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Area forecast discussion 
National Weather Service Jackson MS
405 am CDT Wednesday Aug 20 2014

Short through Thursday night...trending warmer with
lower rain chances through the short term and afternoon heat index
values becoming the main concern. Early morning surface analysis had
a 1017mb ridge nosing west across the northern Gulf from the western
Atlantic Ocean. The resulting low level southerly flow has helped
maintain a rather moist airmass over our area with precipitable waters of two inches
and surface dew points in the lower 70s. Early morning water vapor
imagery/RUC analysis showed the circulation around a middle level
trough over the Great Lakes and middle Mississippi Valley region and
the circulation around the middle level ridge over the northern Gulf.
The middle level trough will shift east while the middle level ridge over
the northern Gulf strengthens and becomes centered over our area by
Thursday evening. Middle level heights are prognosticated to increase from
590dam this morning to 595dam by Thursday evening. This will help
strengthen the surface high that looks to remain centered just south
of our County Warning Area through Thursday. Normal afternoon highs are around 92f
and temperatures will top out warmer than normal this afternoon and
again Thursday afternoon. Gfsmos guidance was a little too warm and
leaned toward a blend of the NAM and European model (ecmwf) MOS guidance for
afternoon highs each day. This will result result in middle 90s at most
sites this afternoon and a degree or two warmer Thursday afternoon.
The heat and humidity will combine to result in maximum heat index
values of 100-103 today and 101-104 Thursday. Models still suggest
isolated afternoon storms will be possible along the Highway 84
corridor this afternoon and in the southwest Thursday afternoon but
rain chances will remain very low elsewhere through the period. /22/

Long term...Friday through Wednesday...the main story for much of
the long term will be the building heat and humidity. The weather
pattern we have seen a good bit this Summer of a trough over the
east and ridge over the west will be reversed for a few days.
Conditions will feel a bit more like a true deep south Summer as a
593dm ridge will set up right over the arklamiss region. This will
allow for temperatures to heat up for the first real time this
Summer with highs reaching into the middle and upper 90s. That...
coupled with dewpoints in the 70s...will allow heat indices to be a
concern through the weekend. It could be possible that dewpoints
will mix out just enough to keep heat index readings a little more
in check. However...the current forecast looks like with those 70s
dewpoints we could see heat indices nearing 105 degrees areawide and
some locations could see slightly higher than this. Overnight lows
should cool enough to preclude the need for a heat advisory. Mex
guidance continues to come in warmer than the other temperature
guidance and have cut highs during this hot stretch by 1-2
degrees...closer to ensemble guidance and the European model (ecmwf). In addition to
the heat...this ridge will keep convection at Bay during this time.

By the beginning of next work week...the center of the ridge will
move north of the region and heights will be slightly lower. This
may allow for some afternoon showers and storms to develop...
especially in the east on Monday and across the south and west on
Tuesday. By Wednesday the region will be sandwiched between the
departing/weakening ridge to the east and an approaching front to
the northwest. This will increase rain chances for the entire area
on Wednesday and keep temperatures cooler in the lower 90s along
with considerable cloud cover.

Further into the extended forecast...the tropics are being monitored
for possible development over the next several days. NHC has a
medium chance of development on an area of low pressure located
several hundred miles east of the southern Windward Islands. The GFS
continues to be the most aggressive in bringing this system as a
very developed tropical cyclone into the Gulf at 240 hours. The
European model (ecmwf) this morning does show this system entering the Gulf as well
before getting swept up with the approaching front. This scenario is
beyond 200 hours and is way too early to make any conjectures yet as
to what will happen...especially considering the system has not
developed yet. We will definitely continue to monitor latest model
trends and forecasts from NHC. /28/


Aviation...satellite imagery only showed a few thin high clouds
over the area and all taf sites were observing VFR conds at 09z. A
brief period of MVFR visibilities will be possible from 10-13z but VFR conds are
expected to prevail through this evening. The exception could be hbg
as isolated thunderstorms will be possible this afternoon along the Highway 84 corridor. S-SW
winds less than 7kts are expected today and tonight. /22/


Preliminary point temps/pops...
Jackson 95 73 97 74 / 8 5 6 5
Meridian 95 71 97 72 / 12 5 5 5
Vicksburg 95 72 96 72 / 8 5 6 5
Hattiesburg 96 75 97 74 / 18 5 12 5
Natchez 94 73 95 74 / 16 5 14 5
Greenville 95 74 96 74 / 6 5 5 5
Greenwood 95 73 96 73 / 6 5 5 5


Jan watches/warnings/advisories...



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