Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
952 FXUS65 KSLC 232233 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 333 PM MST Sat Nov 23 2024 .SYNOPSIS...A strong cold front will cross northern Utah tonight into early Sunday before continuing into central and southern Utah during the day Sunday. High pressure will bring a break in the action for Monday before a moisture-rich system makes its way across the area Tuesday into Wednesday. && .SHORT TERM (Through 12Z Monday)...A broad Pacific Northwest storm system is approaching Utah and southwest Wyoming this afternoon, with the associated cold front nosing into far northwest Utah. Ahead of this system, southwesterly flow has picked up, resulting in breezy winds over much of the area and some strong winds, primarily focused over southwest Utah where a Wind Advisory remains in effect through the afternoon. Precipitation is currently focused over the frontal boundary over northwest Utah, with just a few showers out ahead of it. High res guidance indicates there will be a period of frontogenesis this evening as the boundary continues southeast, moving into the Wasatch Front mid to late evening. This will result in a period of intense snow for the mountains of northern Utah through the early morning. Guidance is trending a bit later with the arrival of the front but a bit faster with its speed afterward, which has brought snow totals down slightly. Still, mountain accumulations will be significant enough to warrant current headlines. Valley snow accumulations remain a bit of a question mark. Given the unseasonably warm airmass over the area, road temperatures will still be high with the front. Additionally, snow levels should not get low enough to warrant snow until a couple of hours before sunrise. Higher rates with the frontal band could still provide light accumulation, but it may not get cold enough until after the most intense precipitation has ended. As the front moves through central and southern Utah late morning into the afternoon, it will lose its upper level support and weaken, resulting a decrease in snowfall rates and thus amounts. Meanwhile, over northern Utah and southwest Wyoming, precipitation is expected to taper off a bit faster than usual, during the early afternoon, with high pressure quickly moving into the area behind the system. .LONG TERM (After 12Z Monday)...A moisture-rich storm system will bring several days of mountain snow and mainly valley rain preceding Thanksgiving. Those with travel plans through mountain passes this week should monitor the forecast, as mountain snowfall could last as late as Thursday morning. Shallow shortwave ridging will favor a relatively quiet Monday morning ahead of the next storm system. Moisture from a weakening atmospheric river will wrap around the southern end of the Sierra Nevada, arriving in SW-UT mid-day Monday and quickly overspreading Utah and southwest Wyoming Monday afternoon. Overall, expect a period of southwesterly flow within deep column moisture between Monday afternoon until the frontal passage sometime late Tuesday. As is typical with atmospheric rivers, snow levels will remain fairly high, resulting in valley rainfall and wet snow in the mountains. Mountains favored in SW to WSW flow regimes will do quite well during this period due to high moisture availability, despite relatively unimpressive synoptic dynamics. A trough will make its way southeastward, reaching our area roughly late Tuesday into Wednesday. There is some uncertainty in its exact track through our area, resulting in uncertainty in which areas will receive the most rain/snow. However, favorable jet support and mid- level dynamics will likely result in heavier precipitation across the area as this trough and surface cold front move through. Behind the frontal passage, lingering low-level moisture will favor mountain showers in northwesterly-favored terrain, potentially lingering as late as Thanksgiving morning. Temperatures at 700-mb are likely to drop to around -8C to -11C, thus many valley locations could see some light snow Wednesday night into Thursday morning, with minimal accumulations. As far as QPF goes, there is still a decent amount of spread due to uncertainties in the location of the best dynamics. Broadly, NBM 50th percentile QPF favors around 0.5-1" in most valleys, with 1- 2.5" in the mountains over a 3-day period. It`s worth noting that the EC Extreme Forecast Index (EFI) is currently highlighting the central mountains, though again, this ultimately will depend on the track of the low. Finally, Thursday and beyond appears to favor a drier pattern as a ridge builds over the west coast. This time of year, this means there is a chance for valley inversions to develop given low sun angle. && .AVIATION...KSLC...A storm system will track in through the evening, with rain and snow into Sunday. Gusty southeast winds will last through around 01Z when winds transition to northwest. Northwest winds will prevail after, with scattered light rain showers pushing in around 04Z. Rain showers are likely through around 08Z. Showers could bring enhanced outflow winds, especially as showers start. Rain will transition to snow likely from 08-10Z. VFR conditions will prevail until rain transitions to snow, with IFR conditions with snow through around 15Z. .REST OF UTAH AND SOUTHWEST WYOMING...Gusty winds from the southeast to southwest will continue into the evening for southwest Wyoming and northern Utah and through the evening for southern Utah. A storm system will bring valley rain that will transition to snow for most northern valleys from roughly 05-10Z. VFR conditions will prevail where there is rain, with a transition to IFR and LIFR conditions with snow. Snow will taper off through the morning for southwest Wyoming and northern Utah. VFR conditions will prevail for southern Utah. Scattered snow showers after 12Z will be capable of MVFR or IFR conditions at KCDC and KBCE. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Winter Weather Advisory until 5 PM MST Sunday for UTZ110>113-117. Wind Advisory until 5 PM MST this afternoon for UTZ122. WY...None. && $$ SHORT TERM...Traphagan LONG TERM...Cunningham AVIATION...Wilson For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity