Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/04/23

the short term forecast discussion. The first is when will

inversions improve and the second is how much snow will the

 Sunday/Monday system bring.

Afternoon upper air and satellite analysis indicates a weak
shortwave trough is currently moving into the western portion of a
broad upper level ridge across the Interior West. Another,
somewhat stronger shortwave trough is located off the Pacific
Coast and will eventually be the impetus for the removal of the
inversions across the northern valleys.

While KMTX is showing light returns, likely flurries at best
across western Utah, so far there has been little response to the
inversion depth or strength based on latest MDCRS soundings. Some
portion of model soundings do indicate the cloud cover overnight
may be sufficient to weaken inversions a bit, but that remains to
be seen if it will come to fruition.

Another day of strong inversions for most northern valley
locations is expected Saturday, with Salt Lake County, Cache
Valley and western Uinta Basin forecast to have red conditions
(unhealthy for all groups) and other monitored basins across
northern Utah to have orange conditions (unhealthy for sensitive
groups). For updated air quality forecasts, please visit
air.utah.gov/forecast.php?id=slc.

By early Sunday, the previously mentioned shortwave trough will be
approaching the Pacific Coast associated with a fairly stout
150kt+ jet max. Strong southwest flow will develop ahead of this
system Sunday morning into Sunday afternoon. This will have the
potential to weaken inversions and ventilate some valley
locations by Sunday afternoon. Currently, this is a low confidence
but optimistic outcome.

Preferential jet dynamics combined with a period of frontogenesis
may bring a band of moderate to heavy precipitation to a portion
of northern or central Utah by Sunday afternoon. Narrowing down
locations of these features this far out is low confidence at
best, however the current mean location would impact a line
roughly from Evanston to Salt Lake City to Cedar City. Snow levels
will be questionable for valley floor snow for this part of the
system, depending on how stubborn inversions are.

This initial band is expected to shift south and east with time as
the jet max and shortwave trough progress southeastward. A
cohesive band of precipitation may continue for a time before
weakening as the best support lifts out of the area.

Another cold front will cross the area Monday, bringing the
threat of snow to valley floors and a period of northwesterly
orographic enhancement to the northern and central mountains and
adjacent valleys. Snow may continue at times in these locations
into Monday evening. This portion of the storm has a high
likelihood (>80%) of dislodging any remaining valley inversions
and ventilating the airmass.

Current snow accumulation expectations are 8-14 inches for the
Wasatch, 6-12 inches for most other mountain areas. Valley
accumulations are less certain.

.LONG TERM (After 00Z Tuesday)...The extended forecast period
will be mostly quiet weather for the CWA with the potential for
some more winter weather towards the end of the period but there
remains plenty of uncertainty at this point. Some light snowfall
to start the extended from a trough feature in the short term will
linger into Tuesday morning before shutting off and turning dry.
A ridge will build in on Tuesday and the uncertainty builds around
the potential for another trough to build in and drive precip or
to hold onto the ridge.

Northwesterly flow on the backside of Monday`s trough will drive
orographic precipitation for the mountains on Tuesday morning
before shutting off. A high pressure ridge will move into the
region, clearing up skies for a majority of the CWA. Temperatures
are not expected to take a large bounce back but rather stay
somewhat chilly with most valleys (mountains) seeing highs in the
mid 30s (low to mid 20s) and overnight temperatures in the upper
teens and low 20s (single digits). Areas in far SW Utah near St.
George however will keep mild with highs in the 50s and overnight
temperatures hovering around freezing. Despite uncertainty in the
precipitation forecast, temperatures are likely to stay within
these ranges until some warming to come by the weekend.

The uncertainty in the precipitation forecast sits within a
potential trough on Wednesday into Thursday. Current deterministic
models are split on a transitory ridge turning to a weak trough
that could graze the northern parts of the CWA and bring mostly
mountain precip. While the other side keep this ridge holding
stronger before developing the trough east of the rockies and over
the plains. Current ensemble clusters are more or less split on
this setup as well. NBM and current forecast are at least in
agreement that this passing trough or ridge could at least drive
some orographic precip over the northern mountains and act as a
weak grazing system on Wednesday into Thursday. This would also at
the bare minimum bring some mixing to the northern valleys that
could use some relief from inversions.

Beyond this we see more uncertainty but at the moment current
model guidance is in favor of a much deeper and more developed PNW
trough to build off the coast and move in by the weekend.
Potential warming and driving of SW Sierra moisture could make
this another widespread precip event for the CWA but still only
~55% of clusters support this. With it being ~day 10 we will
continue to follow trends but in hope we continue to support and
add to the current snowpack.

&&

.AVIATION...KSLC...Visibilities will remain around 5SM throughout
the TAF period. Lower flight categories will be possible
overnight and into Saturday morning as visibilities could drop to
~1SM as the valley inversion is expected to become worse.
Visibilities should increase back up to ~5SM between 18Z and 20Z.
Cloud cover is expected to decrease around 10Z and come back
around 18Z Saturday. CIGS expected to remain above 15kft. Light
northwest winds will transition to light southeast winds around
05Z.

.REST OF UTAH AND SOUTHWEST WYOMING...Valley  inversions will
bring lower visibilities to northern Utah. These visibilities will
mainly be in the MVFR range but some locations could see even
lower flight categories due to lower visibilities. By ~21Z most
northern valleys are expected to be back in the MVFR to VFR range
for visibilities. Light and diurnal winds expected for the
forecast period. Overcast skies will transition to mostly clear
skies overnight, before skies become broken to overcast by
Saturday afternoon.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

$$

Kruse/Selbig/Cecava

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