Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 220954

Area Forecast Discussion
National Weather Service Salt Lake City UT
354 AM MDT Tue Aug 22 2017

.SYNOPSIS...An upper level trough will move north into southern
Utah this morning, then track slowly north across the region
through tonight. Somewhat drier air will follow this trough,
with this drier air covering the entire area by the end of the


.SHORT TERM (Until 06z Saturday)...The shortwave ejecting north
from the upper low off the southern California coast will enter
southern Utah this morning. Scattered showers associated with
this feature have been increasing in areal coverage since
midnight, with isolated thunderstorms also developing across
south-central Utah the past couple of hours.

Dynamic lift associated with the trough supported by fairly strong
upper divergence will keep convection active this morning. This
convection will expand into western/northern Utah this afternoon.
Anticipating scattered convection will continue along and ahead of
the trough this afternoon/evening. Strong convection could develop
as the air mass will have time to destabilize and upper divergence
strengthens across the north late this afternoon and evening.

Convection will be confined to the far north late tonight/early
Wednesday. The trough should exit northern Utah early Wednesday
afternoon, with dynamic subsidence bringing an end to much
convection by late afternoon or early evening.

Somewhat drier air trailing the aforementioned trough will
severely limit diurnal convection during the latter half of the
week. Differential heating could generate a few terrain-based
showers/storms from any residual moisture both Thursday and

.LONG TERM (After 06Z Saturday)...Mean ridging will be in place
across the CWA to start the long term forecast period. A quick
moving shortwave along the Canadian/US border may push a weak cold
front into northern Utah Friday evening into early Saturday.
Amplitude/timing differences in the global models offer a variety of
solutions at this point, with the GFS managing to have a band of
precipitation along with the boundary overnight Friday.  For now,
leaned toward the drier solutions but this is something to monitor
over the next several runs.

Ridging is expected to amplify over the West in the wake of this
system over the weekend. This will bring dry and warm conditions
through the remainder of the forecast period. The ridge may shift
enough to allow a bit of mid-level moisture to creep in to portions
of the CWA...though the main impact looks to be mediocre convection
across the favored locations such as Boulder Mountain and the
western Uintas Monday and Tuesday.


.AVIATION...Southerly winds are expected to continue at the SLC
terminal, shifting to the northwest between 18-20Z. Expect
showers/isolated thunderstorms to impact the terminal through the
afternoon and into the evening. Any showers/tstorms may bring gusty
and erratic winds to the terminal.


.FIRE WEATHER...An upper level trough will enter southern Utah
this morning, then lift slow north across the remainder of the
area this afternoon through the overnight hours. Abundant moisture
already in place will fuel scattered showers and thunderstorms
along and ahead of the advancing weather disturbance. Wetting
rain are expected with many of the stronger showers and storms,
along with gusty/erratic winds through this evening. Showers will
linger across far northern Utah late tonight, though the areal
coverage will be limited and wetting rains are not expected.

Drier air aloft trailing the aforementioned trough will filter
across the entire area by late in the week. Any lingering
moisture will be sufficient for limited terrain-based showers and
storms during the afternoon and early evening hours through the
end of the week.





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