Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 181747
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
1247 PM CDT Fri Aug 18 2017

.UPDATE...
Updated for 18Z aviation discussion

&&

.AVIATION...
18Z TAF discussion:

For the rest of this afternoon sites KHWKS, KJAN, and KHBG will be
in the VCTS, before clearing and being VFR late in the evening.
All other sites will be VFR conditions for the rest of the
afternoon/evening. /12/

&&

.DISCUSSION...
Not much has changed in this morning update, modified the POPs
west of I-55 a bit, a few showers are starting to pop up but
quickly dissipate. Some morning fog was spotted down near Natchez
on visible satellite, but it has already burned off. Partly
cloudy skies will continue through Central MS and ceilings will
gradually raise as we continue to mix throughout the day. Diurnal
driven thunderstorms is still expected later this afternoon. /12/

Prior discussion below:

Today through tonight,

The pattern of near normal high temperatures and above normal
surface dewpoints resulting in higher levels of heat stress will
continue today. A few locations, especially in the Delta region,
could briefly reach heat indices of 105, but most of the area
should see afternoon values top out a bit lower.

Drier mid level air pushing in behind a shortwave trough has
lowered precipitable water values to near 1.5 inches over
northern portions of the ArkLaMiss region as of this morning.
Better moisture convergence is confined to mainly south of
Interstate 20, where daytime heating should support scattered
mainly afternoon storms. Expect any storms to diminish early this
evening with warm and muggy conditions following through the
overnight hours. /EC/

Saturday through next week...

Upper level heights will begin to increase over the region on
Saturday as an upper trough pushes towards the Atlantic Coast,
while a broad mid level ridge remains centered over the ArkLaTex
region. Nearer the surface, a broad surface high will encompass
the SE US. Heat stress will become an issue on Saturday,
especially in the Delta region. 925 temperatures on Saturday
afternoon are expected to range from 25 to 27 degrees. This
usually results in surface temperatures in the upper 90`s.
However, the decision was made to go towards the lower end of
guidance and keep highs in the low to mid 90`s due to possible
afternoon convection and a very moist atmosphere. This moist
atmosphere near the surface will result in dewpoints in the mid to
upper 70s. The combination of this range of temperatures and
dewpoints will lead to heat index values of between 103 and 109
degrees. An elevated risk of hazardous heat conditions was added
to the HWO in the western portions of the ArkLaMiss and a Heat
Advisory may be warranted during subsequent forecast packages.

Upper flow will become zonal by Sunday with weak upper flow
remaining through early next week. Conditions will remain
conducive for limited to elevated heat stress through mid week
with highs reaching the low to mid 90s each day combined with
dewpoints in the 70s. Chances of diurnal thunderstorms will also
be present each day. More organized chances of thunderstorm
activity could develop during midweek as a front associated with
an upper trough developing over the Eastern Plains pushes into the
area as the trough digs east towards the east coast.

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       91  74  93  75 /  35  12  32   7
Meridian      92  73  93  73 /  18   9  20   6
Vicksburg     91  75  94  75 /  44  20  27   9
Hattiesburg   92  74  93  74 /  41  20  30   9
Natchez       89  75  92  74 /  45  20  39  13
Greenville    91  74  92  75 /  17  10  25  18
Greenwood     91  73  92  75 /  10   7  25  17

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.

&&


$$

12



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