Flash Flood Warning 60, NWS Salt Lake City, UT

Area Forecast Discussion
National Weather Service Salt Lake City UT
315 PM MDT Sat Aug 26 2023

.SYNOPSIS...High pressure will bring a drying trend heading into
the upcoming week. A dry cold front will cross northern Utah
midweek. The next surge of monsoon moisture will arrive Thursday,
and remain across the region heading into Labor Day weekend.

&&

.SHORT TERM (Through 12Z Monday)...A mid level ridge axis extends
from the southern Rockies of New Mexico poleward into the northern
Rockies of Idaho/Montana this afternoon. Upstream from this axis,
southwesterly flow aloft has overspread much of the Great Basin,
with drier mid level air advecting from southwest to northeast
across the forecast area. Despite this, lingering boundary layer
moisture characterized by dew points in the low to mid 50s remains
across much of Utah and far southwest Wyoming, which has supported
another afternoon of scattered convection capable of producing
heavy rainfall. The bulk of this activity has become focused
further north across northern Utah as the aforementioned drier air
spreads across southern Utah. This trend will continue through
this evening, with lingering convection largely confined to the
northern half of the forecast area. Hi-res guidance brings a weak
perturbation through northern Utah overnight, which will maintain
a threat of isolated to scattered showers into the overnight
hours mainly north of I-80.

With this drier air in place, any lingering convection across
central and southern Utah will remain isolated, and confined to
the higher terrain from the Wasatch Plateau south to Boulder
Mountain. Further north, better coverage is expected across the
Uintas, as well as areas near the Idaho border, which will be in
proximity to a weak shortwave crossing the northern Rockies.
Max temperatures Sunday will run similar to Saturday and remain
near climatological norms.

.LONG TERM (After 12Z Monday)...Model guidance has been fairly
consistent over the past few runs with the evolution of the large
scale pattern, and thus confidence is fairly high with respect to
the general forecast heading into Labor Day Weekend. Mid level
ridging centered across the region Monday will slide east by
Tuesday, allowing for a warming and continued drying trend across
the forecast area. This warming trend will push max temps 3-5
degrees above climo Tuesday afternoon. By late Tuesday/early
Wednesday an upper trough ejecting through the Pacific
Northwest/northern Rockies will push a cold front through northern
Utah. Could see high based convection ahead of this boundary late
Tuesday afternoon/Tuesday evening...a 20-30 percent probability.
Behind this boundary, max temps will cool back to near climo
across northern Utah, and remain near to slightly above across the
south.

Model guidance has been consistent in bringing a significant
surge of monsoon moisture back into the region beginning Thursday,
and persisting through Friday and likely into Labor Day Weekend,
as a deep upper trough becomes established along the Pacific
coast. This low will allow for a deep layer southerly fetch
extending from the Gulf of California region into the eastern
Great Basin. As such have maintained elevated PoPs across much of
the forecast area beginning Thursday, and continuing through the
remainder of the Long Term period.

&&

.AVIATION...KSLC...Thunderstorms are forecast in the vicinity of the
terminal between 22z and 00z this evening. Thunderstorms and heavy
rain may impact the terminal during this time with brief MVFR
visibilities under heavier rain. Gusty and erratic outflow winds
from thunderstorms are most likely between 22z and 00z with gusts
near 30 knots. The range of possible wind gusts from these
thunderstorms range from 15 kts up to 40 knots. Improving conditions
are forecast after 00z with winds out of the north and broken mid-
level cloud decks. Winds will shift out of the southeast by 04z this
evening at light speeds.

.REST OF UTAH AND SOUTHWEST WYOMING...Across northern and central
terminals through early this evening, scattered thunderstorms and
rain showers are forecast. Gusty and erratic winds in and near
thunderstorms are possible along with briefly reduced visibility in
heavier rain; mid to high based CIG are forecast. As a result, brief
periods of MVFR conditions cannot be ruled out however VFR
conditions are forecast throughout much of the period. Overall
improvement in conditions are forecast after 00z.

Scattered thunderstorms and rain are forecast through early this
evening in BCE. Lowered CIG/VIS may briefly lead to MVFR conditions
resulting from this activity with improving conditions after 23z.
CDC and SGU are forecast to remain at VFR conditions through
tomorrow.

&&

.FIRE WEATHER...Lingering monsoon moisture will maintain showers
and thunderstorms into this evening across northern and eastern
Utah, while drier air begins to spread across southwest Utah. This
drier air will spread across the remainder of the area Sunday,
resulting in a downward trend in daytime humidity. Lingering
moisture will remain sufficient for a few afternoon showers and
thunderstorms across the Uintas, as well as near the Idaho border.

High pressure will maintain dry and mild conditions across the
region through Monday. This high will slide east Tuesday, allowing
for an increase in southwesterly flow, along with a warming and
continued drying trend. Locally breezy conditions will be possible
across western Utah during this time. Warm, dry and locally
breezy conditions will persist through Wednesday across central
and southern Utah, while a dry cold front brings a cooler and more
stable airmass across the north.

The next surge of monsoon moisture will arrive across southern
and central Utah Thursday, then spread across the remainder of the
region Friday. This will bring elevated humidity, along with
several rounds of showers and thunderstorms capable of producing
wetting rains.

&&

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

Seaman/NDesmet

For more information from NOAA's National Weather Service visit...
http://weather.gov/saltlakecity

Preliminary Local Storm Report
National Weather Service Salt Lake City UT
155 PM MDT Sat Aug 26 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0141 PM     Flash Flood      7 WNW Huntington        39.38N 111.08W
08/26/2023                   Emery              UT   Utility Company

            Report of debris with mud in Huntington
            Creek resulting from flow from the Trail
            Mountain Burn Scar.

&&

ND