743
FXUS64 KJAN 271716
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
1216 PM CDT Thu Jun 27 2024

...New AVIATION...

.MESOSCALE UPDATE...
Issued at 830 AM CDT Thu Jun 27 2024

A low pressure system is noted overhead this morning on satellite
and is promoting isolated showers across northern areas. Showers
and storms will be possible this afternoon, mainly east of I-55.
Weak lapse rates could serve as a limiting factor today, however,
heating may steepen lapse rates this afternoon. Given this,
showers and storms should taper off with waning daytime heating
this evening./SAS/

&&

.DISCUSSION...
Issued at 441 AM CDT Thu Jun 27 2024

Today through tonight...

Early this morning, water vapor/synoptic analysis indicate 595DM
500mb mean ridge persisting over the southern Plains to southwest
while shortwave trough analyzed over the Gulf Coast states remains
far south of more stout trough/jet energy across the Great Lakes.
The aforementioned shortwave is driving in some drier air, around an
inch & a half in GOES East total PWs in the extreme ArkLaMiss Delta,
with some deeper moisture closer to the shortwave trough axis. There
should be enough isentropic ascent/deformation along the back side
of the shortwave to squeeze out some additional shower & isolated
thunderstorm development into the aftn to evening hours. The best
moist convergence will be in northeast MS & spreading to the south-
southwest into the aftn to evening. Can`t rule out a stronger storm
or two due to some deep flow around 20-25kts. Developing low stratus
this morning will gradually mix out & aftn heating will be less
prevalent than previous few days. Highs will be less seasonable,
mainly in the mid-upper 80s across a majority of the area, with heat
stress less of a concern, with heat indices peaking only around the
mid 90s to around 100F. As heating wanes, convergence will not be
able to maintain convection & any lingering showers should wind down
by early evening. Lows will be seasonable in the low to mid 70s.
Some patchy fog can`t be ruled out in the Golden Triangle in
northeast MS, where HREF dense fog probs indicate some potential,
but convective allowing models & fcst soundings aren`t as bullish.
Sounding analysis indicate boundary layer mixing possible, which
could keep more stratus rather than fog concerns. /DC/

Friday...

The forecast for the extended period remains mostly on track with no
major adjustments made to the overall forecast. As we head into
Friday morning, global guidance shows a weak frontal boundary moving
southeast towards the Gulf of Mexico. By Friday afternoon, the
aforementioned boundary will remain stalled across coastal MS. This
will allow for local PWATs to exceed 2 inches. Additionally, a deep
layer ridge will build over the Lower Mississippi Valley. The
combination of increased temperatures, along with southerly moisture
flow across the region will help support sfc instability. As a
result of this, scattered to numerous showers and thunder storms
will occur across S/SE MS around this timeframe. As high pressure
ridge builds in late week, dangerous heat stress will be the primary
concern. Afternoon highs are expected to peak in the low/mid 90s
with dewpoints climbing into the mid/upper 70s. This will yield heat
indices in the 105 F - 110 F deg range. No changes have been made to
the heat graphic for Friday, and an "Elevated" heat risk remains in
place for southeast AR, northeast Louisiana and portions of
northwest, central and southern MS. Heat headlines may be needed as
we get closer.

Saturday through Thursday...

Hot temperatures will become more oppressive across our forecast
area as global guidance highlights an upper-level high amplifying
over Texas and gradually building across the Gulf Coast states into
the southeast CONUS. This will bring oppressive heat and humidity
across the area through the weekend into early next week. As we head
into the new work week, global guidance shows the high pressure
weakening, due to height falls from upper level system across the
Great Lakes to northeast states. Heat will persist from the weekend
into early next week, but increased rain and storm chances make
areal configuration more uncertain. We maintained an "Elevated" heat
in the HWO graphic Sunday and Monday, but an additional
"Significant" area in HWO graphics for excessive heat was added to
portions of the ArkLaMiss Delta in Chicot in AR southward to West-
East Carroll and Madison in LA, to along and northwest of a line
from Warren, Hinds northeast into Leflore to Grenada counties. These
areas have seen persistent excessive heat, with less rain and storm
chances Saturday before scattered to numerous coverage late weekend
into early next week. However, excessive heat could be reached prior
to convective initiation after midday, so kept it going through the
weekend and some into early next week. Expect further updates to the
heat graphics as we get closer to the weekend. Heat related
advisories and excessive heat warnings will likely be needed as we
get closer. A frontal boundary is expected to push towards the
southeast, increasing shower/thunderstorm potential Sunday afternoon
and Monday. The potential for severe weather is low around this
timeframe, but there are continued signals in CSU machine learning
probs for marginally severe storms Sunday into Monday. Rain chances
will start to increase especially for areas southeast of the Natchez
Trace into Tuesday. Isolated to scattered showers and storms will be
possible later in the week with the best rain chances across
southeast MS. /CR/DC/

&&

.AVIATION...
(18Z TAFS)
Issued at 1210 PM CDT Thu Jun 27 2024

MVFR/VFR ceilings will prevail over the next few hours. Conditions
should continue to improve as clouds scatter out. A few isolated
showers are possible, with highest likelihood at eastern sites.
Ceilings should lower again across northeastern areas early
tomorrow morning and conditions should be MVFR for a few hours.
Ceilings should improve around mid morning. Winds will prevail
from the north this afternoon, and shift east southeast tomorrow
as a low pressure system pivots across the area./SAS/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       73  91  76  93 /  10  40  10  30
Meridian      72  92  73  94 /  20  50  10  50
Vicksburg     73  93  76  94 /  10  20   0  20
Hattiesburg   74  93  76  94 /  30  70  10  60
Natchez       72  92  75  94 /  10  30   0  30
Greenville    72  94  78  96 /   0  10   0  10
Greenwood     72  92  76  95 /  10  20   0  20

&&

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

$$

DC/CR/SAS20