Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 220842
AFDMEG

Area Forecast Discussion
National Weather Service Memphis TN
342 AM CDT Sun Apr 22 2018

.DISCUSSION...
Showers continue to spread across the Mid-South early this morning
in a warm advection pattern downstream of a deep, slow-moving
cyclone traversing the Southern Plains. Strong forcing for ascent
is noted on water vapor, aiding in the development of these
showers. Instability is generally confined to the Arklatex area at
this time, precluding the development of thunderstorms at the
moment. The subtropical jet on the southern periphery of the
trough will shift slowly eastward today, placing the Mid-South in
the left exit region, favorable for enhanced lift.

As this trough moves across the Mid-South today, the dry slot
will shift over the southern half of the CWA. This should shunt
the main precipitation shield north and east this afternoon.
While this may limit coverage of precipitation this afternoon over
north MS, it will also promote some clearing. Any enhanced
insolation will result in warmer surface temperatures, yielding
greater destabilization of the boundary layer.

Scattered thunderstorms are expected to develop east of the
secondary surface low lifting northeast across MS. Deep-layer
shear will be limited across much of the Mid-South given the
proximity of the vertically stacked cyclone, but is progged to
remain in the 35-40 kt range across northeast MS. This may be
sufficient to support organized thunderstorm updrafts and promote
at least some potential for severe weather. Mainly showery
precipitation is anticipated overnight, but there will be some
elevated instability that may yield some additional thunderstorms.
Rainfall totals through tonight will generally range from 1-2
inches, but higher totals are possible across the Tennessee Valley
and in any areas that experience training convection.

Given the very slow movement of the upper-level trough, rain
chances stick around on Tuesday, with the highest chances
favoring west TN and northeast MS. A brief respite from the
precipitation is expected late Tuesday and Tuesday night, but
another trough will dive southeast across the Ohio Valley on
Wednesday. This system will force a weak cold front through the
area and support additional rain chances. Rainfall looks to be
relatively light with this progressive system and should be clear
of the area Thursday morning.

One more fast-moving trough is progged to affect the Mid-South
late in the week, but the global models are still having trouble
developing a consensus on its timing and evolution. The
GFS/Canadian both cut off a cyclone over the Great Lakes Thursday
night while the ECMWF maintains a positively-tilted open wave.
This ECMWF solution hangs the trough axis back to our west,
delaying the front until Friday, while the former bring the front
through the Mid-South Thursday night. Will maintain PoPs across
portions of the Mid-South for both periods given the uncertainty.

Looking beyond Friday, the global models are developing a blocking
ridge over the central CONUS. This should result in generally
tranquil conditions across the Mid-South Saturday and Sunday -
quite the change from the past several weekends. Temperatures will
generally run 5-10 degrees below normal through the forecast
period. Afternoon highs will be in the 60s and 70s with overnight
lows in the 40s and 50s.

Johnson

&&

.AVIATION...
/06z TAFs/

MVFR cigs have been slow to build in due to the residual low level
dry airmass in place. Moisture has been slowly increasing and MVFR
cigs should eventually build into all of the terminals by Sunday
morning, near or just after sunrise. Rain showers will also
increase in coverage areawide over the next few hours. East winds
will also continue but remain lighter than earlier anticipated.

A dry slot rotating into the southern portions of the region
should allow for improving cigs by afternoon at KMEM and KTUP
along with increased chances for showers and a few thunderstorms.
Some stronger storms tomorrow afternoon could pose a hail threat
if enough instability can develop near KMEM and KTUP.

Cigs will gradually lower again later Sunday night, with IFR cigs
and vsbys expected through much of the night along with isolated
showers.

JLH

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.

&&

$$


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