890
FXUS65 KSLC 131006
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
406 AM MDT Mon May 13 2024

.SYNOPSIS...A weak storm system will graze northern Utah late this
afternoon and into the evening before another system moves
through the area Tuesday into Wednesday, bringing less warm and
more unsettled conditions. High pressure will return late in the
week with a renewed warming and drying trend.

&&

.SHORT TERM (Through 12Z Wednesday)...Seeing clear skies over Utah
and southwest Wyoming this morning under the influence of high
pressure currently centered near the Utah/Nevada border. Under the
influence of the ridge, temperatures across the area will be quite
mild, with maxes averaging 10F above seasonal normals. However,
The ridge is already starting to flatten as a weak wave moves
onshore along the Pacific Northwest coast. This system is on track
to graze northern Utah later this afternoon and into the early
evening, bringing a cold front into the state. Afternoon
convection will be focused along this boundary, and thus
primarily confined to areas near the Utah/Idaho border. Given the
relatively dry lower levels, gusty outflow winds will be the
primary threat with any storms that develop.

The arrival of this initial wave will usher in a period of
unsettled weather for the midweek period. Guidance indicates the
first wave will be followed by a second grazing wave on Tuesday
that will push the frontal boundary into southern Utah. Moisture
and instability with the second wave look to be less impressive
than the first, which was not particularly impressive in and of
itself. Thus, the primary impact will be to make temperatures less
warm across northern Utah, with maxes running 5F above seasonal
normals.

.LONG TERM (After 12Z Wednesday)...Extended forecast period
starts out in a post-frontal environment as Tuesday`s trough
continues to exit the region. Temperatures cool off by another few
degrees across a large majority of Utah and southwest Wyoming. Even
though Wednesday will feature some of the "cooler" temperatures of
the week, highs will still remain about 2-6 degrees above normal for
this time of year (highest anomaly across lower Washington County).
Lingering moisture and mid-level instability draped over the region
will help to bring isolated to scattered showers and thunderstorms
to higher terrain and adjacent valley areas, with a focus across
both the southern and eastern portions of Utah. Minimal impacts are
anticipated from these showers, however, a north to northwesterly
storm motion could allow a shower to build into a flashy drainage in
southern Utah. Thinking the overall probability of this is low (less
than 15%) given PWAT values are right around normal for this time
of year.

Stabilization of the environment ensues heading through Thursday as
high pressure becomes the dominant weather feature over the area.
Generally clear skies and warming temperatures will be the trend
through the end of the week, so long as high pressure remains in
place. As of right now, models are in good agreement of above normal
mid-level heights with a ridge axis to the west (dictating surface
high pressure) through at least Friday. Through then, expect above
normal temperatures across the area alongside dry conditions.

Thereafter, uncertainty in the forecast increases notably. Models
continue to indicate potential for another trough to dive into at
least the northern half of the area out of the PacNW region. The
biggest uncertainty appears to be whether or not the upstream ridge
will expand far enough east to minimize the blow of this potential
trough. Trends amongst the ensemble guidance seems to be favoring a
weaker trough translating across the northern Rockies region,
bringing minimal impacts across our local area. Timing of this
occurrence is also a point of contention as some models (~15%)
support troughing over the region by Friday evening with ~85%
favoring a ridge. For Saturday, ~50% of ensembles favor a weaker
trough with the remaining 50% of ensembles (slightly more) favoring
ridging. Needless to say, the most likely high temperature range for
the weekend is upward of 8 to 10 degrees for some areas. Have
maintained a mostly dry forecast through at least Saturday, with
increasing chances (marginally) for precipitation thereafter.

&&

.AVIATION...KSLC...VFR conditions are forecast over the KSLC
terminal through the valid TAF period. Southerly flow will revert to
a northerly flow between 18 and 19Z today, with potential for gusty
winds later in the evening as area showers develop.

.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions are expected to
prevail across the area, with high based showers developing across
far northern Utah, and isolated areas of southern Utah. Area showers
will have the potential to generate gusty and erratic outflow winds
in excess of 30 mph, but otherwise winds will be generally light and
terrain driven.

&&

.FIRE WEATHER...High pressure over the Great Basin will flatten this
morning as a weak Pacific Northwest storm system grazes northern
Utah this afternoon and this evening, bringing through a weak cold
front. Scattered showers will accompany the front, primarily over
far northern Utah. A second grazing system will push the front
into central Utah for Tuesday, and with the passage of a third
weak system on Wednesday, the front will move through southern
Utah. Overall impact will be to make temperatures gradually less
warm through Wednesday, though highs will still be above normal
for this time of year. Some showers will be possible, with the
best coverage expected over far northern Utah today and across the
remainder of the area on Wednesday, but the system will not be
accompanied by a lot of moisture, limiting convective development.
High pressure will return beginning Thursday, bringing a warming
and drying trend through Saturday.

&&

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

$$

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

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