210 
fxus64 kjan 212130 
afdjan 


Area forecast discussion 
National Weather Service Jackson MS 
330 PM CST Sat Nov 21 2009 


Short term...tonight through Monday night...it has been a wet Saturday 
for some folks across the arklamiss. Surface low pressure system 
along the Gulf Coast is slowly moving east...with upper low/shortwave 
trough across eastern Oklahoma. These features are creating enough 
lift for a shield of showers and one or two thunderstorms across 
southern Louisiana. This activity has slowly been moving north this 
afternoon and affecting locations along and south of the Interstate 
20 corridor. Much of this is light rain with some areas of moderate 
rain. 


For tonight...as the low across the Gulf continues to move from west 
to east...this rain should continue to spread over the area with the 
sref/GFS/local WRF all showing the better coverage of rain remaining 
across central and southern sections at least for the first half of 
the night. For latter portions...the low will continue its track off 
to the northeast and the upper trough moves over the region... this 
will allow the rain chances to begin to diminish for locations across 
the west into west central MS and bring the better chances for rain 
to the east/northeast. 


On Sunday and Sunday night...the upper trough and surface low continue to 
pull off to the northeast and there could be some light rain 
lingering across the east for early Sunday. This is indicated by 
local WRF models as well as sref probs that show the highest probs 
in the Golden Triangle region. Have left in low probability of precipitation for the 
northeast into early Sunday evening for any lingering light rain but 
believe the bulk of this will be out of the region. Skies will begin 
to clear from the west Sunday night. Depending on how much the skies 
clear...there could be some patchy fog given drier air aloft. Have 
kept mention of this in the zones for the south. 


By Monday...the region gets influenced by weak surface high pressure and 
zonal flow aloft. This translates to a dry day with sunny 
conditions. However...during this time an upper trough continues to 
develop across the plains. This will send a cold front our way on 
Tuesday. By Monday night...southerly flow returns and clouds begin 
to increase across the west ahead of the next system. 


Overall...remained close to gui past the first period as conditions 
look to dry out. Did raise probability of precipitation for tonight across the east and 
portions of the central as model gui indicates this will be the most 
likely place for rainfall. /28/ 






Long term...Tuesday through Saturday...a rather flat zonal flow pattern 
will transition back to ridging in the western Continental U.S. And troughing in the 
east during the coming Holiday week. The primary feature for the week 
appears to be a weak frontal system passing through the lower MS 
valley Tuesday and Tuesday night with minimal rainfall chances. This 
boundary is followed by two reinforcing troughs Wednesday night and 
later on Saturday to keep US cooler than climatology. 


The GFS is now mustering up 0.75-1.0 inch precipitable waters  along the 
Tuesday front before returning to 0.25 inches on Wednesday. Pre 
frontal low level ridging along the Gulf Coast should prevent much 
moisture return and do not see much moisture convergence with the 
boundary so will keep mention to light rain. The European model (ecmwf) is actually a 
little wetter with this front as it shows a tenth of an inch qpfs 
hanging on into Tuesday evening over the southeastern portions of our County warning forecast area. 
Beyond that...a quick reinforcing dry trough sweeps through the area 
with a few clouds for Wednesday night. This sets up a chilly cold air advection 
celebration for Thanksgiving day with most lows in the u30s and highs 
in the 50s. 


A 1020+mb surface high over southeastern Texas Friday moves along the Gulf Coast 
for Friday night and Saturday with some moisture return for Saturday 
night. Another weak front could reach the area by that time but it 
also is appearing rather dry with the surface high off the coast of 
northwest Florida. Will have to monitor this time frame as the European model (ecmwf) again a 
little more robust with the mass fields and higher rain chances. 


All in all...the Holiday week should be quite dry and also seasonable 
in the temperature department. The ensemble MOS guidance stays within 
1-2 Standard deviations and in most cases the means are close to the 
operational numbers./40/ 




&& 


Aviation...a low pressure system moving along the Gulf Coast is 
bringing lower ceilings and light to MDT rain to much of the area 
this afternoon...but the dry air is keeping restrictions in the VFR 
range so far. As the rain continues to moisten the lower levels and 
the upper low approaches...look for MVFR restrictions to develop at 
hbg/mei/Jan during this evening...with IFR restrictions possible at 
hbg/mei due to heavier rainfall. Instability will be marginal but 
could support a little thunderstorm activity at hbg/mei. It looks like 
glh/gwo/gtr will stay in VFR category for most of the rain event 
given the dry air currently in place. As the upper low begins to 
move across the forecast area late tonight and Sunday morning... 
rainfall will diminish...but stratus will become widespread 
resulting in MVFR/IFR restrictions at all sites. The stratus will 
hang around through Sunday afternoon and could linger Sunday 
night...especially over central/eastern MS. /Ec/ 




&& 


Preliminary point temps/pops... 
Jackson 50 59 49 66 / 95 20 9 7 
Meridian 50 60 47 66 / 97 39 19 8 
Vicksburg 49 60 46 66 / 81 10 6 6 
Hattiesburg 52 61 48 67 / 97 28 9 7 
Natchez 48 59 43 68 / 82 8 6 5 
Greenville 48 59 47 65 / 55 20 9 7 
Greenwood 48 56 48 67 / 87 28 15 8 


&& 


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


$$ 


28/40/ec