Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 211156 AAA
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
656 AM CDT Mon Oct 21 2019

...SEVERE THUNDERSTORMS POSSIBLE ACROSS THE FORECAST AREA TODAY...

.UPDATE...
Updated for 12Z aviation discussion

&&

.AVIATION...
12Z TAF discussion:
Conditions will vary over the next several hours with LIFR cigs in
the northeast and east, IFR-MVFR cigs in cntrl MS and VFR in the
south. Generally, MVFR conditions will prevail today as light
showers develop ahead of a line of thunderstorms nearing GLH at
1130Z. The line of thunderstorms was ahead of an approaching cold
front that will move across the area today. After the fronts pass,
expect a shift to westerly and then northwesterly winds. MVFR
ceilings and possibly some continued -RA will prevail until drier
air arrives and ceilings begin to clear tonight. /22/NF/

&&

.DISCUSSION...

Today through Tonight:

The primary concern in the short term remains the possibility for
severe weather in our forecast area this morning through this
afternoon. Early this morning, a mostly continuous line of strong
to severe thunderstorms had developed along a cold front that
extended from southeastern Missouri southwest toward east Texas.
This front is associated with a deepening low pressure system over
the Plains states, and should have enough push to be east of our
forecast area by around midnight tonight.

As the front continues to advance east this morning, the ongoing
storms will encounter a strongly sheared, but weakly to moderately
unstable environment. Deep layer shear vectors of 35-50 kts would
support isolated supercells ahead of the line or embedded
supercell structures in the line. Increasing helicity ahead of the
storms and strong low-level shear vectors oriented across bowing
segments of the line will support a damaging wind threat and
isolated tornado threat, but weak lapse rates aloft will limit any
hail threat. There is one big potential limiting factor for
severe weather potential in our forecast area specifically,
though. A separate convective system has developed off the coast
of TX this overnight, and the various hi-res and global model
guidance suggest this activity may disrupt the destabilization
process ahead of the advancing cold front. In fact, the SREF and
HREF ensembles show a decrease in severe parameters farther east
toward central and eastern/northeastern Mississippi by the late
morning and afternoon hours today, and a restriction of the best
parameter space toward the Gulf Coast and southern/southeastern MS
for the afternoon hours. We will expand the "Slight" risk for
severe weather to cover some of our southeastern MS counties
through the Pine Belt to account for some of the coastal system
threat, but will hold off on expanding the Slight risk to
northeastern parts of the state where the situation is a little
murkier.

By late this afternoon and early evening, the convection looks
like it should outrun the cold front and taper off by around
sunset. The final wind shift and arrival of the cold front proper
will be to the Mississippi River by around that time and clear
easter Mississippi by midnight. Low temperatures in the mid 40s to
mid 50s will settle in by tomorrow morning, with a light breeze
expected to keep temperatures from plummeting too quickly in the
wake of the front tonight. /NF/

Tuesday through Sunday:

Cooler and drier Tuesday into Thursday before rain returns
areawide Thursday night. Wet weather looks to linger into the
weekend.

Come Tuesday morning the cold front and associated rain will be
well south of the CWA. Our CWA will still be at the base of a
large upper level trough with a nearly stacked low centered over
the Great Lakes region. This will maintain the flow of cooler and
drier air into our region through the day. The nearly stacked low
will lift north into Canada by evening as a >1022mb surface high
becomes centered over our CWA. This will setup a night of strong
radiational cooling and one of the coldest mornings of the
forecast period. Morning lows Wednesday are expected to be in the
low to mid 40s at most locations. Normal lows run in the lower
50s. The surface high will continue shifting east Wednesday while
upper level troughing deepens over the Northern and Central
Plains. The Canadian and ECMWF are similar in closing off a low
near the Four Corners region by Thursday morning while the GFS
maintains an open trough. The more progressive GFS brings rain
back into our CWA faster Thursday afternoon but model consensus
suggests rain chances will increase arewide Thursday night into
Friday as this low pressure system approaches our CWA. The GFS
dries us out Friday night but have leaned toward the slower
ECMWF/Canadian blend which moves the closed low across the mid
Mississippi valley Sunday maintaining rain chances across our area
until Sunday evening. Cooler than normal temperatures are
expected much of the forecast period but daytime highs are
expected to be near normal in the lower 70s Wednesday and Thursday
before cloud cover and rain chances hold temperatures in the 60s
again going into the weekend. /22/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       76  50  71  44 / 100  44   1   0
Meridian      77  53  73  42 /  81  68   3   0
Vicksburg     75  49  72  45 / 100  14   0   0
Hattiesburg   79  55  72  46 /  81  60   4   0
Natchez       76  51  72  45 / 100  22   1   0
Greenville    71  48  69  44 /  98  11   0   0
Greenwood     72  47  69  42 / 100  17   0   0

&&

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

&&


$$

NF/22


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