727 FXUS65 KSLC 252224 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 324 PM MST Sat Jan 25 2020 .SYNOPSIS... High pressure aloft will settle over Utah through the weekend. A fast moving storm system will impact the area Sunday night into Monday morning. A second storm system will follow for late Tuesday through Wednesday morning. && .SHORT TERM (THROUGH 00Z WEDNESDAY)... A building ridge will continue to strengthen valley inversions tonight into tomorrow. With PM2.5 continuing to increase have added a mention of urban haze along the Wasatch Front and Cache Valley. More importantly is the fog forecast. Yesterday's moisture is trapped in the boundary layer across many valleys. As of mid afternoon, visibilities at most sensors have improved greatly, except the I-84 corridor north of Ogden, near Tooele, Utah Lake and Castle Country. Have these areas mentioned for fog this evening, increasing coverage overnight. However, thick mid/high clouds are expected to arrive overnight which will limit or reverse the trend in decaying visibilities, before clearing early Sunday morning. Visibilities may worsen again with the passage of these clouds. Mid/high clouds increase once again Sunday afternoon ahead of the next trough which crosses overhead Monday morning. Dynamically speaking, not too impressed with this system, given weak jet, splitting nature and modest height falls and subsequent cold advection. Given the splitting nature of this system, expect a relative minimum between Ogden and Provo. North of Ogden, better dynamics exist closer to the northern stream. Another area of grater concern is across the central and southern mountains, along with the I-15 corridor between Nephi and Cedar City. The cold front is frontogenetic across central Nevada, though this weakens greatly once entering Utah. However not fast enough to reverse a period of strong omega through the dendritic snow growth zone. And given this corridor's response to northwest flow, there could be some impacts. Had the lower snow levels well below guidance to match the snow precipitation type along this portion of the I-15 corridor seen on BUFKIT model forecast soundings. Was not quite ready to pull the trigger on a Winter Weather Advisory, but could see one being issued for this area in a future forecast. Building height/anticyclonic flow and warming aloft end the threat of snow showers Monday. A weak trailing wave may keep a chance of snow showers near the Idaho border Monday night. The ridge that builds Monday night looks to weaken Tuesday in advance of the next storm system, with precipitation developing north to south across northern Utah Tuesday afternoon. .LONG TERM (AFTER 00Z WEDNESDAY)... The trough feature moving through late Tuesday from the Pacific Northwest once again (broken record) looks to weaken as it advects southeastward. This is due in part the parent trough splitting and stretching as it becomes positively tilted with the far northern branch up in Manitoba, Canada. Another rather weak baroclinic zone structure will slide southeast through Utah late Tuesday through Wednesday. Precip types at onset for valleys may be some rain/snow mix but by Wednesday morning should be all snow as the airmass cools. Just as quickly as it approaches it will exit by late Wednesday night, thanks to a strong 120kt jet ushering the trough south and east. Another quick 1 to 3 inches for select valley areas might be possible (northern Utah) and twice as much for the mountains. Beyond this, ensembles have been pretty consistent in building in a rather strong ridge from the west through next weekend. Some very weak waves may bring light precip chances to the UT/ID border Friday. && .AVIATION... VFR conditions are expected through the evening at the SLC terminal, with cigs at or below 6000 feet AGL anticipated to return by late evening. There is a 30 percent chance of periods of MFR/IFR conditions developing overnight in fog/stratus. Northwest winds are expected to shift to the southeast between 03Z and 05Z. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && $$ SHORT TERM...10 LONG TERM...Dewey AVIATION...Traphagan For more information from NOAA's National Weather Service visit... http://weather.gov/saltlakecity For frequently asked questions about the Area Forecast Discussion visit... http://weather.gov/saltlakecity/general/afd_faqs.php