Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 231716
AFDMEG

Area Forecast Discussion
National Weather Service Memphis TN
1216 PM CDT Sun Apr 23 2017

.UPDATE...Aviation Discussion.

&&

.PREV DISCUSSION... /issued 1011 AM CDT Sun Apr 23 2017/

DISCUSSION...

Skies remain cloudy over much of the forecast area east of the
Mississippi River with mostly sunny skies elsewhere. Temperatures
are on the cool side this morning with readings in the mid 40s to
mid 50s. Some light rain continues to fall over central portions
of the forecast area and more light rain should fall this afternoon
mainly over eastern sections. Will updated forecast to remove
morning wording with no big changes needed.

ARS

PREV DISCUSSION... /issued 408 AM CDT Sun Apr 23 2017/

DISCUSSION...

An upper level low pressure system will move slowly southeast
across the Mid South today. This will keep wet and unseasonably
cool temperatures in place with most locations east of the
Mississippi River measuring light QPF. High temperatures will
remain in the 50s east of the Mississippi under abundant cloud
cover. Slightly warmer highs in the middle 60s can be expected
west of the river where skies should gradually clear this
afternoon. Cloudy conditions should persist east of the
Mississippi River through this evening with the clearing line only
nudging slowly east through the night. Scattered light rain or
drizzle will continue tonight over eastern sections. Lows will
drop into the 40s areawide.

The upper low will move east by Monday as high pressure builds in
with a return to dry conditions under mostly sunny skies. This
should allow temperatures to rebound back to seasonable averages
in the lower to middle 70s by Monday afternoon. High pressure will
move east by Tuesday with a return to southerly low level flow and
temperatures warming back into the upper 70s and lower 80s. Lows
Monday night will be in the 50s, warming into the lower 60s by
Tuesday night.

By Wednesday, an upper level trough will move east across the Mid
South and take on an increasingly negatively tilt which should
promote increasing instability as low level moisture surges back
over the region. Latest model guidance suggests CAPE values
increasing to between 1000-2000 j/kg, especially along and west of
the Mississippi River, along with mid level lapse rates
approaching 8 c/km by afternoon. In addition, deep layer shear
increases to 60+ kts by afternoon along with 0-1 km SRH values
between 100-200 m2/s2. The combination of moderate instability and
strong shear should support the development of severe
thunderstorms for Wednesday afternoon into Wednesday night. At
this time, it appears there is the potential for all severe
weather modes. This system will need to be monitored closely with
threats refined over the next few forecast cycles. Plan to keep
mention of severe potential in the Hazardous Weather Outlook.

As the upper level trough swings northeast later Wednesday night,
a cold front will push through the region bringing an end to the
thunderstorm chances. This front should stall to the south over
central Mississippi and Alabama on Thursday. This should allow for
mainly dry weather conditions and slightly cooler temperatures for
Thursday.

The front will lift back north as a warm front by Thursday night
and Friday as the mid and upper flow becomes southwesterly in
response to a strong upper low digging across the four corners
region. This warm front should become quite active as a shortwave
trough embedded within the flow moves across the region and
interacts with the front. Strong deep layer shear on the order of
60+ kts precedes the shortwave and overspreads the warm front.
Strong 0-1 km SRH is present in the vicinity of the warm front
with models suggesting values between 300-400 m2/s2 late Thursday
night into Friday. Also, strong instability along and south of the
front with CAPE values near 3000 j/kg could spell an enhanced
severe weather potential with all severe hazards again possible
with supercell thunderstorms forming along the warm front. This
will be closely watched through the forecast period.

By Friday night, the warm front should be well north of the region
with middle and upper level heights rising. This should persist
into Saturday as the upper low and associated deep troughing moves
slowly east into the Plains states. This should result in a mostly
dry, warm, and humid day for Saturday. High temperatures should
reach into the 80s over most locations. Slightly low heights over
western areas could support a few scattered afternoon and evening
storms. The upper trough finally nudges into the area by next
Sunday with numerous showers and thunderstorms expected to end the
weekend. A few of these storms may also be severe and will need to
be monitored through the forecast period. Temperatures should
remain above average through much of next weekend.

JLH


.AVIATION...18Z TAF cycle

Low clouds and light rain are proving to be hard to get rid of as
it typical with these upper level low systems. Think most of the
precipitation has finally ended at MEM and JBR but will continue
through most of the day at MKL. TUP may see a few sprinkles. MVFR
cigs will remain in place where it is raining. Conditions will
improve tonight with all sited VFR by 24/06z. Winds will remain
from the North to northeast around 10kt.

30

&&

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

$$


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