Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 261219

Area Forecast Discussion
National Weather Service Salt Lake City UT
519 AM MST Sun Feb 26 2017

.SYNOPSIS...The next cold Pacific storm system will arrive
late tonight and impact the region through the first half of the


.DISCUSSION...The elongated upper trough that extends across
southern Utah this morning will continue to shift southeast out of
the area. The few snow showers that existed near the trough axis
overnight have now mostly ended. As a result, expect a fairly quiet
weather day as a more stable airmass settle into the area behind the
trough. A low-amplitude shortwave ridge will build briefly into the
area this afternoon with increasing southwest flow in warm
advection. This combined with mostly sunny skies underneath a thin
veil of cirrus advancing into northern Utah should lead to warmer
temperatures today.

The next trough is already moving onto the Pacific Northwest coast
and will carve into Utah late tonight through tomorrow. Snow is
expected to start filling in across northern Utah late this evening.
The midlevel baroclinic zone is then progged to sag into northern
Utah after midnight, which should bring a period of more intense
snow to the area. This baroclinc zone will then continue slowly into
central Utah by late afternoon. The baroclinc zone is expected to
tighten throughout the day as an increasing southwesterly flow
across southern Utah strengthens convergence into the boundary, so
there is a potential for heavier snow across Utah County and into
central Utah. The boundary will then slowly continue south overnight
while gradually weakening.

Precipitation will be widespread with this storm, and all areas but
the lowest valleys of southern Utah will likely see precipitation
fall as snow given the cold northwest flow that develops behind the
front. Significant snow is expected across the mountains with
accumulating snow in many northern, central, and western Utah
valleys as well as southwest Wyoming.

A brief lull in the weather is expected late tomorrow night into
Tuesday morning ahead of a second shortwave trough embedded within
the mean trough over the area. This shortwave will cross the area
Tuesday afternoon and bring a quick burst of snow to mainly the
mountains and adjacent valleys of northern and central Utah.

.LONG TERM (After 12Z Wednesday)...A cool and stable northwest flow
remains over the area on Wednesday, as an upper level ridge
amplifies off the west coast. The models have trended toward
allowing the cold air to linger a little bit longer over the CWA, so
have kept temps fairly cold for Wednesday. Have also cooled them
down a little bit for Thursday, though a 5-10 degree warming trend
is still evident as the ridge axis shifts inland.

A few weak ripples in the northwesterly flow generally pass north of
the CWA late Wednesday through Friday, though some light snow
showers cannot be ruled out across far northern Utah. A larger and
colder trough pushes into the Pacific Northwest on Friday, likely
followed by a decently strong secondary wave on Saturday. Models
have maintained decent agreement that much of this instability and
cold air remains north of the Utah/Idaho border, though the GFS
still has occasional runs that try to dig part of the trough into
the Rockies late Saturday through Sunday. Have kept some low end
POPs across the north over the weekend to account for this
possibility, but have otherwise favored the warmer and drier idea
for now.


.AVIATION...There is a 10 percent chance of ceilings below
7000 feet at the SLC terminal through 16Z, due to some low clouds
currently lingering near the mountains. Southerly winds should
persist through the day at the SLC terminal, with a slight chance
that winds become light and variable at times after 18Z.





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