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fxus64 kmeg 250433 
afdmeg

Area forecast discussion
National Weather Service Memphis Tennessee
1133 PM CDT Wed may 24 2017

Discussion...
updated for 06z aviation discussion.

&&

Previous discussion... /issued 937 PM CDT Wed may 24 2017/

Update...
two distinct cyclonic circulations are noted on the water vapor
this evening. The first is the primary occluded cyclone lifting
north into the Great Lakes with the second moving slowly southeast
over the mid-south (centered very near Memphis at this time). The
cold temperatures aloft associated with this trough resulted in
sufficient instability this afternoon to support scattered showers
and thunderstorms. However, with the loss of diurnal heating,
showers are quickly dissipating and should be a memory by
06z. Thus, no mention of precipitation is carried after midnight.

Sky cover will gradually diminish overnight as the low moves east,
allowing temperatures to fall to near 50 degrees. Some areas may
dip into the upper 40s around sunrise. It's not out the question
that some low-lying areas and river valleys could experience some
patchy fog but this should be relatively isolated and visibilities
are generally expected to remain above 3 miles. Otherwise, expect
light winds and pleasant weather across the mid-south for
Thursday.

Johnson

&&

Previous discussion... /issued 325 PM CDT Wed may 24 2017/

Discussion...
temps across the midsouth were running 15 to 20 degrees below
normal this afternoon, courtesy of an upper level low centered
over MO. Despite the cool boundary layer, temps aloft were
sufficiently cool to steepen low level lapse rates to 8 c/km,
helping to sustain numerous showers. Given sufficiently strong
updrafts, small hail will be possible given freezing levels near
7 kft above ground level. The steep lapse rates may also lead to isolated
occurrences cold air funnels over the Delta until late afternoon.

The upper low will track southeast through the midsouth during
the evening, with gradually shrinking shower coverage mainly south
of/ahead of the upper low center. By sunrise Thursday, the upper
low will have departed with clouds likely cleared except near the
Tennessee River.

Thursday will begin the warming trend, as upper level ridging
builds in. Low level pressure gradient will tighten through Friday
afternoon, under moderately fast zonal flow aloft. Modified
marine air will spread into the midsouth Friday, driving surface
dewpoints into the upper 60s and lower 70s. The boundary of this
marine airmass will set up to the north, near the periphery of
mid level ridge. A few storms may affect northeast Arkansas through
northwest Tennessee Saturday. Despite warm and humid conditions, the
atmosphere will likely be capped to deep convection along and
south of I-40 Saturday afternoon.

Saturday night and Sunday morning should see rain chances
considerably increase over the midsouth, as steep midlevel height
falls occur over the middle and lower MS River Valley help drive
the surface front south. Weak directional shear and timing of the
morning frontal passage will likely limit organized severe
thunderstorm potential. Best chance for severe will likely occur
north of I-14 Saturday evening, where daytime instability is
greatest.

A longwave trof will prevail over the eastern U.S. Early next
week, returning below normal temps to the midsouth. GFS and European model (ecmwf)
depict a secondary cold frontal passage, but differ on the timing.
Confidence on rain chances early next week is thus a little less
than normal at this point.

Pwb

&&

Aviation...
06z taf cycle

VFR this taf period...with the exception for potential MVFR visibility
from light fog at mkl and tup near sunrise. West winds of 4-5 kts
overnight will increase to 10-12 kts by late morning. Winds will
briefly diminish and start backing more southerly late.

Jab

&&

Meg watches/warnings/advisories...
Arkansas...none.
MO...none.
MS...none.

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