Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
927 PM MST Thursday Jan 29 2015
Synopsis...a developing upper low over the southern Great Basin
will spread moisture into Utah tonight through Saturday. The
deepest moisture will remain primarily over central and southern
Discussion...current large-scale pattern as indicated by water
vapor imagery indicates a storm system centered off the Baja California coast
while a couple of other smaller but well-defined lows are evident
over the West Coast states. A weak shortwave disturbance is
currently ejecting north through Utah which helped spread moisture
into the area in the form of abundant middle/high clouds. Weak warm
advection behind this wave allowed some light precipitation to
develop. This wave is reaching northern Utah this evening...just
having crossed a Wendover to Provo line. Although measurable
precipitation is not very likely across much of northern Utah
tonight...sprinkles and high-elevation flurries are possible.
The various pieces of energy mentioned above will eventually wrap
into a single larger low which will track into Arizona tomorrow
evening before retreating south into Mexico Saturday afternoon.
Following the light precipitation with the initial wave reaching
northern Utah tonight...precipitation will then become largely
confined south of a deformation axis that will settle across central
Utah. However...deep tropical moisture is being tapped in the south
flow ahead of the storm so significant precipitation can be expected
within this area. The deep moisture will start pouring into southern
Utah tonight so expect precipitation rates to pick up over southern
Utah after midnight and over central Utah tomorrow morning. There is
still some uncertainty over the northern extent of the precipitation
shield...but most likely this will be near the Provo area.
Relatively warm airmass associated with this storm is expected to
keep snow levels high. Majority of valley locales will see
rain...with the bulk of the snow to exist above 6500-7000ft. Given
the copious amount of moisture...snow accumulations will be
significant on the higher peaks. A Winter Weather Advisory is
already in place for the southern and central mountains and high
points along the San Rafael Swell through Saturday.
Will make minor updates mainly to spread mentionable probability of precipitation
faster/farther into the north for tonight.
Aviation...ceilings at the slc terminal are expected to lower to near
6k feet above ground level by 05z as a weak disturbance moves across northern Utah.
There is a 40 percent chance that ceilings will remain above 7k feet above ground level
through 06-07z. Winds will likely remain light southerly through the
Utah...Winter Weather Advisory until 4 PM MST Saturday for utz010-013-
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For frequently asked questions about the area forecast discussion
http://weather.Gov/saltlakecity/general/afd_faqs.Php (all lower case)