Ephraim, Utah Weather Forecast Discussion

287
FXUS65 KSLC 191533
AFDSLC
Area Forecast Discussion
National Weather Service Salt Lake City UT
933 AM MDT Fri Sep 19 2025
.SYNOPSIS...Moisture will continue to spread into Utah today and
linger through the weekend. Chances for showers and thunderstorms
across the state increase through the weekend before a drying trend
takes hold once again early next week.
&&
...Updated aviation section, remainder is from 405AM MDT...
.SHORT TERM (THROUGH 12Z SUNDAY)...A closed low centered over the
NorCal coast early this morning is expected to gradually weaken
through the day. However, it has already drawn in ample tropical
moisture, some of which continues to spread into Utah from the
southwest. Latest analysis shows between 0.9-1.2 inches of PWAT
across southwest Utah, and between 0.3-0.5 inches across northern
and eastern Utah. A weak disturbance ejecting out out of the low has
aided in the development of precipitation along the moisture
gradient across southwest Utah. This has so far remained stratiform
and weak, given the lack of instability. This area of showers is
expected to shift into central through southeast Utah by midday.
By afternoon, the aforementioned weather disturbance will lift
across northeast Utah, but moisture availability will be too low to
generate much in the way of showers there. During this time, PWATs
also decrease a bit across the south. This, combined with subsidence
behind the aforementioned disturbance, may limit the extent and
strength of any convection across southern Utah at least through the
early part of the afternoon. Later in the afternoon, the airmass
should not be as suppressed, and daytime heating as clouds clear out
may help generate enough instability to bring a better chance of
convection. Focus of this will be mainly across southern and central
Utah. Some of the initial convection, especially over central Utah,
may start out dry with gusty outflow winds. However, as the low
levels moisten, some of the stronger storms could produce localized
heavy rain. The bulk of the convection should trend diurnal,
although a few showers may linger into the overnight hours.
Focus shifts more to the northern half of Utah and southwest Wyoming
tomorrow given forecast PWATs there between 0.75-1+ inches while
drier air continues to gradually spread into southern Utah.
Additionally, another piece of what`s left of the closed low is
expected to ripple into northern Utah, aiding lift. Storms should
trend increasingly wet through the day, but like today, some of the
initial storms could start out on the drier side.
.LONG TERM (After 12Z/6AM Sunday)...By Sunday, a drying trend will
already be in place across the forecast area under subtle ridging.
Scattered showers and thunderstorms will develop mainly across
higher terrain, particularly across northern Utah/southwest Wyoming
where moisture will hang on for a bit longer.
Models have trended slightly cooler and wetter on Monday, with an
overall shift in guidance from a grazing trough to one that moves
through northern Utah/southwest Wyoming on Monday. Compared to
yesterday, ensemble membership for this solution has increased from
19% to 52%, with deterministic solutions now on board. Still, about
half of members favor that grazing trough, which would result in
drier conditions. In either scenario, a much drier air mass will
move in behind the trough, with high pressure building overhead.
The next area of uncertainty is the development of a closed low over
SoCal early in the week. Model guidance has been bouncing back and
forth with its eventual trajectory. If the closed low does move
inland and over Utah, this could bring another round of cooler and
wet weather late in the work week...though forecast confidence is
very low at this point.
&&
.AVIATION...KSLC...VFR conditions will continue with SCT-BKN mid-
level clouds. Southeasterly winds will prevail through the morning,
likely transitioning to northwesterly around 20Z with a low (20-40%)
chance of a delayed switch as late as 22Z thanks to abundant cloud
cover this morning and afternoon. There is also a very low (10-30%)
chance of high-based showers between 20-00z, which would be
accompanied by gusty and erratic winds.
.REST OF UTAH AND SOUTHWEST WYOMING...Isolated to scattered light
rain will continue to move through southern and central Utah through
the morning and northern Utah by the mid afternoon. After ~20z,
showers and thunderstorms are likely to develop across areas mainly
south of KDTA; these storms will be capable of producing gusty and
erratic outflow winds. Winds will be mostly terrain-driven outside
of any showers, with a preference for southwesterly winds across
western Utah during the afternoon.
&&
.FIRE WEATHER...Moisture will continue to work its way into Utah
from the south today. This will bring higher humidities along with a
chance of showers through this weekend. Showers and thunderstorms
today are expected to remain isolated to scattered, and will
primarily remain across southern and central Utah. Some of the
initial thunderstorms may remain high-based and dry, producing gusty
outflow winds. However, as the low levels continue to moisten,
wetting rain chances will increase through the day.
Over the weekend, the focus for showers and thunderstorms shifts to
northern and central Utah while drier air gradually spreads into the
south. Similar to today across the south, initial thunderstorms may
be dry, but wetting rain chances should increase through the day
tomorrow into Sunday. A few showers remain possible across northeast
Utah on Monday, accompanied by cooler temperatures. This will be
follow by drier conditions for Tuesday. Thereafter, another round of
moisture looks possible for mid/late week depending on the track and
position of the next storm system, for which there is currently
quite a bit of uncertainty.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&
$$
Cheng/Cunningham/Van Cleave
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NWS SLC Office Area Forecast Discussion