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Area forecast discussion 
National Weather Service New Orleans la
930 am CDT Wednesday Oct 1 2014

Update...

Updated grids and zone package to increase rain chances
considerably. Areal coverage of showers and thunderstorms on the
warm front moving from southwest to northeast across the area is
much more than originally anticipated. May need a further update
to lower maximum temperatures depending on how quickly this area of
precipitation translates to the northeast. 35

&&

Previous discussion... /issued 354 am CDT Wednesday Oct 1 2014/

Short term...it was a mostly quiet day yesterday a few rain showers broke
out but overall it was dry. Things have remained quiet overnight
with temperatures generally ranging from the lower to middle 70s by 7z.

Rain looks to return today and there is some indication that there
may be some decent rain in spots today...mostly west of the 55
corridor. Moisture is already slowly increasing and there will be a
belt of ll moisture streaming north-northwest across the western half of the County Warning Area
today. This belt will provide some ll convergence and is already
evident to our SW as rain showers activity has picked up in the Gulf just
off the southwestern la coast. As this area moves over our County Warning Area a weak
impulse will also approach the region currently moving through The
Big Bend region of Texas. This should lead to scattered convection this
afternoon across much of the County Warning Area west of the Pearl River with the
highest probability of precipitation around the btr metropolitan.

Not much has changed in the thinking for Thursday and Friday. The l/west trough
moving across the plains will sharpen and continue to slide east. SW
flow aloft will increase over the region with greater broad scale
lift in place on Thursday. Combine that with abundant moisture and broad
divergence aloft we will likely see scattered to possibly numerous rain showers
and thunderstorms and rain Thursday. Convection will likely taper off some Thursday evening but
after midnight things will begin to pick back up as our cold front
front approaches.

Our l/west trough over the central Continental U.S. Will continue to push east with
the trough axis approaching the MS valley overnight Thursday driving our
cold front into the middle and lower MS valley well before sunrise Friday.
This front will have ample forcing and could reach the coast by
midday/early afternoon Friday. Rain showers and thunderstorms and rain will have little trouble
developing ahead and with the front with some lingering light rain showers
immediately behind the front. After frontal passage much colder and
drier air will quickly be on its heels. Still not overly impressed
with the strong/severe potential. There will be some instability to
work with and the middle level flow is a tad better with 500 mb winds near 40
kts. Shear will not be substantial until after frontal passage.
Ahead of the front 0-6km bulk shear only approaches 20kts.
Directional shear is also lacking with winds trying to go
unidirectional before 18z. Middle level lapse rates continue to be rather
shallow at or below 6 c/km and Vermont will only be around 24-25c. Again
cant rule out a rogue strong/severe storm or two but overall not
impressed with the severe potential with this system. The locations
with the greatest risk of seeing any strong storms is along and northwest
of a line from Baton Rouge to Franklinton. /Cab/

Long term...nothing has really changed in the extended portion of
the forecast. The medium range models continue to show very pleasant
autumn weekend in store. Models continue to trend a tad cooler with
the European model (ecmwf) still the coldest. Again will use a blend of the models but
will give a little more weight to the European model (ecmwf) given the trends.

Heading into Friday night and this weekend look for our first real
taste of autumn. Strong cold air advection overnight Friday and the models have
come in a little stronger and faster with this. This cold air advection will
overcome any mixing from winds and should cool things off
impressively with lows Sat morning likely ranging from the middle 50s
in southwestern MS to middle 60s along the coast. If the front is any faster
then lows could be a few degrees cooler. That said look for Sun
morning to be the coldest morning since middle may. As for highs on
Sat...h925 temperatures of 15c would suggest highs struggling to get out of
the 70s!!! combine that with rather breezy conditions for much of
the day and rather decent mixing should help keep highs in the middle
70s for much of the area.

Now looking at Sat night...dewpoints are expected to drop into the
lower 40s if not the 30s across the region and Sat night optimal rad
cooling conditions could set up. There are some timing differences
b/T the models with respect to the surface high but it looks like it will
sit right over the region that night providing rather light winds.
Skies should be clear and ll temperatures will not be warming yet and all
of this would be great for rad cooling potential. If the surface high
pushes east a tad faster than we may start to see return flow in the
ll which could Hurt lows but the other limiting factor could be
ground moisture. If we overachieve with the rainfall on Friday then
there could still be enough moisture to Hurt the cooling potential.
As mentioned earlier the trend from all of the mlds has been to go a
little cooler with each model run and this has been the case for 4
days now. See no reason to disagree with this and have dropped lows
another few degrees in the forecast. The European model (ecmwf) has been the most bullish
and actually shows middle 40s in southwestern MS and some locations of sela
along the 10/12 corridor (45 to be exact in mcb and asd). Still not
going to go that low but will show upper 40s and right at 50 for
some areas. European model (ecmwf) gui actually shows the coldest reading of 42 at
pql and this would be thanks to cold air drainage in the Pascagoula
river basin.

Temperatures begin to moderate sun but we will still be on the cool side
for highs sun and lows Monday morning. Another weak reinforcing front
looks to try to approach the region middle week. /Cab/

Aviation...

Patchy light fog is likely through 13-14z at all taf sites...a few
points...mcb...asd...bxa and hdc may experience IFR conditions with
visibility and ceiling restrictions through 12z. Moisture surge today will
bring some MVFR ceilings along with isolated to scattered rain showers/thunderstorms and rain
mainly west of Lake Pontchartrain. Have maintained prob30 statement
for thunderstorms and rain during the later morning into the afternoon and will
convert to tempo btr...mcb and btr. 18

Marine...

Light east to southeast flow will prevail today through early
Friday. This flow will increase tonight into Thursday as the
pressure gradient increases between a departing high over the
eastern Seaboard and developing low in the plains. A strong cold
front will push across the coastal waters late Friday afternoon into
Friday evening. 1000 to 700mb thickness layers will hover around
3045m before the frontal passage. Strong cold air advection after
the front will allow layers to drop to 2990m by Saturday 12z and now
GFS holds the this layer through through Sunday morning...similar to
Euro. GFS has the surface high over the lower Mississippi Valley
while Euro has the high over central Texas coast. Boundary layer
winds of 23 to 25 knots will mixed down 100 percent to sea surface
Friday night through Saturday morning. As a result...a Small Craft
Advisory headlines will likely be needed for all coastal waters
Friday night into Saturday. 18

Decision support...
dss code...green.
Deployed...none.
Activation...none.
Activities...slurry support.

Decision support services (dss) code legend
green = no weather impacts that require action
blue = long fused watch/warning/advisory in effect or high
visibility event
yellow = heightened impacts with short fused
watch/warning/advisory issuances; radar support
Orange = high impacts - slight to moderate risk severe; nearby
tropical events; hazmat or other large episodes
red = full engagement for moderate to high risk severe
and/or direct tropical threats; events of National
significance.

&&

Preliminary point temps/pops...
mcb 86 72 85 71 / 60 40 60 60
btr 87 72 86 73 / 70 40 60 60
asd 86 73 86 73 / 60 30 60 50
msy 86 76 87 76 / 70 40 60 50
gpt 85 74 84 74 / 50 30 50 50
pql 86 70 85 73 / 40 20 50 50

&&

Lix watches/warnings/advisories...
la...none.
GM...none.
MS...none.
GM...none.
&&

$$

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