Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
954 PM MST Sat Feb 28 2015
Synopsis...an upper level trough will linger over the Great Basin
through Monday then shift east late Tuesday. Several disturbances
will move through this trough having the greatest impact across mainly
central and southern Utah.
Discussion...an elongated upper trough with its axis currently
extending along a line from central Wyoming to the central
California coast will continue to affect the Great Basin through the
early part of the week. Currently...several areas of precipitation
to note. First...showers continue to spread into the south central
and southeast Utah ahead of the trough. This will continue through
the night but with decreased coverage. Northern Utah including the
Salt Lake Valley had a burst of precipitation earlier as a weak
disturbance lifted through the area. Radar still indicates light
precipitation across northern Utah that extends into southwest
Wyoming but this is expected to wind down later this
evening...especially along the Wasatch front as the easterly winds
increase. A deformation zone has developed across central Utah where
southwest flow is converging with north to northeast flow across
northern Utah. Much of the precipitation underneath this deformation
zone exists below the radar coverage...but can be gleaned from the
area of colder cloud tops evident of infrared satellite imagery. This is
consistent with what models have been advertising. This area will
serve as the focus for heaviest precipitation overnight. Much of
this area is already covered with existing winter weather
advisories. However...the west central Utah zone is not and will
leave that zone out as models do indicate a decreasing trend in
precipitation after midnight.
Regarding the easterlies...models show gradient tightening again
across the northern Wasatch after midnight with some weak support at
700mb. Canyon winds are expected again tonight as a result. Winds
may be a bit stronger than they were last night but still remain
localized and should not create significant impacts.
Brief break in precipitation still expected for tomorrow morning.
The pattern then amplifies tomorrow in response to an upstream
trough diving down the West Coast. Increased southerlies and
strengthening warm advection will lift an area of precipitation into
southern...central and eastern Utah late tomorrow afternoon through
Monday. Another trough will then push a cold front through Utah on
Tuesday before high pressure settles back into the area.
Updates made to several weather elements and zones but mostly minor.
However...will cancel the Winter Weather Advisory for the San Rafael
Swell as skies are clearing out and most of that zone is expected to
see little additional precipitation through tomorrow morning.
Aviation...ceilings at the slc terminal are expected to remain
below 6kft above ground level through the evening. Occasional showers will remain
possible through the overnight hours...but mostly through midnight.
MVFR to even IFR conditions are possible in heavier snow showers.
Utah...Winter Weather Advisory until 9 am MST Sunday for
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