Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 171112
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
612 AM CDT Thu Aug 17 2017

.UPDATE...
Updated for 12Z aviation discussion

&&

.AVIATION...
12Z TAF discussion:
A few areas of LIFR/IFR category stratus will lift later this
morning with VFR conditions prevailing at most sites by afternoon.
The exception will be with scattered TSRA that develop with
heating of the day mainly this afternoon...these could result in
temporary visibility/ceiling reductions. /EC/

&&

.DISCUSSION...

Today through tonight:

The weather pattern remains hot and especially humid over the
ArkLaMiss today and have continued the heat advisory which was
already in effect for much of western and central portions of the
forecast area until this evening. Dry bulb temperatures continue
to be very ordinary for mid August with forecast highs even
slightly below normal in some cases, but dewpoint temperatures in
the mid to upper 70s continue to be the largest factor in the
dangerous heat stress levels. With that said, there are some
questions about convective evolution today, and this may have a
lot to say concerning just how high the heat indices will get. If
the current convective system moving through the ArkLaTex region
is able to reach the MS River and make it through the Delta region
before noon as suggested by recent HRRR runs, then heating could
be disrupted before heat indices can rise above 105.

There is considerable low to mid level south to southwesterly
flow by mid August standards supporting some storm organization
and progression of any convective systems approaching from the
west, but a ribbon of drier mid/upper level air with precipitable
water well under two inches is over much of the ArkLaMiss this
morning, and as the previously mentioned MCS approaches later this
morning, it may tend to diminish with much of eastern MS not
receiving much in the way of rainfall. Storms would have the
potential to produce strong wind gusts given favorable directional
shear this afternoon. As we move into the evening, expect deep
convection to diminish with another warm and muggy overnight
expected. /EC/

Friday through next Thursday...

Continuing days of heat stress and thunderstorm chances will be
the story of this period as PWats remain between 1.75"-2.25" and
850 temps hold steady between 19-21 deg C. On Friday, a weak
boundary associated with an upper trough pushing off the eastern
seaboard will provide enough lift to the region to result in some
scattered thunderstorm activity mainly along and south of the I-20
corridor. A warm airmass will be in place over the ArkLaMiss with
850 temps approaching 20 deg C. Sites that aren`t impacted by
thunderstorm activity could see heat index values rise to around
105 degrees, causing heat stress.

Midlevel ridging will begin to take place on Saturday as an upper
level trough swings through the upper MS Valley. A disturbance
embedded within this upper flow pattern will result in increased
thunderstorm chances during the day on Saturday. Near to slightly
above normal temperatures on Saturday will combine with dewpoints
in the mid to upper 70`s to once again increase heat stress in
areas not affected by thunderstorm activity. Sunday could be the
warmest day of the period as upper level heights begin to
increase and convection becomes more diurnally driven. This
pattern will remain in place through at least Tuesday. On
Wednesday, a building ridge in the west and falling heights in the
east will result in NW flow aloft for the region. Disturbances
embedded in this NW flow pattern could result in more organized
thunderstorm chances for the region from Wednesday through the end
of next week. /JPM3/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       92  75  92  75 /  21  24  47  10
Meridian      92  75  91  74 /  20  17  48   9
Vicksburg     92  76  92  75 /  40  25  47  13
Hattiesburg   93  75  92  75 /  20   8  47  18
Natchez       90  74  92  75 /  28  18  41  11
Greenville    90  74  93  74 /  51  28  28  18
Greenwood     90  74  91  73 /  51  38  30  16

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Heat Advisory from 9 AM this morning to 7 PM CDT this evening
     for MSZ018-019-025-027-034>036-040>043-047>049-053>055-
     059>062.

LA...Heat Advisory from 9 AM this morning to 7 PM CDT this evening
     for LAZ007>009-015-016-023>026.

AR...Heat Advisory from 9 AM this morning to 7 PM CDT this evening
     for ARZ074-075.


&&


$$



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