393
FXUS65 KSLC 032201
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
401 PM MDT Fri May 3 2024

.SYNOPSIS...An approaching storm system will bring much warmer
conditions Saturday with strong afternoon winds for portions of
Utah. A cold front will track into Utah Sunday. Lighter winds,
cooler conditions, valley rain, and mountain snow are likely once
the front pushes through.

&&

.SHORT TERM (Through 12z/6AM Monday)...Satellite imagery shows a
shortwave ridge continuing to shift eastward through the Great
Basin and into Utah. Thus, skies will continue to clear heading
into the late evening and overnight hours. Also seen is a strong
closed low off the coast of British Columbia that will eventually
produce winter-like conditions across much of our area later in
the weekend.

The shortwave ridge axis will pass quickly to our east by mid
Saturday morning, with increasing southerly flow as the
aforementioned closed low pushes inland. In this pre-frontal
environment, strong warm-air advection will produce Saturday high
temperatures that are 10-20 degrees above Friday highs across all
but far southern Utah. The main concern for Saturday, however, is
gusty southerly winds across western valleys picking up in the
afternoon and peaking overnight. Many western valleys will reach
high-end Wind Advisory criteria (45-58 mph), with the highest
gusts likely across western Juab and Millard counties, reaching
upwards of 60 mph (70% chance in most areas). H7 winds around
50kts will likely mix well to the surface given steep lapse rates
and a dry air mass, however increasing mid-level clouds could act
to limit this mixing...therefore there is still some uncertainty
in peak gusts at this time. This main core of winds will shift
eastward by Sunday, with winds picking up Sunday morning across
southeastern valleys, peaking Sunday afternoon. A High Wind Watch
has been issued for these areas to highlight the highest risk
areas.

A potent cold front will bring quite the contrasting weather to
the area on Sunday, with a stark transition to much cooler
temperatures, plentiful valley rain, snow down to 5000 feet, and
weaker northwesterly flow. This cold front will be quite strong,
also featuring the potential for thunderstorms along and behind
the front on Sunday. This front will likely enter northwest Utah
Sunday morning, reaching the Wasatch Front by mid day and southern
Utah by evening.

Widespread precipitation will mainly begin along the frontal
passage, with a few rogue showers possible just ahead of the
front. Periods of heavy precipitation are possible, including
heavy mountain snow. In terms of QPF through Monday, the Wasatch
Front could see 0.8-1.4" of rain, with the northern mountains
receiving upwards of 2" or more of liquid equivalent. These
amounts could be even higher with any lake-enhancement late Sunday
night. Snow levels, initially around 9000-9500 feet, will plummet
with the frontal passage down to 5000 feet. The highest snow
amounts up to 2 feet are expected in the Upper Cottonwoods and
Ogden area mountains, given an extended period of unstable west to
northwesterly flow and orographic enhancement behind the front.
Thus, Winter Storm Warnings have been issued for the northern
mountains, especially given the potential for surface
transportation impacts and unseasonable nature of the system.

In summary, expect strong warming and southerly winds ahead of the
storm system late Saturday into Sunday, with an abrupt transition
to winter-like conditions on Sunday.

.LONG TERM (After 12Z/6AM Monday)...Northwest flow will be our
dominant flow pattern early next week behind the passage of a low
pressure system and strong cold front. A series of shortwave troughs
are forecast to track through the Intermountain West early in the
week as the low tries to track to our northeast, which will bring
valley rain showers, thunderstorms and mountain snow across northern
Utah and southwest Wyoming. The exception here will be Monday
morning; wherein snow levels are forecast to be low enough to bring
snow to area benches in the Wasatch Front. Accumulating snow is
quite possible though most likely to be an inch or less. There`s a
less than 40% chance for more than that at this point.

Otherwise, across most of northern Utah and southwest Wyoming, from
Monday morning through Tuesday evening, on and off rain showers are
forecast. What is a bit more favorable, unsurprisingly, is the
persistent mountain snow. Snow amounts Monday alone across the
northern Utah mountains are forecast to range between 5 to 12 inches
(3 to 8 inches in the western Uintas) while amounts Tuesday will
range from 4 to 10 inches (2 to 4 inches in the western Uintas). The
confidence in snowfall amounts is lowest by the end of this event,
on Tuesday evening.

Additionally, there remains potential for lake effect driven showers
every morning from Monday through Wednesday which would bring
additional QPF amounts to favored areas downstream. The latest
guidance is favoring Wednesday morning, interestingly.

While strongest winds are forecast over the weekend, Monday
afternoon looks to continue with that trend with some stronger winds
for the Uinta Basin and southwest Wyoming, potentially impacting
travel on I-80. Gusts in the 50+mph range are forecast and may
warrant headlines in the future.

Dry conditions are forecast across central and southern Utah early
next week with the exception of the central mountains and the Tushar
Mountains where a few inches of snow are forecast.

Normally for early May, high temperatures for Salt Lake City will
reach the upper 60s to 70 degrees. However, forecast high
temperatures this Monday, Tuesday and Wednesday are forecast 15 to
20 degrees below average and will instead barely climb into the low
50s. A similar trend is noted for minimum temperatures. Temperatures
are expected to be coldest Wednesday morning, so cold in fact that
low temperatures are expected near or below the freezing for several
valley locations. The EFI and Shift of Tails guidance support these
anomalously cold temperatures for this time frame. If these trends
persist, certainly freeze headlines would be warranted. If you need
to plan ahead for agricultural reasons now is your time to plan for
frost and freeze.

A fairly dry forecast remains in the forecast for the remainder of
the week however toward the end of the week Utah may see some wrap
around moisture associated with the same area of low pressure from
earlier in the week. Deterministic models are showing this low
tracking back through Utah Friday and bringing modest amounts of
moisture with it. Positioning of the low and how much moisture it
would bring are of course, pretty uncertain at this point. Right now
eastern Utah and southwest Wyoming are the favored locations for any
additional precipitation impacts.

&&

.AVIATION...KSLC..VFR conditions will remain in place through the
valid TAF period. Northwesterly winds will prevail through the mid-
evening, transitioning to a southerly flow around 04Z. South winds
remain in place through the day tomorrow, with gusts up to 30kts
expected by the early afternoon.

.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions are expected
across the area through the valid TAF period. Isolated showers
across northern Utah will diminish through the early evening hours,
giving way to mostly clear skies overnight. Tomorrow, winds will
increase out of the south, with peak gusts across the West Desert
expected to exceed 50 kts. Along the I-15 corridor, peak gusts will
vary between 30 and 35 kts.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...High Wind Watch from Saturday afternoon through Sunday morning
     for UTZ115-122.

WY...None.
&&

$$

Cunningham/NDeSmet/Webber

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