Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 161701

Area Forecast Discussion
National Weather Service Salt Lake City UT
1001 AM MST Fri Feb 16 2018

.SYNOPSIS...A weak system will graze far northern Utah tonight. A
large cold upper trough will move slowly through the region Sunday
through Tuesday.


.DISCUSSION...The persistent northwest flow downstream from the
Gulf of Alaska ridge remains over the eastern Great Basin this
morning. A few wave stratocumulus are lingering over the far nrn
mtns and a band of high clouds is crossing the far south, with
sunny skies over the rest of the CWA.

A weak short wave in the nw flow will slide thru the nrn Rockies
late today thru tonight clipping the far nrn CWA. This feature
looks to be dry for our area with some cloudiness and an increase
in winds across the north. There is a very small chance of light
snow or flurries late tonight in the far nrn and nern mtns in warm
advection in the wake of this wave but that`s about it.

The flow starts to back on Sat ahead of a deepening trof over the
PacNW and swrn Canada with a warming airmass and breezy south
winds developing.

Models continue to indicate this wave will continue to deepen
into a large cold trof over the western states Sun into Mon. This
sends a strong cold front into nrn UT on Sun that moves south at
the speed of the upper trof (slowly) thru the day reaching SLC in
the aftn. The front accelerates overnight as the trof deepens to
our west exiting srn UT early Mon. The heaviest precip with the
front looks to be across the nrn and central CWA over and west of
the mtns.

Much colder air follows the front into the state with precip
changing over the snow fairly quickly once the front passes. It
looks like there will be significant accumulation starting Sun
aftn north of SLC and swd along the I-15 corridor almost to Cedar
City overnight into Mon morning. Instability snow showers and
favorable orographics should keep snow showers going in these same
areas right into Tue.

Am leaning towards issuing a winter storm watch for about the nw
half of the CWA to address this upcoming winter storm, and will
finalize that decision once we have a full suite of new 12z

Winds ahead of the front also look to become strong and a wind
highlight may also be needed for portions of the wrn CWA on Sun.

Temps will get quite cold as this trof moves into the Great Basin
with single digit lows fairly common by Tue morning, even lower in
the normally colder spots. This could have a big impact on any
plants or trees that have been fooled into budding due to the warm
temps so far this month.

Updated forecasts earlier to lower or remove pops across the north
this aftn and overnight. Also lowered sky cover for most of the
CWA today. No additional updates planned.


.AVIATION...The SLC terminal will see VFR conditions throughout
the day with some scattered high clouds. Southeast winds are
expected to shift to the northwest between 20Z and 22Z, but there
is a 30 percent chance of southerly winds persisting throughout
the day.





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