539 
fxus63 kind 211103 
afdind 


Area forecast discussion 
National Weather Service Indianapolis in 
700 am EDT sun Mar 21 2010 


Aviation...for 12z tafs 
low pressure over Arkansas will move into western Tennessee by 18z 
and to northeast Kentucky by this time tomorrow. For today ceilings 
will be 6 to 8 thousand with scattered very light showers. An area 
of MVFR ceilings and rain should remain to our west as a east 
northeast flow continues across our region. 


As the low pressure moves closer rain will spread into the Ohio 
Valley by midday and across central Indiana by evening. Model 
soundings indicate ceilings and visibilities should approach IFR 
category kind...khuf and southward by 03z-05z tonight. Somewhat 
drier air will remain across northern Indiana and conditions there 
may remain VFR even though rain should spread as far north as 
klaf. 


As the low approaches northeast winds with gusts 20 to 25 knots are 
possible late today and tonight. 


&& 


Discussion... 


Forecast focus is on rain chances into Monday night along with 
temperatures. 


At 06z the front had settled not too far south of the forecast area. 
A surface low was across Arkansas...with the upper low across 
northeast Texas. Precipitation was across western Illinois and 
across western Tennessee. Movement was generally to the north. 


Models were in pretty good agreement with main features. Of course 
they have been in decent agreement recently but all were too fast 
with precipitation moving into the area. For this run decided to go 
toward the slower end of the models for precipitation...otherwise 
went with a blend. 


Isentropic lift continues throughout the day today...but best push 
of moisture and additonal dynamic lift does not occur until late in 
the day. Except for the southern third of the area...will keep the 
area dry this morning and then increase probability of precipitation from south to north 
during the afternoon. By 00z will have likely or higher probability of precipitation across 
the southern third of the area. Northeast flow at the surface will 
help slow arrival of rain across the northern area...so will only 
have low probability of precipitation there. Slower arrival of the rain should allow 
temperatures to warm to near the warmer mav numbers...which are 
supported by the sref mean. 


Tonight the surface low moves through Kentucky. Isentropic lift and 
qvector forecasts show forcing focused mainly across the southern 
two thirds of the area. Will go categorical probability of precipitation across this 
area...with likely probability of precipitation across the remainder. Mav seems to have a 
good handle on forecast lows with cooler temperatures northwest 
/where there will be less rain/. Will thus stick close to mav for 
lows. 


Lift wrapping around the backside of the system will continue to 
provide likely probability of precipitation across much of area on Monday. With the slower 
progression of the system...continued probability of precipitation all areas on Monday 
night. Rain will keep temperatures down on Monday...but some 
sunshine on Tuesday will allow a rebound to around 60 degrees. 


&& 




Ind watches/warnings/advisories...none. 


&& 


$$ 


Aviation...jh 
public...50