Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 220231 AAB

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
931 PM CDT Mon Aug 21 2017

Updated for evening discussion.


Adjusted short-term forecast elements to reflect latest trends in
temperature, dew points, and cloud cover. Removed POPs for the
rest of tonight as the last cluster of thunderstorms is departing
the northwest portion of our forecast area, and only the
occasional isolated shower is possible overnight. Some patchy fog
may develop in the early morning hours, but dense fog is not
anticipated. Muggy and warm in the morning, with calm winds and
low temps a few degrees warmer than normal. /NF/

Prior discussion below:

Tonight through Tuesday:

A strong mid level ridge will maintain the hot and humid airmass
over the ArkLaMiss in the near term. There is sufficient instability
(ML CAPE near 3500 J/KG) over northwest/north central portions of
the forecast area for scattered, strong thunderstorm activity, and
seabreeze convergence related deep convection is working toward the
Highway 98/Pine Belt area of south central MS. Expect this activity
to continue for the remainder of the afternoon before diminishing
early this evening.

Otherwise, the main story continues to be the heat with heat indices
in excess of 105 at some locations this afternoon. There may be a
limited threat for heat danger Tuesday as well given little change
in the pattern/airmass, but it appears that slight weakening of the
mid level ridge may help to keep the low level thermal ridge/sfc
drybulb temps a degree or two cooler. As we go into Tuesday, expect
diurnal convective development could be a little more pronounced
over southern portions of the forecast area with greater presence of
deep moisture. /EC/

Tuesday night through Sunday:

Another humid night with above normal temperatures is expected
for the whole CWA Tuesday but relief from the heat and humidity is
still expected for at least the northern half of the CWA for the
end of the week.

A nearly stacked low swinging into Quebec Tuesday night will send an
associated cold front into our area Wednesday. A few storms ahead of
the cold front may spread into our northern zones before sunrise but
pops will increase through the day along and ahead of the cold
front. The Canadian is the most aggressive and has the front south of
our CWA by midnight Wednesday night but consensus is slower and has
the front nearly stalled across the central portions of our CWA at
the same time. Considering our moist airmass with lower heights and
daytime heating, convection along and ahead of the should be
numerous and hold afternoon highs slightly cooler than normal. By
Thursday morning the cold front is expected to be near our Highway
84 corridor with dew points in the 60s north of Interstate 20. A
shortwave dropping around the backside of the closed low over Canada
and across the Great Lakes region Thursday afternoon will support a
>1020mb high dropping over the Great Lakes region Thursday night.
This will push the the The front south of our CWA by Friday morning.
Daytime heating Thursday will contribute to scattered coverage of
storms across our south into Thursday evening but a much drier
airmass will have filtered into our whole CWA by Friday morning.
The stalled front is expected to be just south of our CWA Saturday
morning and the models agree that the remnants of Harvey will be
over south Texas. As the large surface high to our continues
shifting east through the weekend, the stalled boundary is expected
to drift back into our CWA while drier air hangs on across the
north. This will warrant pops increasing from the south Sunday.
Otherwise, cooler than normal afternoon highs are expected Thursday
and Friday; mainly in the upper 80s. Afternoon highs will top out
closer to normal Saturday and Sunday. Lows will be cooler than
normal across most of the area Thursday and Friday morning but be
near normal across the south during the weekend as moisture slowly
increases northward each day. /22/


00Z TAF discussion:
VFR conditions expected to prevail through the TAF period at all
sites. There is a slight chance for some 5 to 6 SM BR to develop
around 12Z Tuesday, however chances for any MVFR or lower
visibility are too low to include mention in TAFs. Chances for
showers and storms increase by around 18Z Tuesday for sites along
and south of the Interstate 20 corridor. Local restrictions to
visibility and gusty winds could accompany the stronger storms.


Jackson       74  92  74  91 /  12  40   9  62
Meridian      74  92  74  90 /   8  38  14  61
Vicksburg     74  92  74  91 /  12  36   9  60
Hattiesburg   73  91  75  92 /  30  40  22  53
Natchez       73  90  74  89 /  28  40  12  60
Greenville    75  93  75  89 /  22  18  23  59
Greenwood     75  93  74  88 /  19  22  20  59





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