500
FXUS65 KSLC 162145
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
345 PM MDT Mon Sep 16 2024

.SYNOPSIS...A fall storm system will cross the area tonight into
Tuesday, bringing much cooler temperatures. Cool and unsettled
weather will continue for much of the remainder of the week.

&&

.SHORT TERM (Through 12Z Wednesday)...A broad low pressure system
has moved into the Great Basin this afternoon. Ahead of it,
southerly flow has increased quite noticeably over the area,
resulting in some gusty winds. Winds have been strongest over
western Utah where some gusts in excess of 50 mph have been
observed. In the moisture and instability ahead of the system,
have seem scattered showers and thunderstorms develop over
northern Utah, where more favorable instability exists in the
vicinity of the upper level jet. Some of these storms have
produced gusty microburst winds and the threat will continue into
the early evening.

The cold front in association with the low is expected to move
into western Utah this evening, spreading northeast through
Tuesday morning, with the associated upper low following close
behind. This will keep precipitation, rain with snow above 9000
feet, going through Tuesday morning before it lifts out Tuesday
afternoon and evening. More notable, however, will be the drop in
temperatures. Maxes Tuesday are expected to run 10-15F below climo
tomorrow, feeling very much like fall.

.LONG TERM (After 12Z Wednesday), Issued 418 AM MDT... A cool and
wet pattern will remain in place for the latter half of the week
as a weakening upper level low approaches the Great Basin,
replacing the early week low that will be exiting to the
northeast. Temperatures will be running ~10 degrees below normal
areawide for this time of year. Stratiform rain will transition to
more of a diurnally driven showery precip regime (with less
coverage) as this low shifts east. There still remains some
uncertainty regarding the pattern following the departure of the
aforementioned low. ~37% of guidance brings another trough through
the Great Basin that would reinforce the cool airmass and lead to
more precipitation. However, the remaining ensemble members
suggest that ridging will build back into the area that would
result in drier and warmer conditions.

By Wednesday morning an upper level low will be centered off the
coast of northern California. Across the Great Basin, a cold front
ahead of the trailing low pressure will move through the area with
increasing cloud cover that will inhibit temperatures from warming
much throughout the day. As the low slides down the west coast
northern Utah will be positioned on the left exit region of ~100kt
jet. This will help to increase ascent across northern Utah/SW
Wyoming resulting in some showery precipitation. By Thursday this
low starts to progress inland while filling in and weakening as it
does so. Even still, PVA will help to enhance lift across most of
the CWA on Thursday and Friday resulting in more widespread light
stratiform precipitation. As the cold core moves over the Great
Basin snow levels will generally be ~10kft with some light snow
accumulations across the highest elevations.

This low exits the area to the northeast by the weekend, however
steep lapse rates and lingering moisture left in the wake of the
low will help to spark some diurnal showers Saturday and
potentially Sunday across northern Utah and SW Wyoming. These will
likely be spotty showers that could contain some graupel and
gusty winds. As mentioned, the pattern following this exiting low
remains in question as a minority of ensemble members bring in
another trough, whereas most begin a drying and warming trend
thanks to a ridge building back into the area.

&&

.AVIATION...KSLC...Gusty south winds will prevail over the KSLC
terminal through around 02Z, with area showers continuing through
much of the evening and overnight hours. Passing showers will have
potential to produce wind gusts in excess of 25kts. Lowering cloud
bases are anticipated through the night, with a round of persistent
showers expected between 02-10Z. A brief break in activity will
occur thereafter, before another round of showers develop mid-
morning.

.REST OF UTAH AND SOUTHWEST WYOMING...Gusty south winds are expected
across the region through the remainder of the daylight hours.
Widely scattered showers and an isolated thunderstorm are expected
across the norther half of Utah and southwest Wyoming through the
next 16 hours. During this period, cloud bases are expected to lower
and begin to obscure the high peaks of the Wasatch. Most areas are
expected to maintain south winds through the overnight period,
however, gusts will drop off outside of passing showers.

&&

.FIRE WEATHER...Winds have been gusty today ahead of an approaching
fall trough, with gusts in excess of 50 mph reported over parts of
western Utah. However, relative humidities have been high enough
to avoid critical fire weather conditions. Showers and
thunderstorms have developed over northern Utah, with a few
strong to severe storms possible into the early evening. As the
trough moves in tonight, precipitation will become more widespread
over northern Utah, persisting through Tuesday as the trough
moves through. The area will see much cooler temperatures in the
trough`s wake, up to 20F below highs observed today. Gusty
southerly winds will persist over southeast Utah, however, and
relative humidities values are expected to drop enough there to
result in marginally critical fire weather conditions. Unsettled
conditions will continue through much of the week, with a second
trough on Thursday bring a reinforcing shot of cooler air.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory until 9 PM MDT this evening for UTZ115-122.

WY...None.
&&

$$

SHORT TERM/FIRE WEATHER...Traphagan
LONG TERM...Mahan
AVIATION...Webber

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