Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 251557
AFDMEG

Area Forecast Discussion
National Weather Service Memphis TN
1057 AM CDT Fri May 25 2018

.UPDATE...

Latest water vapor imagery depicts two decaying Meso Convective
Systems over central Missouri and central Arkansas. These systems
may eject MCVs by early afternoon and could enhance convective
activity west of the Mississippi River by late afternoon. To our
south, low level moisture is surging north increasing cloud cover
across the entire area. Latest radar trends show showers just
beginning to pop up over west Tennessee. Overall, temperatures
are running a couple of degrees cooler than yesterday due to the
enhanced cloud cover.

Made a couple changes to the forecast to account for short term
trends. Went ahead and bumped up POPs over portions of west
Tennessee and northeast Mississippi and adjusted the temperature
curve for this afternoon. The rest of the forecast is in great
shape.

AC3

&&

.PREV DISCUSSION... /issued 635 AM CDT Fri May 25 2018/

UPDATE...

Updated for the 12Z Aviation Discussion

&&

.PREV DISCUSSION... /issued 309 AM CDT Fri May 25 2018/

DISCUSSION...
A band of showers and (a few) thunderstorms developed early this
morning, mainly affecting portions of north MS. This activity
isn`t expected to be very intense but may wake a few folks up this
morning as it drifts slowly to the north. The upper-level flow
remains weak downstream of the subtropical ridge building over the
western CONUS. A strong shortwave trough over the Canadian
prairie provinces is moving slowly northeast with its trough axis
rotating eastward across the Plains. This trough will move across
the Mid-South late today and tonight and should add some
enhancement to the convective potential for today.

A moist, moderately unstable air mass will support scattered
showers and thunderstorms across the CWA today. MLCAPE of
1000-1500 J/kg will support some strong updrafts but vertical
shear will be very weak. Thus, only pulse storms are expected
again today. Weak 700- 500mb lapse rates (~6.5C/km) will limit the
hail potential, but a few storms could produce localized gusty
winds. The forcing associated with the aforementioned trough axis
may allow precipitation to continue well into the evening hours
tonight, so will carry PoPs throughout the overnight period.
Expect afternoon temperatures generally similar to those on
Thursday.

The focus this weekend shifts to the developing tropical system off
the Yucatan. Model consensus (and NHC) agree on a high likelihood
for further development over the weekend or early next week as it
moves north into the Gulf of Mexico. As this wave moves poleward,
a SW-NE oriented ridge from the Southern Plains into the Ohio
Valley will cause this system to slow or stall near the Gulf
Coast. However, this ridge is forecast to weaken early next week
as a strong trough moves across the Northern/Central Plains,
allowing the tropical system to accelerate northward. How far
west the circulation moves will be the key for determining impacts
across the Mid-South. At this time, there is decent agreement
amongst the medium range models, but the ECMWF does stand out a
bit as having a stronger cyclone and being slightly farther west.

Should this system intensify, there is potential for a drier,
subsident regime to develop northwest of the low which may result in
a relative lull in convective activity across portions of the
Mid-south by early next week, but confidence is not high. Will
continue to monitor trends at this point. At the least, we should
see increasing column moisture with precipitable water approaching
2.0" as the system moves north through midweek. The main
potential impact across the Mid-South is localized heavy rainfall
(primarily over northeast MS), but this is highly dependent on
the track of the low and the threat will mostly like be focused to
our southeast.

The Plains trough will move across the region late in the week and
should shunt a good amount of the tropical moisture eastward. The
subtropical ridge is forecast to build over the southern Plains
Friday into the weekend. We look to be the eastern periphery of the
ridge with northwesterly flow aloft. Rain chances will decrease and
temperatures should increase if this pattern develops as
anomalously high 500mb heights develop over the region.

Johnson

&&

.AVIATION...
12Z TAF cycle

Some patchy areas of fog have developed mainly in the KMKL which
should burn off by later this morning. Otherwise, VFR conditions
should prevail for most of the forecast period. Some scattered
showers and thunderstorms are expected to develop by this afternoon
and will continue into the overnight hours. Some fog may develop
overnight tonight in the KMKL area. Winds outside of thunderstorms
will be light and variable for much of the forecast period.

ARS

&&

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

$$


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