592
FXUS65 KSLC 171011
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
410 AM MDT Fri May 17 2024

.SYNOPSIS...An active, unsettled pattern will continue through at
least the first half of next week.

&&

.SHORT TERM (THROUGH 12Z SUNDAY)...Just a few clouds so far this
morning as Utah remains under a dry WNW flow aloft. Upstream, an
upper trough is noted over the PacNW. This trough will track across
Idaho and Montana today, pushing a relatively shallow cold front
through northern and central Utah this afternoon and evening. Gusty
postfrontal winds can be expected especially across portions of
northern Utah and southwest Wyoming, but speeds should remain well
below criteria for wind highlights. Despite the cold front,
afternoon max temperatures should generally remain similar to or
warmer compared to yesterday, due to better mixing and the idea that
H7 temperatures start out warmer and do not cool until late in the
day.

Latest CAMS are still hinting at the potential for some high-based
showers near the boundary, especially across central Utah.
Instability is forecast to be on the low side today, with the HREF
only showing local areas with ensemble means of 100-250J/kg SBCAPE.
As such, the convection is not expected to be strong, but have
maintained isolated thunderstorms across some localized high terrain
areas as per the NBM. The greatest threat with the showers will be
strong, gusty microburst winds owing to the dry boundary layer.
Looking at probabilistic guidance, though, the HREF only has around
a 10% chance of gusts 40 mph or greater in isolated areas, although
feel that this might be slightly underdone.

The frontal boundary will weaken and stall tonight after it moves
through central Utah. Tomorrow, the upper trough will have moved off
into the northern Plains while the next upstream system begins to
deepen into the PacNW. This will bring a return of southwesterly
flow to Utah, lifting the boundary back northward. Convection is
expected to develop again along the boundary, but with the low
levels having moistened a bit, greater instability and an increased
chance of measurable rain can be expected. However, that is not to
say that the microburst threat is over. The HREF probabilities show
isolated 10-25% chances of gusts 40 mph or greater, greatest chance
over west-central Utah.


.LONG TERM (After 12Z/6AM Saturday)...Models continue to trend in
favor of a deeper longwave trough digging into the forecast area
Sunday through Tuesday, favoring cooler and wetter conditions across
at least the northern half of the region. Current deterministic
guidance supports a cold front dropping into northern Utah some time
late Sunday morning to early Sunday afternoon, progressing through
much of Utah by Monday morning. Initial lack of significant moisture
will allow for the front to progress through the area without
causing much in the way of precipitation, however, at least isolated
to widely scattered showers will be possible along the boundary.
With a colder airmass in place, Monday will feature temperatures
that are 5 to 15 degrees colder than the day prior (about 5 to 10
degrees below average for this time of year). Precipitation is
likely to be tied to the frontal boundary, where coverage may be
greater as the environment becomes more moist. Again, the best
chances for precipitation may be confined to the northern half of
the area, but we`ll dial in those details soon.

There is some uncertainty with how far south this front will
progress, which is continuing to introduce around 7-8 degrees of
spread in the temperature forecast for the St. George area for
Tuesday. At the very least, there is higher confidence in more
extreme cooling across the northern half of the area, with lesser
confidence over the southern and eastern halves.

A brief break in activity is forecast heading through Wednesday as
the initial trough lifts out of the area. However, just upstream
models indicate potential for another trough to drop out of the
PacNW region. With another trough following quickly in the wake of
the aforementioned, should see cooler and wetter weather prevail
through the second half of the week.


&&

.AVIATION...KSLC...VFR conditions are expected over the KSLC
terminal through the valid TAF period. Gusty northwesterly winds are
expected during the afternoon hours, and may begin to gust out of
the west to southwest around 15-20kts before 18Z.

REST OF UTAH AND SOUTHWEST WYOMING...Gusty afternoon winds out of
the west to northwest are expected across at least the northern half
of the forecast area today. VFR conditions will prevail across the
region with increasing mid-level clouds during the afternoon hours
across central and southern Utah. Isolated showers will be possible
in this area, and will have the potential to generate gusty and
erratic outflow winds in excess of 35kts.

&&

.FIRE WEATHER...A storm system will graze northern Utah today,
pushing a cold front through northern and central Utah this
afternoon and evening. This front will be accompanied by gusty
winds, while high-based showers could lead to isolated strong
microbursts. The boundary will gradually lift back to the north
through the day on Saturday, accompanied by isolated to widely
scattered showers and thunderstorms. Southwest winds increase again
on Sunday ahead of the next storm system which will continue to
bring unsettled weather to the area through at least the early part
of next week.

&&

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

$$

Cheng/Webber

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