Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 220241

Area Forecast Discussion
National Weather Service Salt Lake City UT
841 PM MDT Tue Aug 21 2018

.SYNOPSIS...Showers and thunderstorms will continue in monsoonal
moisture tonight and tomorrow, bringing some locally heavy
rainfall, especially over central and southern Utah. High
pressure will bring a drying and warming trend beginning Thursday.


.DISCUSSION...A positively tilted trough extending from the
northern Great Basin into the northern Rockies, coupled with a mid
level ridge centered over the southern Great Plains, is resulting
in a southwesterly flow across the forecast area. This is helping
advect monsoonal moisture northward across much of the forecast
area, and allowed for an active convective day. Deep layer shear
supported strong updrafts with produced hail in addition to
locally heavy rainfall. Much of this activity has been on the
decline over the past few hours across southern and eastern Utah,
however the models have been insistent scattered showers and
isolated thunderstorms will persist into the overnight hours
across these areas. Meanwhile northern Utah became active this
evening as outflow gradually worked its way northward into a
marginally unstable airmass. This activity has been weakening and
shifting northeast over the past 30-60 minutes or so. Updated
earlier to drop going Flash Flood Watch as heavy rain threat had
abated, as well as adjusted PoPs based on ongoing convective

The upstream trough is expected to slowly work its way eastward
during the day Wednesday. With moisture remaining in place should
see another active day with deep layer shear supporting organized
convection, with gradual drying working its way into western Utah
as the afternoon progresses. As this wave passes east of the area
Wednesday night drier air and subsidence will allow for a dry end
of the work week.


.AVIATION...Showers and thunderstorms may impact the KSLC
terminal through at least 04Z, and possibly into the overnight
hours, bringing the potential for lightning and brief MVFR
visibilities in heavier rain. Winds will remain predominantly from
the south, but could become gusty and erratic near storms through
the remainder of the evening.





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