656 
fxus63 kind 111018 
afdind 


Area forecast discussion 
National Weather Service Indianapolis in 
618 am EDT Sat Oct 11 2008 


Aviation...discussion for 12z tafs 


With temperatures close to dewpoints at bmg would not rule out a brief period 
of MVFR fog at the beginning of the period...but confidence is low here. 
Otherwise expect VFR conds through the taf period at all sites. Few cumulus 
possible this afternoon otherwise scattered cirrus. Winds will increase to near 
10kt today then diminish after sunset. 


&& 


Discussion... 
the main weather factor to work with on the short term are the 
temperatures. A large area of high pressure extends from the East 
Coast into Indiana. This will provide dry and warm conditions 
through the weekend. The NGM maximum temperature forecast for Friday was right 
on or only slightly off. The GFS has been consistantly too warm. 
This morning the GFS has decreased the maximum temperature forecast to near NGM/NAM 
values. 850 mb shows only slight warm air advection. So will lower forecast temperatures some 
to go near not as warm guidance values. 


Tonight 850 mb shows a degree or so of warm air advection. Clear conditions with 
light winds will allow for good radiational cooling. With the warm air advection 
will go toward the slightly warmer Eta model values. 


On Sunday cross sections of all models show very moist upper levels. 
These clouds will hold temperatures down some. The ecm shows the strongest 
warm air advection. This is only around 2 degrees. This warm air advection should counter the 
denser cloud cover. Through out the NGM forecast for Sunday which shows 
a temperature drop up to 5 degrees. Will go near the more consistant 
NAM/GFS. 


On Monday temperatures should continue some as a cold front continues to 
move toward Indiana. 


As for the extended...the European model (ecmwf) has slowed the progression of the 
approaching cold front to Tuesday afternoon into Wednesday. This seems quite 
reasonable given the strength of the large ridge across the eastern 
United States. Hence will push precipitation chance back another 12 hours or 
so...leaving all of Monday and Monday night dry. 


GFS and European model (ecmwf) suggest a lingering frontal boundary across the Ohio 
Valley on Thursday and Friday...but for at this time moisture will be limited in 
the wake of the previous front. Hence will leave precipitation out for 
Thursday...however by Friday...an area of low pressure may push along the 
front and provide some forcing. Hence will include some low chance probability of precipitation 
for then...but confidence in that remains low. 


&& 


Ind watches/warnings/advisories...none. 


&& 


$$ 


Aviation...cs 
public...sh