Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 061614

Area Forecast Discussion
National Weather Service Jackson MS
1014 AM CST Fri Dec 6 2019

Updated for morning discussion.



A line of thunderstorms continues to progress through the region
as an upper shortwave digs into the area. There has been enough
elevated instability to result in a few strong thunderstorms
across the region and this threat will continue over the next few
hours along and east of the I-55 corridor. The main threat with
any strong storms this morning will be small hail, gusty winds,
and frequent lightning strikes. The threat will begin to diminish
this afternoon as drier air continues to filter into the region
from the west.

Prior discussion below:

Today through tonight: A compact shortwave trough will steadily
move across the ArkLaMiss region in the near term. While
instability and moisture are not impressive (MU CAPE ~ 400 j/kg,
PW < 1.2 inches), there will be a several hour window for when
cyclonic vorticity advection/lift will peak over northern portions
of the forecast area this morning. This will support a convective
system rooted above the cool boundary layer moving across north
central MS, and per latest CAM guidance, localized rainfall
amounts of one to two inches will be possible. Cooling cloud tops
in latest IR loops and increasingly active radar/lightning trends
support the heavier convective guidance solutions, but not
expecting rainfall rates to raise flooding concerns at this point.

The surface low pressure system will weaken and move east of the
ArkLaMiss region later today and tonight with a weak cool advection
regime setting up. The result will be a lengthy duration of low
clouds and light drizzle going through tonight. Temperatures will
not cool all that much behind the departing system. /EC/

Saturday through Sunday night: Though much of the column will dry
out behind today`s quick moving system, a thin layer of low level
moisture will persist in convergent cyclonic flow around the
lingering surface low over the northeastern Gulf. Even with
measurable rain likely out of the picture, drizzle will be possible
through the morning Saturday, and somewhat dreary conditions are
anticipated through the entire day. Unfortunately, the clouds may
hang around for the entire weekend, as they increase again Sunday
ahead of the next storm system. An upper jet streak will extend from
the Southern Plains into the Ohio Valley ahead of a longwave upper
trough by Sunday night. In increasing warm advection ahead of this
system, a few sprinkles or light rain are possible, though more
appreciable rainfall will hold off until the new work week.

Monday through Tuesday night: A surface low will drag a cold front
into the Mid South by the daytime Monday, with rain chances
beginning to increase. There is improving model agreement in the
highest rain chances with this system occurring Monday night into
Tuesday. Ahead of the front, weak instability may support isolated
thunder on Monday night. Tuesday is currently looking like a rather
nasty day, with the front clearing the area but postfrontal rain
showers continuing as a cool northerly wind kicks in. There is a
guidance trend toward rain chances ending more abruptly Tuesday
evening into Tuesday night. Given poorer model agreement in recent
previous runs, the official forecast was trended toward lower PoPs
without removing them entirely for the overnight hours.

Wednesday and Thursday: A surface high will build in across most of
the area on Wednesday. With the baroclinic zone lingering just off
the coast, we can`t entirely rule out an isolated shower across the
southern portion of the forecast area, but overall guidance is
trending drier during this time frame. /DL/


12Z TAF discussion:

The weather will be rather poor for aviation interests this
forecast period with widespread MVFR/IFR ceilings developing
across the entire area as we go through the morning. A quick-
moving upper level trough will bring a period of moderate to
locally heavy SHRA/TSRA to especially the GLH/GWO/GTR corridor
during the pre dawn and morning time frame. For sites farther
south, less significant and shorter duration rainfall is
expected. In the wake of the system later today into tonight, a
weak cold advection pattern will bring IFR category stratus and
perhaps some drizzle. /EC/


Jackson       64  49  59  48 /  86   9   9   6
Meridian      62  49  59  48 /  81  27  11  20
Vicksburg     67  50  59  48 /  68   6   5   5
Hattiesburg   69  52  61  49 /  49  29  14  15
Natchez       69  51  60  48 /  60  16   9   6
Greenville    61  46  55  46 /  83   5   3   3
Greenwood     60  47  57  48 /  97   9   3   7





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