943 
fxus63 kind 181655 
afdind 


Area forecast discussion 
National Weather Service Indianapolis in 
1255 PM EDT Friday Jul 18 2008 


Aviation...discussion for 18z tafs 


Scattered cumulus will dissipate and winds will diminish after sunset. Expect 
MVFR fog to form once again as conds will be similar to previous nights. 
As with previous nights cannot rule out brief IFR conds at all xcpt ind 
but some high clouds moving in late should help keep things MVFR. 


Fog will burn off by 13-14z. Weak wave moving in from the west will 
bring in more middle and high clouds on Sat as well as a small chance 
for thunderstorms and rain. Chances too low to mention in tafs. 


&& 


Discussion... 


Forecast focus remains on temperatures and precipitation chances through the weekend. 


GFS/NAM diverge on surface pattern beyond 24 hours. Model suites 
including European model (ecmwf)/sref favor a version closer to the NAM. Will stay 
close to the going forecast for precipitation chcs/temps. Despite the 
differences between the NAM/GFS only minor differences in precipitation 
chances/temperatures noted with GFS cooler by sun. 


Today...a check of the 1000-850mb thicknesses and 850mb temperatures 
suggests that highs today should be within a degree or so of Thursday 
highs. Will go with a persistence +1 forecast for today with some high 
clouds and cumulus expected today. 


Sat...GFS version of a lead wave appears overdone and favor the 
NAM/European model (ecmwf) which would focus convection across northern Illinois/in but 
also suggests at least some small chances across the far northern 
counties of the County Warning Area. 850mb thermal ridge becomes stretched east out 
of the plains with 1000-850mb thicknesses higher than the previous 
few days which suggests hotter temperatures and will increase highs by a 
degree or two over Friday maximum temperatures. 


Sun and beyond...the region will remain within an active upper flow 
with several shortwave troughs expected to dig into the Great Lakes. 
Each will enhance a surface wave along a wavy frontal boundary which 
will also be located somewhere across the area at some point sun 
into early next week. Obviously...the details remain uncertain but 
the larger scale pattern suggests increasing precipitation chances Sat-Monday 
with some potential for moderating/cooling temperatures Monday-Tuesday of next 
week. 


&& 


Ind watches/warnings/advisories...none. 


&& 


$$ 


Aviation...cs 
public...Colorado