Sunrise 6:14 AM   Sunset 8:07 PM Moonrise 1:14 AM   Moonset 10:36 AM

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FXUS65 KSLC 292137 AFDSLC

Area Forecast Discussion National Weather Service Salt Lake City UT 337 PM MDT Mon Apr 29 2024

SYNOPSIS
A cold front will cross northern Utah and southwest Wyoming through the early evening before stalling over central Utah. A secondary cold front will cross the area Tuesday night bringing much cooler temperatures for Wednesday. A warming trend is expected late in the week and into the upcoming weekend.

.SHORT TERM (Through 12Z/6AM Wednesday)...Seeing a breezy southwest flow across Utah and southwest Wyoming this afternoon as a Pacific Northwest trough moves into far northwest Utah. This trough is accompanied by a fairly potent upper level jet, bringing increasing instability. In this environment, scattered showers and a few thunderstorms have developed over northern Utah and southwest Wyoming. Temperatures remain very much on the mild side areawide, with maxes running 5-8F above seasonal normals.

The previously mentioned trough is on track to slide across northern portions of the forecast area this evening and into the overnight hours, bringing a frontal boundary through as it does so. Thus, associated showers and thunderstorms will hang on into the evening, with a low chance (20 percent) of a few hanging on during the overnight hours. Given the dry lower levels in the airmass currently over the area, cannot rule out microburst winds with any storms that develop, something to watch through the evening.

The passage of the system will have a more noticeable impact on temperatures, however, with maxes over the northern half of the area expected to run near seasonal normals while southern Utah remains quite mild, up to 10F above climo. Behind the exiting trough, the region will be under a drier and more stable zonal flow, keeping conditions dry.

.LONG TERM (After 12Z/6AM Wednesday)...A broad trough centered over southern Saskatchewan will slowly meander through the end of the week. Our area will be on the southern periphery of this trough resulting in some shortwave troughs grazing by the northern portion of the CWA Moisture will be lacking with these shortwaves, so the biggest impacts will be cooler than normal temperatures along with gusty winds over eastern Utah on Wednesday along the lee side of the mountains. The first of these shortwaves arrives Wednesday morning with southwest flow transitioning to northwest flow behind a mostly dry cold front. A few showers are possible across the high terrain, but little to no measurable precipitation is expected.
Temperatures will drop about 10 degrees Wednesday compared to Tuesday. Far southern Utah will see a less dramatic temperature fall ~5 degrees which will keep temperatures near normal across lower Washington county and areas near the Arizona border. Post frontal northwest winds across eastern Utah will accelerate along the lee side of the terrain. Some locations could flirt with advisory level winds with probability of exceeding 50 mph ~70% across lee side valleys of Carbon, Emery, and Duchesne counties.
Probability of exceeding 58 mph is much lower, ~<30% chance. A second shortwave arrives on Friday with slightly better moisture, but still little to no measurable precipitation is expected outside of the highest terrain of northern Utah/SW Wyoming.

The broad trough ejects further east by the weekend and a shortwave ridge builds across the Great Basin. This will keep conditions dry with warming temperatures a few degrees above normal.
Guidance starts to differ by early next week when a trough moves into the western CONUS. 70% of guidance brings this trough into the Great Basin by Monday. Moisture won't be lacking with this trough given its maritime origin. However, 30% of members suggest a slower progression of the trough with its placement further west on Monday and mostly dry conditions across the Great Basin until later in the week.

AVIATION
KSLC...Quick impulse will nudge a cold frontal boundary through Monday evening. If not already switched, this will push winds NW, with some likely gusts accompanying the front. While mostly dry, some isolated to scattered shower activity is possible, though largely expect VFR conditions to prevail. Winds begin to relax Monday night and are generally favored to remain out of the NW into the day Tuesday, though guidance hints at a brief period of light VRB to S flow possible in the morning (best likelihood currently indicated ~14z-18z).

REST OF UTAH AND SOUTHWEST WYOMING
A quick system will push a cold front through northern terminals Monday evening into the early overnight hours. Front is fairly dry, but will likely trigger some isolated to scattered showers. Even then, VFR conditions generally expected to persist. Front will also likely cause a period of gusty winds (generally NW) before relaxing moving further into the night.
Following the front, anticipate remaining VFR cloud cover to largely clear. At southern terminals, expect mostly clear skies with some modestly gusty conditions Monday becoming lighter overnight into Tuesday.

SLC WATCHES/WARNINGS/ADVISORIES
UT...None.
WY...None.

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