Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 202230

Area Forecast Discussion
National Weather Service Salt Lake City UT
330 PM MST Mon Nov 20 2017

.SYNOPSIS...A weather system will brush by northern Utah and
southwest Wyoming this evening. Strong high pressure aloft will
follow for the middle and latter portions of the week.


.SHORT TERM (Through 00z Friday)...Deep layer moisture continues
to stream across northern Utah in advance of a weak short wave
trough poised to translate across Idaho/Wyoming over the next 12
hours. WAA and weak upglide has been sufficient for periodic light
snow showers over the highest terrain in the north, but in large
precip has remained virga due to dry low levels in place. Have
noted a gradual moistening from the top down over the last few
hours, so anticipating the potential of some rain showers to
increase along the UT/ID border region this eve. This said,
anything that reaches the surface will remain very light due to
increasingly stable vertical profiles.

Low amplitude ridging in place will begin to amplify over the
eastern Great Basin beginning Tuesday. Do anticipate maintenance
of a fair bit of mid level cloud cover over the far north Tuesday due
to the ridge axis remaining west for the time being, but a
continuation of warm advection will allow for a marked warming
trend to ensue. Late week temps look poised to run some +10-15
degrees above climo for most locales as said axis shifts east and

.LONG TERM (After 00Z Friday)...A large ridge over the Desert
Southwest will continue to be the dominant feature through the
extended forecast. On the north end of this ridge, a shortwave
trough is expected to slide through primarily Idaho and Montana on
Thursday night and Friday, which should increase cloud cover across
northern Utah, and potentially bring some light precipitation to far
northern Utah.

The ridge amplifies further on Saturday and Sunday. Additional weak
waves could brush across far northern Utah, but in general the
weekend should be warm and dry across the forecast area.

For now, global models like the idea of a trough pushing into the
west coast Sunday night and Monday, with increasing southwesterly
flow across the Great Basin. There is then considerable disagreement
about how far south the trough digs as it travels eastward on
Tuesday. Details remain low confidence, but models holding onto this
trough for a couple runs at least builds hope that there will be
something other than a ridge to look at by the end of November.


.AVIATION...The SLC terminal will see VFR conditions through the
evening with mostly cloudy skies. There is a 20 percent chance of
cigs briefly dropping to or below 6000 feet AGL through the early
evening with precipitation in the vicinity of the terminal.
Southerly winds are expected to prevail through the evening, but
there is a 30 percent chance of winds returning to the northwest for
a time before about 00Z.





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