329 FXUS65 KSLC 180349 CCA AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 948 PM MDT Sun Mar 17 2019 .SYNOPSIS...High pressure aloft will shift north into western Canada and the northern Rockies early this week. The next storm system will arrive midweek, with impacts primarily across the southern and central portions of the forecast area. && .SHORT TERM (Through 00Z Thursday)...The dominant upper ridge across the western CONUS is in the process of evolving into a closed high center over BritCol/Pacific Northwest for Monday. This evolution has allowed the mid-latitude westerlies to work east across the region today. Moisture embedded in these westerlies will remain at the mid/high levels the next couple of days. A shortwave moving south along the east side of the high will move into Montana shortly, then weaken considerably as it shears apart near the Utah/Idaho border Monday. See no chance for precip with this feature as moisture is severely lacking and lift minimal at best. A shallow surface boundary nudged south by the shortwave will cross northern Utah and southwest Wyoming. This boundary will likely stall the recent warming trend across the north, and may even lower temps degrees across the far north. Areas south of the boundary could still see a few degrees of warming the next couple of days. The first in what will be a series of storms impacting the western states will reach Utah by late Wednesday. This feature could be a slow-mover as the aforementioned high center shift southeast into the northern Plains/northern Rockies and serves as a block to the advancing storm. The initial precip will be convective in nature and confined mainly to southern and western Utah Wednesday afternoon. Lift at this point does not appear to be particularly strong, though with good surface heating, upper divergence and sufficient moisture would expect scattered convective precip developing during the afternoon. .PREVIOUS LONG TERM (After 00z Thursday)...An active long term forecast period continues to be the rule with today's afternoon package. A large...573 dm...500mb ridge will be in place across southern Alberta into Montana. A trough will be attempting to undercut the ridge across the Desert Southwest with the remnants of another feature that moved down the east side of the ridge across Colorado and into the central High Plains. Given the ridging...the trough will gradually shift eastward and fill...but should provide enough forcing for precipitation across much of the central and southern portions of the CWA through Thursday...possibly spreading northward later Thursday into Friday. This is not an exceptionally cold system, so expect mainly valley rain/mountain snow. GEFS probabilities have dropped somewhat from yesterday regarding the potential for heavy rain across southern Utah later Wednesday into Thursday. Looking at the operational runs of both the GFS and EC indicates favorable upslope flow with PWAT values in the 90th+ percentile. Something to continue to monitor over the next several days. It should be noted that the GEFS has trended a bit further north with this system but the remainder of the ensemble guidance is following a more southerly solution. A break in the action is expected Saturday morning into Saturday afternoon before the next trough crosses the region. This trough looks to maintain strength as the upper level ridge shifted northward. This trough is also colder...and may bring snow levels lower than the previous trough. Not seeing March going out like a lamb through next weekend. && .AVIATION...VFR conditions will prevailing under mostly clear skies through the current TAF period. Light west-northwest winds will switch to light southeast winds between 05z-06z, then return to the northwest between 17z and 19z Monday. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && $$ CONGER/BONNETTE 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