Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
FXUS64 KMRX 230725
Area Forecast Discussion
National Weather Service Morristown TN
325 AM EDT SAT JUL 23 2016
.SHORT TERM (Today and Tonight)...
A strong upper level ridge continues across the Central U.S. with
500 mb heights in the 596-598 dm range in the center. Closer to
home, water vapor imagery and RAP upper air analysis indicates a
weak shortwave trough across the Tennessee Valley rotating around
the periphery of the upper level ridge. Radar imagery shows a
couple of isolated showers continuing early this morning as this
wave rotates through.
For today, the shortwave trough will continue to slowly rotate
through the area with weak cyclonic flow aloft for much of the day.
Models indicate that PW values will increase across the region with
values ranging from 1.6-2.0 inches with lower values across SW VA
and the higher values across the Souther Valley. The upper end of
these values are up into the 90th percentile for mid-July. The
latest suite of models have also increased the coverage of showers
and storms this afternoon, especially over the Southern Valley.
Therefore, increased PoPs in the forecast for today and lowered high
temperatures some due to the increased coverage of showers and
storms. It will still be a hot and humid day across the area with
most locations experiencing low 90s for highs with dewpoints in the
upper 60s and low 70s. SBCAPE values will range from around 750-1500
J/Kg with even the more aggressive models keeping values under
2000 J/Kg. The 0-6 km deep layer shear is a minuscule 10-15 kts,
therefore, not expecting any strong to severe storms. Convection
will decrease near sunset due to the loss of daytime heating and
as the weak shortwave through pushes off to the southwest.
.LONG TERM (Sunday through Friday)...
High pressure in control early in the period...keeping hot and
humid conditions in place through at least Monday. Strong diurnal
heating and a couple of weak impulses moving through the upper flow
will allow scattered shower/thunderstorm development both Sunday
and Monday...centered mainly around the afternoon hours. Models
trending slower with the high dampening over the area...and it now
looks like it will be Tuesday before the flow aloft becoming more
zonal as a weak boundary approaches from the north. The boundary
will become broad and diffuse as it settles over the area and
temperatures should cool slightly by mid week. The boundary will
stall over the region and act as a focus for scattered convection
each day through the rest of the extended period.
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 93 74 96 75 / 50 30 20 20
Knoxville McGhee Tyson Airport, TN 93 74 93 72 / 20 20 20 20
Oak Ridge, TN 93 73 93 72 / 20 20 20 20
Tri Cities Airport, TN 92 69 92 69 / 20 10 30 30