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fxus64 klix 101313 
afdlix 


Area forecast discussion 
National Weather Service New Orleans la 
713 am CST Wednesday Mar 10 2010 


Update... 
sounding discussion... 


The atmosphere has become unstable and remains very moist up to 
just below 11k feet with dry air present aloft...precipitable water 
value is 1.17 inches and the lifted index value is -5.2. An 
inversion is present near 1500 feet and a secondary inversion near 
3700 feet. Winds are out of the southwest near the surface and out 
of the west aloft...strong upper level winds. 


&& 


Previous discussion... /issued 536 am CST Wednesday Mar 10 2010/ 


Update... 
a dense fog advisory has been issued until 9 am CST for lakes 
Pontchartrain and Maurepas...and for the Gulf coastal waters from 
the mouth of the Mississippi River to Pascagoula out 20 nm. 


Previous discussion... /issued 346 am CST Wednesday Mar 10 2010/ 


Short term... 
an active period is in store for the forecast area during the 
next 24 hours. A vigorous middle/upper low over New Mexico early this 
morning will move across the Southern Plains today and then into 
the Missouri Valley tonight. Although the best dynamics associated 
with this feature will remain to the north and west of the forecast 
area...large scale ascent associated with this system will 
increase across the lower Mississippi Valley and central Gulf 
Coast today. This ascent will be enhanced be a very strong upper 
level jet extending across northern Mexico and Texas that will 
nose its way into into the central Gulf Coast region maintaining 
substantial divergence aloft across the region. In addition... 
low level warm air advection and moisture advection will continue 
in advance of the system moving through the Southern Plains as a 
low level southerly to southwesterly jet develops across the lower 
Mississippi Valley. Model forecast soundings indicate significant shear 
developing across the area this afternoon which should help 
promote the development of rotating storms. Forecast helicity 
values indicate the potential for a few tornadoes as well. 
Instability is forecast to be somewhat modest...however any breaks 
in the cloud cover today will help promote additional instability. 
At this time...it appears that the main threat for severe weather 
will occur during the afternoon and evening hours. The severe 
weather threats will run the gamut with damaging winds...hail and 
a few most likely weak tornadoes possible. The convection will end 
from west to east tonight as a pre-frontal tough moves across the 
forecast area. 


Long term... 
quiet weather will return to the forecast area for the end of the 
work week and into the weekend. The large upper trough/low over 
the central Continental U.S. Will slowly make its way east into the eastern 
Continental U.S. During this period. An associated cold front will push 
across the area late Thursday night and Friday. An isolated shower cannot 
be ruled out with the passage of this front and with the eastward 
moving upper trough/low from Thursday night into Friday night...especially 
across northern sections of the region.Somewhat cooler air will 
return for the weekend. 


The next chance for rain will be Monday night or Tuesday as the 
next upper low/trough moves out of the western U.S and into Texas 
early next week before advancing toward the lower Mississippi 
Valley. Medium range model solutions associated with this system 
have not been consistent from run to run. 11 


Aviation... 
ceilings should stay in the 400-800 feet range through much of the morning 
then lift to 1500 feet. Visibility will periodically be reduced due to rain 
and fog through the morning as well. Thunderstorms are expected to 
develop later today and a few are expected to become severe. Strong 
wind gusts near any taf site due to strong to severe ts today will 
cause strong shear for any takeoff and/or approach. 17 


Marine... 
synoptic forcing over the marine environment is causing winds to mix 
down this morning. Wind speeds should increase to around 20 knots by 
this evening. Caution statements have been posted for today over all 
open Gulf waters but have held off on issuance over the lakes for 
now. This may change though as we get into the late morning hours. 
Did the same for advisories for the open Gulf waters by holding off 
for now. Winds should fall right at the 20 knot mark for the Gulf 
waters by this evening. Will hold for the day shift and 12z run 
before bringing advisories up. A reinforcing surge of dry air moves 
over the northern Gulf Friday night causing winds to increase once 
again. The next system will begin to affect the area Monday night 
and Tuesday. This one will be much stronger and may be much farther 
south over the Gulf. Placement will be important with this system as 
gales may evolve around the center of the low. 17 


&& 


Preliminary point temps/pops... 
mcb 72 58 75 48 / 70 70 10 10 
btr 73 59 76 49 / 70 70 10 10 
asd 73 59 76 49 / 70 70 10 10 
msy 73 60 76 52 / 70 70 10 10 
gpt 71 60 75 51 / 70 70 20 10 
pql 72 60 76 52 / 70 70 20 10 


&& 


Lix watches/warnings/advisories... 
la...none. 
GM...dense fog advisory until 9 am Wednesday for the following zones: 
coastal waters from Pascagoula MS to the Southwest Pass of 
the Mississippi River out 20 nm...and Lake Pontchartrain 
and Lake Maurepas. 


MS...none. 
GM...dense fog advisory until 9 am Wednesday for the following zones: 
coastal waters from Pascagoula MS to the Southwest Pass of 
the Mississippi River out 20 nm...and Lake Pontchartrain 
and Lake Maurepas. 


&& 


$$