684 FXUS65 KSLC 071047 CCA AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 343 AM MST Sun Nov 7 2021 .SYNOPSIS...A weak cold front will bring scattered rain and snow showers for southwest Wyoming and northern Utah Sunday into Monday. The next system will bring the best chance for impactful, accumulating mountain snow Tuesday night into Wednesday. A ridge will build in later in the week with drier conditions following. && .SHORT TERM (Through 12Z Wednesday)...A longwave trough positioned off the PacNW coast will bring several shortwaves into southwest Wyoming and Utah during the beginning of the week. The best chance for impactful precipitation will be Tuesday night into Wednesday as the longwave trough moves through. A shortwave in broad southwest flow is apparent on satellite over portions of northwest Utah into Nevada and Idaho. A boundary that is nearly stationary has produced light stratiform showers in northwest Utah this morning. A baroclinic zone will gradually slide southeast and bring better chances for precipitation into southwest Wyoming and more of northern Utah late Sunday into Monday before it lifts northeast. Rainfall totals are generally expected to be less than 0.1", with snowfall totals in the mountains mostly under 1". Temperatures will be 5-15F cooler in the north compared to Saturday, but remain similar in the south where southwest winds gusting around 30 mph are expected. Another shortwave is progged to move through the north Monday afternoon, bringing scattered mountain snow showers with minor accumulations. Later Tuesday into Wednesday offers the best chance at impactful weather conditions as the aforementioned longwave trough moves east, bringing better dynamics into southwest Wyoming and Utah. Tuesday afternoon and evening, guidance places northern Utah in the left exit region of the jet stream, allowing for enhanced synoptic lift. That will remain in place going into Wednesday morning. A cold front will transition winds from southwest to northwest, brining cooler conditions and lowering snow levels from roughly 7500 ft. Tuesday morning to 6000 ft. Wednesday morning. Orographic enhancement within northwest flow is expected after most of the moisture exits late Wednesday morning, which will bring more snow in the northern mountains in the afternoon. Liquid amounts of 0.25-0.75" are expected in many northern valleys, with 0.5-1" in the mountains. Snow ratios will be rather low for this storm of Pacific origin, but mountain accumulation of 4-8" with locally higher amounts are expected in the Wasatch, Uinta, and Bear River ranges. While the front is expected to move through Utah, lower moisture amounts are expected further south. Model soundings show increased clouds, but dry enough conditions closer to the surface that minimal precipitation is expected. A ridge building in later in the week will bring drier conditions. .LONG TERM (After 12Z Wednesday)...Ensemble and deterministic members are in reasonable agreement in their respective depictions of the long-wave pattern through the period. Broad northwest flow is forecast to become well-established on Wednesday in the wake of a departing system. The broad northwest flow is forecast to take up residence through the remainder of the week. Stepping back to Wednesday, moist west-northwest flow is forecast to be in place through much of the day, with the best moisture quality relegated to the first portion of the day. This will promote continued upslope-enhanced showers along the Wastach, Bear River Range, northern portions of the central mountains as well as the Uintas. With snow levels forecast to be in the 5,500-6,000 foot range, all rain is expected in valleys of the Wasatch Front, with even benches remaining primarily rain. Showers will tend to linger in valleys through the morning before precipitation becomes more upslope dominate by afternoon. Precipitation will largely shut off by Wednesday evening with a couple of exceptions. An occasional weak wave and associated uptick in mid-level moisture may promote an occasional round of mountain snow showers over the Bear River Range and Uintas through Thursday. Temperatures will remain generally near seasonal normals through the end of the week. Heading into the week, all available model guidance strongly favors an incoming high pressure ridge, first building across California and Nevada by late week before building across the Great Basin over the weekend and at least into early next week. An analysis of clusters reveals minor differences in the amplitude and position of the ridge. Some members of the solution space favor a flatter ridge and the associated persistence of northwest flow over the northern half of the forecast area -- but at this time the majority of the solution space is dominated by the depiction of a more pronounced ridge across the Great Basin by the weekend. This most likely scenario would result in dry conditions, mainly light terrain-driven winds and above average temperatures in the range of 5-15 degrees, with the largest temperature departures across mid and upper slopes. Patterns such as these dominated by strong ridges would also favor the development of valley inversions -- and future forecasts will allow for a better idea of how strong and prolonged inversions may become. && .AVIATION...VFR conditions are likely through the valid TAF period with a low-end chance of MVFR stratus Monday morning with showers in the vicinity. The wind direction forecast is highly uncertain as a frontal zone will linger in the area through much of the day. The most likely scenario suggests northwest winds will prevail through the period, with a low-end chance of brief southerly wind development through 18Z this morning and again after 06Z Monday morning, but again winds should remain generally out of the NW and less than 12kts. REST OF UTAH AND SOUTHWEST WYOMING...A cold front will bring occasional rain showers to ENV, LGU, HCR and EVW through Monday morning, with precipitation type mixing with -SN at LGU after 12Z, and mixing with and changing to -SHSN after 09Z Monday morning at EVW. Farther south towards PVU, shower chances will be less. Best chance for deteriorating categories will be across LGU and EVW with MVFR or brief IFR conditions possible Monday morning. Elsewhere, VFR conditions are expected. Gusty S-SW winds of 30-35kts expected again this afternoon at CDC and BCE. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && $$ SHORT TERM...ADeSmet/Wilson LONG TERM...ADeSmet AVIATION...ADeSmet 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