Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
410 am MDT Tuesday Jul 29 2014
Synopsis...a very moist air mass will remain over the area through
early Wednesday. A slow drying trend will take hold beginning
Wednesday as high pressure aloft strengthens across the interior
Discussion...two identifiable middle-level circulation centers will
impact Utah today. One of these features is clearly defined in
water vapor imagery over extreme southwest Utah at time...while
the second can be located in radar animation across far northern
Utah. The more active feature is the northern one...with
scattered showers and a few thunderstorms ongoing across the
northern forecast area. This convection...though moving slowly
north...will probably not leave the state entirely as the remnant
of the circulation center remains in the vicinity of extreme
southeast Idaho or southwest Wyoming today.
The other feature over extreme southwest is generating far less
convection early this morning. Suspect that this will change later
today...even though this circulation is forecast to become a weak
open wave as it moves into central/northern Utah later today. The
dynamic lift from this weakening system combined with the moist
and unstable air mass already in place should be more than
adequate to generate convection across the northern half of the
state this afternoon/evening. Areal coverage of convection will
likely be substantially less across the south due to subsidence it
the wake of the system moving to the north later this morning.
A modest drying trend is anticipated beginning on Wednesday. This
drying will be in response to building heights across the interior
west. The resultant ridge will remain the dominant feature over
Utah through the upcoming weekend. The only wrinkle in the
forecast will be the shortwave lift northeast on the back side of
the ridge Thursday night/Friday. Trajectory of this feature would
bring the best threat for precipitation back to the northwest quadrant
of Utah. With linger moisture and dynamic lift...have increased
probability of precipitation a bit to account for this feature late Thursday night/Friday.
The global models are advertising a new slow-moving shortwave
lifting north through the western Great Basin late Sunday/Monday.
This feature appears to originate over Arizona in the moisture
rich environment over southern/central Arizona. This feature will
likely tap into some of this moisture and drag it north into
southwest Utah through west-central Utah Sunday. Have boosted
probability of precipitation a bit over the southwest Sunday...then focused the highest
probability of precipitation across central/northern Utah heading into early next week.
Aviation...VFR conditions are expected through the taf period at
the slc terminal. Light and variable or light northerly winds are
expected. Showers and thunderstorms in the vicinity of the terminal
will cause periods of gusty and/or erratic winds this afternoon.
There is a 30 percent chance of showers and a 10 percent chance of
thunderstorms through 18z. There is also a 20 percent chance of MVFR
conditions in heavy rain after 18z.
Fire weather...deep monsoon moisture has spread across the entire
district and surface humidity values have risen sharply. Scattered
to numerous showers and thunderstorms will again develop today
across the district this into the evening hours. Isolated showers
and thunderstorms will linger this morning...mainly across the
northern half of the fire district. Expect minimal drying today with
humidity remaining very elevated into Tuesday. The potential for
wetting rains will remain high. A drying trend will spread north
Wednesday but sufficient moisture will remain across the region for
afternoon and evening mountain thunderstorms each day through the
end of the week. Wetting rains...on the other hand...will be on the
decrease. Outside of convective activity...winds should remain
rather light and variable.
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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)