205 FXUS65 KSLC 241622 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 1022 AM MDT Sat Oct 24 2020 .SYNOPSIS...A strong cold front will sweep south across the area late today through Sunday. This front will bring much colder temperatures along with precipitation for mainly areas east of the I-15 corridor. High pressure aloft will expand east across the Great Basin beginning early next week. && .SHORT TERM (Through 12Z Tuesday)...The upper trough advancing south out of western Canada currently straddles the US/Canadian border this morning. The main trough will remain over the northern Rockies into Sunday, with a second vorticity lobe on the western flank of the trough racing south through the Pacific Northwest and into the western Great Basin by Sunday afternoon. Light precipitation ahead of the trough has settled in far northern Utah/southwest Wyoming this morning. This precip likely driven by weak lift generated from low/mid-level warm advection along the Idaho border. Increasing low-level frontogenesis across northern Utah beginning late this afternoon will lead to an increase in shallow convective precip along the near 700mb baroclinic zone this evening. Precip along the baroclinic zone will shift to areas along and east of the I-15 corridor later tonight, then become less organized over eastern/central Utah on Sunday as the low-level forcing moves further away from the mid- level trough over the northern Rockies. Much colder air pouring into the state from the north will bring temperatures down considerably for Sunday/Monday. Readings are expected to come in between 15 to 25 degrees below normal Sunday and Monday. Precipitation-types will also be impacted as snow levels will drop down to even the higher valley locations late tonight and Sunday. Some concern around the idea of lake-enhanced precipitation off of the GSL exists for late tonight through Sunday morning. Local guidance does point towards a period of potential lake-enhanced precip southeast, then south of the GSL focused on Sunday morning. Not looking at a banded structure to the precip, but rather a broader area of downrange precip from the lake. Will evaluate the potential for lake-enhanced precip after examining the morning model guidance. .LONG TERM (After 12Z Tuesday)...As the trough digs further south and eventually shears apart, a cut-off low is expected to form. The mean of the EPS, GEFS, and CMC place it near the Arizona/New Mexico border Tuesday afternoon. Dry conditions are expected through the area as anticyclonic flow aloft develops with the incoming ridge. As the low moves northeast, higher heights will build in. It will provide a change from northerly mid and upper-level flow to a zonal to southwest pattern. Southern Utah will warm quickly, back into the 60s in Cedar City and 70s in St. George Wednesday afternoon. Northern Utah will be mainly in the 50s around this time, including Ogden, Salt Lake City, and Provo. Nighttime lows will be around freezing for northern and southern Utah. The warming trend will continue through Friday, before flattening out into the weekend. Highs are expected to be a little warmer than average at that point across Utah and southwest Wyoming. && .AVIATION...VFR conditions are expected at the SLC terminal through 10z Sunday, with MVFR expected between 10-18z due to reduced visibilities with scattered snow showers possibly mixing with rain. There is a 40% chance conditions will remain VFR Sunday. The cold front will move through the terminal between 23-01z today, with winds gusting to 20 knots for a brief period. CIGs will drop to 5kft behind the front, starting around 02-03z with scattered rain showers. There is a 30 percent chance periods of rain could cause temporary MVFR with visibilities to 5SM between 02-10z. && .FIRE WEATHER...West to southwest winds will increase across central and southern Utah today ahead of an approaching cold front. Critical fire weather conditions will occur in many fire weather zones over the southern half of the state. Will have the day crew consider issuing RFW for the Western Uinta Basin as winds will definitely be sufficient but the RH may be just a little high, although close enough considering the antecedent drought conditions. The cold front will slip through northern Utah tonight with rain changing to snow down to valley floors by late tonight or early Sunday. The brunt of the precipitation, albeit light for most areas, will be along and east of the I-15 corridor. Most areas within this area will receive from 0.05 to 0.20 of an inch, while west of the I-15 corridor precip amounts will be less than 0.05 of an inch. The storm system will exit the area by Monday afternoon with the last showers occurring over the southeast. Very cold temperatures will prevail Sunday through Monday but then warm by about 10 degrees per day Tuesday and Wednesday and then reach or slightly exceed normal levels for the end of the week. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Red Flag Warning until 9 PM MDT this evening for UTZ489-492-494- 495-498. WY...None. && $$ CONGER/BURGHARDT/STRUTHWOLF/WILSON 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