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Area forecast discussion 
National Weather Service Jackson MS
336 am CDT Sat Aug 30 2014

Short term...active weather day on tap as highly moist airmass will
fuel rain showers/thunderstorms and rain today as a disturbance lifts northward out of the
norther Gulf and S-central sections of la. Recent days we have been
advertising the potential for locally heavy rainfall and some
potential for flash flooding. This risk still exists as efficient
rains will be possible as forcing for ascent will make the most of
the 2.2-2.4 in precipitable water airmass. However...an additional threat for gusty
and possibly damaging winds exists as well. The reason for this new
threat resides in the increased flow between the 2-12 kft layer.
Nearly all guidance indicates this layer will contain 30-40 kts of
flow. While heating today will be limited and the thermodynamic
profile will be quite tame...mid/upper 80s degree temperatures will support
SBCAPE near 2000 j/kg and this will be more than enough energy to
support deep convection (esp with the disturbance providing strong
forcing). Furthermore...organizing convection will be able to
utilize the increased flow to organize cold pools. If any cold pool
organizes in a fashion where it moves in tandem with the flow below
12kft (which looks to be in a north-northeast direction) bowing segments will be
possible and likely efficiently bring down the stronger winds aloft. In
turn...this will increase the wind damage potential. It is also Worth
noting that the increased flow will also increase the low level
helicity to values that could support a brief tornado. While this is
not a primary threat...it can't be ruled out. Due to added
risks...will introduce a limited severe risk for damaging winds. As for
a location...most of the area will have a risk...the exceptions look
to the be the far SW and the I-59 corridor. Best timing would be from
11am to 5pm. The severe weather potential statement/graphics will highlight the timing and threat
area.

As for other forecast elements (pops and weather)...guidance probability of precipitation
were higher from the previous runs and I followed those high values and
increased some locations to stay in line with previous forecasts. The
main timing for this activity was adjusted...the SW looks to be the
area that gets it first and earliest with the remainder of the area
sometime between late morning and late afternoon. For this
eve/overnight...much more of tricky forecast exists for tonight. It
seems like there will be a lull period from late afternoon into most
of the evening...then activity could pick up after midnight over the northwest/north
areas. The S half looks to see less activity than previous expected as
drier air moves northward in the wake of the main shortwave.

Sunday looks to be less active as well thanks to the drier air
moving up from the S/southeast around the evolving ridge. Still...enough
moisture will exist for some isolated/scattered activity. The GFS was really low
with probability of precipitation and I used a blend of the GFS/Euro for the pop forecast.
With less precipitation around...look for warmer temperatures (90-95). /Cme/

Long term...Monday through next Saturday

Near to slightly above normal temperatures in the low to middle 90s and
typical 20-30% afternoon chances of showers/storms through most of
the week as a high pressure ridge builds over the southeast/central Continental U.S..

The current system responsible for elevated rain chances this
weekend will pull off to the NE by Labor Day and a subtropical 700 mb-500 mb
ridge looks to build in from the Atlantic while the northern stream flow
becomes mostly zonal. Despite low-level high pressure axis and slowly
building height influence over region most of the week, precipitable waters will
remain elevated /near 2"/ and combined with daily afternoon
instability /2000 j/kg+/, isolated/scattered showers/storms will be
likely. Overall coverage wont be great but feel best coverage will
be in S/se/E where sea-breeze convergence and highest precipitable waters will
exist. Heat indices Monday and Tuesday should reach into the low
100s for a few hours with lows only falling into the low to middle 70s
through much of the week.

On Tuesday, a slightly stronger shortwave trough across the corn belt
will attempt to bring a boundary south towards the region but feel
it stay north and thus kept probability of precipitation/showers out of forecast for
northern areas. For Wednesday through Friday, ridging will remain
over area and strengthen slightly but sea-breeze initiated and
diurnal activity should continue to be a good possibility each day.
By Saturday, the ridging slips farther west and places region in
slightly greater north/NE flow that could enhance shower coverage
possibilities. /Allen/

&&

Aviation...look for ceilings to trend downward to MVFR with a site
or two seeing IFR for a period. There will also be precipitation moving
northward which will serve to keep ceilings in the MVFR category
while also lowering visible at times. The main precipitation will exist between
14-21z for the taf sites and I will focus the worst conditions then.
There will also be the risk for gusty winds with some stronger
storms. After that...improvements will occur...but not last too
long. Look for a trend back to MVFR/IFR ceilings toward the last
quarter of the taf period. /Cme/

&&

Preliminary point temps/pops...
Jackson 88 73 93 74 / 87 37 22 7
Meridian 90 72 93 72 / 71 27 19 7
Vicksburg 85 73 92 72 / 96 40 25 7
Hattiesburg 91 75 96 74 / 74 19 12 13
Natchez 85 73 92 74 / 92 30 18 12
Greenville 84 73 91 73 / 98 60 39 6
Greenwood 86 74 92 73 / 96 58 39 6

&&

Jan watches/warnings/advisories...
MS...none.
La...none.
Arkansas...none.
&&

$$

Cme/Allen/

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