Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 122326
Area Forecast Discussion
National Weather Service Salt Lake City UT
426 PM MST Thu Jan 12 2017
.SYNOPSIS...A low pressure system moving south along the west
coast will continue to spread moisture into the region through
Friday. A drying trend will follow into early next week before an
active pattern redevelops by the middle of the week.
.SHORT TERM (Through 00z Monday)...An upper low spinning over
northern California will continue to drift slowly south along the
coast tonight through Sunday, eventually winding up in the Baja
region by Saturday morning. Weak isentropic ascent downstream from
this low continues to fuel light snow across northern Utah, and
this will likely continue into the early evening hours before
diminishing. Went ahead and dropped the Winter Storm Warning for
zone 6 where any additional accumulation will remain minimal.
Otherwise maintained going headlines for the northern mountains as
well as the central valleys through the evening hours.
Meanwhile further south a subtropical moisture plume coupled with
the entrance region of an upper jet continues to bring areas of
rain and snow to southern Utah, with snow levels hovering around
6000 feet. As the upper low continues to drift south along the
coast, this area is expected to become increasingly diffluent
aloft overnight which should aid in additional precipitation, with
snow levels falling to near 5500 feet. Given the warm surface
temps in southwest Utah, held off on any winter weather headlines
for now. This precipitation should diminish Friday afternoon as
the upstream low drifts further and further south.
Northern Utah is expected to remain dry and cool through the
upcoming weekend, however southern Utah will maintain a chance of
precipitation as moisture wrapping around the north side of the
upper low spreads back into the area Saturday night through
Sunday. For now have kept POPs in the chance category given that
the parent upper low is well south of the Mexican border during
.LONG TERM (After 00z Monday)...A weak and continental in
nature short wave dropping down the mean long wave trough remnant of
the previous desert southwest low will track west/south of the area
through Monday. Not much to note from this feature outside of a net
maintenance of temps aloft and increasingly dry conditions beneath a
light northerly flow aloft.
A positively tilted mid level ridge will then build heights from the
west Monday night/Tuesday packing modest WAA advection aloft, likely
capping valleys briefly into the midweek period. Not looking for a
significant or prolonged inversion event however. Have maintained a
dry forecast into Wednesday, and held valley temps down a bit vs.
the majority of guidance.
Period of greatest focus across the western CONUS in the long term
(regarding sensible weather) remains mid/late week as the next storm
cycle impacts the coastal areas and points interior. What is fairly
high confidence in guidance is the presence of a strong near zonal
jet, deep moisture impacting the coastal areas and potentially areas
downstream across the eastern Great Basin, and several embedded
waves/troughs in the mean flow. Current trajectories aren`t the best
for an inland penetrating river event locally (downstream of the high
Sierra Mtns), but confidence in detail lacks this far out. Still
banking on a period of unsettled and warmer conditions sensibly Wed
on, but outside of that details on significance locally will have to
fall out over the next few/several days.
.AVIATION...IFR conditions are expected to remain in place at the
KSLC terminal through 01-02z today due to low stratus, light snow
and BR. Conditions are expected to improve to VFR conditions by
03/04z. West to northwest winds are expected to continue, becoming
light and variable after about 07-08Z. There is only a 20 percent
chance the typical nocturnal southerly wind will kick in through
UT...Winter Storm Warning until 11 PM MST this evening for UTZ007>010.
Winter Weather Advisory until 11 PM MST this evening for UTZ004.
Winter Weather Advisory until 11 AM MST Friday for UTZ011-012-
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