Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
416 am MDT Thursday Jul 24 2014
Synopsis...moisture has spread across most of Utah this evening.
A dry cold front will sweep this moisture out of northern Utah
Thursday while it remains in place across the south into the
Short term (through 06z monday)...southwesterly flow aloft
prevails across the forecast area this morning...sandwiched
between a middle level ridge axis extending from the southern
rockies back into the Desert Southwest...and an upper low lifting
northeast through the Pacific northwest. A plume of
moisture within this flow extends across all but the northwest
quarter of Utah this morning. The entrance region to a 90kt jet
associated with the Pacific northwest trough is helping to
maintain weak convection roughly along and south of a line from
Dugway-alpine south and eastward...while north of this area drier
air along with a surface cold front has spread across far
northwest Utah. Could still see some of this activity spill over
into portions of Salt Lake County for a time early this morning.
However...this front and attendant drying will continue across
the north through the morning...with any lingering convection
this afternoon becoming confined to southern and eastern Utah.
In the wake of this front 700mb temperatures cool 4-5c...which should
knock maximum temperatures back down into the low to middle 90s along the
As the Pacific northwest low races eastward today through
tonight...a drier westerly flow will linger across northern Utah
Friday into Saturday...while moisture remains in place...and even
increases gradually with time...across southern Utah maintaining a
threat for showers and thunderstorms. Little variation in daily
temperatures is expected over the north through Saturday with maximum
temperatures running near climatology...while temperatures cool slightly over
the south with the slow influx of moisture.
The middle level ridge is forecast to amplify across the region late
Saturday through Sunday...and with the axis remaining east of the
area...southerly flow should advect the moisture across southern
Utah and Arizona northward across the remainder of the area by
Sunday afternoon. Also notable is a wave forecast to rotate around
the mean ridge position and lift northward across the forecast
area during the day Sunday. As such have introduced a small
chance for showers/thunderstorms across northern Utah Sunday while
increasing the south by 10 percent or so.
Long term (after 06z monday)...the upper level ridge centers itself
over the Great Basin late Sunday...then the axis slowly shifts over
the Utah/Colorado border for Monday. Following the return of
moisture to northern Utah on Sunday...this deeper moisture will
remain over pretty much the entire area for Monday as well...with
precipitable water values currently forecast to be around an inch.
Southwesterly winds shifting over the area for Monday should also
help to create a hot day to start the work week.
For Tuesday through Thursday...both the GFS and European model (ecmwf) set up the
high pressure circulation over northern Arizona...leaving most of
the forecast area in a westerly flow on the north side of this high.
This pattern slowly dries the airmass...with the deeper moisture
moving eastward into Colorado. Because of this drier and less active
pattern...have kept mentionable probability of precipitation mostly tied to the higher
terrain through the extended. Temperatures look to remain slightly
above climatological normals under this ridge.
Aviation...there is a 20 percent chance of showers and
thunderstorms impacting the slc terminal between 10z and 15z
today...with gusty erratic winds being the most likely impact. A dry
cold front will switch winds to the northwest today...likely between
15z and 17z. Winds could be gusty at times behind this cold front
through the late morning and early afternoon.
Fire weather...a dry cold front will move through the northern half
of Utah today...switching winds to the west-northwest. Isolated
critical fire weather conditions are possible both ahead of and
behind the cold front...particularly in the western half of Utah. In
the southern and eastern portions of the state...showers and
thunderstorms will continue through today...with some of these
storms producing gusty erratic winds...as well as the chance for new
fire starts. There is generally about a 10 percent chance of wetting
rain at any given spot in southern and eastern Utah.
Gusty southwesterly winds will develop across the southern half of
the state again Friday. Winds will finally lighten over the
weekend...as high pressure builds over the region. Thunderstorm
activity should be confined to southern and eastern Utah for Friday
and Saturday...before moisture returns to the rest of the state
Sunday and and Monday.
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)