Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 141742
AFDMEG

Area Forecast Discussion
National Weather Service Memphis TN
1142 AM CST Thu Dec 14 2017

.UPDATE...

Updated for the 18z Aviation Discussion.

&&

.PREV DISCUSSION... /issued 1042 AM CST Thu Dec 14 2017/

Cool high pressure is building into the region. Low level CAA is
increasing across the north half of the Mid-South where stratocu
has been developing. As a result temps should remain in the lower
and mid 40s north of I-40. Areas across north Mississippi should
warm close to the mid 50s under sunny skies.

SJM

&&

.PREV DISCUSSION... /issued 307 AM CST Thu Dec 14 2017/

Temperatures this hour ranged from the mid 30s where winds are
calm...to the low and mid 40s where a light breeze was being
observed. Most locations were clear to mostly clear...but low and
mid clouds were advancing both south and east on IR satellite.

For today and tomorrow...cooler temperatures will be the rule as
surface high pressure tracks south along the Front Range. Winds
will start off north at 5 to 15 mph...but will back westerly
tomorrow. 850mb temperatures will drop from near +3C this morning
to roughly -5C by this evening...before modifying some tomorrow.
Thus CAA along with cloud cover seen advancing south will keep
high temperatures in the lower to mid 40s in the north...while
most of the south should reach near 50F with more sun. Lows
tonight will mainly be in the 20s area wide. Cooler weather and
lighter winds will help give the region a break from fire danger.

Saturday...models continue their agreement with tracking a
shortwave/closed from northern Mexico into the Ozarks. After a
freezing start high level cirrus will gradually thicken and lower
ahead of the system. This will prevent the region from seeing
it`s max temperature potential as depicted down from 850mb...so
highs will remain in the 50s. Southerly winds will become breezy
west of the Mississippi River in the afternoon...but the gradient
is expected to weaken over the entire area well before the energy
reaches the Ozarks. Rain will move into the Delta counties as
early as mid evening...reaching Memphis metro near midnight.

Sunday through Tuesday...a wetter and mostly cloudy period as the
aforementioned low ejects northeast as an open wave first...then
the passage of the main trough 48 hours later second. WPC QPF
amounts still targeting points along and south of I-40 in
receiving an inch or more rainfall...with the far northwest
counties seeing closer to a half of an inch. The brunt of the
rain will fall between 3am to 1pm Sunday. Behind the wave
southwest flow aloft coupled with a near saturated boundary layer
will leave the region in a weak WAA and wind flow pattern. So the
region could potentially end up with a stretch of fog and stratus
coupled with light rain or drizzle up until the main trof passage
Tuesday. Not good flying weather. The ECMWF remains the faster
model with trof passage...with the GFS slower. Have leaned more
with the GFS...since runs have been more consistent...with drier
air working its way in late Tuesday. Despite the weather
temperatures this period will be above normal.

Next Wednesday...drier with increasing surface pressure and a
near zonal flow aloft. Above normal temperatures will continue.

JAB

&&

.AVIATION...18Z TAFs

VFR conditions will persist through the period, although cigs may
drop to near MVFR this afternoon into tonight especially at
northern locations.

Winds will remain light north to northwesterly through the period.

JLH

&&

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

$$



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