Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
412 PM 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 low pressure system nudged northeast today through
the Great Basin...ushering a very moist airmass from southern
through northern Utah. Many areas saw precipitation amounts near
an inch...with radar estimates above an inch in several southern
and central locales. Though isolated convection plagued the
southern third of Utah earlier today...sufficient cloud cover
remained across the state to suppress convective activity in most
of the state this afternoon. Most precipitation as well as the isolated
thunderstorms currently popping in southern Utah should diminish
after sunset this evening...with some lingering activity streaming
northeast from Nevada across the west desert.
The low will shift eastward on Monday...maintaining a moist
boundary layer and promoting lingering showers in NE Utah.
Expecting showers to regenerate across the north as the low passes
through Utah...with enough dynamics to support isolated
thunderstorms over the higher terrain.
The action quiets down by Monday evening as a high pressure ridge
moves in and amplifies through midweek...ramping temperatures back
above climatology statewide. Models agree on the presence of a deep low
making its approach toward Utah Thursday into the early weekend...though
timing as well as extent of precipitation and cooling remain disparate.
Have leaned toward the slightly warmer and quicker GFS solution
at this point. Winds are expected to increase significantly
Thursday into Friday ahead of a significant cold front.
Aviation...winds at kslc are expected to remain predominantly
southerly through the evening...but may be influenced by outflow at
times from passing showers resulting in variable wind directions.
Occasional showers...with a 30 percent of a thunderstorm...will
continue to impact the terminal through the evening...with the most
likely timeframe coming between 01-06z. Brief MVFR conditions will
be possible with the heaviest showers.
Fire weather...with deep moisture in place...the reminder of 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...raising 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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