130
FXUS65 KSLC 052129
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
329 PM MDT Wed Jun 5 2024

.SYNOPSIS...An early season heat wave will impact the area through
the work week, with record-challenging temperatures anticipated
Thursday into Friday. As the ridge flattens for the weekend, the
warming trend will curb and some moisture will move into the area,
increasing the threat of convection.

&&

.SHORT TERM (Through 12Z Friday)...Water vapor satellite imagery
this afternoon shows a broad area of anti-cyclonic flow over the
Southwest US. This high pressure aloft will slowly shift eastward
over the next several days, with the ridge axis moving over our
area tomorrow afternoon. 700MB temperatures look to rise to 13-17C
over northern Utah and 16-19C over southern Utah, translating to
well above normal temperatures. Based on latest forecast guidance,
have extended the Excessive Heat Warning for lower elevations of
Southern Utah to include Saturday, and added southwest Utah to the
Heat Advisory.

Moisture aloft begins to increase late Thursday, as seen in model
soundings above approximately 10kft AGL. With that moisture,
models are showing convective potential brushing the northwest
corner of Utah by late tomorrow afternoon into the evening. This
primarily looks to impact the Raft River mountains, but also other
areas from approximately Wendover to Snowville. By Friday, mid-
level moisture will overspread the entire CWA, with increased high
clouds. Such cloudiness could cap daytime highs, but also bring
warmer nights, leading to a bit of uncertainty in the temperature
forecast. Additionally, some uncertainty in temperatures is
related to the National Blend of Models not having been trained on
the type of temperatures coming up. Some oddities noticed in the
NBM include the deterministic forecast for KSLC tomorrow landing
at the 10th percentile of the probabilistic forecast distribution.
Regardless of these small differences, the overall message remains
that this will be an usually hot period for this early in the
summer. For example, the forecast at St George tomorrow is 108,
and the usual first occurrence of 108 is July 4th. Add that to
the fact that this is the first extended period of heat for the
season (e.g. St George just reached 100 for the first time this
season yesterday).

With the warmer temperatures comes increased snowmelt. We are
keeping a close eye on stream gauges that are forecast to
approach action stage across northern Utah. Observed streamflow peaks
this evening and overnight will help us have a better idea of
what to expect going forward. And, regardless of whether a
waterway is technically flooding, many will be running fast and
cold; with the hot weather making such water more desirable,
folks should be aware of the risks.

.LONG TERM (After 12Z Friday), Issued 350 AM MDT...
As clouds increase later Thursday into Friday, cooling Friday
morning will be limited. Low temperatures will be the upper 60s to
around 70F for the urban corridor of northern Utah and in the mid
70s around Lake Powell and lower Washington County. Shortwave
energy will track into southwest Wyoming and Utah as a ridge
tracks slightly to the east, which will bring enhanced clouds into
Friday. As conditions warm during the day, isolated to scattered
showers and thunderstorms are likely. With weak forcing, minimal
wind shear, and low moisture, showers and thunderstorms will
primarily be around terrain. Gusty, erratic outflow winds would be
likely. With high pressure positioned to the southeast, most
showers and thunderstorms will likely be around the northern
mountains. Temperatures aloft will be nearly the same as Thursday,
and forecast highs are similar. Mid to upper 90s are likely for
most valleys, with 100s around Lake Powell and lower Washington
County.

The ridge will track further east into the weekend, but ensembles
are in good agreement on another building in quickly. Temperatures
Saturday will be slightly cooler than Friday, but stay more than 10F
warmer than normal. Isolated to scattered showers and thunderstorms
for portions of northern Utah are likely. Another ridge will track
into Utah for the end of the weekend. There will likely be fewer
showers and thunderstorms, with shortwave energy further north.

There is uncertainty early in the week as to if ridging will
dominate or if more showers and thunderstorms would be expected.
Most ensemble members keep ridging with occasional shortwaves and
isolated to scattered showers and thunderstorms. Some members bring
remnants of a closed low tracking northward from off the Baja coast
with better moisture advection into Utah. While there is uncertainty
on details, warmer than normal temperatures will likely last through
at least early in the week.

&&

.AVIATION...KSLC...Northwesterly winds will transition to light and
southeasterly around 03-04z. Winds will likely be light and somewhat
variable overnight. High density altitude could become a concern as
high temperatures at the surface increase to the mid-90s
Thursday through Saturday.

.REST OF UTAH AND SOUTHWEST WYOMING...Light and diurnally-driven
winds will prevail across much of the area, with the only exception
being southwestern WY where winds will continue to gust to 25kts out
of the west this afternoon/evening. High density altitude could
become a concern as surface temperatures continue to increase over
the coming days.

&&

.FIRE WEATHER...High pressure will continue to build over Utah
through tomorrow, bringing stable and very dry conditions with
light winds. Temperatures across the area will steadily warm
through Friday, with highs running 15 to 20 degrees above normal
for this time of year by the end of the work week along with RHs
dropping to near single digits over southern Utah lower elevations.

The ridge axis will move east of the area Friday as the ridge
weakens. This will curb the warming trend and allow some moisture
to return to the area. The moisture will bring a threat of high-
based showers and thunderstorms with a minimal chance of wetting
rains, thus bringing a threat of dry lightning and gusty and
erratic winds. A daily threat of afternoon thunderstorms looks to
then continue into early next week, primarily over the higher
terrain, with temperatures remaining above normal each day.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Heat Advisory from 11 AM Thursday to midnight MDT Friday night
     for UTZ121-122-128>130.

     Excessive Heat Warning from 11 AM Thursday to midnight MDT
     Saturday night for UTZ123-124-131.

WY...None.
&&

$$

SHORT TERM...
LONG TERM...
AVIATION...
FIRE WEATHER...

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http://weather.gov/saltlakecity