Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 260211 AAA

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
911 PM CDT Fri May 25 2018


Updated for evening discussion.



Evening update discussion:

Most of the previous shower and thunderstorm activity across
central and eastern Mississippi is in the process of diminishing,
or has already disappeared at this point in time. Convection
through the afternoon in these areas was widespread enough to
effectively use up most of the low level instability. However, in
western zones there are still active showers and storms pushing
east toward the MS River, mainly because convection in those areas
waited until later in the day to initialize. Of course our region
remains underneath a modest trough aloft and this feature is
providing a little synoptic lift to aid in convection lingering,
despite relatively weak instability. The presence of this trough
will also keep the potential for at least isolated showers and a
few storms popping up again in even central and eastern zones
later tonight, although significant convection and/or hazardous
weather is not anticipated. Otherwise, I dropped low temperatures
a touch in most areas given the rain-cooling taking place in
widespread fashion since this afternoon. Patches of fog and low
clouds will be possible late tonight through daybreak Saturday in
areas that manage to clear out decently after midnight. Since
confidence is not at all good on where this clearing might
manifest, we will hold off on hitting fog hard yet in the HWO or
official forecast. /BB/

Prior discussion below:

Rest of today through tomorrow: Weak upper-level troughing and
cyclonic flow remain over the region with subtle upper-level
divergence from a weak jet. The troughing working in combination
with daytime heating in a moist environment has resulted in
multiple clusters of thunderstorms across the area this afternoon.
A few of these storms have become strong to severe, especially
where storms/outflow boundaries have merged. There are two main
areas of convection that will be the main focus through the
evening hours - 1) the ongoing storms and outflow moving southeast
towards the Jackson metro, and 2) a cluster of storms and outflow
moving north from the Gulf Coast in association with the sea
breeze. Storms will be likely through early evening along and
ahead of these two areas. A few strong to possibly severe storms
will remain possible, primarily where storms/outflow boundaries
merge. Locally heavy rainfall and flash flooding remain possible
over the southeast, especially where these aforementioned outflow
boundaries merge and enhance the moisture convergence within an
already saturated environment with PWATs near 2". As such, the
ongoing limited risk for flash flooding remains well placed for
now. For tonight, expect this activity to wane with loss of
daytime heating, however a few showers and perhaps a storm could
linger overnight. Some patchy fog will be possible for any
locations that see rain, especially over the southeast.

For tomorrow, expect another round of numerous diurnally driven
showers and storms to develop by the mid to late morning hours and
persisting through the day. The thermodynamic environment will be
somewhat better over the Delta where lapse rates will steepen to 6-
6.5 C/km. The greatest threat for strong to isolated severe storms
with microbursts will be located here, however strong storms cannot
be ruled out where storms/outflow boundaries merge. In addition,
locally heavy rainfall could also result in isolated flash flooding.
Given uncertainty regarding the areal coverage of both threats will
hold off on mentioning severe of flooding potential in the
HWO/graphics and will wait for further analysis. /TW/

Saturday night through Friday: Main focus in the long term will be
dictated by the eventual track, speed and intensity of now
Tropical Storm Alberto which at last Advisory was meandering over
the northwestern Caribbean Sea. Currently, the most likely
arrival time of any tropical storm force winds over our CWA is
Monday along with flooding potential across our Southeast. Current
thinking suggests four to seven inches of rain will be possible
especially along the Interstate 59 corridor. There will likely be
quite a qpf gradient across the western portions of our CWA that
stands to see the least amount of rainfall through the forecast
period. In addition, the warmest temperatures are expected over
the western portions of our CWA through the period as well.
Alberto looks to shift east of our CWA during the day Wednesday
followed by mid level ridging from the southwest. A disturbance
is expected to drop southeast around the top of the mid level
ridge Wednesday night and across northeast Mississippi Thursday. A
few storms may drop south across our northeast zones during this
timeframe but much of the area will return to warm and drier
conditions. /22/


00Z TAF discussion:

Showers and thunderstorms got an earlier start today than
yesterday, and thus will be coming to an end earlier this evening
in most areas than was also the case yesterday. Highest potential
for inclement conditions this evening on station will be around
GTR/CBM where thunderstorms could briefly lower flight cats to
IFR and surface winds will be a little gusty and erratic.
Otherwise, some lingering showers, rumbles of thunder, and
potential for brief MVFR conditions will be found at
GLH/GWO/NMM/MEI. Locations that have mid to high layer clouds
clear out tonight could experience some low clouds and fog come
daybreak Saturday. Right now this looks more likely in eastern
MS...but it is also not out of the realm of possibility elsewhere.
Unfortunately, a repeat of scattered to numerous (mainly
afternoon) thunderstorms are on the docket for tomorrow with
surface winds away from thunderstorms mainly light and from the
south. /BB/


Jackson       67  86  69  85 /  21  64  42  22
Meridian      68  86  67  84 /  35  67  49  47
Vicksburg     69  88  68  88 /  45  66  29  34
Hattiesburg   67  87  68  83 /  19  68  50  66
Natchez       68  88  68  87 /  45  66  32  31
Greenville    68  88  70  88 /  31  61  25  38
Greenwood     68  86  69  87 /  22  65  29  35





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