Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Memphis Tennessee
100 PM CDT Thursday Jul 28 2016
updated for 18z aviation discussion below.
Previous discussion... /issued 958 am CDT Thursday Jul 28 2016/
Current radar sweeps depict only isolated shower activity
occurring in the the eastern portions of the mid-south. Short
term-high resolution models suggest that most of the mid-south may
remain dry today, with only convective thunderstorms developing
mainly in north Mississippi and west Tennessee near the Tennessee River
as the day progresses. Widespread cloud coverage should keep
temperatures below average throughout the mid-south today.
However, some locations, primarily in the western portions of the
mid-south, could see temperatures reach 90 degrees as cloud cover
Previous discussion... /issued 643 am CDT Thursday Jul 28 2016/
updated to include the 12z aviation discussion below.
Previous discussion... /issued 234 am CDT Thursday Jul 28 2016/
Showers continue to spin around the upper level low that is
located over the mid-south. Expect most of the showers to be
confined to areas of west Tennessee near the Tennessee River by
7-8 am CDT as the upper low moves to the northeast.
Based today's forecast on the short term models hrrr, 4km NAM,
WRF, and rap. The models were very good at predicting how
convection developed yesterday. All are now in pretty good
agreement that convection today will fire up along some old
outflow boundary that is located from near Greenville, Mississippi
to Starkville, Mississippi. As a result, put highest probability of precipitation along
the extreme southern portions of the County Warning Area. By the afternoon, some
of this convection may move further north affecting more of
northeast Mississippi. Outside this area of expected convection,
expect coverage to be scattered at best with development more
diurnally based due to a broad upper level trough that will
continue to sit over the region.
With less thunderstorm coverage expected over most of the cwa,
have bumped up high temperatures into the lower 90s across Memphis
and north Mississippi. Guidance was horrible yesterday and highs
were well above what guidance was showing. It seems that if a
location does not receive any convection that highs will reach
into the lower 90s easily which is near normal for this time of
year. However, if a location does receive rainfall temperatures
remain in the mid to upper 80s. Trying to pinpoint where
convection will develop through the weekend will be hard to do as
models such as the NAM, GFS, and European model (ecmwf) are having a hard time
picking up on the mesoscale features that have been the trigger
points of where the convection has been developing. Beyond today,
have leaned on the 4km NAM through Friday night. After the early
evening hours, the model does not have much convection so have
lowered probability of precipitation to 20s except for areas near the Tennessee River.
Looks like the next decent chance for thunderstorms may come on
Friday as models are showing a thunderstorm complex developing
over Kansas, Oklahoma, SW Missouri, and northwest Arkansas during the
overnight hours tonight. The 4km NAM shows this complex
approaching the mid-south around sunrise Friday morning, but
dissipates it before it actually moves into the County Warning Area. However, the
model shows redevelopment along outflow boundaries in southern
Missouri and northern Arkansas that will likely be leftover from
the complex. This development will push into the mid-south by
mid-day and affect much of the County Warning Area during the afternoon hours.
Some of these storms could be strong to severe.
Over the weekend, chances for showers and thunderstorms will
continue as the broad upper trough sits over the region. However,
trying to pinpoint where and when the best chances will occur is
just to hard. For now, just have kept 40 and 50 probability of precipitation across the
area. Since the airmass is very moist any thunderstorms that
develop from today through the weekend have the potential to
produce localized heavy rainfall which could lead to flash
By Monday, the upper trough will begin to shift east as an upper
ridge begins to build into the mid-south. Chances for showers and
thunderstorms will diminish from west to east and will become more
diurnally driven by Tuesday and Wednesday. Highs will begin to
creep back into the mid 90s. As a result, heat advisories may
become necessary again by Tuesday and Wednesday as the combination
of highs in the mid 90s and dewpoints in the mid 70s will produce
heat index values around 105 degrees.
Midday radar showed scattered rain showers with isolated thunderstorms and rain east of mem.
This activity should remain east of the mem tracon initially, but
may expand westward with daytime heating.
VFR should prevail areawide during the evening, followed by
increasing chances of IFR during the overnight as moist boundary
layer cools. An approaching disturbance may bring rain showers/thunderstorms and rain into
jbr prior to 12z. Not sufficiently confident to include thunderstorms and rain for
mem toward 12z, but may include in a later update.