919
FXUS65 KSLC 161745
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
1145 AM MDT Sat May 16 2026

.KEY MESSAGES...

- Areas of critical fire weather conditions will return to
  portions of southern Utah through Sunday afternoon.

- A quite unseasonably cold storm system will result in
  temperatures 10-20F below normal for Sunday and Monday along
  with accumulating mountain and mountain valley snow, significant
  for the Western Uinta mountains and in southwest Wyoming.

- Freeze conditions will impact many Utah valleys outside of the
  Wasatch Front Monday and Tuesday mornings. Some areas that might
  see a hard freeze include the Cache Valley, Wasatch Back, west
  central Utah, southwest Utah, and the Sanpete Valley.

&&

.DISCUSSION...A broad, cold storm system has moved onshore along
the Pacific northwest coast this morning, with an ejecting wave
from the system currently moving over Nevada. Ahead of the
ejecting wave, clouds are increasing over Utah and southwest
Wyoming, primarily along and behind a weak frontal boundary
situated near a KTPH-KEVW line. Some weak echoes have developed on
radar in the vicinity of the boundary, though little
precipitation looks to be hitting the ground at this time.
Temperatures will stay mild, up to 10F above seasonal normals, for
areas ahead of the front, with areas behind the front cooling to
near seasonal normals.

The boundary will track slowly south during the day, acting as a
focus for some more substantial convection, scattered in nature,
this afternoon and evening. Lower levels remain very dry, so gusty
and erratic winds will be the primary threat with any storms that
develop, with the focus over central Utah. Synoptic winds will
also be on the breezy side today, particularly ahead of the
boundary. Relative humidities remain quite low for southern Utah,
so this will bring areas of critical fire weather conditions. See
the fire weather section of the AFD for more details.

The main Pacific Northwest trough is expected to phase with the
initial wave overnight as it begins its dive southeast, crossing
the forecast area Sunday afternoon through Monday. This system
will bring a much more potent front along with it, resulting in
high temperatures up to 20F below seasonal normals for both Sunday
and Monday across the area, temperatures more typical of early
March. It also possesses a good amount of moisture and
instability, so it is set to bring accumulating snow to all the
mountains of Utah and with snow levels bottoming out around
5000-6000 feet Monday morning, likely to the mountain valleys as
well. Guidance has been consistent in showing a high chance of
significant accumulations for the western Uinta Mountains and
southwest Wyoming, so have issued a Winter Weather Advisory for
those areas with this package. Forecast snow numbers have overall
come up in this package compared to previous forecasts, and now
put the central and southern mountain forecast totals marginally
into the advisory range. Given more uncertainty here and the later
onset of precipitation for those areas, have opted to go without
headlines in those locations at this time.

With the quite unseasonably cold airmass in the wake of the
trough, freezing overnight lows look to become widespread for most
valleys of Utah (excluding the Wasatch Front and far southern
Utah) with a good chance of a hard freeze for many outlying
valleys, particularly Tuesday morning with less cloud cover
expected. This will bring impacts to agricultural operations and
will impact other sensitive vegetation as well.

There is good agreement that the main trough will move east of the
forecast area Monday evening, though one last weak trailing wave
will follow for Monday night into Tuesday, allowing the threat of
precipitation to linger, especially for northeastern portions of
the forecast area. After that, the strong ridge off the Pacific
coast is expected to build eastward, bringing a warming trend back
to the area. This morning`s guidance increasingly favors a
solution that would slide a weakening trough over the ridge and
across the forecast area Wednesday night into Thursday. Associated
moisture and instability looks unimpressive, but this solution
would slow down the warming trend, delaying the onset of above
climo high temperatures until Friday, leading into a very warm
upcoming weekend.

&&

.AVIATION...KSLC...VFR conditions are expected through the day under
broken to overcast middle and high level cloud cover. Breezy
northwesterly winds will persist throughout the afternoon hours,
with peak gusts around 20 knots. A frontal boundary will move into
the area this evening, bringing an increase in northerly wind gusts
to around 30kts by 04Z. There is around a 25-30% chance that this
front arrives around 03Z. High-based showers will also form this
afternoon, primarily south of the terminal, bringing a low end
chance (20%) for gusty southerly outflows through the afternoon.

.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions are expected
across the area with high-based showers and thunderstorms forming
through the late morning and afternoon hours. Gusty and erratic
outflow winds will be possible near showers and thunderstorms.
Breezy west to southwest winds are expected across the southern and
eastern half of the area through the day today, with the northern
and western portions of the area expected to see breezy
northwesterly winds. A frontal boundary will move from north to
south through the evening hours, moving along the Wasatch Front from
01-05Z and bringing an increase in northerly wind gusts to around 30-
35kts. This boundary will continue southward through the morning
hours, becoming more diffuse as it reaches KCDC.

&&

.FIRE WEATHER...An initial weak cold front has moved into central
Utah. Winds ahead of the front will becoming increasingly breezy
as relatively humidity values remain very low, so southern Utah
will see areas of critical fire weather conditions and a Red Flag
Warning is in effect. Scattered showers and a few high based
storms will develop this afternoon, primarily along the frontal
boundary. Any storms that develop will be capable of producing
gusty and erratic winds as well as isolated dry lightning. The
main storm system will cross the area Sunday afternoon through
Monday, bringing much colder temperatures, and accumulating snow
to the higher terrain of Utah. Winds will remain elevated over
southern Utah, and while relative humidities will be increasing,
they will remain critically low over far southern Utah, where a
Red Flag Warning will remain in effect tomorrow. Behind the
exiting system, conditions will trend drier and warmer for the
remainder of the upcoming week.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Weather Advisory from noon Sunday to 6 PM MDT Saturday
     for UTZ112.

     Red Flag Warning until 9 PM MDT this evening for UTZ489-494-495.

     Red Flag Warning until 9 PM MDT Sunday for UTZ497-498.

WY...Winter Weather Advisory from noon Sunday to 6 PM MDT Saturday
     for WYZ021.

&&

$$

Traphagan/Webber

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