Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 261126

Area Forecast Discussion
National Weather Service Memphis TN
626 AM CDT Fri May 26 2017

Updated to add 12Z Aviation Discussion.


.PREV DISCUSSION... /issued 356 AM CDT Fri May 26 2017/


Upper level ridging will build over the Mid South today as low
level moisture increases under strengthening southwesterly low
level flow ahead of surface low pressure over the Southern Plains.
This should allow for mainly dry weather along with a warm up in
temperatures and increase in humidity levels this afternoon. High
temperatures should reach into the middle and upper 80s with
dewpoints rising into the 60s. A few warm advection showers may
develop late this afternoon and overnight mainly north of
Interstate 40 as a shortwave over the Southern Plains lifts
northeastward into the Middle Mississippi Valley. Lows tonight
should remain in the upper 60s to lower 70s.

Isolated showers will continue into Saturday as broad
southwesterly moist low level flow continues. Strong mid level
capping associated with an elevated mixed layer spreading east
should prevent most thunder potential. An isolated lightning
strike will be possible, but is not likely to be widespread.
Temperatures will again rise into the middle and upper 80s as
dewpoints surge into the lower and middle 70s.

The upper level ridge should break down some by Saturday night as
another low amplitude shortwave moves across the region. This
should help to initiate numerous showers and thunderstorms across
the Mid South Saturday night. A moderate to strongly unstable
airmass should remain in place with MLCAPES between 2000-3000
j/kg, LI/s between -6c and -8c, and mid level lapse rates around
8.0 c/km, even overnight. Deep layer shear (0-6 km) between 30-40
kts should be sufficient to allow storms to organize. The
combination of moderate to strong instability and modest shear
should support severe thunderstorm development Saturday night over
much of the area. The greatest severe weather threat should exist
along and north of Interstate 40 where an Enhanced Risk for severe
weather has been posted. The remainder of the region will be under
a Slight Risk for severe storms Saturday night. The primary severe
weather hazards will be damaging winds and large hail as a
Mesoscale Convective System (MCS) forms. An isolated tornado will
also be possible, especially where any discrete storms form ahead
of the line or with any embedded supercell thunderstorms. Any
overnight convection should wane in intensity by Sunday morning.

Convective focus for Sunday will shift back to the northwest as
a more amplified shortwave approaches and advances a cold front
southeast across the area through Sunday night. There are some
questions regarding how worked over the atmosphere becomes after
Saturday night convection. At this time though, models are
suggesting that moderate instability will develop by afternoon
with SBCAPES between 2500-4000 j/kg and mid level lapse rates
around 8 c/km. Deep layer shear should weaken to around 30 kts
with increasingly uni-directional flow. A few severe storms will
still be possible Sunday and Sunday night ahead of the front with
damaging winds and large hail the main threats. A Slight Risk for
severe storms has been issued for much of the Mid South on Sunday
and Sunday night.

The front should push south into northern Mississippi on Monday
with continued chances for showers and thunderstorms mainly south
of Interstate 40. To the north of Interstate 40, expect dry
weather along with a return to seasonable temperatures as high
pressure builds in. The front should stall just south of the area
through Tuesday night with continued isolated storms possible
across portions of north Mississippi.

The front will lift back north as a warm front on Wednesday with a
moist and unstable airmass overspreading the region. The front
should stall near the area through the end of next week. Scattered
showers and thunderstorms will be possible through much of the
extended forecast period along with continued seasonably warm



12Z TAFs

VFR conditions expected to persist through much of the period with
a potential for MVFR conditions to develop late tonight. South
winds expected to increase throughout the day and become gusty
with winds diminishing this evening.



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