368
FXUS64 KJAN 250355 AAA
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
955 PM CST Sun Nov 24 2024

...New MESOSCALE UPDATE, AVIATION...

.MESOSCALE UPDATE...
Issued at 954 PM CST Sun Nov 24 2024

Rest of tonight...

Warm, moist southerly flow will keep a warmer night in store for
the Gulf Coast region. Low level flow is on the uptick, with
nearly 20kts at 925mb. HRRR fcst soundings around daybreak Monday
indicate an uptick in low-level moist advection, indicative of
saturation of the boundary layer & light sfc flow, while stronger
to the west. HREF probs of 40-60% indicate potential for lows
reaching near or even super-saturation. HREF/HRRR & other
aviation guidance indicate river valley fog formation. Radiative
cooling will be efficient, with HREF probs sfc dewpoints (Td)
above 60F & lows falling below that threshold, some 4-6F below
(53-55F). This could support at least some patchy to at times
patchy dense fog. Forecast was mostly on track, other than to add
some patchy dense fog & HWO graphic for late tonight into early
Monday morning. Lows will be seasonably warm (10-20F above) in
the mid-upper 50s (56-60F) west of I-55 & low-mid 50s (50-55F) to
the east. Updates are out. /DC/

&&

.DISCUSSION...
Issued at 252 PM CST Sun Nov 24 2024

Through Tonight:

Warm, moist return flow on the backside of departing surface high
is evident in afternoon cumulus field spreading north and east
across portions of LA and far southern MS this afternoon. The
returning moisture will boost overnight humidity levels and could
be a concern for patchy fog especially where winds go light to
calm by early Monday morning. Latest HREF probabilities for fog
development favored the Pine Belt and areas northward into east
central Mississippi, where currently clear skies would support the
best potential for radiational cooling and moisture advection to
overlap. Added patchy fog wording to the river valley areas east
of Interstate 55 overnight, but may have to upgrade fog messaging
if confidence in dense fog increases.

Monday through Sunday:

An upper-level short-wave trough moving east from the Plains on
Monday will bring the next cold front into our area late Monday
afternoon into the overnight, though moisture return should be
minimal enough to limit thunderstorm potential. Can`t rule out a
few rumbles of thunder overnight with weak elevated instability,
but mostly a mundane frontal passage is expected.

What will have more significance is the next shortwave crossing
the Rockies Wednesday into Thursday. This wave should spin up a
low pressure system in the Southern High Plains that quickly moves
east along the Interstate 40 corridor, with more moisture
recovery and warming occurring over our area in advance of its
arrival. Latest model guidance remains in poor agreement with the
timing of this low-amplitude wave, but a corridor of warm, moist
advection along the Mississippi River Valley will increase
instability Wednesday into Thursday regardless. While the wave
will be positively-tilted and low-level flow will become more
south-southwesterly ahead of the approaching system`s cold front,
a strengthening upper-level jet streak associated with the system
will intersect the developing warm sector along the Gulf Coast.
Modest wind shear and decent instability will likely support at
least a Marginal chance for severe thunderstorms as the system
moves through our area late Wednesday into Thursday. This does
include the Thanksgiving Holiday, so area residents and visitors
should pay attention to changes in the forecast and updates to
timing for best thunderstorm chances.

Potentially stronger high pressure arriving behind the cold front
should give us another chance for frost and freeze conditions
heading into next weekend. While there is less confidence than
usual for the Wednesday/Thursday pattern, more substantial
disagreements with trajectory and strength of arctic air mass
coming south out of Canada introduces even more uncertainties for
our region next weekend. Peaking a little ahead into early the
following week, this signal for potentially cold air mass
affecting the region persists for a few days. Will keep an eye on
the trends regarding freeze potential in the region. /NF/

&&

.AVIATION...
(06Z TAFS)
Issued at 954 PM CST Sun Nov 24 2024

VFR flight categories prevail, with sfc winds winding into the
evening. Southerly sfc winds will linger at northwest sites of GLH
& GWO while light in southeast MS TAF sites (I-59 & Hwy 84
corridors). In addition, low-level wind shear (LLWS) >30kts can`t
be ruled out at GLH & GWO, persisting through daybreak. Light
winds & moisture advection, especially nearby river valley
corridors, could lead to some MVFR patchy to areas of fog/BR to
even locally patchy dense fog. Can`t rule out brief sub IFR vsby
or stratus/ceiling near daybreak. These flight restrictions last
through mid-morning 25/14-16Z Monday. Southwesterly sfc winds
will be predominant after 25/15-17Z Monday, sustained up to 20mph
& gusts around 25mph. Low probs of light rain showers will build
in northwest TAF sites near the end of the 06Z TAF period, so
added some showers after 26/03Z Tuesday. /DC/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       56  78  52  65 /   0  10  80  10
Meridian      52  75  52  64 /   0   0  60  10
Vicksburg     58  80  49  64 /   0  10  50   0
Hattiesburg   53  79  58  69 /   0   0  50  10
Natchez       58  79  53  65 /   0  10  40   0
Greenville    58  77  44  59 /   0  20  40   0
Greenwood     57  77  46  62 /   0  20  60   0

&&

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

$$

DC/NF/DC