Area Forecast Discussion
Issued by NWS Jackson, MS

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523
FXUS64 KJAN 281141 AAA
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
641 AM CDT Sun May 28 2017

.UPDATE...
Updated for 12Z aviation discussion

&&

.AVIATION...
12Z TAF discussion:
A patchy MVFR stratus deck exists across the region this morning.
Through the day, ceilings will rise to VFR thresholds. A weakening
band of SHRA and isolated TSRA is advancing southward toward the
I-20 corridor. This activity is expected to weaken this morning,
with additional development anticipated later this afternoon and
evening. This may bring brief visby reductions in heavier periods
of rain. Also some storms may become severe with gusts to 50 kt
and hail. Overnight tonight into early Monday morning, additional
low stratus clouds are expected to develop, with ceilings at many
sites falling to MVFR or IFR. /DL/

&&

.DISCUSSION...
Today and tonight: We are faced with a somewhat complicated and low
confidence forecast for today, with several mesoscale factors in
play and poorly-initialized model guidance.

First things first...an outflow dominant band of showers with
isolated embedded thunderstorms has been slowly sinking southward
into the far northern portion of the CWA this early morning. More
vigorous convection along this line either weakened or moved
eastward into North AL. Farther west, a second complex of more
robust convection was ongoing across west/central AR near the
convergence of separate areas of westward and southward moving
outflow. Ahead of these lines, a fairly unstable airmass remains in
place across the area, thanks in part to a rather moist boundary
layer. However, this instability is largely capped between 700-850
mb. Through the remainder of the morning, our primary focus will be
on whether or not activity over AR can sustain itself into the
Delta. If it does, there remains lower end potential for damaging
wind gusts or marginally severe hail. Given this possibility, a
Severe TS Watch remains in effect until 13Z for the far northern
portion of the area.

Lingering boundaries from the weakening morning convection will play
a big role in how things evolve later on today. For now, it appears
the mostly likely scenario is that the complex over AR will weaken
as it approaches the Delta, with new development occuring this
afternoon across South AR/North LA, spreading eastward across our
area from the late afternoon through the evening hours. With
moderate to strong instability and somewhat steep mid level lapse
rates expected to exist ahead of this development and sufficient
deep layer shear in place, some of the storms could become severe
with damaging wind gusts and marginally severe hail. In addition,
the presence of strong instability and multiple low level boundaries
will create some potential for training/repetitive convection in a
few areas. This could result in localized flooding. Both the severe
and flooding threats will continue to be advertised in HWO/graphical
products. Though at this stage we`d prefer to offer more specific
timing for the severe threat, there remains a bit too much
uncertainty to be more specific quite yet.

Ahead of the storms, another warm day is expected as low/mid level
temps and heights remain unseasonably high and steady WAA
continues over the area. Temperatures will again approach 90, and
heat indices could again creep to near the triple digits in a few
spots. /DL/

Monday through Saturday...Monday the stalled front is expected to be
across the northern portions of our CWA. Wl still have a moist
airmass in place with surface dew points around 70F and PWATs in
excess of an inch and three quarters. There will likely be morning
convection but a subtle shortwave within the west southwest flow
aloft will combine with daytime heating to enhance storm development
during the afternoon into the early evening especially over east
central Mississippi where a few severe storms may develop. The main
threat Monday will be damaging straight line winds but, quarter
sized hail and locally heavy rainfall will also be possible. The GFS
progged another timely shortwave over our CWA Tuesday afternoon and
although wl still have a moist airmass in p[lace, meager lapse rates
and weak deep layer shear should mitigate storm strength. Model
consensus is weaker and farther west with a shortwave trough for the
weekend than last night`s run. Instead of increasing rain chances
going into the weekend, Wednesday through the end of the week will
feature a slow warming trend with mainly scattered afternoon and
early evening coverage of convection. Morning lows will continue to
be at or above normal through the period. Cooler than normal
afternoon highs are expected Monday and Tuesday, warming back above
normal by the end of the week. /22/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       89  70  82  67 /  32  59  67  52
Meridian      89  70  82  67 /  30  51  64  50
Vicksburg     90  70  82  66 /  48  67  63  56
Hattiesburg   91  71  85  69 /  21  27  66  52
Natchez       90  70  82  67 /  31  52  66  51
Greenville    87  69  82  66 /  73  66  60  40
Greenwood     86  70  81  66 /  70  64  58  51

&&

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

&&


$$

DL/22



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