438
FXUS65 KSLC 162155
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
355 PM MDT Fri May 16 2025

.SYNOPSIS...Significant changes in the weather pattern arrive on
the doorstep tomorrow as a cold core trough moves into Utah and
southwest Wyoming. A period of moderate to heavy precipitation is
expected across much of the forecast area as the associated cold
front moves through, with well below normal temperatures following
early next week. High pressure reestablishes by the middle of the
week, bringing much warmer and drier conditions.

&&

.SHORT TERM (Through 12Z/6AM Tuesday)...A significant late season,
cold storm system will bring varying impacts across Utah and
southwest Wyoming from Saturday through Monday.

* Enhanced fire weather conditions due to strong winds and low
  afternoon humidity across southern and eastern Utah Saturday
  afternoon.

* Widespread high elevation snowfall across Utah`s mountains, with
  storm total accumulations ranging from 1 to 4 inches for
  elevations between 8,000ft and about 9,500ft, and upwards of 6
  to 12 inches for elevations above 9,500ft with locally upwards
  of 15 inches in the high elevations of the central Wasatch.

* Risk of freezing temperatures in areas where agricultural
  efforts may already be ongoing (i.e. southwest Utah, Sanpete
  Valley, and the Rush Valley).

Isolated showers remain prevalent across Utah today as lingering
moisture exists across mainly the northern portion of the forecast
area. Very little, if any, impacts are anticipated from these
showers through the remainder of the afternoon and evening hours.
Heading into Saturday, however, increasing moisture overhead
paired with deep mixing will create an environment ripe for high-
based convection capable of producing strong outflow wind gusts
across the northern portions of the forecast area. As of 11AM, NWS
SPC maintains a marginal risk (level 1 of 5) for severe weather
across northern Utah and southwest Wyoming.

For the southern half of the forecast area, strong pre-frontal
winds (30-40 mph) are expected to combine with critically dry
afternoon relative humidity values (10-20%) to generate enhanced
fire weather conditions. See the fire weather discussion for
additional information.

The cold frontal boundary associated with the cold longwave
trough begins pushing through Utah during the evening hours
tomorrow. A band of enhanced showers and embedded thunderstorms is
expected to develop along this cold frontal boundary and bring a
period of moderate to heavy high elevation snowfall and valley
rain as it moves across the forecast area. This boundary is
expected to arrive on the Wasatch Front as early as 8-9PM on
Saturday, but most likely around 3AM on Sunday. There is
uncertainty in how long the precipitation lingers due to the
precise speed at which the front progresses, however, most
guidance shows the boundary through the Wasatch Front by around
noon Sunday and through the rest of northern Utah/ southwest
Wyoming by late Sunday afternoon. Behind the boundary,
precipitation mode will transition to more showery conditions with
snow levels falling as low as 6,500-7,000ft in northern Utah as
the colder airmass settles into the region.

Will need to continue monitoring trends in a trailing shot of cold
air that will bring another period of enhanced showers to central
and southern Utah through Monday. Current guidance shows this
airmass being cold enough to support snowfall to valley floors,
however, it may be difficult to accumulate much of any snowfall if
we`re into the daylight hours. Areas most likely to be impacted by
snow will be the mountain passes on I-15 and state routes in
central and southern Utah early Monday morning... but will need to
continue to monitor trends closely.

Lastly, with the colder airmass in place, there is an increased
risk of freezing temperatures in areas that may already have
ongoing agricultural efforts. Areas with the highest risk for
freezing temperatures include, southwest Iron County, the Sanpete
Valley, and the Rush Valley both Monday and Tuesday morning.


.LONG TERM (After 12z/6AM Tuesday)... General consensus among
ensemble guidance following 12z Tuesday is for riding building in
across the southwestern U.S. bringing Utah and southwest Wyoming
back to a period of relatively dry, warm, and benign conditions once
again through the long term forecast. Ridging is expected to build
in following the departure of an upper trough with westerly flow
aloft filling in its wake as the center of the ridge remains to our
south. Rain remains relatively unlikely for the majority of the long
term, though some stray showers are possible along the UT/ID border
Tuesday afternoon as some enhanced westerlies pass to our north.
Otherwise, the period remains quite dry.

As geopotential heights continue to build across the forecast area,
a notable and welcomed warmup (from this forecaster) appears quite
likely with more summertime temperatures expected. On Wednesday,
afternoon highs are expected to shoot up about 5-10 degrees from
what is expected on Tuesday, with most valleys seeing temperatures
range from the mid 70s to low 80s. Lower Washington county will also
see temperatures return to the low to mid 90s. With the pattern
remaining relatively stagnant during this period, temperatures will
only continue to climb with most valleys seeing temperatures reach
into the low to mid 80s by Friday with lower Washington county
seeing temperatures in the upper 90s, perhaps breaking 100 degrees
as well.

&&

.AVIATION...KSLC...Northwest winds will persist through early
evening before returning to southeasterly around 03Z. VFR
conditions will prevail with cigs generally remaining above 7
kft through this evening. Late tonight through early Saturday
morning there is a 30 percent chance for rain showers dropping
cigs below 7 kft.

.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will
continue across the area through tonight. Isolated showers
and thunderstorms will remain possible through this evening across
the general area, with additional showers mainly impacting
northern Utah late tonight through Saturday morning. Gusty south
winds will develop across central and southern Utah Saturday, while
a cold front accompanied by showers and thunderstorms will impact
northern Utah Saturday afternoon.

&&

&&

.FIRE WEATHER...A brief warming and drying period is expected to prevail
into Saturday ahead of an approaching storm system. Overnight
humidity recoveries will be fair to poor across the southern and
eastern portions of Utah, especially Utah`s Mojave. Tomorrow,
winds increase in speed out of the southwest (30-40 mph gusts)
with afternoon relative humidity values ranging from the upper
single digits to around 20 percent in southern and eastern Utah,
creating areas of critical fire weather conditions. Across the
northern and western area, afternoon humidity will be quite a bit
higher (around 35-45%) with winds only gusting as high as 25 mph.
That said, moisture increasing ahead of the incoming storm system
will provide an environment favorable for high-based showers and
thunderstorms, increasing the overall risk of dry lightning and
gusty and erratic outflow wind gusts.

After Saturday evening, the fire weather pattern shifts
significantly as this colder and wetter storm system moves into
the region. Much of the forecast area is poised to receive at
least 0.1-0.25 inches of rainfall with high elevation (8,000ft+
MSL) snow. Northern areas will receive significantly more
precipitation than the southern and eastern areas of Utah, with
mountainous terrain expected to see upwards of 1-2 inches of liquid
equivalent precipitation from Saturday evening through Monday
afternoon. The pattern flips once again as we head into the
middle of next week as ridging builds back into the region,
introducing a prolonged period of a warming and drying trend.

&&

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

$$

SHORT TERM...Webber
LONG TERM...Worster
AVIATION...Seaman
FIRE WEATHER...Webber

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