902 
fxus63 kind 070745 
afdind 


Area forecast discussion 
National Weather Service Indianapolis in 
340 am EDT Tuesday Oct 7 2008 


Discussion... 


Forecast focus will be rain chances later today through Wednesday 
night. 


At 06z strong upper ridge extended from Georgia through the eastern 
Great Lakes while a strong upper trough was moving east from the 
Great Plains. Satellite showed high clouds spreading east across 
our area and showers were increasing across the middle Mississippi 
Valley. 


The models move the upper trough east into our area by early 
Wednesday. As it does the models especially the NAM shows some 
tendency to split the upper trough with the heaviest precipitation areas 
passing to the north and south of US. GFS shows this tendency 
too...but not as quickly. The NAM is slower to bring in precipitation 
later today while GFS spreads it across most of our area by early 
afternoon. Will go with model blend here. Precipitation already developing 
more quickly and is farther east than NAM. However dry east flow may 
slow down precipitation onset some later today. 


NAM gives US less than a quarter inch total quantitative precipitation forecast...while GFS has just 
over an inch. It looks like best chances of precipitation will be tonight 
and early Wednesday. Lightning chart shows isolated thunderstorms 
across Missouri and Iowa. Stability charts show a little instability 
across our west late today and over our region tonight and early 
Wednesday so will mention isolated thunderstorms. But no severe 
threat expected. 


Models this run are a little quicker to end precipitation on Wednesday. 
Will start likely probability of precipitation in the morning diminishing to a chance in the 
afternoon and ending most areas by Wednesday night. 


Only minor changes to rest of forecast. I did go a little warmer 
late this week...but not as warm as new mex. 


&& 








Aviation...discussion for 06z tafs 
VFR expected through the majority of the taf period. 


Low level moisture is slowly returning to central Indiana ahead of a 
low pressure system and cold front that will reach central Indiana 
on Tuesday evening. Strong warming ahead of the cold front...which 
isnt expected to pass through the state until Wednesday...will allow 
for some instability and possible thunderstorms. At this time 
thunder isnt expected to be widespread enough to include in the 
taf...especially this far out so will continue with cumulonimbus until better 
timing can be achieved. 


As moisture continues to increase...especially after 18z 
Tuesday...clouds will thicken and eventually become MVFR but that 
may not happen until after the end of this taf valid time. 


By 00z-03z rain will likely have spread into all taf sites and will 
add this to the 06z issuance. 


&& 


Ind watches/warnings/advisories...none. 


&& 


$$ 


Aviation...Sally 
public...jh