018
FXUS65 KSLC 232139
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
339 PM MDT Sun Jun 23 2024

.SYNOPSIS...Dry and hot conditions will continue across northern
Utah through Tuesday as lingering moisture keeps a threat of
showers and thunderstorms over southern Utah. Showers and
thunderstorms can be expected across the area Wednesday before
drier conditions move in late in the week.

&&

.SHORT TERM (Through 12Z Tuesday)...High pressure is in place over
Utah and southwest Wyoming this afternoon, though the ridge axis
has shifted just east of the area to western Colorado. Seeing a
light west to southwest flow over the area because of this, which
is allowing deeper moisture over the area to roughly stay put over
southern Utah. Seeing satellite derived PWs in the 0.7 to 0.9 inch
range over southern Utah and in the 0.5 to 0.6 range over northern
Utah and southwest Wyoming. In the more moist airmass and some
lingering instability, have seen widely scattered convection
develop over southern Utah with some isolated flash flooding. The
threat of storms will continue into the early evening before
diminishing. Meanwhile, northern portions of the forecast area are
seeing quite unseasonably hot conditions with maxes running 10-15F
above seasonal normals, approaching daily records in some areas.
Excessive Heat Warnings and Heat Advisories remain in effect
through early this evening for many northern Utah valleys.

With some flattening of the ridge anticipated overnight due to a
storm system moving across southern Canada, will see temperatures
running a bit less hot for Monday, keeping maxes away from record
values. The drier airmass will also allow for more overnight
recovery, so see no need to extend heat headlines into tomorrow.
Meanwhile, little change in the pattern is anticipated over
southern Utah to start the work week, so the more moist airmass
will remain in place, and so will the threat of afternoon and
early showers and thunderstorms capable of producing heavy rain
that could lead to flash flooding.

.LONG TERM (After 12Z Tuesday), Issued 330 AM MDT...Tuesday looks
to be the hottest day of the long term period as strong ridging
across the south central to southwest CONUS continues to exert
influence upon the local forecast region. Afternoon highs along
the Wasatch Front once again generally range from the low 90s to a
little over 100, and for Lower Washington County a bit above 105
of so. Areawide, these temperatures are around 5 to 15 degrees
above climatological normal for late June. Compounded with very
mild overnight lows, HeatRisk once again highlights Tuesday as a
potential candidate for heat related headlines (primarily across
northern Utah). However, given it looks somewhat borderline as
forecast, and there`s a non-zero chance clouds could increase a
bit ahead of schedule and keep temps a little better in check,
will hold off on any issuance with this forecast package. In any
case, as has been mentioned in several previous discussions, it
will be hot out there regardless. Heat related safety should still
be kept in mind, especially for those working or recreating
outdoors. Stay hydrated and take frequent breaks if at all
possible, and ideally wear light and loose fitting clothing. Aside
from the heat, will still see sufficient lingering moisture in
combination with afternoon heating to trigger isolated to
scattered afternoon convection. Largely expect activity to fire
off terrain and drift into adjacent valley locations, with highest
coverage across southern Utah. While not anticipated to be overly
widespread, those planning any recreation in rain sensitive areas
should remain weather aware.

Wednesday will see the first semblance of a shift in the ongoing
pattern, as a trough deepening into the PacNW will help flatten
and shift the ridge a bit eastward. Combination of the flattened
and slightly displaced ridge along with increasing mid level
moisture and associated cloud cover will help afternoon high
temperatures begin to trend downward. Additionally, will see some
increasing (but still fairly weak) PVA in the enhanced
southwesterly flow between the deepening trough and ridge, so will
see an expansion of isolated to scattered precipitation chances
across the majority of the forecast region.

The aforementioned Pacific trough continues to deepen a bit as it
shifts inland Thursday and Friday. While guidance continues to
carry some differences in just how deep and how quickly the trough
advances eastward, there remains fairly good consensus that it
will push a cold frontal boundary southward towards and likely
into the forecast region. So far, most likely timing of this
feature is later Thursday on into early Friday, with elevated
precipitation chances maintained until after frontal passage and
subsequent advection of some drier post-frontal air. This will
result in a continued downward trend in temperatures, with Friday
currently looking like the coolest day of the forecast period,
with afternoon high temps generally near to even a bit below
climatological normal. That said, overall deepness of the trough
will impact how far south the front progresses and just how cool
things get, and there`s still a decent amount of spread in
guidance. For example, at KSLC for Friday the NBM 25th percentile
high temperature (stronger trough scenario) is 84 degrees, and the
NBM 75th percentile high temperature (weaker trough scenario) is
95 degrees. In any case, it looks like the trough will at least
give the area a reprieve from some of the more excessive heat from
earlier in the week.

Moving into the weekend, guidance currently leans in favor of a
gradual restrengthening of ridging, and thus yields a warming
trend back to above normal. Most guidance also currently seems to
suggest limited moisture availability, so with the subsident
effect of the building ridge, precipitation chances remain limited
with this forecast package.

&&

.AVIATION...KSLC...Northwest flow at the SLC terminal should persist
until the regular or slightly delayed diurnal shift. There is a low
chance that convection further south of the area could push gusty
outflow winds towards the terminal for a few hours this evening,
with no convection anticipated directly near the terminal. Only
limited mid level cloud cover is anticipated through the period.

.REST OF UTAH AND SOUTHWEST WYOMING...Dry weather is
expected to continue at northern Utah terminals this evening, with
limited mid level cloud cover. Depending on how far north convection
develops across Utah, there is a low chance (less than 20%) gusty
outflow winds could push northward toward some of the northern
terminals. At southern terminals, isolated to scattered convection
is expected to continue into early evening. These terminals will see
better odds of gusty outflow winds and lightning with anything that
drifts over a terminal. After convection wanes, winds are expected
to follow a more typical diurnal pattern overnight.

&&

.FIRE WEATHER...Little change in the weather pattern is anticipated
through Tuesday. Under high pressure and relatively light flow,
moisture will remain trapped over southern Utah, resulting in a
daily threat of showers and thunderstorms capable of producing
heavy rain and gusty winds. Over northern Utah, conditions will
remain dry with unseasonably hot temperatures. By Wednesday, south
to southwest flow is expected to increase as a Pacific Northwest
trough moves onshore, drawing the moisture over southern Utah
northward across the entire state, thus increasing the threat of
convection areawide. This system is expected to graze northern
Utah on Thursday, bringing a front through. This would shift the
flow aloft to the west, allowing drier air to move in as winds
increase, bringing a threat of critical fire weather conditions to
southern Utah late in the week.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Excessive Heat Warning until 9 PM MDT this evening for
     UTZ101>105.

     Heat Advisory until 9 PM MDT this evening for UTZ106-107-116-118-
     119.

WY...None.
&&

$$

SHORT TERM/FIRE WEATHER...Traphagan
LONG TERM...Warthen
AVIATION...Verzella

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