Area Forecast Discussion
Issued by NWS Memphis, TN
FXUS64 KMEG 262128
Area Forecast Discussion
National Weather Service Memphis TN
328 PM CST Sun Feb 26 2017
At 3PM, a dry and pleasant late Winter day taking place across
the Mid-South. Temperatures are in the mid to upper 50s areawide
with a light southeast wind under increasingly cloudy skies.
Relative humidity values have fallen below 30 percent nearly
areawide, due to the very dry arctic airmass. However any fire
weather concerns will be squashed, as the airmass quickly
moistens tonight as an approaching shortwave moves into the area.
Latest water vapor imagery currently depicts a weak shortwave
digging across Texas Panhandle at this hour. This wave will
quickly traverse into the lower Mississippi Valley by this
evening. Hi-res short term guidance, develops a cluster of storms
into a meso-convective system during the overnight hours. This
area of showers and thunderstorms will move through the southern
half of the Mid-South through tomorrow morning. QPF values will be
between a quarter inch in the north to near an inch further south.
Storms may continue over northeast Mississippi as the MCS
propagates eastward before dissipating through late Monday morning.
Other than morning activity, Monday will be mostly dry and cloudy
with low POPs throughout the afternoon and early evening hours.
Temperatures mainly in the 60s.
By Monday night, a warm front will begin to lift northward across
the area. As is does, scattered showers and thunderstorms will
possible overnight. By Tuesday, the Mid-South will be fully
encompassed by a broad warm sector characterized by mid to upper
60s dewpoints and CAPE in the 1500 to 2000 J/kg range. A few weak
impulses in the mean upper level flow may kick off a few
thunderstorms during the day.
By Tuesday night, A broad surface low over the Plains will deepen
as it lifts across the Northern Plains. Concurrently, a broad
longwave trof will swing across the central U.S. and overspread
100 meter height falls over Eastern Arkansas. A mixed mode of
convection is expected in this region, with multicluster storms
as well as possible supercells, due to the dynamic and unstable
environment. The main threats at this time appear to be large hail
and gusty winds with storms of the elevated nature. Quite a bit of
uncertainty still remains due to the lack of any identifiable
mesoscale boundaries or features at this time.
Deep layer shear and plenty of instability will continue to fuel
strong and severe thunderstorms through the overnight hours as the
trof takes on a positive tilt and swings into the Mississippi
Valley. Convective activity may congeal into a line as the cold
front swings into the Mid-South on Wednesday morning. Largely
unidirectional hodographs will likely push a squall line through
West Tennessee, the Missouri Bootheel, and north Mississippi
during the morning to early afternoon hours. The main threat would
likely be damaging winds, especially with any bowing segments
that break from the main line. The cold front is expected to move
out of the area by late Wednesday night, bringing an end to rain
Surface high pressure will build into the Mid-South on Thursday,
with a reinforcing dry front moving in on Friday. Dry weather will
persist through late Sunday, before rain chances return Sunday
VFR to prevail through the late evening, as increased moisture
in the FL050 to FL100 layer arrives from the southwest,
overspreading an initially dry layer below.
Primary forecast concern is timing and position of a marine warm
front overnight. NAM model depicts a shallow marine layer surging
north into the north MS toward 12Z, ahead of a midlevel disturbance.
TSRA will be possible along and north of the advancing surface
warm front. This would provide MEM and outside chance of thunder
between 08Z and 10Z, based on projected warm front placement and
midlevel disturbance timing. Further north near JBR, reinforcing
cooler air should provide better chances for LIFR toward 12Z. TUP
will see most persistent TS chances into the daylight morning
hours, until the convectively-enhanced midlevel disturbance