Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Memphis Tennessee
1234 PM CDT Sat Jul 30 2016
updated for 18z aviation discussion below.
Previous discussion... /issued 947 am CDT Sat Jul 30 2016/
Update... morning update.
WSR-88D scans show a complex of sub-severe thunderstorms moving
into the eastern portions of the mid-south. Well initiated short
term models depict thunderstorm coverage increasing throughout the
late morning in west Tennessee near the Tennessee River and
northeast Mississippi as the shortwave causing these thunderstorms
moves through that region before exiting the mid-south. Pops were
increased in these areas to reflect the increasing coverage. Pops
were also slightly lowered between 18z and 00z in the eastern mid-
south. Expect thunderstorms associated with another shortwave to
begin to approach the region from the west later this afternoon.
Highs today should be near normal.
Previous discussion... /issued 635 am CDT Sat Jul 30 2016/
Update for the 12z aviation discussion
Previous discussion... /issued 303 am CDT Sat Jul 30 2016/
the subtropical ridge remains centered over the southwest Continental U.S.
This morning, with a broad trough over the east. Northwest flow
aloft over the plains will continue to provide a steady diet of
weak shortwave troughs for the mid-south this weekend. This will
result in mostly cloudy skies and scattered showers and
thunderstorms, especially during the afternoon and evening hours.
The primary forecast challenge for the weekend will be timing
individual shortwave troughs. As these waves approach, we'll see
an uptick in convective coverage. The strongest forcing will
remain to our north in the westerlies, but we should see some
influence from these systems in the coming days. Temperatures
in the upper 80s and lower 90s this afternoon will support MLCAPES
of 1500-2000 j/kg, but deep layer shear will be lacking for
organized updrafts. However, a pulse storm or two will still be
capable of producing wet microbursts.
We will see a slight increase in column moisture today, with
precipitable water values generally at or above 1.75". As we've
seen the past few days, slow moving thunderstorms will be capable
of producing locally heavy rainfall in a very short period of
time. The scenario for Sunday is very similar, with rain chances
again coming down to about a 50/50 shot for any particular point
in the County Warning Area.
The subtropical ridge will expand early next week, building a bit
farther north and east. While subsidence associate with the ridge
should limit the coverage of diurnal convection, we do anticipate
sufficient moisture to maintain 20-30% pops for much of the week.
We will, however, experience an increase in surface temperatures.
Afternoon highs will gradually climb into the mid 90s by Tuesday,
remaining slightly above climo through the remainder of the week.
Corresponding heat indices will approach 105 degrees in some areas
Tuesday through Thursday. Expect overnight low temperatures
generally in the mid 70s.
A few short term thunderstorms and rain concerns to near the southern vicinity of
tup, associated with an exiting midlevel disturbance and trailing
surface boundary. Upstream thunderstorms and rain was noted on radar moving from
northeast OK into northwest Arkansas. The parent shortwave circulation
associated with this activity will not likely reach the jbr or
mem areas until after daytime heating has peaked. As such,
hrrr/NAM/RUC models and associated soundings show limited chances
for thunderstorms and rain formation near the midsouth terminals through early evening.
Light or calm winds, residual low level moisture and scattered
high clouds will lead to areas of fog/low stratus toward 12z.
Otherwise, VFR through 18z.