Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 261016

Area Forecast Discussion
National Weather Service Salt Lake City UT
416 AM MDT Wed Apr 26 2017

.SYNOPSIS...A series of progressively colder systems through
Saturday, with high pressure returning late in the weekend.


.SHORT TERM (Through 00Z Sunday)...The next shortwave trough to
impact the forecast area is currently moving onshore along the
Pacific Northwest coast, and will quickly translate southeast
through the northern Great Basin today, before crossing the
forecast area tonight. This feature is along the nose of a strong
Pacific jet, which is associated with an atmospheric river
extending across much of the Pacific. Warm advection ahead of this
wave is currently overspreading northern Utah resulting in a few
showers along the Idaho border. As this wave approaches today, the
flow is expected to back which will strengthen warm advection, and
result in an increase in valley rain/mountain snow across
northern and eventually central Utah.

The cold front associated with this wave is expected to sweep from
west to east across the forecast area this evening, likely
enhancing precipitation for a time, as well as spreading this
precip south into southern Utah, with precipitation becoming more
orographic in nature from late evening into the overnight hours

A relative lull in precipitation is expected Thursday aside from
perhaps some light orographic snow along the higher terrain, with
a colder wave dropping in from the north Thursday night into
Friday. This wave looks to be associated with a continental
airmass and thus considerably drier, but will also drop snow
levels to most valley floors late Thursday night into Friday
morning, with some valley accumulation not out of the question on
elevated/grassy surfaces. A cold northerly flow will linger into
the day Saturday, and with the cold pool aloft still overhead
could certainly see snow showers continue into Saturday before the
trough begins to pull off to the east late in the day.

.LONG TERM (After 00Z Sunday)...As the trough continues to exit
to the east on Saturday night, a weak ridge will build over the
Great Basin, with clearing skies and another cold morning Sunday.
The ridge flattens and stronger northwest flow returns through the
day Sunday, as another trough pushes across Idaho and Montana.
For Sunday and Monday, at least, Utah and southwest Wyoming will
remain on the southern fringes of this trough. This should leave
most of the forecast area dry, though some stray showers are
possible across the north.

The trough intensifies and digs south late Monday into Tuesday,
though there is still some discrepancy about whether the brunt of
the storm will primarily impact Colorado, or whether it will make
a pit stop in Utah on the way there. For now the forecast is a
compromise between the colder/wetter solutions in the GFS and
Canadian, and the somewhat warmer/drier ECMWF solution.

Either way, showers look to decrease in coverage across the area
Wednesday as the trough moves toward the Four Corners. Looking
ahead to days 8-10 (Thursday-Saturday), models are hinting at what
has become a rare phenomenon: a high amplitude ridge over the
Intermountain West. Don`t get too excited yet, or you might just
scare it away.


.AVIATION...Ceilings at the SLC terminal are expected to drop
below 7000 feet between 16Z and 19Z today, though there is a 30
percent chance that these lower ceilings hold off until after 21Z.
Showers will fill in across northern Utah through the afternoon,
with a 70 percent chance of MVFR conditions developing between 22Z
and 03Z. Erratic winds will again be possible near showers this





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