Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 260939
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
439 AM CDT Sun Mar 26 2017

.DISCUSSION...

Today through Monday night:

A weak low level trough and moisture axis lingering in the wake
of the disturbance that passed through yesterday will likely
trigger a few isolated showers over eastern zones as we go through
the day today. Even a stray thunderstorm cannot be ruled out
generally down the I-59 axis from MEI to HBG, but no severe
weather is anticipated. Clouds associated with this trough
currently running from central to northeast zones will keep those
spots largely free of much fog concerns this morning. However, on
the periphery of these clouds is where there will be the potential
for patchy, possibly dense, fog through 9 AM. The mention of this
will be included in the HWO and graphics. After this morning
anticipate clouds to gradually disperse through the morning hours
although tending to hang on a little more stubbornly in portions
of eastern MS, coincident with the lingering slight shower/storm
chances. Temperatures will be much warmer than yesterday with
south to southwesterly flow in the low levels boosting highs at
least into the lower 80s in most locales.

Tonight our attention will begin focusing back out to the west as
another potent piece of shortwave energy starts heading our way
from out of the Southern Plains. This disturbance and associated
frontal system out that direction should kick up a good deal of
vigorous thunderstorms in the afternoon and evening with the
potential the very southeast edge of overnight organized storm
clusters could impinge on far northwestern zones toward daybreak
Monday. Any potential for worrisome storms, even in the far
northwest, should likely hold off until after daybreak. Otherwise,
expect mild lows with low clouds again building north late in the
night.

The aforementioned storm system approaching from the west tonight
will be impacting our region on Monday. The bulk of large scale
forcing and best wind shear will be focused to the north of our
region but the combination of various surface troughs and outflow
boundaries coming in from the west/northwest should be enough to
trigger scattered to numerous thunderstorms in the midday through
evening hours, especially along and north of I-20. The environment
these storms will be forming in should feature moderate to high
instability (thanks to cold temperatures aloft) and wind shear
capable of organizing storms (although not certainly not high wind
shear). The primary risk with any severe storms (especially with
any supercells) will be large hail and damaging winds. Low level
shear levels will be marginal for tornadoes but given the
impressive expected instability (MLCAPE values of 1500+ j/kg) it
is still hard to rule out a tornado. Our HWO/graphics will cover
risks and will probably be beefed up some later today in
collaboration with the Storm Prediction Center. Temperatures
preceding storms should be in the mild low to mid 80s in most
locations. Anticipate the bulk of storms to be moving out by the
late evening through overnight hours. /BB/

Tuesday through next Sunday morning:

In the wake of the cold front and severe weather that is expected
to move through on Monday, anticipate a less active pattern at
the start of the forecast period. At the surface a cold front will
draped across the Appalachians through central portions of the
ArkLaMiss and this will only gradually slide to the south through
the day. A lingering shear axis will be present over the area but
gradually pulling off to the east as the upper ridge continues to
build in and the low pressure moves off east of the mid-Atlantic
states. Expect some chances of some showers/storms there on
Tuesday, with the best chances increasing midday. Wouldn`t rule
out a stronger storm but with increasing heights and little
forcing, not expecting much with these. With the ridge building
over the area into Wednesday, expect a warm period as boundary
layer temperatures increase to near 16-17 deg C at 925mb. This
will support low to mid 80s areawide, some 10+ degrees above
normal.

An active period of severe weather potential will again be
possible as we continue through the work week. By Wednesday, a
strong Pacific jet (~100kts at 300mb) and closed upper low will be
diving down into the Desert southwest. This will promote strong
cyclogenesis over the central to southern Plains, helping a
~1000mb strong low to develop and associated cold front moving
into the southern Plains into Texas by midday Wednesday. Expect
another warm afternoon Wednesday with increasing moisture through
the day. Some showers/storms can`t be ruled as more moisture
transport picks up but shouldn`t be too much during the day.

This strong cold front will move into the area by late Wednesday
night through Thursday. SPC put our western areas Wednesday night
and entire area on Thursday with a slight risk. This system has
strong mid-deep layer shear, more than these past two systems (40-
50kts 0-6km & 30-40kts 0-3km bulk shear) with steep 700-500mb lapse
rates around 6-7 deg C. Strong height falls and strong
shear/clockwise curving hodographs with a strongly unstable
environment is supportive of severe weather potential. There are
some uncertainties, however, as the operational GFS and its ensemble
mean show the trough and associated surface low digging further
south towards the lower Mississippi Valley whereas the Euro/Canadian
and their ensemble means and the CFS weeklies show more of a track
into the central-southern Plains through middle Missouri area.
Stayed towards the thinking of the Euro/Canadian, their ensembles
and CFS. With a compact strong surface low and surface pressures
less than 1010mb, expect winds to be gusty out of the south. Right
now it looks like as a QLCS may move in our western Delta zones
Wednesday night, while more widespread convection is possible to
break out areawide Thursday afternoon. This environment on Thursday
could support supercells. All modes of severe weather may be
possible. If the storms overnight do not move in and wash out the
environment, which would be similar issue to this past weekend, then
Thursday afternoon should be primed for severe weather potential.
Stay tuned as these details will be ironed out. With efficient
moisture advection and PWs approaching 1.75 inches, some locally
heavy rain could not be ruled out. Introduced a slight for the
entire area in the HWO/graphics.

Expect this cold front to move through by Thursday afternoon,
leading to somewhat drier conditions with PWs falling to around a
little less than an inch. This will be a short drier period as
slightly warmer boundary layer temperatures filter back in before
more storms are possible through the weekend. Another strong frontal
system and deep trough will dig down into the southern Plains. This
system has quite a bit of uncertainties, with the GFS/Canadian
digging the trough/cutoff low down much further south, whereas the
Euro is not cutoff and more progressive. Regardless, increasing
moisture and storm chances will be possible as we go into late next
weekend. These details will be ironed out as we get closer and more
run-to-run consistency. /DC/

&&

.AVIATION...
06Z TAF discussion:

Expect lots of low clouds and patchy fog around tonight with
widespread MVFR to IFR flight cats around daybreak and lasting
through 10 am. Some tempo LIFR flight cats will also be possible
around the region as well at daybreak due to same concerns. A few
showers will be found tonight into tomorrow morning at
GTR/CBM/HKS/JAN/PIB/HBG/NMM/MEI, but most areas will remain dry.
The risk of an isolated shower or stray storm will linger much of
tomorrow in far eastern MS but generally anticipate that by late
morning and through the afternoon tomorrow will feature VFR
conditions and south to southwest winds blowing up to 10 mph at
times. /BB/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       82  63  83  64 /   8   7  50  46
Meridian      81  62  82  63 /  18   9  47  42
Vicksburg     84  64  82  63 /   6   8  51  45
Hattiesburg   83  63  83  64 /  16  10  33  20
Natchez       84  66  83  66 /   8   8  39  30
Greenville    79  63  79  59 /   2  16  62  37
Greenwood     79  62  80  59 /   4  11  63  49

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.

&&

$$

BB/DC


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