Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 221430 AAB
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
930 AM CDT Tue Aug 22 2017

.UPDATE...
Updated for morning discussion.

&&

.DISCUSSION...
Most of the area is off to a mostly sunny start today, save for
portions of East MS where patches of stratus clouds linger. The
nearest rain is still off the Gulf Coast at this time. Heading
through today, it appears the best rain chances will be during the
afternoon with seabreeze activity across the south and with a
weak disturbance across the northeast/east portion of the area.
Made some tweaks to POPs/Wx to reflect this thinking and to remove
mention of morning fog. No other significant adjustments are
planned for the forecast at this time. /DL/

Prior discussion below:

Today and Tonight: Mid level troughiness over the mid MS and OH
river valleys along with TUTT low over the western Gulf of Mexico
will join forces to create a weakness in the mid level ridge
positioned over the forecast area. This will result in better
convective coverage than yesterday, especially over the south
where 2+ inch PWs exist. Locally heavy rainfall will be possible
with the southern storms as light and variable 0-3km bulk shear
vectors will result in slow storm movements. Will not mention
flash flood potential in the HWO for the moment as convective
coverage will be too limited.

More cloud cover and convection will help keep maximums a little
lower over the area compared to yesterday, but mid 70s dewpoints
in the ArkLaMiss Delta region will still allow heat indices to
briefly push 105 there.

For the most part, convection will wind down during the early
evening. However, an approaching cold front will be close enough
after midnight for some scattered thunderstorms over the far
northwest.

Wednesday through next Tuesday morning: Overall a cold front will
bring increasing chances of convection mid-week before some drier
air & more seasonable conditions move in the wake through the
week. By early next week, remnants of a slow-moving tropical
system over the western Gulf could potentially bring some heavy
rain & flash flooding potential & more inclement weather.

As a deep upper trough & cold front move through eastern Canada &
the northeastern states, this front will be draped down into our
area (northern Mississippi) by Wednesday morning. Upper ridging will
be gradually weakening its grip on the region as heights begin to
fall. This will help more widespread chances of convection move in
the Delta by Wednesday morning & gradually spreading east-southeast
through the mid-morning & into the afternoon. Best forcing still be
off to our east-northeast but overall there should be enough
moisture & lift aloft to help widespread showers & storms to be
possible. With nearly 2 inch PWs can`t rule out some quick & heavy
downpours & some light Corfidi vectors (5-10kts) indicate any
training storms could produce heavy downpours. In addition, there
will be some warming ahead of the front & destabilization/vertical
totals (even with modifying some forecast soundings) for some
potentially a few stronger storms. However, higher moisture, weaker
vertical lapse rates & light flow should preclude much in the way of
stronger storms. With increasing rain chances, temperatures will be
cooler than normal in the north.

Strong ridging will help build in drier air in the wake of the cold
front, with PWs falling less than an inch & a half to near an inch
in the Highway 82 corridor while better moisture will reside to the
south closer to the front, mainly along & south of the I-20
corridor. Dewpoints will fall into the low 60s to possibly upper 50s
in the Delta to Highway 82 corridor (global models show this idea).
This drying & cooler thermal profiles will lead to more seasonable
temperatures through the weekend, with some cool night time lows
even into the mid-upper 60s. Rain & storm chances will become more
confined to the front, which will gradually stall to our south over
the northern Gulf by late week & into the weekend. Remnants of
Harvey look to also bring an interesting possible scenario by late
weekend but mainly into next week. By Thursday & into the weekend,
the cold front will be moving off the Gulf Coast. This will open
help block our area (for now) of any impacts, while models
(GFS/Euro/Canadian) have shifted remnants of Harvey to the north-
northwest near the Texas coastline by late week into weekend. This
system looks to stall over Texas & slowly lift up northeast. Models
seem to indicate this will phase & get pulled up into our area by
late weekend but likely into early next week. Due to very slow
movement and 2.25-2.5 inch PWs & slow movement, torrential rainfall
looks probable as it slowly drifts northeast. Models are already
hitting hard on QPF with 10-15+ inch amounts over Texas & spreading
northeast towards our area. This is far out but will have to be
monitored because as it phases, GFS & Euro paint a definite flash
flooding possibility by early next week (Monday-Wednesday
timeframe). In addition, shear profiles look decent for some
potential for severe weather. With phasing & timing issues uncertain
& how much development occurs, this will not be mentioned in the
HWO/graphics. However, if this trend continues, will likely be
needed in later packages. /DC/

&&

.AVIATION...
12Z TAF discussion:
MVFR visibilities will be possible in fog through mid morning,
otherwise VFR conditions will prevail. Isolated thunderstorms will
dot the landscape this afternoon and briefly lower ceilings and
visibilities at impacted TAF locations./26/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       93  74  90  72 /  18  14  60  38
Meridian      91  74  90  72 /  31  17  62  39
Vicksburg     93  73  90  71 /  15   8  52  36
Hattiesburg   91  73  91  75 /  22  18  55  43
Natchez       90  73  89  74 /  18  12  51  38
Greenville    94  74  87  66 /  11  18  57  33
Greenwood     93  74  87  67 /  17  13  61  35

&&

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

&&


$$

DL/26/DC



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