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Area forecast discussion 
National Weather Service Jackson MS
425 PM CDT Tuesday Aug 4 2015


Tonight through Wednesday night...

The main weather story over the arklamiss continues to be the very
hot temperatures with another day of 100+ degree f highs mainly along
the I-20 corridor. Mixing/winds have been slightly less and boundary
layer moisture slightly greater for much of the area...although
afternoon relative humidity values were still very low in the Jan-mei corridor. Deep
layer moisture has shown a slight increase as well and this has
allowed for isolated showers/thunderstorms over mainly southern/western portions of
the forecast area...but expect the activity to diminish quickly as we
approach sunset.

The trend for muggier nighttime conditions will continue with lows
expected to be a little warmer tonight. Increasing humidity will
result in increasing heat stress for Wednesday as temperatures reach
the middle/upper 90s at most locations. The arklamiss Delta Region could
see heat indices briefly reach 105 f...but a heat advisory does not
appear warranted at this time. Along with the increasing
moisture...there will be better chances for diurnal shower/thunderstorm
activity. Given very steep low level lapse rates...any storms that
develop may produce strong gusty winds. The better chance for any
organized multi-cell storms should hold off until Thursday into Friday.

Long term update: the potential for record-breaking heat is
increasing for the weekend into early next week...mostly likely to be
centered on Sunday/Monday. With both the European model (ecmwf)/GFS continuing to show
an intense low level thermal ridge over the arklamiss with h850 temperatures
in the 24-27 degree c is quite plausible that a few locations
will see surface temperatures reach the 104 to 107 degree
mark...especially in the arklamiss Delta Region. The previous long
term discussion follows. /Ec/

Thursday through Monday...models are in good agreement that Thursday
will be the "coolest" day with the greatest chance for rain of the
long term period. Sunday and Monday will be the two hottest days of
the long term. Thursday our County Warning Area will be downstream of a large 594dam
high centered over the Desert Southwest. A shortwave topping this
ridge will move from the middle Mississippi Valley across the Tennessee
Valley by Thursday evening. Convection associated with this shortwave
will spread south over our County Warning Area during the heat of the day. The
greatest probability of precipitation will be carried over the northeast half of the area
through Thursday with lowest probability of precipitation over our west. Will have a moist air
mass back over our County Warning Area with precipitable waters between 1.75-2.0 inches and surface
dew points in the low to middle 70s. Other environmental parameters
suggest a few strong storms with wind gusts of 40 to 50 miles per hour will be
possible Thursday afternoon and evening. The shortwave will shift
east of our region Thursday night but the weak surface low associated
with the shortwave will track east as well and try to drop a weak
cold front into our County Warning Area. This will help prolong low chances for rain
over our northern zones Thursday night.

The stalled front is expected to be just north of Highway 82 Friday
and serve as a focus for convection before dissipating by Friday
evening. Middle level ridging will continue to limit coverage to
isolated in the west with scattered coverage in the east. Saturday
the large middle level high will begin building east over our County Warning Area while
the surface ridge shifts from the Gulf Coast to the central Gulf.
This will result in hotter and drier conditions over our County Warning Area through
the weekend into the start of the work week.

Highs will reach or exceed 100f at most locations Sunday and Monday
with some readings near or exceeding 105f possible. The heat will
combine with high humidity to result in heat index values exceeding
105 Saturday. Even higher heat index values are expected Sunday and
Monday. A heat advisory will likely be needed this weekend for much
of the area. /22/


Aviation...expect VFR conditions to continue through tonight at all
taf sites. Not expecting any restrictions to visibility at the taf
sites early Wednesday. Expect showers and some thunderstorms to
develop across the region on Wednesday which may provide some brief
restrictions to visibility...mainly during the afternoon. The winds
will generally be light and variable tonight and light out of the
south on Wednesday. /17/


Preliminary point temps/pops...
Jackson 74 98 74 96 / 7 26 23 38
Meridian 71 96 73 94 / 5 35 29 51
Vicksburg 74 98 75 97 / 9 18 17 22
Hattiesburg 75 95 75 95 / 10 35 29 55
Natchez 75 94 76 97 / 10 23 19 21
Greenville 74 98 76 96 / 10 23 24 45
Greenwood 72 96 74 94 / 6 28 32 55


Jan watches/warnings/advisories...




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