Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 212122
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
322 PM MDT Sat May 21 2022

.SYNOPSIS...A grazing trough tomorrow will bring increased winds
and a few showers to the northern mountains. Another weak system
will follow late Monday into Tuesday before high pressure returns
midweek along with significant warming.

&&

.SHORT TERM...Satellite imagery this afternoon infers a broad
trough over the western CONUS centered east of our area, although
with little in the way of associated synoptic clouds over the
Great Basin and Central Rockies. Afternoon cumulus buildups are
present over the higher terrain roughly north of Bryce Canyon.
while area radars show little to no precipitation from this
largely fair-weather convection. At the surface, the few spots of
gusty canyon winds over northern Utah this morning have long since
calmed, with temperatures running around 5-10 degrees below
normal. Expect another night of cool overnight temperatures for
this time of year, though not as cold as last night.

Looking ahead to tomorrow, another shortwave trough on the
backside of the western CONUS longwave trough will slide through
the Northern Rockies, with the axis brushing northern Utah and
southwest Wyoming tomorrow afternoon. This will bring another push
of cooler air to the northern 2/3rds of the forecast area, though
warming temperatures aloft tonight in advance will result in
700MB temperatures post-frontal tomorrow actually running around
3C warmer than today. For most locations, the only noticeable
change will be a bit more cloud cover tomorrow afternoon compared
to today from around I-80 northward and northerly breezes. For the
higher terrain east of I-15, expect a few scattered showers and
even a rumble of thunder or two thanks to a bit of instability
aloft associated with the trough passage. Farther south, breezy
winds gusting to 30mph or more can be expected, especially east of
the Wasatch Plateau and south of Bryce Canyon. More information on
the fire hazards associated with this event can be found in the
fire weather discussion. One other possibility with this wind is
areas of blowing dust, which have been introduced to the forecast
over southwest Utah (in an area of northerly winds) and Kanab to
Lake Powell area (in an westerly winds), as depicted in the GEFS-
Aerosols model`s depiction of dust tomorrow.


.LONG TERM...Early this upcoming week Utah and southwest Wyoming
will find themselves continuing under a northwest flow regime.
Similar morning temperatures are forecast Monday compared to
Sunday morning with temperatures just a few degrees below seasonal
normals. Any potential moisture for Monday is expected to be up
in the highest elevations and as such a slight chance of snow
exists in the Uintas. Headed into Tuesday, a shortwave trough in
the flow tracks into the region from Idaho and is expected to
bring the next opportunity for showers and thunderstorms. There is
one cluster of ensembles that is not too supportive of this
shortwave trough and is instead in favor of continued northwest
flow for Tuesday. These clusters are mostly from the Canadian
ensemble members. We will place low end chances for precipitation
in the forecast at this time and continue to monitor trends.
Rainfall amounts at this point are relatively low and in fact
quite dry with this trough. Areas between Provo to Logan to
Evanston, WY will have the best chance for any rain showers and
thunderstorms. Snow showers are once more expected in the Uintas.
Less than 1/2 inch of accumulation is forecast during the
afternoon and evening hours.

The middle and latter half of the week will bring a building
ridge of high pressure and warming temperatures across the region.
This is a trend favored by all clusters of ensemble members.
Thursday is expected to be the warmest day this week before a
decreasing trend begins headed into the weekend. Temperatures
Thursday have a 100% chance of climbing above 90 degrees in St.
George and a 60% chance of climbing over 97 degrees. In Salt Lake
City, temperatures on Thursday have about a 50% chance of climbing
over 90 degrees. The record high temperature for Thursday in Salt
Lake City is 92 degrees, which was set in 1958 and thus we look
to be shy of that record. While these values are expected to be a
moderate heat risk for those sensitive to heat, we are not
currently expecting any heat advisories.

Friday afternoon will bring the next possibility of rain showers
across northern Utah, if we believe the clusters of GEFS members
that quickly bring in the next approaching trough and cold front
from the west. Most ensemble model solutions wait longer to bring
this trough into our region until early Saturday, which would
leave Utah dry and warm under southwest flow Friday. That said,
the official NBM forecast does have a slight chance of rain
showers along the ID/UT border Friday to account for that
scenario favored by GEFS members, with additional chances for
rain from the ID/UT border extending southward into Saturday to
account for much of the remaining ensemble solutions. A cooling
trend is forecast for Saturday behind a cold front.

&&

.AVIATION...KSLC...VFR conditions and light, diurnal wind switches
are expected through early tomorrow. Stronger northwest winds,
gusting to 25 knots potentially in the afternoon, are expected
tomorrow as a mostly dry cold front pushes through.

.REST OF UTAH AND SOUTHWEST WYOMING...Widespread VFR conditions
expected across the forecast area through the TAF period, with a
few cumulus buildups over northern Utah mountains. Winds will
remain generally light and terrain driven as high pressure
becomes established across and to the north of the forecast area.
Stronger, generally northerly winds can be expected tomorrow along
with some showers over the northern mountains as a cold front
moves through the area.

&&

.FIRE WEATHER...Little more than afternoon cumulus development and
a stray rain shower over the northeastern portion of the state is
expected this evening with only limited instability being
observed this afternoon. The arrival of a weak shortwave trough in
the northern third of the forecast area Sunday afternoon will
bring with it increased wind speeds for central and southern Utah.
Given the now more widespread potential for gusts 25-35 mph
through the afternoon along with daytime minimum relative
humidities nearing the single digits, the San Rafael Swell and
Grand Staircase are expected to meet critical fire weather
conditions. For the northeastern corner of the forecast area,
expecting the potential for some afternoon convection producing
isolated to scattered showers and thunderstorms. Further south,
the mid-level cooling and instability associated with the trough
will be undermined by continued advection of warm and very dry
air, limiting the chance of notable weather in the area beyond the
increased winds.

Monday will see a brief break before the next system. As one more
shortwave trough and associated large-scale forcing swings
through the northeastern corner of the state on Tuesday, expecting
increased potential for shower development in northern Utah
throughout the day, with the potential for isolated to scattered
thunderstorm development in the afternoon as the trough moves
through and the main drivers of precipitation shift over to a more
convective mode. A ridge of high pressure will finally build back
in for Wednesday, kicking off a stout warming and drying trend
with some of the warmest temperatures of the season so far
expected on Thursday. By Thursday evening, the next storm system
tees up, with winds increasing out of the southwest through the
evening.


&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Red Flag Warning from 1 PM to 9 PM MDT Sunday for UTZ489-498.

WY...None.
&&

$$

SHORT TERM...Van Cleave
LONG TERM...NDeSmet
AVIATION...Van Cleave
FIRE...Wessler

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

For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php


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