840 
fxus64 kjan 240829 
afdjan 


Area forecast discussion 
National Weather Service Jackson MS 
329 am CDT Thursday Jul 24 2008 


Short term...surface analysis this morning shows the remnants of 
the boundary stretched across northern portions of the forecast 
area. Water vapor imagery shows drier air moving into the area. 
Upper level ridging exists over the plains states with the trough 
over the northeastern Continental U.S.. 


Ridging is expected to begin to build over the County warning forecast area over the next 
couple of days. The remnants of the boundary is expected to wash out 
over the next couple of days as well. Shower and thunderstorm 
activity today will be hampered by rising heights and warming middle 
level temperatures...as well as the drier air moving into the 
region. The sea breeze will contribute a little more support for 
the southern half of the County warning forecast area. Overall do not expect much more than 
isolated convection this afternoon. Any activity that develops today 
will struggle to develop until the afternoon hours...and should 
quickly die off after sunset. With these features acting against 
convection today...strong to severe thunderstorms will be harder to 
come by this afternoon. High pressure will continue to build over 
the region as we move into Friday. There will be a slight increase 
in moisture over the region. With more moisture there may be more 
convection on Friday than today. However upper level ridging will 
again hamper activity from becoming too widespread. As a result 
have lowered probability of precipitation in a few locations to reflect more isolated 
coverage for Friday over the forecast area. Activity that develops 
Friday will again die down quickly after sunset. 


Temperatures for today and especially on Friday will begin to be a 
little warmer...especially across the northwest. High pressure 
building into the region and warming middle and low level temperatures will 
aid in warming temperatures. Have went ahead and raised 
temperatures for today and Friday for a few locations...especially 
across the Delta where ridging will be strongest. Over these 
locations temperatures should reach the upper 90s with middle 90s 
experienced elsewhere. /14/ 




Long term...main focus for the extended will be with high temperatures and 
the heat. The area will see the upper ridge peak on Friday and then see 
the center retrograde for the rest of the weekend into next week. 
This will allow for the low level flow to become out of the west/northwest for 
an extended period of time and really push in extremely warm 
925/850mb temperatures. The area should see 925mb temperatures 27-30c and 850mb 
temperatures 21-23c from sun through at least Tuesday. Using these 
values...climatology suggests 98-102 degrees easily for a few days. 
Localized effects will likely result in a few locations peaking 
higher...but at this point...getting the forecast in the ballpark is 
the best course of action while forecasting near record type heat. 
Guidance temperatures support this...but are likely not warm enough in most 
locations. I have continued the trend of raising maximum temperatures above guidance. 


As for what the heat index will be...that's a tougher question. 
Latest guidance suggests that Sat-Mon...solid mixing will occur and surface 
dewpoints will likely drop into the 63-68 degree range. If this 
occurs...then heat index values will be held in check and only top 
out between 100-105 degrees. If surface dewpoints can hold in the upper 60s 
to around 70...then values >105 will be possible. Either way...it 
will be hot and a portion...if not all...of the County Warning Area may need a heat 
advection at some point. Details will determine that in the coming days. 
As for now...I will continue to mention the heat in the severe weather potential statement. 


As for precipitation potential...the way things look now...no real day has 
any decent shot. Guidance wants to hold onto better 850mb moisture on 
Sat...especially across the east...but feel that is the only 
positive for supporting convection. Guidance probability of precipitation seemed good and have 
followed. Look for 10% in the west to 30% in the east. Drier low 
level air is expected to move in for sun-Tuesday and the heat will 
really be on. For this period...I have only gone with 10% probability of precipitation for 
the afternoon and early evening. By Wednesday...things begin to change 
some as slightly better moisture moves in as low level flow become 
more out of the SW/S. Additionally...the possibility of a short wave or two 
may drop S/southeast out of the plains as northwest flow will be in place. As is 
the case with this type of pattern and extreme temperatures...any 
convection in the Monday-Wednesday timeframe will have to be watched closely 
as solid lapse rates will exist. /Cme/ 




&& 


Aviation...VFR flight categories will prevail through the next 24 
hours. A few sites mainly over the east will experience some MVFR to 
IFR patchy fog this morning due to moist grounds. This will mainly be 
between 09-14z and should quickly lift after sunrise. Isolated 
showers and thunderstorms will be possible over the area 
today...mainly for areas south of the Interstate 20 corridor. This 
could bring brief periods of lowered flight categories. Any activity 
that develops this afternoon should quickly dissipate this 
evening...leaving a quiet night for the entire region. /14/ 




&& 


Preliminary point temps/pops... 
Jackson 94 72 95 73 / 16 9 20 11 
Meridian 94 70 94 71 / 20 11 20 18 
Vicksburg 96 73 94 73 / 16 10 22 9 
Hattiesburg 95 72 96 72 / 24 15 21 23 
Natchez 93 72 93 73 / 24 13 24 16 
Greenville 97 72 97 73 / 11 8 23 6 
Greenwood 94 73 96 74 / 14 8 23 10 


&& 


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


$$ 


14/cme