133
FXUS65 KSLC 052135
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
335 PM MDT Sat Oct 5 2024

.SYNOPSIS...High pressure will remain the dominant weather feature
through late next week bringing warm and mainly dry conditions.
Temperatures will trend a bit warmer each day through Thursday,
remaining well above normal for early October.

&&

.SHORT TERM (Through 12Z/6AM Monday)...Early Saturday afternoon
analysis indicated a mid-level trough across the Northern Plains
quickly moving eastward. This trough was responsible for the
passage of last night`s weak, dry cold front that made it into
southern Utah before washing out. Meanwhile, mid-level heights
were building across Utah and SW Wyoming in response to a building
mid-level ridge across the area. Model consensus does indicate
flattening of the northern periphery of the ridge on Sunday as a
weak shortwave progresses eastward through the Northern Rockies.
PW plots and soundings do reveal a modest increase in mid-level
flow as well, with an attendant slight increase in mid/high level
clouds across central and southern Utah Sunday afternoon. We
can`t rule out an isolated, high-based shower across these areas
as well tied to this increase in mid-level moisture, but there is
a very low (<15% chance) of measurable precipitation. By Monday,
mid- level height rises return to the area as a trough amplifies
offshore of California. By the second half of Monday, southwest
deep-layer flow begins to become established across Utah and SW
Wyoming, and another modest increase in mid-level moisture is
poised to advect into the area tied to this feature. Thus,
additional high-based showers are in the offing Monday afternoon
and early evening, with gusty microburst winds potentially
accompanying some of this activity thanks to a continued dry low
level environment.

With northwesterly low to mid-level flow in place across the very
active Yellow Lake fire, wildfire smoke has been advecting across
the Uinta Basin today. With little change in the flow expected
through Sunday, wildfire smoke will continue to advect into this
region.

Temperatures, while having cooled slightly off their recent
records, will remain 10-15F above normal through Monday.

.LONG TERM (After 12Z/6AM Monday)...High pressure will reside
over the area to start the long-term, with temperatures continuing
to sit around 10-15 degrees above normal. Despite this high
pressure largely persisting, increasing moisture in the mid- to
upper- levels coupled with subtle upper-level diffluence will
result in isolated convection across higher terrain on Tuesday
afternoon. Model soundings show very dry low levels and an
inverted-V, thus isolated dry microbursts are possible. One
limiting factor will be limited instability, with model guidance
suggesting storm development mainly over higher terrain.

Wednesday and Thursday will likely be dry and mild once again, with
current forecast highs approaching 20 degrees above normal in some
areas. Beyond Thursday, uncertainty in the longwave pattern
increases noticeably.

Most model guidance hints at some form of pattern change heading
into the weekend, but there is plenty of spread in the extent of
this change. Interestingly, deterministic models and ensemble
guidance reveal very different scenarios. The GFS, EC, and Canadian
each suggest a broad western US trough developing and transitioning
into a closed low overhead or just to our south, which could bring a
potent cold front and precipitation through the area. Ensemble
guidance, however, is much less aggressive, overall featuring a
shallower/weaker trough over the western US. By Saturday evening,
only 22% of ensemble members favor a stronger trough. All this to
say...we are likely to see a pattern change this weekend, though any
more details than that are highly uncertain at this time.

&&

.AVIATION...KSLC...Light northwest winds will transition to
southeast around 03Z. Clear conditions will continue, with a
transition to northwest winds around 18Z.

.REST OF UTAH AND SOUTHWEST WYOMING...West winds will gust around 30
knots in southwest Wyoming through around 01Z. Relatively light
winds will continue throughout Utah. Clear conditions are likely
throughout southwest Wyoming and most Utah, with locally dense
wildfire smoke in portions of eastern Utah.


&&

.FIRE WEATHER...Enhanced west to northwesterly postfrontal winds
can be expected through the early evening hours today across
northeast Utah, strongest in favored downslope areas of the
eastern valleys. These areas will see marginal critical fire
weather conditions due to these winds and marginally critical
humidity through early this evening. High pressure will then
settle into the area through much of the coming week, maintaining
above-normal temperatures and bringing lighter winds. Periods of
midlevel moisture may bring spotty high-based showers at times,
especially Monday and Tuesday afternoon and evening.

Otherwise,expect gradually warming temperatures by a degree or
two each day through Thursday, along with generally poor overnight
recovery each night through Thursday. Some uncertainty in the
forecast begins to appear by Friday through next weekend, as there
is a trend in some of the model guidance that brings either a low
pressure trough or closed low pressure into the area, along with
cooler temperatures, higher humidity and increasing precipitation
chances. As it stands currently, this is one of two potential
forecast outcomes for the upcoming Friday-Sunday timeframe. The
other potential outcome is slight cooling, slight moistening but
otherwise remaining dry with a continuation of above normal
temperatures. We will continue to monitor these trends to see
which scenario wins out.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...Red Flag Warning until 7 PM MDT this evening for WYZ277.

&&

$$

ADeSmet/Cunningham/Wilson

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