Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
1045 am MDT sun Sep 21 2014
Synopsis...an upper low will lift northeast across the Great
Basin today through tonight then move off to the northeast
Monday. High pressure will follow for middle week.
Discussion...a closed low lifting toward Utah this morning has
advected a juicy airmass into Utah with dewpoints in the upper
50s and precipitable water values over an inch across much of the western third
of the state. Areas in south central Utah have received
precipitation amounts near an inch so far while northern mountain
and west desert areas are beginning to see amounts in excess of a
half inch. Increased late am probability of precipitation for this region in morning
update. Convective activity reigned in the southwest corner of
the County Warning Area this morning but has since shifted to the south central
Central and northern Utah become the focus of forcing this
afternoon...promoting locally heavy rain and widespread thunderstorms.
The amount of persistent cloud cover will play a significant role
in the degree of destabilization this afternoon. While drier air
is expected to infiltrate SW Utah as the day progresses...heating
and decreasing winds will maintain the threat of locally heavy
rain in this region as well...along with the potential for
isolated flash flooding. Decreased SW valley afternoon probability of precipitation
Activity is expected to diminish from south to north after sunset
though precipitation will likely linger in the north. As the low
shifts to a more NE track and westerly winds dominate...moisture
becomes focused on the northeast third of the County Warning Area and keeps good
precipitation potential well into Monday in this area.
Aviation...VFR conditions at the slc terminal are expected through
the valid taf period...with a 30 percent chance of MVFR and ceilings
below 7000 feet between 18-21z in association with scattered showers.
There is a 20 percent chance for a thunderstorm today as well.
Southeast winds will shift to a more southerly flow by noon.
Fire weather...with deep moisture in place...today will be the
most widespread chance of rainfall as a weakening storm system
crosses the eastern Great Basin. Locally heavy rainfall and
copious lightning are expected. This pattern will bring expansive
cloud cover...rising humidity levels and cooling temperatures.
Convection lingers tomorrow across the north and east...decaying
for good tomorrow evening.
A warming and drying trend will begin tomorrow across the southwest
and be in place across the entire region through middle week as a ridge
of high pressure amplifies overhead.
There remains uncertainty regarding the timing of a strong cold
front late in the week. Critical fire weather conditions will be
possible ahead of the cold front with strong gusty south winds
developing...before convective chances once again increase next
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