Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 180133

Area Forecast Discussion
National Weather Service Memphis TN
833 PM CDT Sat Mar 17 2018

Updated to increase cloud cover this evening and to remove slight
chance of PoPs over the far south.


Satellite showing mid and level moisture surging in from the west
faster than forecast this evening. Likewise short term models have
held of on any shower or storm activity to affect the far
southwest counties until after 10z late tonight. Thus have added
mostly cloudy skies in the evening cloud forecast and removed
the slight sliver of evening PoPs in the south.



.PREV DISCUSSION... /issued 727 PM CDT Sat Mar 17 2018/


Updated for the 00z Aviation Discussion.

PREV DISCUSSION... /issued 346 PM CDT Sat Mar 17 2018/

At 3PM, A gorgeous late Winter day taking place across the Mid-
South. Temperatures are in the mid to upper 70s under mostly sunny
skies. A cold front nearly bisects the Mid-South, south and
nearly parallel to I-40. South of the front, a rogue shower or
thunderstorm cannot be ruled out through early evening as the
front progresses southward. Behind the front, drier and cooler air
will filter into the entire Mid-South through the evening hours.
Overnight temperatures will drop into the 40s areawide by Sunday

Short term...Sunday morning through Wednesday...
The aforementioned front is expected to stall just to the south
of the forecast area, before lifting back north during the late
afternoon hours on Sunday. Meanwhile, A potent shortwave is
expected to eject across the Rockies into the Southern Plains
during the day on Sunday. Ahead of the main shortwave,
perturbations in southwest flow aloft will enhance lift across the
area. Clouds and a few thunderstorms are expected to spread
across the forecast area through late morning, with more
widespread activity expected late Sunday night into Monday
morning, as a warm front lifts north across the area. A mid-level
50 knot jet is expected to pass over north Mississippi enhancing
lift across the area. A few strong or possibly severe storms will
be possible in close proximity to the warm front as it lifts
across the area late Sunday night. Large hail and perhaps a
damaging wind threat would be possible.

By Monday morning, much of the Mid-South is expected to be in the
warm sector of a 997 mb surface low, characterized by low 60s
dewpoints and backed winds. The surface low will quickly traverse
from the Arkansas and Oklahoma border to the Missouri Bootheel by
early afternoon and swing a cold front through the entire Mid-
South by early afternoon. All models generate quite a bit of
instability over northeast Mississippi and portions of West
Tennessee with SBCAPE values of 1000 to 1500 J/kg, LIs around -4C,
and 60 knots of deep layer shear. 500mb height falls look to be
around 40 meters over the area, which should support robust
updrafts containing large hail, damaging winds, and perhaps a
tornado or two. The best risk of severe weather will likely be to
the east of our forecast area, but northeast Mississippi and
portions of West Tennessee could see at least a few severe storms.
If any storms can get going ahead of the main front, storm mode
would likely by supercellular with a large hail and tornado risk.
The most likely storm mode with be multi-cellular with a damaging
wind threat. The details are still a little unclear, as the speed
of the system has accelerated with each new model run, and the
shortwave acquires more of a neutral tilt over our area. Timing
issues may limit the amount of daytime heating to realize the
instability needed in our area to support severe thunderstorm
development. Nonetheless, at least a few strong to severe storms
are possible over the eastern half of the forecast area. Will
continue to mention large hail, damaging winds, and isolated
tornadoes with a focus placed on the eastern half of the area.

By Monday night, the cold front will be well east of the area. A
few lingering showers will be possible overnight with another
chance of light showers on Tuesday as another shortwave passes
overhead. Temperatures Tuesday through Thursday will be about 10
to 15 below normal as we remain under the influence of a large
scale trough.

Long term...Thursday through next Weekend...
Details through this period are a bit skewed at this time, due to
large difference in the handling of the large scale trough. Both
models, however, bring another cold front into the area next
weekend with increasing chances for showers and thunderstorms and
warming temperatures.



.AVIATION.../00z TAFs/

A cold front will move through the TAF sites early this evening
with winds becoming northwesterly around 10 kts for a few hours.
Winds eventually will shift to the northeast and diminish in

VFR cigs are anticipated over the next 24 hours. Lowering cigs to
MVFR levels are expected by Sunday evening at KMEM along with
chances for showers and a few thunderstorms. Winds will shift to
east southeast by Sunday evening.




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