Sunrise 5:58 AM   Sunset 8:22 PM Moonrise 12:04 PM   Moonset 1:33 AM

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FXUS65 KSLC 151002 AFDSLC

Area Forecast Discussion National Weather Service Salt Lake City UT 402 AM MDT Wed May 15 2024

SYNOPSIS
One last weak trough will bring another round of isolated to widely scattered convection to higher terrain areas east of I-15. High pressure will build Thursday into Friday, bringing dry conditions with a warming trend. An unsettled and less warm pattern will develop for the weekend and into early next week.

.SHORT TERM (Through 12Z Friday)...A cold front is situated near a KSGU-KGJT line this morning and is tracking south as the last in a series of weak waves moves into northwest Utah. Seeing just a few showers over southeast Utah along the boundary that will tend to dissipate over the next couple of hours. Behind the front, maxes will tend to average 2-5F above seasonal normals, the least warm day of the week.

The shortwave is on track to move northwest to southeast across Utah during the day today as a Pacific ridge builds over the Great Basin. As a result, associated afternoon convection will be primarily confined to higher terrain areas east of I-15, and even with that in mind coverage will be a bit less than has been observed the past couple of days, with widely scattered coverage at best anticipated later today. In the wake of the exiting trough, the ridge will continue to build eastward over Utah and southwest Wyoming, resulting in dry conditions Thursday with maxes running 5-8F above normal for this time of year.

.LONG TERM (After 12Z Friday)...Models have come into seemingly better alignment on what is to come from an active storm track to the north of the area, however, uncertainties remain in place for the forecast past Saturday. At this point in time, expecting temperatures across the region to see a gradual downward trend as the influence from a ridge is slowly diminished as a mean trough begins developing over the West. Dialing in the specifics on when and where precipitation will be seen over the area is one of the uncertainties to work through as models are still having difficulty coming to a consensus on the amplitude and phase of an anticipated trough early next week.

For Friday, a low amplitude trough grazing across the far northern portion of the forecast area will drop a weak cold front into Utah and southwest Wyoming. Very little, if any, precipitation will be associated with this boundary, and best chances (albeit low) will be confined to the northern mountains and adjacent high elevation valleys. Really, the biggest change in conditions will be seen in the temperatures and wind. Max temperatures will spike as warm air gets one last surge ahead of the boundary which is currently progged to push through the area Friday evening through Saturday morning.
Breezy conditions are anticipated ahead of, and behind, the boundary on Friday, with areas like the western Uinta Basin having some potential for gusts in excess of 45 mph. Will continue to monitor this trend in the models. Gust potential elsewhere looks to be around 30-35 mph during the afternoon hours on Friday. Temperatures cool by ~2-5 degrees (higher end in the north, lower end in the south) in the post-frontal environment on Saturday, with potential for isolated showers in the central Utah mountains.

As has been the story for the past several days, uncertainty increases as we head into the late weekend/ early next week as models are generally in support of a trough developing over the West. While there is good agreement on the development of a mean trough (which would suggest cooler temperatures and relatively wet conditions), there is a fair amount of uncertainty revolving around how quickly this feature develops over the area. To give an example for the forecast on Sunday, ~15% of models support continued above average mid-level heights (in favor of above average temperatures and dry conditions), ~15% supporting near to below average heights (supporting cooler and wetter conditions), and the remaining 70% supporting a mix of both (supporting higher chances for cooler and wetter up north, and warmer and drier down south). By Monday/ Tuesday, a large majority of ensemble members are in support of this trough settling into place. Even then, NBM shows upwards of 10 degrees of spread in the most likely max temperatures in the SLC area for early next week.

AVIATION
KSLC...VFR conditions are expected over the KSLC terminal today under partly cloudy skies. Light southerly flow will transition to a northerly flow between 15-16Z, prevailing out of the north thereafter.

Rest of Utah and Southwest Wyoming
VFR conditions are expected across the region today with isolated to scattered showers and isolated thunderstorms expected over the mountainous terrain (especially across southern Utah). Winds will favor a northerly direction shortly after sunrise. Gusty and erratic outflow winds in excess of 30kts will be possible is passing showers.



FIRE WEATHER
A weak storm system will pass northwest to southeast across Utah during the day today, bringing enough moisture and instability for isolated to widely scattered showers and thunderstorms over the higher terrain east of I-15. Temperatures will be the least warm of the week today, with highs averaging 5F above normal for this time of year. Behind the trough, high pressure will build over the area Thursday into Friday, bringing dry conditions and a steady warming trend. By Saturday, a grazing trough will bring a mostly dry cold front into northern Utah, with increasingly unsettled conditions developing for early next week.

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

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