Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 212207
Area Forecast Discussion
National Weather Service Salt Lake City UT
407 PM MDT Fri Apr 21 2017
.SYNOPSIS...High pressure will build in Saturday bringing a
warming trend into Sunday. However, an active weather pattern is
expected for next week, as a series of storm systems are forecast
to pass through the region.
.SHORT TERM...The mid level cold pool still lingering over
northern Utah and southwest Wyoming will continue to trigger
isolated showers into early this evening. Clouds should dissipate
rapidly by midnight allowing for temperatures to get rather
chilly. Recent precip should help prevent a hard freeze from
occurring in northern Utah valleys but across central and
southwest valleys (excluding Dixie) the air mass is considerably
drier and temperatures are forecast to fall into the mid 20s.
Therefore, a hard freeze warning has been issued.
The ridge builds in Saturday but due to a northerly surface
gradient temperatures are not expected to reach their full
potential. Have trimmed max temps by a couple of degrees across
eastern and northern portions of the CWA. Temperatures over
southern Utah will warm the most as southwest winds begin to
increase late in the day.
The EC is a little more energetic with the short waves moving
into northern Utah Sunday into Monday. Have increased the PoPs
accordingly as other MOS guidance support higher PoPs than the GFS
is showing. Both the GFS and EC keep the influence of the
shortwaves across northern Utah through Monday. Depending on the
timing on of the cold front on Sunday will determine how warm
northern Utah sites will reach. Current timing is about midday
which will allow temperatures to warm to above seasonal norms but
.LONG TERM (After 00Z Tuesday)...The moist west-northwesterly flow
remains over the region heading into Monday night and Tuesday, with
a series of shortwaves continuing to ripple over the area. This
pattern makes periods of precipitation likely, especially across
northern Utah and southwest Wyoming. Timing the best periods of
precipitation may be difficult, but models are currently in decent
agreement about bringing the stronger waves through Monday night,
followed by Tuesday night into Wednesday. Have kept POPs and sky
cover high through this period, with temperatures generally 5-10
degrees below climatological normals.
Global models begin to diverge late Wednesday into Thursday. The GFS
strengthens and deepens the trough considerably overhead, with an
even colder airmass moving into the area. Meanwhile, the ECMWF and
Canadian are more progressive, with flat shortwave ridging Wednesday
night, followed by another Pacific trough diving in from the
northwest Thursday/Friday. For now, the forecast is a compromise
between these solutions, keeping a chance of precipitation through
the entire period, but retaining some of the more mild temperatures
from the EC/Canadian. Details aside, the big picture message
continues to be a very wet work week, especially across the north.
.AVIATION...Winds at the SLC terminal are expected to switch back to
the southeast around 03-05Z, though there is a slight chance that
northerlies persist through 06Z. Showers should largely remain north
of the terminal, but there is a 20 percent chance of brief ceilings
below 7000 feet and/or erratic winds between 22Z and 01Z if these
showers slide far enough south to clip the terminal.
UT...Hard Freeze Warning from midnight tonight to 9 AM MDT Saturday
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