841 
fxus64 kjan 131415 aaa 
afdjan 


Area forecast discussion...updated 
National Weather Service Jackson MS 
915 am CDT Monday Oct 13 2008 


Update...thicker cloud cover than past two days and surface 
trajectories suggest temperatures will struggle to reach more than 76-81f 
again today. Some patchy drizzle/mist reported all the way into the 
Delta already so have gone ahead with a slight adjustment to hourly 
temperatures/maxes and weather grids. New data has posted...and no other 
changes expected for this morning as weak inverted trough axis across 
Alabama at 500mb moving west into MS under 596dm anticyclone situated over 
eastern Kentucky./40/ rest of previous discussion follows: 


Tonight through Tuesday...the highly amplified trough ridge pattern 
over the Continental U.S. Will begin to break down with the trough in the west 
lifting north over the high in the east as it shifts south. This will 
result in high pressure surface and aloft strengthening over our 
region on Tuesday. For today...regional radars do show a few 
sprinkles over southeast Mississippi with more scattered convection 
occurring over the northern Gulf. Models still show an increase in 
moisture as the inverted trough moves west across the area. Precipitable waters  near 
one and a half inches surge north to the Interstate 20 corridor 
before much drier air moves in from the east Tuesday. Guidance probability of precipitation 
came in lower over our northern counties with mainly slight chance to 
chance probability of precipitation over our southeast. Thick cloud cover was already over 
the eastern half of our County warning forecast area this morning. The cloud cover will hold 
temperatures down today. As high pressure surface and aloft strengthens 
over our region Tuesday much drier air with precipitable waters  below one inch will 
filter in from the east. This should end our rain chances Tuesday 
despite a cold front that will try to approach our northwest counties. 
This cold front is expected to stall northwest of our County warning forecast area until later 
in the week. There will likely be some morning stratus/fog Tuesday 
but more insolation expected during the day will help temperatures 
rise into the middle 80s at most sites Tuesday afternoon. /22/ 


Long term(tuesday night through monday)...the medium range models 
continue to show a fast moving fall-like highly changeable upper 
pattern for the upcoming period which gradually transitions to a zonal 
pattern by Thursday. As we go toward the weekend...the upper pattern 
transitions again to a ridge-trough amplified pattern. The upper 
trough develops over the eastern US for this weekend...while an 
amplified ridge builds in The Rockies and plains. By Sunday the upper 
trough will push off the East Coast as the upper ridge stretches and 
flattens from the eastern rockies to the Mississippi Valley. The Flat 
Ridge pattern will extend into early next week. 


On the surface the medium range models show that a cold front will 
push into the region on Thursday then stall with a good chance of 
rain in the northern zones according to the GFS...while the European 
model showed good chances of rain across the whole region through 
Friday. A stronger cold front will push into the region on Friday and 
combine with the first front...taking it to the coast by Saturday 
morning. The stronger front will be associated with a strong 
shortwave trough...which will help to transition the pattern to a 
ridge-trough formation by the weekend. As a result our best rain 
chances for this week will be on Friday followed by cooler than 
normal temperatures and drier weather for the weekend. Surface high 
pressure moved into the region for this weekend. The European model 
showed stronger high pressure of 1032mb than the GFS 1024mb. 


Normals for this time of the year at most sites are in the lower 50s 
for lows and middle 70s for highs. For daily temperatures mex and MOS guidance 
looked a little cool at night especially with the cloud cover especially 
Wednesday through Friday. Otherwise went close to MOS guidance for 
the other days. Daily lows will be mainly in the 60s for Wednesday 
through Friday before dropping into mainly the 50s for Saturday 
through Monday after the frontal passage. For daily highs will be in 
the lower to middle 80s for Wednesday and Thursday...then lower 80s 
for Friday. For the weekend into early next week mainly the middle to 
upper 70s. Went with mex guidance for Wednesday through Friday...then 
went close to the ensemble average for the weekend. 


As far as probability of precipitation were concerned went with the wetter European model with 
the two fronts on Thursday and Friday. So went closer to high end 
ensemble probability of precipitation for the period./17/ 


&& 


Aviation...MVFR to IFR ceilings and visibilities are being 
observed at all taf sites across the area this morning...as a 
weak disturbance pushes west across the region. Regional radars 
also indicate some very light shower activity over portions of the 
area which is aiding in these lower ceilings and visibilities. 
Through the remainder of the morning and into the afternoon...look 
for ceilings around to just below 1000 feet and decreasing 
visibilities due to the light shower activity to spread further west 
into central and west Mississippi...and eventually into extreme 
southeast Arkansas and northeast Louisiana. Meanwhile across east 
Mississippi...ceilings will slowly begin to lift and by 18-19z this 
afternoon...VFR conditions are expected across the area as ceilings 
lift to above 3000 feet. Stratus/fog is expected to develop tonight 
with lowest ceilings and visibilities in the southeast. /19/ 


&& 


Preliminary point temps/pops... 
Jackson 79 65 84 62 / 17 9 6 5 
Meridian 78 63 84 57 / 24 10 6 5 
Vicksburg 82 65 86 62 / 10 9 8 5 
Hattiesburg 79 66 85 59 / 27 10 7 5 
Natchez 83 67 84 64 / 16 7 6 5 
Greenville 80 65 86 62 / 5 10 14 5 
Greenwood 79 65 85 61 / 7 10 9 5 


&& 


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


$$