St. George, Utah 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

885
FXUS65 KSLC 202124
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
324 PM MDT Fri Sep 20 2024

.SYNOPSIS...Low pressure crossing the Desert Southwest will bring
showers and thunderstorms Saturday, primarily to southern Utah. A
mostly dry front will cross northern portions of the area on
Monday before high pressure moves in for much of the remainder of
the upcoming week.

&&

.SHORT TERM (Through 12Z/6AM Sunday)...A broad low is currently
centered over southern California this afternoon and is making its
way to the east. Ahead of the trough, a few showers have developed
over southwest Utah, though they appear to be generally weak. The
remainder of the area remains dry with just some scattered cumulus
clouds and temperatures near normal for this time of year.

By sunrise tomorrow, the center of the low is on track to move
into southern Arizona. The position of the low will bring a bit of
east to northeasterly flow to northern Utah during this time,
which could result in some enhanced canyon winds over the prone
areas of northern Utah, including parts of the Wasatch Front.
Guidance overall has backed off on the strength of the winds owing
to a relative lack of cold advection and a shorter period of
easterly flow.

As the low moves into Arizona, the threat of showers will spread
across southern Utah, with enough instability for scattered
coverage of precipitation overnight. With daytime heating, the
threat of showers and storms will spread northward to include the
higher terrain of central and northern Utah, primarily east of
I-15, bringing isolated showers as far north as the southern half
of the Wasatch Front. By Saturday evening, the low is expected to
continue into New Mexico, allowing coverage of showers over the
area to quickly diminish.

.LONG TERM (After 12Z/6AM Sunday), Issued 429 AM MDT...To close
out the weekend, deterministic global solutions and ensemble
solutions begin the period in good agreement regarding the large-
scale pattern. We kick things off with a closed low over/near the
Colorado Front Range on Sunday, with lingering early Sunday
cyclonic flow extending westward into extreme eastern Utah, with a
very low (<15% chance) for a shower for these extreme eastern
areas Sunday. Otherwise, Sunday is expected to be precipitation-
free with temperatures just a shade below seasonal normals. The
journey into the long term portion of the forecast is a short one
before model spread is introduced, with deviating solutions
arriving as early as Monday. First, we`ll dive into where
solutions are aligned: there is agreement that a ridge will build
offshore of the western CONUS with a trough diving down the
periphery of the ridge across the Rocky Mountains Monday and
Tuesday. Two forecast scenarios are in play regarding the
evolution of this trough. There is a subset of the ensemble
solution space (as well as the deterministic ECMWF) that closes a
low off directly over Utah on Monday, with the low lingering
around through Wednesday. This would result in cool, showery
conditions for the start of the workweek. This outcome is
represented by a minority of the solutions, and interestingly the
NBM is more reflective of this solution, with mentionable
precipitation across the southern half of Utah on Monday and
closer to the Arizona border Tuesday. The alternate scenario is
one with a progressive trough which would maintain seasonable
temperatures and dry conditions for the early portion of the
workweek.

Ensemble spread then decreases (with an associated increase in
forecast confidence) for the mid to late period, with consensus
showing positive height anomalies gradually building across the
Great Basin, resulting in a gradual warming and drying trend through
the remainder of the week. While there are a few ensemble members
that want to bring a trough through the northern tier and knock down
the ridge, the overwhelming consensus maintains positive height
anomalies/ridging across the region, resulting in stellar weather to
kick off the official start of the Autumn season.

&&

.AVIATION...VFR conditions are expected through the period.
Northwesterly winds will likely transition to a period south to
southeasterly drainage winds between 03-06Z, with a shift to
west- northwest to northwest between 06-08Z. Northwest winds are
likely to continue into the day Saturday.

.REST OF UTAH AND SOUTHWEST WYOMING...Terrain based convection will
continue across portions of central and southern Utah through the
evening. Convection may linger across southwestern Utah into the
overnight hours. More widespread showers and thunderstorms will
develop across southern and eastern Utah Saturday afternoon and
evening.

&&

.FIRE WEATHER...An upper low currently centered over southern
California will make its way east across the Desert Southwest
through Saturday. This will bring enough moisture and instability
to the area for development of showers and thunderstorms,
primarily over southern Utah where coverage will be fairly
widespread. The main threat with any storms that develop will be
gusty downburst winds, but there is a chance of heavy rain that
could lead to wetting rainfalls. Drier conditions will move in
Sunday behind the exiting trough as temperatures stay near to 5F
below normal for this time of year. A grazing storm system will
then bring a mostly dry cold front to northern Utah Monday. High
pressure will move in thereafter, bringing drier and warmer
conditions.

&&

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

$$

SHORT TERM/FIRE WEATHER...Traphagan
LONG TERM...ADeSmet
AVIATION...Kruse

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