Dust Storm Warning 2, NWS Salt Lake City, UT

Area Forecast Discussion
National Weather Service Salt Lake City UT
534 AM MDT Sat Jun 18 2022

.SYNOPSIS...A deep and potent trough over the West Coast continues
to impact the region, with very strong winds expected area-wide
again today. Showers and thunderstorms will remain possible,
especially in eastern areas. Cooler air will spread into the area
tomorrow, with showers across the north and lingering gusty winds
across the south and east.

&&

.SHORT TERM (THROUGH 12Z MONDAY)...An elongated upper trough remains
in place over the West Coast states this morning with Utah under a
strong south-southwesterly flow aloft. An upper jet associated with
the leading edge of the trough is over eastern Nevada, and is
responsible for the band of clouds and weak showers/virga near that
same area. Meanwhile, moisture remains in place across eastern Utah
with PWATs near 0.75 inches. A few showers continue across the far
eastern portions of the forecast area owing to this moisture and
some weak instability.

Winds are expected to increase again by late this morning or
afternoon across the forecast area, with widespread strong gusty
winds not to dissimilar to yesterday. This is due to the upstream
trough and associated cold front continuing to approach the area,
with a deepening surface low over northwest Utah and H7 winds of 40-
50kt.

Showers and thunderstorms will increase with daytime heating. While
models indicate some moisture briefly increasing westward, showers
are still not expected to make it much farther west than the I-15
corridor. Some CAMS do indicate a potential for showers along the
portions of the Wasatch Front, otherwise the bulk of the showers
will remain over the spine of Utah and eastern valleys. The greatest
instability is still expected to remain over northeast Utah and
southwest Wyoming, which will likely see the bulk of any
thunderstorms and strongest convection. Any convection, whether
strong or weak, will have the potential to produce microburst winds,
as low-level moisture is still expected to be lacking in many areas.
The best chance for wet storms will be over and near the Uinta
Mountains. The heavy rain potential for most other areas will be
more limited. Showers are expected to continue through the nighttime
hours across northeast Utah as the aforementioned upper jet shifts
east towards that area to provide large-scale lift.

Meanwhile, the cold front will push into northwest Utah this
evening, then continue to move east-southeast through the forecast
area into tomorrow. Southwest winds will remain strong across
southern and eastern Utah through tomorrow afternoon ahead of and
with the cold front, and wind highlights may eventually need to be
extended. Otherwise, drier air will spread into southern Utah then
eventually punch into northeast Utah by mid/late afternoon. As
showers across northeast Utah gradually diminish through tomorrow
afternoon, they should increase across the northwest owing to
increasing instability due to advection of colder air aloft as the
trough axis shifts into the area.

.LONG TERM (After 12Z/6AM Monday)...By Monday morning, the longwave
trough axis will be roughly located over our area, with the cold
front fully through the area. The trough is expected to lift quickly
out of the area, but lingering vorticity maxes on the backside of
the trough combined with weak upper-level jet support could produce
some orographic showers over the Uinta Mountains Monday
afternoon/evening. Because a drier air mass will have set in at this
point, showers are likely to be low in coverage, and limited to
mountainous terrain.

Temperatures will start out the long-term period around 5-15 degrees
below normal, but as the trough lifts out and weak ridging sets in,
temperatures are expected to rebound through the week, reaching 5-10
degrees above normal by Friday.

Deterministic models suggest a feature breaking off from the main
trough and regressing to the west towards CA before being absorbed
back into the mean flow. There is some disagreement on how exactly
this feature progresses. The EC suggests a cutoff low forms, moving
to the west back into CA, and then slowly making its way back into
the mean flow. The GFS and Canadian both depict a weaker feature
that is absorbed back into the mean flow more quickly. In any case,
this won't be a super impactful feature, likely only providing
additional lift for shower and thunderstorm potential sometime
between Thursday and Saturday.

Flow across northern UT and southwest WY is expected to be generally
zonal at the upper-levels beginning mid-week, but with a stronger
ridge setting up to our east, southerly flow may advect some
moisture into the region towards the end of the work week. The
timing and strength of this moisture surge is still fairly
uncertain, however this feature appears to be less strong than the
feature influencing our weather this weekend. Ensemble members
suggest PWAT values generally between 0.6-1", with GEFS members
favoring a wetter solution than EC or Canadian members. Fifty-nine
percent of ensemble members favor some showers across southern UT by
00z Friday, and potentially again by 00z Saturday.

One last feature to keep an eye on is another trough that is
expected to develop over the northeast Pacific and move south down
the coast. By the end of the long-term period, this feature is still
far to our west, off the coast of the PacNW likely. Depending on its
progression, this feature could cause more unsettled weather,
however this is still highly uncertain.

&&

.AVIATION...KSLC...Southeasterly winds are expected to remain near 5-
10kts near the surface with stronger southwesterly winds up to 30-
35kts around 2000ft AGL. Thus, have included LLWS in the TAF until
15z, when surface winds are expected to increase. Expect peak gusts
up to 30-40kts between 17-00z. There is a 15% likelihood of blowing
dust causing MVFR VIS during these stronger winds. Isolated showers
between 00-03z will remain within the vicinity on the eastern side
of the valley.

.REST OF UTAH AND SOUTHWEST WYOMING...Strong southerly flow is
expected to return between 15-17z across the area. Locations prone
to blowing dust across the western deserts may see MVFR VIS during
peak gusts, likely between 20-00z. Scattered rain showers moving
from south to north between 17-07z will likely remain east of I-15.
These showers may cause periods of gusty, erratic winds. There is a
20-30% likelihood of thunder east of KHCR's longitude and north of I-
70.

&&

.FIRE WEATHER...Widespread strong gusty winds will continue today
ahead of an approaching storm system. The strongest winds are
expected over western Utah where gusts to 60 mph or greater will be
possible. Moisture will remain confined to the mountains and east
today, with showers and a few thunderstorms focused across that
area. The best chance for thunderstorms will be over northeastern
Utah. Showers will trend wetter over this area as well. Otherwise,
thunderstorms elsewhere will be more isolated and drier with a
potential for gusty microburst winds.

The upstream storm system will push a cold front into the area from
the northwest tonight through tomorrow. Southern and eastern Utah
will be quite dry ahead of and near this front, with strong gusty
winds expected once again. Critical fire weather conditions extend
into Sunday as a result. Cooler conditions and generally lighter
winds will then settle into the area through the early part of next
week.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...High Wind Warning until 10 PM MDT this evening for UTZ101-102-
     105-115-122-123.

     Wind Advisory until 10 PM MDT this evening for UTZ103-104-
     106>108-116-118>121-124-126>131.

     Red Flag Warning until 10 PM MDT this evening for UTZ478-492-495-
     497.

     Red Flag Warning until 10 PM MDT Sunday for UTZ484-489-493-494-
     496-498.

WY...None.

&&

Cheng/Cunningham

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

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