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fxus64 klix 030529 
afdlix 


Area forecast discussion 
National Weather Service New Orleans la 
1129 PM CST Tuesday Dec 2 2008 


Aviation / 06z tafs /... 


VFR conditions are expected through tonight. As a low pressure 
system approaches Louisiana Wednesday...the pressure gradient over 
the lower Mississippi Valley will tighten. This will lead to gusty 
southerly winds across the area. No precipitation is expected at 
msy...btr...gpt...mcb through 06z...the better chance for rain 
will be early Thursday morning through the day Thursday. Ceilings 
should remain 4000 feet or better as clouds increase during the 
day Wednesday. 


&& 


Previous discussion... /issued 944 PM CST Tuesday Dec 2 2008/ 


Update... 
temperatures have been falling more than previously expected...so 
decided to drop overnight lows across the area. Min temperatures will 
likely be reached not long after midnight and begin slowly rising 
through the night as moisture increases across the area. 
Otherwise...no changes made. 


Previous discussion... /issued 323 PM CST Tuesday Dec 2 2008/ 


Synopsis... 
surface high pressure is centered over the northeastern Gulf of 
Mexico with clear skies across the forecast area. A surface low 
with accompanying cold front is located norther of Minnesota. 


Short term... 
the deep upper trough currently dominating the eastern half of the 
Continental U.S. Will broaden and lift out of the area overnight tonight. As 
the core of the cold airmass moves away from the region...low 
temperatures tonight will not be nearly as cold as last night. 
Generally forecasting temperatures in the upper 30s to around 40 
degrees north of the lake and middle to upper 40s south of the lake. 


Return flow will continue to pump moisture into the area Wednesday 
as the next frontal system takes shape over the plains states. 
Models are in good agreement that the front will begin to move 
through the local area Wednesday night and that it will slow near 
the coast as flow becomes more westerly aloft. Forecast soundings 
do not support severe weather with this frontal passage and it 
appears as though most of the surface based instability will be 
limited to the Gulf waters. However...with a bit of instability 
still forecast above 850 mb...will continue to mention a slight 
chance of thunder along the frontal boundary as it moves through 
the region. 


Long term... 
no real problems in the extended period. As high pressure builds 
in behind the cold front...another round of colder weather can be 
expected. On the North Shore of Lake Pontchartrain...highs and 
lows are forecast around 10 to 15 degrees below normal Friday and 
continuing into Saturday morning. South of the lake...the 
differences will be much more noticeable during the afternoon 
hours with highs about 10 degrees below normal on Friday. Lows are 
only forecast around 5 degrees below normal for Friday and 
Saturday. The airmass will begin to moderate on Saturday as the 
surface high lifts out of the area. 


The models have had consistency issues...both run to run 
and between the individual models...concerning the next frontal 
passage. As of the 12z model runs...the actual frontal passage 
appears to be some time next Tuesday or Wednesday...which is just 
outside the current forecast period. However...the large 
differences in timing and strength also lead to differences in 
the few days leading up to the frontal passage. Currently...the 
European model (ecmwf) carries a slower...but more potent system with the upper 
trough and surface front not clearing the area until late Tuesday 
night or early Wednesday morning. The GFS on the other 
hand...carries a faster and weaker system...and pushes both the 
upper trough and surface cold front through the region early 
Tuesday evening. 


Given the uncertainties...have made very few changes to the 
extended as there is very little confidence in any one solution. 
The current forecast seems to be a fairly good blend with a 
slight warming trend Sunday and Monday and a slight chance of rain 
beginning Monday night as the front should be approaching the 
area by that time. 


Marine... light and rather variable winds across the coastal 
waters this afternoon will become southerly overnight and increase 
Wednesday and Wednesday night in advance of a cold front forecast 
to push across the coastal waters during the day Thursday. Small 
craft should exercise caution headlines may be needed Wednesday 
and Wednesday night. Strong offshore flow will develop in the wake 
of the front Thursday afternoon and will persist into Friday 
before diminishing as high pressure builds into the Gulf Coast 
region. Winds may increase somewhat again by Sunday as high 
pressure is reinforced across the region. 


&& 


Preliminary point temps/pops... 
mcb 33 70 51 56 / 0 10 60 30 
btr 37 73 55 60 / 0 10 60 40 
msy 40 72 59 63 / 0 10 40 50 
gpt 35 68 57 64 / 0 10 30 50 


&& 


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


$$