551 
fxus64 kjan 061545 aaa 
afdjan 


Area forecast discussion...update 
National Weather Service Jackson MS 
1030 am CDT Sat Sep 6 2008 


Update...combination of low level trough stalled from southwest to 
northeast across the region and abundant lower atmospheric and 
ground moisture is keeping lower clouds thick across much of the 
arklamiss as of 10 am this morning. Expecting these clouds to be 
slow to disperse (or stubborn all day) along the axis of the Natchez 
trace corridor...while at least a few sunny breaks are anticipated 
elsewhere. Temperatures should be able to respond upward quickly to 
sunshine...which makes the cloud cover forecast critical. Right now 
I anticipate many locales in a wide berth around the Natchez trace 
corridor will struggle to get much above 80 degrees...although 
locations in the northwest and southeast peripheries of the County Warning Area 
could get into the at least to 85 if given adequate sun. 
Overall...high temperatures today have been revised downward from previous 
expectations. 


In addition...enough deep moisture and marginal instability will 
exist in extreme southeastern Mississippi to give the potential for 
a few showers to develop come this afternoon on the east side of the 
mentioned trough. However...significant precipitation is not expected and 
probability of precipitation kept below 20 percent. /Bb/ 


&& 


Discussion... 
short term...a narrow low level trough that has stalled over the 
arklamiss has trapped a deck of low clouds over the area. The trough 
will shift southeastward during the day to allow clearing from the northwest. Clouds 
will significantly hamper daytime heating...resulting in afternoon 
temperatures lower than those advertised by MOS for some southern and eastern zones. 
The 850 mb trough is forecast to continue over southern zones tonight. 
Increased overnight lows a degree or two to reflect cloud cover. 


The 850 mb trough continues over southern zones Sunday. The associated 
surface trough remains stalled across Alabama today...extending southwestward near 
the MS coast. This feature will begin to pivot back over inland 
areas during the day Sunday to contribute to forcing and result in 
slight rain chances over southern zones Sunday afternoon. Once again MOS 
temperatures look a bit too warm Sunday and have cut them back slightly. 
/03/ 


Longer term...medium range models show that flat ridging will allow 
some diurnal convection. A weak boundary will push into the region 
on Tuesday...which will push into the flat upper ridge. This will 
help provide some convergence for some diurnal convection. The 
boundary will wash out on Wednesday. Daily temperatures for Monday through 
Wednesday will push into the upper 80s to lower 90s. Went close to 
MOS guidance on daily highs. Nightly lows through Wednesday morning 
will be from the middle 60s to the lower 70s...which is close to mex 
guidance. Went also with mex probability of precipitation. 


The next item of concern is the uncertainty of the track of Ike 
into the Gulf region. Models vary from the northeast Gulf to south 
Texas...while the GFS tries to bring it across the region. The latest 
forecast from NHC brings Hurricane Ike south of Florida into 
the southeast Gulf of Mexico next Tuesday or Wednesday. The affects 
of this system will be closely monitored. Otherwise made some slight 
adjustments to GFS numbers since GFS tries to bring the system into 
the region. /17/ 


&& 


Aviation...ceilings will gradually rise this afternoon across the 
forecast area...with slowest improvement from IFR to MVFR to VFR 
expected at Jan/mei/gtr where frontal boundary is in closest 
proximity. By this evening expect VFR conditions at all taf sites. For 
tonight...some stratus/fog redevelopment will be possible after 
midnight...but the set-up is not as favorable given forecast for the 
low-level thermal trough to weaken significantly so will not go too 
pessimistic with tafs for Sunday morning. /Ec/ 


&& 


Preliminary point temps/pops... 
Jackson 81 64 88 66 / 2 1 8 13 
Meridian 82 65 90 65 / 8 3 9 11 
Vicksburg 82 63 89 65 / 1 0 8 13 
Hattiesburg 86 70 88 68 / 12 5 22 13 
Natchez 82 66 86 68 / 3 0 19 13 
Greenville 83 59 91 64 / 0 0 3 8 
Greenwood 82 60 91 62 / 0 0 3 8 


&& 


Jan watches/warnings/advisories... 
MS...none. 
La...none. 
Arkansas...none. 
&& 


$$ 


Bb/ec