Weather

971 
fxus64 klix 060326 
afdlix 


Area forecast discussion 
National Weather Service New Orleans la 
926 PM CST Monday Jan 5 2009 


Marine... 
have extended exercise caution headlines over coastal waters 
through 18z Tuesday. New 00z NAM shows pressure gradient not as 
strong as previously forecast across our area through 00z 
Wednesday. May even be somewhat of a lull during the afternoon 
Tuesday as frontal boundary oozes slowly eastward. Expect we will 
get into Small Craft Advisory conditions about 24 hours from now. 
NAM solution shows strongest winds will actually hold off until 
Wednesday morning. 


Tidal lakes will likely be borderline for exercise caution for a 
few hours around midday...but will give middle shift another look at 
it as winds are only 10-12 knots over the lake right now. 35 
&& 


Previous discussion... /issued 332 PM CST Monday Jan 5 2009/ 


Short term... 
weak area of low pressure developing along the central Louisiana 
coastal plain. Weak stationary front appears to be drifting north 
and extends from the low pressure area eastward into the Florida 
parishes. Temperatures have risen to the middle 70s to the south of 
the front while to the north widely scattered showers and thick 
low clouds have kept temperatures to 60 degrees or less. With 
upper level trough so far to the west tonight and low level south 
flow...expect more fog to develop tonight. So a dense fog advisory 
may be needed later tonight for both land and marine areas. 


Long term... 
full latitude 500 mb trough develops in the southern rockies 
overnight in response to digging jet coming out of the Pacific 
northwest. This will cause southwest jet extending from Texas Big 
Bend to the arlatx to strengthen over night and into Tuesday. Low 
and middle level flow should respond to this scenario as Louisiana comes 
under the influence of the right rear quadrant of a 130 knot 300 
mb jet on Tuesday. 


Meanwhile a slow moving cold front will be approaching southeast 
Louisiana and southern Mississippi during the day and should pass 
through the County Warning Area by Wednesday evening. 


Due to the slow movement of the cold front and strong upper level 
divergence associated with the 300 mb jet...have continued with 
threat of heavy rain associated with numerous thunderstorms. 
Numerous showers and embedded thunderstorms will continue through 
most of Tuesday evening until the upper level trough and 300 mb 
jet moves east of the lower Mississippi Valley. Expect 2 to 3 
inches of rainfall across the area mainly Tuesday and Tuesday 
evening. This is just below flash flood guidance...so have elected 
not to issue a Flash Flood Watch at this time...but have left the 
door open for one later tonight. 


Aviation... 
00z taf issuance/ 
MVFR and IFR conditions will generally be the rule across the area 
tonight and Tuesday. IFR and LIFR ceilings are expected to 
prevail through the night associated with a stalled frontal 
boundary lingering across southeast Louisiana and southern 
Mississippi. Rain chances will increase tonight as a surface low 
develops over the northwestern Gulf of Mexico. The low will track 
across the area Tuesday...bringing with it widespread 
thunderstorms capable of producing heavy rain and gusty winds. 
There is a slight chance of severe weather during the afternoon 
hours for kmsy and kgpt that has been left out of the tafs as the 
probability of severe weather at any given location is low. 


Marine... 
moderate onshore flow will continue through the night tonight and a 
small craft exercise caution headline has been hoisted for the Gulf 
waters. A surface low is expected to develop over the northwestern 
Gulf of Mexico tonight and begin moving northeast. The low will move 
through the area Tuesday resulting in widespread showers and 
tunderstorms with it. Mariners should exercise caution when in 
the vicinity of thunderstorms as they will be capable of producing 
strong gusty winds and locally heavy rainfall that can 
significantly reduce visibilities. Wind speeds will continue to 
increase on Tuesday ahead of the cold front and small craft 
advisories will likely be needed over the tidal lakes and Gulf 
waters by noon Tuesday. Will hold off on issuing the advisory for 
now as there is still a bit of uncertainty concerning the onset 
time of the stronger winds. Behind the front...expect strong 
offshore flow to set in as a strong surface ridge builds into the 
area. As the high becomes more centered over the area on 
Thursday...expect winds and seas to begin calming. The high will 
remain in place through Friday with another cold front expected to 
affect the area Saturday night. 


&& 


Preliminary point temps/pops... 
mcb 63 65 42 60 / 80 80 40 0 
btr 64 66 44 62 / 60 80 40 0 
msy 66 76 45 62 / 60 80 50 0 
gpt 65 72 44 59 / 60 80 60 0 


&& 


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


$$