Scientific Forecaster Discussion
fxus64 kmeg 261114
Area forecast discussion
National Weather Service Memphis Tennessee
614 am CDT sun Mar 26 2017
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.
12z taf set
IFR and MVFR ceilings are occurring over much of the mid-south east of
the Mississippi River at this time. Expect ceilings to lift to VFR
between 14-17z. A broken 4000 feet deck may then linger at kmkl until
the afternoon hours otherwise expect clearing skies through 21z.
Winds will turn around to the south-southwest today and increase to between
8-10 kts. Around 00z, speeds will diminish as direction shifts to
the southeast ahead of a warm front. Expect the warm front to move
into the area between 6-9z. At that time a broken 4000-6000 feet deck
may develop from kjbr southeast to ktup. Winds will turn around
to S and increase to 10 kts behind the warm front. In addition, remnants
of a squall line ahead of the next low pressure system could
approach NE Arkansas after 9z. Have added vcsh wording at kjbr for now.