Eureka, Utah Weather Forecast Discussion

827
FXUS65 KSLC 292154
AFDSLC
Area Forecast Discussion
National Weather Service Salt Lake City UT
354 PM MDT Mon Sep 29 2025
.SYNOPSIS...A storm system to the west will affect weather
conditions through the week. For Tuesday, a weak wave associated
with that will bring showers and thunderstorms. Drier conditions
will build in for Wednesday and Thursday. With the storm to the
west but approaching, southwest winds will enhance. More
precipitation is likely Friday into Saturday as the storm system
tracks into Utah.
&&
.SHORT TERM (Through 12Z/6AM Wednesday)...Remnants of a closed low
that was to the south from Friday through the weekend have lifted
north. As it tracked near the Utah and Colorado border, enough
forcing has remained to produce scattered rain showers, primarily
around mountainous terrain in northeast Utah and into southwest
Wyoming.
A longwave trough in the eastern Pacific will be the main feature
that will bring a range of conditions through the week. A piece
of energy will break off the main trough and track eastward into
Utah early Tuesday. The associated baroclinc zone will result in
cooler conditions, with valley highs for much of Utah in the low
70s. In addition, there will be sufficient forcing for strong to
severe thunderstorms.
Moisture primarily associated with the system through the weekend
will remain in place, with precipitable water values ranging from
0.75-1" for southwest Wyoming and northern Utah and from 0.5-0.75"
elsewhere in Utah. MLCAPE values will range from around 250-500
J/kg, but HREF model soundings for different portions of Utah
indicate that CAPE in a deep cloud layer, with LCL-EL wind shear
around 30 knots. With that, the main impact will likely be locally
heavy rain capable of flash flooding for northern Utah burn scars
and urban areas. Showers and thunderstorms will be relatively
quick, but training and likely multiple times of locally heavy
rain will increase the threat. There will be less forcing further
south away from the cold front, but sufficient moisture for
isolated to scattered showers and thunderstorms. The main impact
for these portions of Utah will be similar, with strong to severe
thunderstorms and localized flash flooding for slot canyons, dry
washes, and burn scars.
.LONG TERM (After 12Z/6AM Wednesday)...An active pattern looks to
develop across the forecast area as a longwave trough amplifies over
the western U.S. On Wednesday, generally zonal flow aloft will
exist as a shortwave trough grazes NW UT as it ejects off to the
northeast. A broad longwave trough will be approaching the west
coast of CA at this time which will lock southerly winds in place
at the surface across the forecast area keeping temperatures
around 5F above average through Thursday evening despite
geopotential height falls gradually occurring. The majority of the
forecast area should remain dry through Thursday afternoon,
though chances begin to increase across NW UT late Thursday
evening as the aforementioned longwave trough pushes inland,
amplifying as it approaches the area.
On Friday, a cold front associated with the upper trough is expected
to move in from the northwest sweeping across the area throughout
the day. Ample ascent associated with the front with forcing aloft
will yield scattered showers and thunderstorms across the majority
of the state with dry conditions behind the front. However, this
solution comes with a considerable amount of uncertainty at this
time. Long-range guidance appears to be struggling with the timing
of the trough and attendant cold front as it progresses east toward
the forecast area. As a result, considerable spread exists with the
high temperatures on Friday, and perhaps overall storm coverage /
strength. Currently, the NBM 1D Viewer shows that KSLC has a high
temperature spread of 64F-76F, which isn`t really helpful when
attempting to make a deterministic forecast in the long range. An
earlier solution would favor weaker storms with likely less coverage
overall and the cooler end of the temperature range whereas a later
solution may give these storms a bit more juice and keep us slightly
above average with temperatures for one more day. This forecast
should be refined over the coming days. Regardless, precipitation
(perhaps even some light snow accumulation across the high Uintas
and other higher elevation locations across the state) and a
cooldown is expected to occur as we head into the weekend, it is
just a matter of when it occurs on Friday.
Following the passage of the cold front, temperatures are expected
to drop to near or just below average as we head into the weekend.
While the majority of the area is expected to remain dry as
northerly flow filters cold and dry air into the region, some
moisture may linger across our higher terrain mountains. As a
result, some more scattered snow showers are expected particularly
above 10,000ft as snow levels remain high. Finally, near or below
freezing temperatures are possible Saturday and Sunday mornings
across lower elevation valleys in the Cache Valley. Unfortunately,
spread in the temperatures remain high at this time with KLGU
ranging from just below freezing to 39F. Compared to previous
forecasts, it appears the trend has become somewhat warmer, though
it still remains possible that freezing overnight temperatures are
reached this weekend. This cooldown is expected to persist into
early next week, so be sure to get outside and enjoy fall while it
lasts!
&&
.AVIATION...KSLC...Winds remain predominantly southerly through the
TAF period, with a brief shift to southeast between 03-09z Tuesday.
A brief period of enhanced southerly winds is expected between 09-
12z Tuesday, with gusts to around 18-20 kts possible. A line of
widely scattered showers moves into the terminal after 16z, yielding
a 30% chance for thunderstorms to produce erratic winds and heavy
rainfall through around 00z Wednesday. Heavier cores moving over the
terminal may drop CIGS/VIS into MVFR during this period.
.REST OF UTAH AND SOUTHWEST WYOMING...Largely dry conditions prevail
across the airspace, except southwest Wyoming and high terrain of
eastern Utah, where isolated showers have developed this afternoon.
Overall VFR conditions prevail into late tomorrow morning before a
line of widely scattered showers and thunderstorms tracks through
Utah and southwest Wyoming during the afternoon and evening
hours. Terminals under heavier cores may see conditions briefly
dip into MVFR CIGS/VIS through this period. Winds remain
predominantly south to southwest for all terminals through the TAF
period, though showers and thunderstorms in the vicinity may
bring gusty and erratic winds Tuesday afternoon and evening.
&&
.FIRE WEATHER...Energy associated with a storm system in the
eastern Pacific will break off and track into Utah Tuesday. That
will result in a cold front pushing through during the day. With
enhanced moisture content from the previous storm system along
with support from the incoming front, showers and thunderstorms
are likely throughout northern and central Utah.
Showers and thunderstorms will primarily be capable of locally
heavy rain and lightning from Tuesday morning through much of the
day. Precipitation totals will generally range from 0.10-0.40",
although there will likely be locally higher amounts.
Precipitation will taper off between 6-9 p.m.
The main storm system will linger to the west through later in
the week, so there will be dry conditions Wednesday and Thursday.
Each day will have enhanced southwest flow, with gusts from 20-30
mph.
Precipitation will become more likely later Friday into Saturday
as the storm pushes in from the west. There is uncertainty on
details, including timing and how much rain will come with the
event. It will bring much cooler conditions throughout Utah by the
weekend.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&
$$
SHORT TERM...Wilson
LONG TERM...Worster
AVIATION...Whitlam
FIRE WEATHER...Wilson
For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity

NWS SLC Office Area Forecast Discussion