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fxus64 kjan 150311 
afdjan

Area forecast discussion
National Weather Service Jackson MS
911 PM CST Sat Dec 14 2019

Update...
updated for evening discussion.

&&

Discussion...
expect mostly cloudy skies tonight as moisture continues to build
back into the region. Patchy fog is expected area wide tonight into
tomorrow morning, with dense fog expected for most areas along and
south of Interstate 20, where a dense fog advisory is in effect
until 15z tomorrow morning. Lows tonight will range from the lower
40s north to around 50 south. /27/

Prior discussion below:



Tonight and sunday: an upper trough is swinging east of the
region with more zonal flow moving overhead. This is keeping some
higher clouds present across the area. Morning low clouds were
slow to move out as a result but some locations have been able to
clear out and see some peaks of sun. This zonal flow will continue
across the region as low level moisture builds back into the
region. This will result in another night of low stratus likely
plaguing the region. It won't be out of the question for more fog
to develop but confidence in widespread dense fog is not high
thanks to increased wind speeds that should not diminish tonight.
This comes as a low pressure system develops to our west and the
pressure gradient tightens across the region. These winds will
remain breezy tomorrow as the low over Texas develops. Dry
conditions should otherwise mostly prevail during the short term.

A disturbance riding through the zonal flow may clip the northern
part of the forecast area starting late tomorrow afternoon. This
could bring some light rain to the western and northwestern part
of the arklamiss. Thanks to potential for cloud cover and
increased warm advection, overnight lows will be slightly warmer
tonight. Highs tomorrow will be warmer with readings in the mid to
upper 60s north of I-20 and into the 70s for the remainder of the
forecast area. /28/

Sunday night through Friday night: an area of surface low
pressure over nm will track eastward toward the area as a
positively-tilted trough dives down through the Great Basin. In
response, cyclogenesis will begin by Monday morning over the
arklatex. A weak surface low will lift through the mid-south
through the day Monday along a frontal boundary which will push
through our area that afternoon/overnight. The conditions
associated with this system still warrant a slight risk for severe
storms as cape, lapse rate, and shear values all remain strong.

Even though these core parameters and values will be in place, a
few issues exist with this system. The main issue is the
orientation of the positively-tilted mid-level trough. The deep
layer shear vectors will be nearly parallel to the associated
frontal boundary and therefore the storm development and
progression will likely be messy with a mix of line segments,
clusters and possibly discrete cells. Also, the confidence for
severe storms is not as high for the southeast/Pine belt as the
forcing over that area will be weaker and the storms will be
moving through there after peak heating. Given these concerns, a
slight risk remains in place for Monday with damaging wind gusts,
a few tornadoes, and large hail all possible. Stay tuned though as
there could be changes to the slight risk area in the upcoming
forecasts.

Behind the frontal passage, a drier and colder air mass will make
its way into the region. Temperatures will drop 30-35 degrees from
Monday into Tuesday morning with lows expected in the 30s to low
40s. Highs then will remain chilly with conditions warming only into
the 40s to low 50s. As a surface high works its way over the region
on Wednesday and Thursday, radiational cooling will allow low temps
to drop into the 20s areawide both mornings. By Thursday day, an
increase in southerly flow will help to moderate the temperatures
finally as highs reach normal values in the 50s. By Friday, the
evolution of the upper pattern remains uncertain as the global
models all show a cutoff low developing over the central US but with
Stark differences in the latitude of development, which in turn
means big differences in the weather over the arklamiss. We shall
see what the next model runs reveal for this time frame. /10/

&&

Aviation...
00z taf discussion:
VFR/MVFR conditions this evening will drop to IFR by midnight as
low ceilings and some fog develop. These conditions will linger
into mid morning Sunday then improve to VFR by afternoon. /Gg/

&&

Preliminary point temps/pops...
Jackson 46 71 61 75 / 6 14 22 94
Meridian 45 69 59 78 / 9 9 21 88
Vicksburg 47 74 63 77 / 6 18 39 97
Hattiesburg 48 73 60 78 / 6 8 12 84
Natchez 50 75 64 76 / 5 13 37 97
Greenville 44 66 60 69 / 6 27 60 98
Greenwood 44 67 61 71 / 5 23 45 98

&&

Jan watches/warnings/advisories...
MS...dense fog advisory until 9 am CST Sunday for msz043>066-072>074.

La...none.
Arkansas...none.

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