227
FXUS64 KJAN 231120 AAA
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
620 AM CDT Sun Jun 23 2024

...New AVIATION...

.DISCUSSION...
Issued at 303 AM CDT Sun Jun 23 2024

Today and Tonight...High pressure aloft will overall remain in
control of the weather across the region through much of the period.
While this high aloft drifts further west of the region, northwest
flow aloft will setup across the forecast area.  Meanwhile at the
surface, south to southwest flow across the region will result in
increasing moisture and heat across the CWA today.

With the mid/upper level high center drifting further west
overnight, its weakening presence over the region will allow a weak
frontal boundary to sink south into the forecast area around day
break Monday.  This will also allow for some isolated showers to dot
skies over far northern portions of the CWA at the end of the period
early Monday morning.  Otherwise, with increasing clouds overnight
into Monday morning, expect mild lows as they range from the mid 70s
to around 80.

The bigger story during the period will be the increasing heat
stress across the region this afternoon. As eluded to above,
moisture will be on the increase across the area today, especially
across western portions of the CWA where dew points will reside in
the low and middle 70s as highs climb into the upper 90s.  This
level of heat and humidity will result in afternoon heat index
values between 105-110 degrees.  As a result, the "Heat Advisory"
that was initially in effect for northwest portions of the Delta,
will be expanded to cover portions of West Mississippi and all of
our Northeast Louisiana parishes.  Elsewhere, the combination of
highs in the mid and upper 90s and dew points in the mid 60s to
around 70 will yield heat index values near 105. /19/

Monday and Tuesday: With generally southerly low level flow,
moisture will continue to increase across the area Monday.
Meanwhile, with the mid/upper ridge retracting westward, a weak
surface front will slip into northeast MS, stalling through the day.
Isolated showers will be possible ahead of this feature as early as
Monday morning, with greater coverage possible by afternoon with the
aid of daytime heating. It is possible slightly drier air with the
front may sneak into the Golden Triangle, but most areas will see
dewpoints in the 70s through the day. A similar regime will prevail
Tuesday, with rain chances mainly following driven by diurnal
instability, though stray showers couldn`t be ruled out any time of
day given the abundantly moist airmass. Outside of the rain and
clouds, it will be very hot with temps in the upper 90s to around
100 each day. Unfortunately, with the humid conditions expected,
this will result in heat indices meeting or exceeding critical
thresholds in most areas. It is likely the Heat Advisory will need
to be expanded both in time and area for Monday and Tuesday.

Wednesday and Thursday: With the upper ridge temporarily retreating,
there will be perturbed NW flow aloft, which along with PW
surpassing 2 inches at times, will provide the ingredients for
greater coverage of convection on Wednesday into Thursday. Clouds
and rain will be more likely to limit daytime temperatures than on
previous days, but in any areas where clouds/rain are limited, heat
stress may continue to be an issue with heat indices still
potentially reaching dangerous thresholds. Upper ridging will begin
to build eastward again on Thursday, and this will begin to limit
rain chances across AR/north LA/northwest MS.

Friday and Saturday: The upper ridge will continue to build over the
area, with temperatures trending back upward. The seasonably moist
airmass will remain, fostering mainly diurnal convection each day.
Additionally, heat stress concerns will continue to be in the
picture outside of relief from any rain. Not that there was
any doubt before, summer is here. /DL/

&&

.AVIATION...
(12Z TAFS)
Issued at 619 AM CDT Sun Jun 23 2024

VFR flight categories will prevail at area TAF sites over the
next 24 hours. Winds will increase late this morning, becoming
west southwesterly between 5-8 knots. /19/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       96  76  96  77 /   0  10  20  10
Meridian      98  75  99  74 /   0  10  20  10
Vicksburg     96  77  96  76 /   0  10  20   0
Hattiesburg   97  76  98  76 /   0   0  40  10
Natchez       95  75  96  76 /   0  10  20  10
Greenville    98  78  99  79 /   0  10  10   0
Greenwood     97  76  99  76 /  10  10  10   0

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Heat Advisory from noon today to 8 PM CDT this evening for
     MSZ018-019-025-034-035-040-041-047.

LA...Heat Advisory from noon today to 8 PM CDT this evening for
     LAZ007>009-015-016-023>026.

AR...Heat Advisory from noon today to 8 PM CDT this evening for
     ARZ074-075.

&&

$$

19