ut discuss
Office: SLC
FXUS65 KSLC 020959
AFDSLC
Area Forecast Discussion
National Weather Service Salt Lake City UT
359 AM MDT Thu May 2 2024
.SYNOPSIS...A relatively cool and unsettled pattern will persist
through the remainder of the week, with the next weather system
bringing showers to northern Utah and southwest Wyoming Thursday
night into Friday. A rapid warmup Saturday will precede a strong
storm system and associated strong cold front that will arrive
this weekend. This system will bring strong, gusty winds and snow
to the mountains.
&&
.SHORT TERM (Through 12Z/6AM Saturday)...Early Thursday morning
analysis reveals the continued presence of an energetic jet
stretching across the region with a pair of departing disturbances
across MT/WY. Meanwhile, another upstream impulse can be seen
entering the PacNW at this time. This wave will race eastward
today and propagate into southern Idaho this afternoon. Most
likely scenario then depicts this system briefly amplifying across
northern Utah and SW Wyoming through Friday before exiting to the
east Friday night.
Showers associated with this incoming system are expected to
commence across northwestern Utah early this afternoon, before
scattered showers gradually overspread northern Utah and SW
Wyoming during the remainder of the afternoon hours. This activity
will persist through the evening and much of the overnight hours,
centered across northeast Utah and SW Wyoming. The bulk of the
activity this afternoon and evening will largely occur north of
I-80, although we can't rule out an isolated shower occurrence
south of this delineation. NBM and SPC calibrated thunder
probabilities indicate a 10-20% chance of lightning across
northwest Utah, with lightning probabilities elsewhere under at
or below 10% with this system, suggesting most of us will not
experience lightning and thunder activity. With steep low to mid-
level lapse rates this afternoon and modest 700mb flow in the
20-30kt range, a few cells will be capable of producing gusty
outflow winds, with a 50% chance for gusts in the 30-40 mph range
with the strongest cells, mainly across northwest Utah and
stretching east across the Great Salt Lake.
Model consensus suggests a few, light showers will continue across
northeast Utah and SW Wyoming Friday morning into the early
afternoon hours. In terms of snowfall, most likely range is in the
1 to 3 inch range above ~6500 feet elevation, with a few isolated
totals upwards of 6 inches possible on the high end of the
distribution (10% chance) at the highest peaks or where showers
are the most persistent.
In the wake of this system, a shortwave ridge axis will move into
the Great Basin Friday night, bringing a brief return to tranquil
conditions late Friday afternoon through Friday night beneath
strong mid level warm advection.
.LONG TERM (After 12Z/6AM Saturday)...Distinctly different weather
conditions are expected for each weekend day, with Saturday more
like summer and Sunday more like a chilly spring or winter day in
the mountains. A stout longwave trough with a closed low will track
into the PacNW Saturday. A shortwave ridge axis will track east of
Utah early Saturday, and as the aforementioned trough digs through
the day, winds aloft will increase. Strong warm air advection and
strong southwest winds will build into Utah, especially for the
afternoon. With largely clear conditions to start Saturday, lows
will be in the 30s for many valleys. As flow increases, with roughly
50 knots at 700 mb likely by the evening, afternoon highs will climb
more than 35 degrees from morning lows throughout southwest Wyoming
and Utah.
National Blend of Models 50th percentile, or 50% chance of being
reached or exceeded, for maximum wind gust Saturday is almost 50
knots at Milford and St. George and over 50 knots at Cedar City.
That 50 knot threshold would be High Wind Warning criteria for those
valleys. At least Wind Advisory criteria winds are likely. Blowing
dust will be a threat with winds of that magnitude. That number
drops of some further north, with the Tooele valley around 45 knots
and the Salt Lake Valley around 30 knots. Flow aloft will peak
Saturday night into Sunday as the trough approaches. That will
likely be the peak in mountain wind gusts, where gusts exceeding 65
knots are likely throughout western Utah. Valley winds will taper
off some Saturday night, but stay strong until a baroclinic zone
pushes through Sunday.
Variance with ensemble guidance is around the trough axis, coming
from timing differences with ensemble members. There is high
confidence that the cold front will track into western Utah Sunday
morning. There is some uncertainty in precisely when, but it is most
likely that the cold front will push into the urban corridor either
late in the morning or early in the afternoon. Strong pressure
falls, cold air advection, and precipitation will come with the
front. There is a low, roughly 15%, chance for isolated thunder and
lightning near the front. Conditions will stay warm enough for
valley precipitation to be rain through the day, with snow levels
initially around 8000 feet, dropping to 5000-5500 feet into Monday.
Post-frontal west to northwest flow will bring orographic
enhancement for some places. Snow ratios will start rather low, but
increase as colder conditions push in, with dense, wet snow to start
transitioning to less dense snow into Monday.
Water content of 1-2 inches is likely for the northern mountains.
Snowfall totals will be highly related to elevation within the
mountains, with much of the northern mountains from roughly 6-12
inches, but localized totals of more than 20 inches. Precipitation
will generally be lighter to the south. Valley rain will last
through the day for most of Utah once the front tracks through.
Before the trough exits, there is a low chance for snowflakes to
reach valley floors early Monday.
The trough will lift Monday with conditions drying through the day.
Several shortwave troughs could bring more precipitation through the
week, with the first for Tuesday.
&&
.AVIATION...KSLC...Light southeast winds will prevail through around
19Z when winds transition to northwest. Clouds will increase for the
afternoon and evening. A cold front will bring isolated to scattered
rain showers from roughly 06-12Z. VFR conditions could lower into
MVFR range with rain showers.
.REST OF UTAH AND SOUTHWEST WYOMING...Light winds with clear or
mostly clear conditions will last through the morning. Winds will be
gusty much of the afternoon, especially for southwest Wyoming and
southern Utah, with southwest to northwest gusts around 30 knots.
Clouds will increase for the afternoon and evening in southwest
Wyoming and northern Utah. Isolated to scattered rain showers are
likely from roughly 03-15Z. VFR conditions could lower into MVFR
range with rain showers.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Freeze Warning until 9 AM MDT this morning for UTZ103-106.
WY...None.
&&
$$
ADeSmet/Wilson
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