Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 101752 AAA

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
1152 AM CST Sat Dec 10 2016

Updated for 18Z aviation discussion


18Z TAF discussion:
VFR conditions will prevail through the period. Some low-mid level
stratus is getting closer to GLH and could move near the TAF site
early afternoon after 10/18-20Z or so but most should erode over the
next few hours. Winds will be from the east-southeast today around
5-7kts before gradually turning more from the southeast tonight,
mainly after 11/03Z. Some lower-mid level stratus and high clouds
could move back in around 11/10Z on Sunday at northwest TAF sites,
mainly near GLH and possibly GWO. /DC/


Overall not much changes needed to the going forecast. Broad upper
trough is center over most of the north and east CONUS with surface
ridging underneath in the lower Mississippi Valley. The 1038mb
surface high is centered over western Tennessee and slowly building
east as the trough departs off of the Atlantic seaboard. There is
still a 925mb and 850mb temperature trough over the north and
northeastern portions of the area but we have warmed some 4-6 degrees
at 925mb. For this afternoon, we should be able to mix somewhat to
help highs increase around 4-7 degrees, with areas in the Highway 82
corridor, especially NW Delta, struggling to reach the 50 degree mark
due to cold low level boundary air sticking around. Winds will be lighter
today from the east-southeast before the ridge builds into the
Appalachians late today into tonight and a surface low begins to
develop late tonight over the central Plains due to broad jet
dynamics. This will slowly increase the pressure gradient over the
Delta, beginning to increase as we go into late tonight. In
addition, there are some low stratus clouds that are advecting from
low-mid level moisture right up on our border or advecting near us
into central Louisiana and south-central Arkansas. Some of these
could briefly advect into the northwest Delta near Greenville before
clearing up mostly after 18Z but some remnants could hang on near the
western areas before better moisture advection and clouds increase
tonight. Due to dry air today and warming highs, some fire weather
concerns are possible due to low humidity over the east Mississippi.
However, with recent rainfall helping to moisten soils and light
winds, for will leave out of the HWO. /DC/

Prior discussion below:

Today through Tonight:

Latest satellite and model analysis showed a broad upper trough
centered over the Eastern Conus. On the surface a 1038 mb high was
centered over the Mid Mississippi River Valley in a north-south
oriented ridge. Predawn temperatures were in the middle 20s to the
lower 30s under clear skies and light winds. The surface high will
shift to the east to near the Eastern Seaboard by this evening.
This will bring east to southeast light flow across the CWA by this
afternoon. 925 mb temps will rise to the 2-5C range which will send
afternoon highs ranging from the middle 40s north to the lower 50s
south, which will be 10 to 15 degrees below normal for this time of
year. May see some high clouds across the delta region by this
afternoon. With teen dewpoints over our eastern counties we will see
minimum humidity dip to around 22-30 percent with light winds.
However with recent rainfall over moist soils do not see any fire
danger issues. So will keep that out of the HWO. For tonight as the
surface high pushes to the Eastern Seaboard we will start to get
some better low level return flow. Dewpoints leave the teens and 20s
as we start to get some 30s dewpoints over our western areas by
Sunday. Model cross sections and buffer soundings shows that there
will be enough moisture return for increasing clouds across the
delta region ahead of our next system coming out of the plains. With
a gradual increase in low level moisture our freezing temps will be
confined to our eastern counties. Overnight lows will range from the
lower 30s east to the upper 30s west./17/

Sunday through Friday:

Temperatures and rain chances will be on the increase over the
ArkLaMiss as we finish up the weekend and go into early next week,
but more uncertainty exists for the expected weather pattern for mid
to late week given close proximity of shallow cold air and Gulf
moisture in what should be a fast and transitioning upper level

Cold high pressure is forecast to shift east of the area Sunday, and
the resulting return flow will quickly increase moisture ahead of a
weak shortwave trough and associated cold front. The bulk of
guidance points to the Delta region late Sunday night as the area
for greater rainfall chances and moderate rainfall amounts. There is
even some thunder potential given the ECMWF output showing a few
hundred joules of most unstable CAPE and near -2 Showalter Indices.
From there, expect the better moisture convergence to shift
southeast through Monday into Monday night as the trough shears
eastward and leaves behind a weak frontal boundary.

The general thinking is that the weak front and associated moisture
axis will linger along/south of the I-20 corridor from Tuesday into
Wednesday with subsequent minor shortwave troughs helping to incite
additional showers and perhaps a few thunderstorms. At the same
time, the shallow colder air will push southward into northern
portions of the ArkLaMiss, eventually deepening enough to surge
through the entire forecast area, thus bringing a temporary end to
rain chances. Having said all of this, confidence in specific
temperatures/rain chances is quite low due to what may eventually
turn out to be a sharp thermal/moisture gradient.  Weather impacts
for the mid week should not be all that great with rainfall on the
light side and colder temperatures not too extreme, but would not be
surprised if Thursday turns out to be a colder day than forecast,
particularly in the upper Delta region due to the shallow airmass
anchored by strong high pressure over the mid MS Valley region.

Going into next weekend, there has been a trend toward more
amplification of a developing western trough/eastern ridge longwave
pattern resulting in the potential for tremendous baroclinity as
arctic air clashes with rich Gulf moisture somewhere over the
central CONUS. In the least, it looks to be an active weather
pattern for the ArkLaMiss as we go beyond week one of the forecast
with latest SLU CIPS analogs showing a developing heavy rain signal.


Jackson       52  35  66  57 /   0   1   6  35
Meridian      51  31  65  54 /   0   1   3  31
Vicksburg     51  34  67  57 /   0   1  10  45
Hattiesburg   53  33  68  54 /   0   1   2  22
Natchez       51  37  66  59 /   0   1  10  33
Greenville    47  35  61  55 /   0   2  13  68
Greenwood     47  33  62  55 /   0   2  10  64





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