Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
411 PM MST Sat Nov 22 2014
Synopsis...a cold and energetic storm system is moving through
northern and central Utah this evening...and unsettled weather
will linger through Monday. High pressure will build for midweek.
Short term (through 12z wednesday)...a moist and energetic storm
system has entered Utah and southwest Wyoming this
afternoon...with the associated cold front near Salt Lake City as
of 23z. Precipitation has been locally intense under the cold
frontal band...with moderate to heavy rain in the valleys and snow
in the higher terrain. There have been several lightning strikes
along and ahead of the front...with good instability as the middle
level cold pool and strong jet begins to move over the area. Snow
levels will continue to fall through the evening...with the best
chance of accumulating valley snow between 00z and 06z. Model
forecast temperatures do not look cold enough for a true lake
effect snow band to form overnight...but enhanced showers
downstream of the Great Salt Lake are still possible.
After lingering snowfall overnight...showers are expected to
taper off through the day Sunday...as the best forcing with the
initial wave moves off to the southeast. However...another
shortwave is expected to move through the northern half of the County Warning Area
in the strong northwest flow on Sunday night and Monday. This
should initiate some more snow showers...and while this wave is a
fair amount weaker than the initial system tonight...snow may
stick more efficiently with the colder airmass already in place.
After the shortwave exits the area on Monday afternoon...a moist
northwest flow remains in place Monday night through Tuesday
night...which could allow snowfall to continue in the mountains of
northern Utah. This increased flow and cloud cover could also help
keep the northern valley locations from developing too strong of
an inversion...so have kept a warming trend in the forecast
through Tuesday and Tuesday night. This moisture slowly pushes off
to the northeast Tuesday night...as the ridge over the West Coast
begins to push inland.
Long term (after 12z wednesday)...developing ridge expected to
strengthen for Wednesday through Friday under a drying northerly
flow. No big change in previous forecast temperatures for the middle week
period...although temperatures could be on the warm side if
extensive snow cover remains in place and any inversions set up in
the valleys. Temperatures should continue a slight warming trend
Models in fair agreement that a weak shortwave breaks underneath the
West Coast ridge Friday...although exact timing still iffy. A short
wave ridge will fall between this first weak trough and a stronger
system expected for Saturday. As a result...could see a few hours of
gusty southwest winds ahead of the Saturday system. Will continue to
hold off on any chances of precipitation until Saturday night when
the the trough moves across the Great Basin and bulk of the moisture
Aviation...at the slc terminal...conditions are expected to bounce
between MVFR and low-end VFR in the near term...though visibilities
may briefly drop into the IFR range in heavier rain. The transition
to snow is expected to occur between 01z and 03z...with a 20 percent
chance that it will occur later than expected. Northwest winds are
expected through the evening.
Utah...Winter Weather Advisory until 5 PM MST Monday for utz006-010.
Winter Storm Warning until 5 PM MST Monday for utz007>009.
Wind Advisory until 2 am MST Sunday for utz005.
Winter Weather Advisory until 6 PM MST Sunday for utz517.
Wyoming...Winter Weather Advisory until 9 am MST Sunday for wyz021.
For more information from National oceanic and atmospheric administration/S National Weather Service visit...
http://weather.Gov/saltlakecity (all lower case)
For frequently asked questions about the area forecast discussion
http://weather.Gov/saltlakecity/general/afd_faqs.Php (all lower case)