wednesday and Thursday (i.e. the post frontal environment), particularly across the southern half of the area. At this point in time, there is still about a 6-10 degree spread in the most likely temperature range for the Salt Lake City, Cedar City, and St. George areas. Precipitation will accompany this system, but again, not expecting any significant impacts as the high end of the most likely scenario (e.g. 75th percentile) is generally less than 0.05" of rain. Will likely see snow mix in at the higher elevation valleys, but not expecting measurable amounts... moreso just snow in the air. Moving past this trough there is a considerable amount of uncertainty revolving around how quickly this trough moves out of the area and how quickly a ridge builds in its wake (if at all). Current model guidance is favoring a ridge developing over the West late in the week/ early in the weekend. However, there are about 20% of ensemble members that continue to favor a trough over the West. Furthermore, there is even more uncertainty revolving around how quickly the aforementioned ridge moves out of the region thereafter... still a lot to work through, but thinking a warming trend will be introduced through the second half of the week as the aforementioned trough moves east of the area. && .AVIATION...KSLC...VFR conditions are expected to prevail over the KSLC terminal through the valid TAF period. Light southerly winds will persist through the morning hours, reverting to a northerly flow around 18Z. Afternoon cloud development is expected to generate bases around 5kft AGL, which will likely lead to obscuration of local topography. .Rest of Utah and Southwest Wyoming...VFR conditions are expected across a majority of the forecast area, with localized MVFR to IFR conditions expected at higher elevation valleys across northern Utah and southwest Wyoming. Isolated to scattered showers are expected across the northern half of the area, however, no major impacts to terminals are expected. Winds will favor diurnal trends through the early morning, with northwesterly flow dominating most of the area during the afternoon hours. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && $$ Seaman/Webber For more information from NOAA's National Weather Service visit... http://weather.gov/saltlakecity