Scientific Forecaster Discussion
fxus64 kmeg 261826
Area forecast discussion
National Weather Service Memphis Tennessee
126 PM CDT sun Mar 26 2017
Updated for the 18z aviation discussion.
Previous discussion... /issued 945 am CDT sun Mar 26 2017/
updated for cloud cover.
Adjusted the morning and afternoon cloud cover forecast for most
of the region as satellite trends show nice clearing region slowly
spreading north and east out of the southwest Delta counties. All
other forecast parameters are currently on track.
Previous discussion... /issued 422 am CDT sun Mar 26 2017/
Relatively quiet weather expected across the midsouth today,
behind a departing upper low and under low amplitude shortwave
Active weather will return Monday, associated with a northern
branch upper low moving into MO. Short range models depict the
associated midlevel trof axis impinging on a moderately unstable
airmass over the midsouth Monday afternoon. Scattered morning
showers may precede a multi-segment line of storms forming along
or west of the MS river around midday. With 850-500mb lapse rates
progged above 7 c/km during the early and middle afternoon, and
surface-based convective available potential energy near 2000 j/kg, the strongest storms will be
capable of producing large hail. In addition, NAM bufr soundings
depict dcape in excess of 4000 j/kg, suggestive of damaging wind
threat. Given the track of the surface low well to our north, low
level winds will begin veering prior to the time the cap breaks,
which should limit low level shear and associated tornado potential.
The upper low will lift into the Ohio Valley Monday evening, but a
few showers and thunderstorms could persist along a surface cold
front as it drops through the midsouth.
Tuesday will see dry conditions prevail, with light easterly
winds, mild temps and low to moderate humidity.
Attention will then turn toward a large closed upper low lifting
east into Texas and OK on Wednesday. Today's 00z GFS has returned
closer to the medium range model consensus with respect its
handling of this upper low, though differences remain. In any
case, it appears that the cold front that dropped through the
midsouth Monday evening will return as a warm front on Wednesday,
under strengthening diffluent southwest flow aloft. With deep
height falls occurring over the lower MS River Valley Wednesday
night, it appears thunderstorms will likely lift into the MS river
Delta area of the midsouth during the predawn hours Thursday,
with coverage expanding eastward through the morning. Too early
to pin down storm types, as model differences remain with respect
to the upper low.
A respite from storms appears likely Friday and Saturday, as the
upper low lifts into the Ohio Valley and upper ridging builds in
from the west. By Sunday, it appears another southern branch upper
low will lift out from southern TX, returning showers and
thunderstorms to the midsouth.
VFR conditions will prevail through the early morning hours of
Monday at all terminals. Southwest winds around 10 kts will
gradually diminish early this evening.
A decaying squall line will move into eastern Arkansas just prior
to sunrise and impact kjbr with MVFR cigs/vsbys along with showers
and thunderstorms. This line should continue to fall apart as it
approaches the Mississippi River after sunrise. Tempo showers have
been added to kmem and kmkl along with MVFR cigs for Monday
morning. Overall confidence on coverage remains lower than
preferred. South winds will increase later Monday morning with a
possible break in activity. Ktup should remain dry through the
Additional development of showers and thunderstorms will be
possible later Monday afternoon but will be dependent upon how
much the atmosphere can recover and destabilize after the morning
activity. This will be better resolved in later forecasts.