910 
fxus64 klix 062033 
afdlix 


Area forecast discussion 
National Weather Service New Orleans la 
333 PM CDT Monday Oct 6 2008 


Short term... 


A strong slightly negatively tilted short wave trough will 
continue to advance through the plains and into the Midwest and 
Tennessee Valley tonight into tomorrow. As the trough pull 
eastward...a developing area of low pressure and associated cold 
front dive through the Southern Plains toward the lower 
Mississippi Valley. All of the models are in good agreement on the 
evolution of the system...but there are timing differences on the 
frontal passage Tuesday night into Wednesday. The GFS is most 
aggressive with the front...while the European model (ecmwf) and NAM are a bit 
slower and keep lingering moisture across the area through 
Wednesday. Have decided to go with a blend of the models...with a 
bit more emphasis on the GFS solution. 


With this in mind...expect weak inverted trough in the north 
central Gulf to continue to pull moisture into the region tonight. 
Scattered showers currently moving onshore should overspread the 
forecast area overnight...and have bumped up probability of precipitation to high end 
chance to reflect this. Deep moisture combined with a marginally 
unstable atmosphere and a broad area of lift throughout the 
atmospheric column will support likely probability of precipitation tomorrow in advance of 
the approaching trough axis and frontal boundary. 


Going into Tuesday night...expect the frontal boundary to pass 
through the forecast area. Model soundings indicate a marginally 
unstable atmosphere will be in place as the front pulls through. 
However...the possibility does exist for a squall or some bowing 
segments to develop as a strong speed shear from 0 to 3 km of 
around 20 knots will be place. Keep probability of precipitation up into the likely 
catagory for eastern and southern zones...with high end chance 
probability of precipitation elsewhere. On Wednesday...expect some lingering clouds and a 
few showers on the back side of the upper level low as it slides 
through the southeastern states. Strong subsidence and dry air 
advection will take hold by Wednesday night allowing for clearing 
skies and lower dewpoints. Some weak cold air advection should 
also accompany the high building into the region...allowing 
temperatures to fall slightly below normal. 


Long term... 


The latter part of the week and into the weekend...an upper level 
ridge and associated surface ridging will be the dominant features 
across the County Warning Area. This strong ridging will allow for dry conditions 
and a large diurnal temperature range Thursday through Saturday. 
However...the ridge will begin to pull eastward by Saturday...as a 
strong upper level trough digs into the western half of the 
nation. Southerly flow will redevelop across the area Friday night 
into Saturday...allowing for Gulf moisture to slowly move back 
over the region. Enough upper level should be in place...as a weak 
short wave moves through this weekend to spark off some showers 
over western zones...as the moisture will be deeper in this 
region. By Monday...deeper Gulf moisture should overspread the 
region...allowing for a slight chance of showers across the County Warning Area. 
These showers will be sparked by a difluent flow aloft...and thus 
a broad area of ascent. Temperatures will also rebound this 
weekend as the Gulf moisture spreads in...with lows climbing back 
into the upper 60s and lower 70s...and highs rising into the 
middle to upper 80s. 


&& 


Aviation... 
most weather issues at terminal locations will involve lowering of 
ceilings from low end VFR to MVFR later tonight and IFR around 12z 
Tuesday. Will show prevailing rain showers coverage all terminals after 12z 
but there may be breaks at times...but difficult to gage timing and 
areal extent...so will indicate for entire period 12z through 18z...and 
may need to be extended next taf package beyond 18z. May have to 
consider amendments for kgpt to address thunderstorms and rain approaching coast from 
nearby waters but these storms have been lingering out there all 
morning and early afternoon...weakening and dissipating farther 
north. As column moisture deepens...convection will have better 
chances to maintain over land. Frontal passage now appears to be 
early Wednesday morning with improving conditions throughout the 
morning Wednesday. 24 


&& 


Marine... 
persistent easterly winds into the east facing shores have brought 
an increase in tide levels about 1 to 1.5 feet above 
normal...including the tidal lakes. Will not issue any standalone 
product to address this since is should be confined to high tide and 
become mitigated by frontal passage late tomorrow night/early 
Wednesday morning. Will mention in coastal waters forecast. 
Otherwise...east to southeast winds around 15 knots and seas 4 to 6 
feet prior to frontal passage and wind shifting to offshore 
component wedneday morning. 24 


&& 


Preliminary point temps/pops... 
mcb 68 83 64 82 / 50 70 50 20 
btr 71 85 64 82 / 50 70 50 20 
msy 73 85 68 83 / 50 70 60 20 
gpt 70 82 68 81 / 50 70 60 30 


&& 


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


$$ 


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