Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 172046

Area Forecast Discussion
National Weather Service Memphis TN
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 morning.

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.



18Z TAF cycle

Clouds still over much of the Mid-South, expect some of the
northern sites to get more clearing as higher clouds move into the
area this afternoon/evening. Winds should be become less gusty
this evening as they veer toward the north. On Sunday, more clouds
move in. Near the end of the forecast period clouds should start
to lower. Should stay VFR for next 24 hours. Precipitation will
hold off till after the TAFs are completed.   TLSJr



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