Scientific Forecaster Discussion
Area forecast discussion...corrected
National Weather Service Salt Lake City Utah
438 am MDT Wednesday Jul 30 2014
Synopsis...a weak weather disturbance centered over northern Utah
combined with a very moist air mass will lead to additional showers
and thunderstorms again today. A second weather disturbance will
move into the region from the southwest late in the week. High
pressure aloft will strengthen across Utah early this weekend.
Discussion...the weak upper low across southwest Wyoming with a
trough axis extending west along the Utah/Idaho border will remain
the focus for showers/storms again today. This upper level feature
will gradually work east-southeast through the very moist air mass
across the region during the day. Dynamic lift along with
destabilization due to cooling aloft this afternoon could bring
about organized convection near the trough axis over northern Utah
through southwest Wyoming. Locally heavy rainfall looks to be in
play this afternoon due to anticipated slow movement of the
convection and strong lift associated with the trough. Showery
precipitation will likely persist tonight...though most of the activity
will remain across the northeast portion of the forecast area.
Southern and central Utah may get off to a slow start convection-
wise today. Isolated air mass convection should form beginning
late this morning/early afternoon...then gain some organization as
the above mention upper trough approaches central/eastern Utah.
Locally heavy rainfall may develop late this afternoon...though
the areal coverage should be quite limited.
The vorticity maximum to the southeast of Southern California at time
will be the next feature to watch for Thursday. Even though precipitable water
values are prognosticated to decrease somewhat...plenty of moisture will
still be in place as this next feature reaches northern/western
Utah. Dynamic lift along with a modest amount of middle-level
cooling associated with the vorticity maximum will work towards
generating convection for Thursday afternoon/evening. The greatest
instability will remain across northwest Utah near the middle-level
cold pocket and best lift. Have boosted probability of precipitation considerably over
areas of the north and west where the environment is most
favorable for organized convection.
The first half of the upcoming weekend looks to be the driest as
the upper ridge strengthens across Utah. Still looking at enough
lingering moisture to drive diurnal convection Saturday afternoon.
The slow-moving easterly wave in guidance moving across northern
Mexico late in the week will turn north through western Arizona
Saturday...then track through eastern Nevada/western Utah late in
the weekend through Monday. The moisture pooled across northern
Mexico/southern Arizona will get tapped by this wave and accompany
the system into the great early in the week. Looking at another
round of monsoonally-induced scattered convection and heavy rain
late in the forecast cycle.
Aviation...VFR conditions are expected to prevail through the taf
period at the slc terminal. Winds should stay generally light and
variable or light southerly through around 16-18z. There is a 30
percent chance that winds turn northwest at times before 18z. Winds
should become predominately northwest after noon and could see gust
to 15 miles per hour. As moisture drifts off to the east this evening...skies
should begin to clear and winds should turn back to the southeast.
Fire weather....monsoonal moisture remains trapped over much of
Utah as it wraps around the low center over southwest Wyoming
through northern Utah. Showers and thunderstorms will linger
across the district but gradually decrease as the day wears on.
Any early morning storms have the potential for wetting rainfall.
The district will see a slow drying trend through the day...however
..more than enough moisture will remain in place for isolated to
widely scattered afternoon convection with some lingering into the
evening hours. Under the influence of high pressure...winds will
be generally light over the next few days across the district
outside of thunderstorms.
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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)