Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 171803 AAA

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
103 PM CDT Sat Mar 17 2018

Updated for 18Z aviation discussion


18Z TAF discussion:
MVFR cigs were still being reported at a few TAF sites at 1730Z
but wl continue to improve to VFR conds by 20Z. Sct SHRA/TSRA wl
affect HBG this aftn but end by 00Z SUN. Elsewhere, VFR conds wl
prevail from 20Z until after 06Z when CIGS wl lower to MVFR and
IFR. IFR conds wl prevail at most TAFS sites through 14Z Sunday
with the exception of GLH-GWO where TSRA activity wl be psbl and
may briefly improve conds. /22/


Latest satellite imagery and surface observations show the morning
fog has dissipated and stratus was breaking up. This will allow
for sunshine today and warmer than normal temperatures in the
lower 80s at many locations. Morning surface analysis had a
1009mb low centered over southern Illinois and a 1020mb high
centered over the Florida peninsula ridging west across the Gulf
coast states. The surface low will track east and drop a weak cold
front toward our CWA while the surface ridge shifts south over
the northern Gulf. This will result in more of a west wind across
our area holding moisture across our southern zones but negative
thetae advection is expected across our north. Thus, rain chances
this afternoon look to remain limited to our southern half. Local
radars were showing showers developing over southern Louisiana
that should spread northeast into our CWA. The forecast was
updated to remove the fog wording and adjust rain chances to the
latest radar trend. /22/

Prior discussion below:

Today and tonight: A mid level shortwave along the MO/IA border
this early morning will continue to dampen as it moves eastward
today. Consequently, the associated surface low will weaken with
time and the associated cold front will begin to stall. Though the
front will hang up just northwest of the forecast area through
much of the day, a drop off in deep layer moisture is expected
well southward through the morning. As this occurs, the ongoing
light shower activity will decrease from NW to SE with time
through the morning. By this afternoon, forcing will remain
limited, so convection will be primarily diurnal in nature, mostly
tapering off with the loss of daytime insolation this evening. It
should also be limited to mainly south of I-20, where the more
moisture- rich environment will exist. Assuming we see healthy
breaks in the low stratus deck currently enveloping the area,
temperatures should soar to near 80/low 80s today given the
unseasonably high low level heights forecast and continued WAA.

After a lull during the early evening, convection will increase
again overnight into Sunday morning as isentropic ascent begins to
overspread the region and a few ripples of mid level vorticity
propagate eastward. In particular, high res guidance is hinting
at the development of a west-east oriented band of showers and
storms near the quasi-stationary front which will sag southward
toward the US 82 corridor overnight. /DL/

Sunday through Friday: Amplified mid level pattern at the beginning
of the period looks to break down somewhat as a series of shortwaves
move through then amplify again by the end of the period. During the
day Sunday, a stalled boundary will be present over the northern
portions. Though low level wind fields are weak, the best
forcing/ascent will occur along the boundary where the best coverage
of convection will occur. Daytime heating will increase
CAPE/instability where combined with deep layer shear of 50-60 knots
some vigorous convection looks to get going. Weak low level winds
may limit tornado potential, but large hail and damaging wind will
be in play. While best combination of shear/instability will occur
over the south, lack of a focus will limit overall coverage there.

As the mid level cold core moves into the central Plains Sunday
night, better wind fields will aid in better convective coverage.
Instability/shear will remain substantial enough to continue
severe threat for a good portion of the night, but does look to
diminish toward dawn Monday. This will be temporary as the cold
front moves into eastern portions during peak heating Monday
afternoon, severe storms will again be possible.

Though cooler air will be building into the area Tuesday, a passing
mid level shortwave will bring cloud cover and a few showers to the

Flow pattern begins to amplify by Wednesday with ridging to our
west. Surface high pressure ridge will settle over the forecast area
and aid in good radiational cooling conditions again for Tuesday
night and Wednesday night. Mid 30s appear possible over the eastern
portions where concerns for frost will occur again./26/


Jackson       83  61  76  62 /  16  42  63  62
Meridian      81  61  75  62 /  27  26  71  65
Vicksburg     83  62  75  63 /  11  50  62  59
Hattiesburg   80  63  77  64 /  52  30  61  51
Natchez       83  64  77  65 /  24  41  63  46
Greenville    80  56  67  58 /   8  33  65  65
Greenwood     80  57  69  60 /  10  37  56  73





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