Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
1023 am MDT Thursday Jul 31 2014
Synopsis...a weak disturbance will move out of Nevada and into
the northern half of Utah for later today through early Friday.
High pressure aloft will strengthen across the interior west over
the weekend. A stronger weather disturbance will lift north
through the Great Basin late Sunday through Monday.
Discussion...a fairly moist airmass remains in place over Utah
and southwest Wyoming this morning...helping to produce partly
cloudy skies over much of the area as of 16z. This is despite the
fact that deep moisture has generally been on a downward trend the
last 24 hours in a drier northwest flow...with the precipitable
water values dropping from 1.32 inches to 0.90 inches between
yesterdays and todays 12z slc soundings.
Still...enough moisture remains in place for another active day
convection- wise across the area. Some thunderstorms will initiate
off The Spine of Utah...while more activity moves into the area
from Nevada due to a weak shortwave sliding through the region.
The biggest uncertainty with the short-term forecast is which part
of Utah this wave will slide through...and how much it will drive
evening and overnight convection. Global and mesoscale models
produce a variety of options...but the most likely scenario at the
moment is that the wave will slide through the west-central part
of the state in the afternoon and evening...and then linger in the
east- central or southeast part of the state to help produce some
isolated convection overnight.
Have updated the forecast this morning...primarily to adjust probability of precipitation
for this afternoon and overnight. For this afternoon...increased
probability of precipitation in the south and east...as models currently indicate the best
heavy rain moving through the San Rafael Swell and along the
Arizona border through the afternoon. For the evening and
overnight...spread out probability of precipitation a bit to indicate the uncertainty of
the wave placement...and tweak the location of the highest probability of precipitation
based on current model trends. No further updates are planned for
Aviation...winds at the slc terminal will be light and variable
through early afternoon...with the most probable direction being
northerly. The north winds should become more established and
increase in speed by 19-20z. There is a 20 percent chance of
showers/thunderstorms impacting the terminal between 22z-02z...with
ceilings 6000ft or lower developing in conjunction with those storms.
Any showers/thunderstorms may produce gusty and erratic winds at the
Fire weather...a moist airmass remains in place across the fire
district today. Expect scattered wet thunderstorms to develop again
this afternoon and overnight across a good portion of the fire
district. Slight drying tomorrow and Saturday will lead to storms
becoming more isolated before the next moisture surge arrives on
Sunday. Bottom line...fire weather issues not especially significant
due to moisture and generally light winds.
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)