Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 090857
AFDMEG

Area Forecast Discussion
National Weather Service Memphis TN
357 AM CDT Sun Aug 9 2020

.DISCUSSION...
The upper-level ridge will continue be a key player across the
Mid-South over the next few days. The trough over the east coast
is finally lifting out while a strong shortwave trough is moving
across Alberta and Manitoba. Geopotential heights at 500 mb will
flirt with 594 dam over the southwest portion of the CWA today and
tomorrow per the NAEFS and EPS, which is approximately in the 90th
percentile of climatology. Associated subsidence will maintain a
cap across much of the Mid-South, limiting the potential for
convection through tomorrow. However, the flow aloft is from the
northwest and that tends to make things a bit messier.

An MCS is ongoing over eastern MO, and moving southeast toward the
TN River Valley. This convection will weaken as it moves into a
more hostile environment, though additional development is
possible along the outflow boundary as daytime heating enhances
lift. This could produce a few thunderstorms northeast of a
Kennett-Savannah line today. A stray air mass thunderstorm could
punch through the cap elsewhere, but coverage will be very
limited. Otherwise, we`re looking at hot and dry weather across
the CWA. Afternoon temperatures will be similar to yesterday, or
perhaps a degree or two warmer in some areas. Increasing low-level
moisture will yield higher heat indices (HI) of 98-105F across
most of the area. Given the spotty nature of 105+ HI values, a
Heat Advisory isn`t warranted.

Generally dry weather is expected again tonight, though there is a
potential for another MCS to develop to our north. Again, any
convection would likely weaken as it approaches given the warm
temperatures aloft, but should this activity hold together, the
area most likely to be affected will be the TN Valley. Additional
isolated convection will be possible during the afternoon hours,
but the cap should again keep most areas dry with hot and humid
conditions persisting area wide. Forecast HI values exceed 105F in
some areas and will continue to mention this hazard in the HWO.

A shortwave trough will move across the Ozarks late Monday night.
Convection will be possible during the evening hours to our north
and forcing associated with this wave may sustain convection into
the Mid-South. Large scale ascent will cool mid-level temperatures
and weaken the cap, so slight chance PoPs were included across
much of the CWA, mainly after midnight. Guidance is having a
difficult time with this wave as the GFS/GEM deterministic
solutions close off a weak low while the ECMWF maintains an open
wave. Either way, this system is forecast to push a weak cold
front close to the area Tuesday or Wednesday, but this boundary
may remain to our north. A few strong to severe storms are
possible Tuesday and Wednesday given strong instability,
precipitable water near 1.8", and steep low-level lapse rates.
Shear will remain weak so storm mode will be pretty junky with
damaging winds and locally heavy rainfall being the primary
threats.

Thunderstorm chances will continue through the remainder of the
week and into the weekend as deep moisture remains in place and
the subtropical ridge migrates back to the west over the Four
Corners. This will us back into northwesterly flow aloft and in
the path of any southern branch troughs riding over the top of
the ridge. Temperatures will trend back down to near 90F with HIs
back to a more manageable 100F or so.

MJ

&&

.AVIATION...
/06z TAFs/

Expect VFR conditions to continue across much of the Mid- South
during the forecast period. A few showers may move across extreme
northern sections of the Mid-South during the overnight hours.
Some patchy areas of fog may develop overnight in the KMKL area.

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.

&&

$$


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