722 
fxus63 kind 180732 
afdind 


Area forecast discussion 
National Weather Service Indianapolis in 
332 am EDT Thursday Mar 18 2010 


Discussion...today through Sunday night. 


At 07z across the forecast area...a quiet night was shaping 
up...with temperatures in the lower 30s to the middle 40s and dewpoints 
as low middle 20s...under clear skies and a light north/northwest flow. 


Forecast issue of the day is temperatures...with very benign weather 
expected through the end of the work week. Secondary focus on precipitation 
late in the short term. 


Evening model runs were in relatively good agreement on the major 
features through Friday night...with the exception of the NAM which 
displays a significantly weaker and more progressive system 
approaching the area late in the week and through the weekend. 
Remaining guidance was in better agreement with respect to a potent 
cutoff low forming...but significant differences remained regarding 
placement of these features. A blend was used Sans NAM. 


Decent subsidence and dry air at the surface and aloft under the 
ridge will keep sensible weather none through much of the short 
term...with only a slow but steady increase in cloud cover late 
tonight into Friday night as first high clouds and then midlevel 
clouds build in ahead of approaching system. 


Evening runs were in good agreement in producing a decent round of 
precipitation...mainly late Saturday afternoon through Sunday...although 
lingering showers on the periphery or underneath the upper low 
appear possible Sunday night...along with the possibility that the 
system will be slower than depicted to push eastward...as is 
occasionally seen west/ these sorts of systems. Mav/mex probability of precipitation looked 
acceptable with minor tweaks. Model thicknesses are appreciably 
higher than the morning runs...and have removed snow mention from 
Sunday night. 


For temperatures...mav guidance looked relatively okay through the 
short term given evolution of expected 850 mb temperatures and 
expected cloud cover or lack thereof. Bumped guidance up a couple of 
degrees on maxes today and Friday based on 850 temperatures...decent 
mixing...and strong insolation...as well as upstream and local maxes 
yesterday. Guidance mins looked fine beyond tonight with only minor 
tweaks based on sky cover and precipitation expectations. Weekend maxes 
remain near ensemble means with major spread continuing in ensemble 
MOS. 


No changes day 5 and beyond. 


&& 


Aviation... 


Discussion for 18/0600z tafs. 


VFR through the period. A high pressure ridge was from the Central 
Plains to the Great Lakes early this evening. Models shift ridge 
axis slowly south to Ohio River 19/0000z resulting in light 
northwest wind and westerly Thursday remaining below 10 kts. 


Very dry air with surface dewpoints well below forecast min temperatures 
should result in fog free night despite clear sky and light wind. 


Slight amount of moisture around 5000 feet Thursday not expected to 
produce more than few cumulus...if even that...during day. Advancing 
cirrus late Thursday well ahead of approaching system in northern 
plains. 


&& 


Ind watches/warnings/advisories...none. 


&& 


$$ 


Public...nield 
aviation...tucek/jh