311
FXUS65 KSLC 271117
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
517 AM MDT Sat Apr 27 2024

.SYNOPSIS...An upper low crossing the region will maintain cool
and unsettled conditions through tonight. A gradual warming trend
will follow Sunday into Monday, with another series of mostly dry
cold fronts crossing the region beginning midweek.


&&

.SHORT TERM (Through 12Z/6AM Monday)...Early morning satellite
imagery and objective analysis show an upper low spinning across
southern Utah, with a TROWAL structure wrapping around the north
side of this low across northern Utah. This feature is maintaining
a broad area of stratiform precipitation across much of northern
Utah west of I-15 within a light easterly flow. Meanwhile
precipitation is more showery across central and southern Utah in
closer proximity to the upper low.

As the upper low slowly progresses eastward this morning, the
region of warm advection across northern Utah will persist, and
likely spread south with time into west central and southwest
Utah. As the upper low continues east this afternoon, the flow
aloft will transition to northwesterly as the airmass slowly
dries. Lingering moisture coupled with daytime heating will
support afternoon convection mainly east of I-15. Temperatures
this afternoon will run roughly 10F below climo in the wake of the
upper low.

A general northwest flow aloft will persist through Sunday, with
a weak embedded wave bringing a small chance of showers across
mainly northern Utah/southwest Wyoming. Rising heights and warming
aloft will allow temperatures to rebound 5-8F across the area
Sunday afternoon, remaining slightly below climo for late April.

.LONG TERM (After 12Z/6AM Monday)...Active weather resumes over the
northern half of the forecast area on Monday as a series of troughs
begin sweeping across the PacNW/ northern Rockies region. There is
some uncertainty in the progression of this active storm track and
just how far each expected trough progresses into Utah, however,
what once looked like a week of relatively inactive weather is
seeming to lack support from guidance. While we are expecting a
warming trend through the week, it is likely that the aforementioned
troughs will curb the warming trend and even bring periods of
cooling over at least the northern half of the area.

Monday through Tuesday morning, models maintain good agreement on a
trough progressing across southern ID/ northern UT region. Not only
will this trough interact with the existing lower level moisture, it
will also advect more moisture into the region. While guidance does
not point toward any significant precipitation accumulation, there
will be enough energy and moisture to kick off isolated to scattered
showers, and perhaps an isolated thunderstorm, during the afternoon
hours on Monday and through a portion of the overnight hours. The
quickly progressing trough is expected to depart the region
overnight, allowing for drying conditions on Tuesday. That said,
can`t rule out a stray shower in the mountains. A cold front will
drop into northern Utah Monday evening through Monday night, setting
up Tuesday to see cooler temperatures (right around, or just below,
seasonal normals).

Late Tuesday forward is where the real uncertainty begins. A second
trailing shortwave trough is anticipated to follow behind the
aforementioned from late Tuesday through Wednesday, however, models
are seeming to struggle with the amplitude of this trough. The
portion of the forecast where this is driving the most uncertainty
is the temperature forecast, with the precipitation forecast being
the secondary uncertainty. About 65% of ensemble members show a
trough deep enough to drive another cold front into at least the
northern half of the forecast area, with about 20-25% of those
members supporting a much deeper trough that would drive a cold
front into southern Utah. The remaining 35% of ensemble members
produce a much shallower trough that wouldn`t bring much of a front
at all... in fact, some members support the start of a warming
trend. Model output of high temperatures range from 54 to 67 (25th
to 75th percentile) for Wednesday in SLC and from 59 to 74 for
Thursday. For Cedar City, these temperatures range from 62 to 74.
Quite a bit of uncertainty at this point, however, odds are favoring
a more shallow trough that would impact the northern half of the
area while the southern half remains unscathed.

From a precipitation perspective, again, not looking at any signals
for significant forecast precipitation. What will be the most likely
outcome at this point in time is a round of scattered mountain
showers across northern Utah and adjacent valley areas/ southwest
Wyoming.

Heading into the late week/ weekend, there is uncertainty in how
quickly the aforementioned trough exits the region and whether or
not ridging will establish over the western U.S. At this point in
time, it`s a nearly 50/50 split between trough vs. ridge... so
continue to monitor forecasts through the upcoming week.


&&

.AVIATION...KSLC...Low CIGs and rain showers will continue through
the morning and early afternoon hours today over KSLC. Showers will
become a bit more scattered as we move into the late afternoon
hours, however, local mountain obscuration is expected to continue
through the evening hours. Clouds begin clearing slowly during the
overnight hours. Otherwise, northerly winds are expected to be the
dominant flow pattern, however, periods of variable/ south flow will
be possible while showers persist.

Rest of Utah and Southwest Wyoming...A storm system will continue to
bring low ceilings and mixed precipitation across the region today.
A mix of VFR and IFR to LIFR conditions are expected across the
area, with the most likely areas to see poor conditions due to mixed
precipitation at the KBCE and KEVW terminals. Persistent,
widespread precipitation will become more showery as we head
through the afternoon hours, with conditions drying from north to
south. That said, northern Utah and southwest Wyoming will continue
to see precipitation and poor conditions through the evening
hours.&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Weather Advisory until 6 AM MDT Sunday for UTZ111-112.

     Winter Weather Advisory until 6 PM MDT this evening for UTZ113-
     117-125.

WY...None.
&&

$$

Seaman/Webber

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