Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 211402 AAA
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
902 AM CDT Mon May 21 2018

.UPDATE...
Updated for morning discussion.

&&

.DISCUSSION...
Current forecast is still on track for a good convective coverage
for this afternoon...esp in the delta region. This should
gradually decrease for tonight as we lose daytime heating. The
latest microburst checklist showed a very limited potential for
this afternoon. Made slight adjustments to afternoon highs with
readings in the middle to upper 80s./17/

Prior discussion below:


Today and Tonight:

Although high pressure at the surface remains wedged into the
region from the east, troughing aloft will continue increasing
across the Lower Mississippi River Valley today. This, coupled
with afternoon temperatures climbing into the upper 80s and lower
90s, increasing moisture and instability across the region during
the afternoon, combined with any outflow boundaries leftover from
Sunday`s convection still meandering about, will again set the
stage for for showers and thunderstorms developing across the
forecast area during the afternoon and early evening hours.

A few strong storms, and perhaps an isolated storm reaching severe
limits, cannot be ruled out today.  Gusty winds will be the primary
concern with such storms.  Frequent lightning is expected as well.
Also, due to weak flow across the region, convection will be slow-
moving and could produce some heavy rainfall rates as precipitable
H2O values sit around 1.75 inches.  This could result in the ponding
of water on roads and in low-lying, poor drainage areas.  If
multiple slow-moving storms repeatedly move across the same locales,
some localized flash flooding will likewise be possible.

Again convection will likely linger a few hours into the tonight
period.  However, it should gradually dissipate during this time due
to the loss of heating.  With partly cloudy skies expected tonight,
lows will continue to be mild and only fall into the upper 60s to
lower 70s. /19/

Tuesday through next Sunday:

A chaotic upper level pattern typical of late May will continue
to evolve mid/late this week bringing more active weather to the
ArkLaMiss. Expect complex interactions between the ridge over the
Gulf coastal states and weak cold core upper low over the eastern
Gulf of Mexico, but global models show that the upper trough will
become the more dominant feature this weekend as it becomes more
connected to the westerlies and develops generally northward
toward the lower MS Valley region. It should be noted that a
substantial portion of the guidance spectrum, including the ECMWF
and several GEFS members, signal for warming aloft and surface
reflection suggesting some transition to a more tropical-like
feature by the end of the week over northern portions of the GOM.

In terms of sensible weather for the ArkLaMiss, the result will be a
continued active convective pattern as very warm and humid low level
air combines with conditionally unstable air aloft to create a
favorable environment for mainly afternoon/evening shower/
thunderstorm activity. Convective precipitation could be
more organized with greater coverage this weekend due to greater
influence from the upper low, which may also keep high
temperatures slightly lower. The threat for a few strong storms
and locally heavy rainfall, as has been the case in recent days,
will likely continue. /EC/

&&

.AVIATION...
12Z TAF discussion:
A mix of MVFR/VFR categories are being observed this morning,
thanks to some low stratus and patchy fog developing over portions
of East Central and Southeast Mississippi. This will erode through
the morning, with VFR flight categories expected to prevail at
sites by late morning, and continuing through the course of the
day. During the afternoon, another bout of showers and storms will
be possible across the region, lingering a few hours into
tonight. This will again bring about a brief reduction to both
ceilings and visibiltiies, thus reducing flight categories
MVFR/IFR if observed on-station. Light to calming winds this
morning, will give way to winds generally between 3-8 knots from
the east by late morning. /19/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       88  68  89  69 /  52  41  47  16
Meridian      87  68  89  67 /  45  36  47  22
Vicksburg     90  69  90  70 /  59  41  39  14
Hattiesburg   87  68  89  67 /  52  42  52  27
Natchez       89  69  89  69 /  53  38  46  17
Greenville    88  70  88  71 /  60  44  44  15
Greenwood     89  69  89  70 /  57  45  37  12

&&

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

&&


$$

17



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