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Area forecast discussion 
National Weather Service Indianapolis in 
1024 am EST Wednesday Mar 10 2010 


Update... 


With dry slot on the way in satellite...and temperatures already 
pretty warm...will update to take todays maximums closer to mav. Slight 
chance of thunderstorm looks OK with more unstable air advecting in 
at low levels...but models agreeing about q vector convergence aloft 
by evening. 


Aviation...discussion for the 10/12z tafs. 


MVFR ceilings expected for the first 4-6 hours of the period...and 
then again late in the period as next more widespread round of 
precipitation moves into the area. Middle 12-15 hours of the taf period 
expected to be VFR...W/ broken-overcast deck around 3.5kft. With minor 
amounts of instability available today...outside possibility of 
isolated afternoon thunderstorms and rain...but confidence and coverage much too low 
in their occurrence to include any sort of mention in this package. 


Otherwise...southerly winds of 10-14 g18-20kts expected this 
afternoon. Winds at or below 10 knots through the remainder of the 
period. 


&& 


Discussion... 
near term... 
analysis as of 3 am this morning depicts a surface/500 mb low spinning 
across the northern plains. This system continues to produce widely 
scattered showers across the forecast area this morning...and will 
continue to do so as the low shifts northward...eventually tapering 
off toward the afternoon hours. Some elevated convection was noted 
earlier...mainly across portions of southern Illinois where they had a 
few rumbles of thunder. Additional elevated convection may be 
possible through this morning (based on radar trends and model 
soundings) especially across the southern tier, so opted to 
include some isolated thunder through this morning. Later this 
afternoon model soundings show more impressive elevated cape 
values over central in...but moisture will be problematic by this 
time as the initial low moves further north and weakens, leaving 
US in a dry slot...so have limited probability of precipitation to slight chance 
showers/thunder. Warmer temperature trends continue today...highs 
low 60s north to upper 60s S. 


For tonight all models are in agreement with a lull in precipitation 
activity...especially across the northeast. Depending on 
timing...the warm front approaching from the southwest could bring 
an initial round of showers to southern in overnight. Decided not 
to stray far from current probability of precipitation in the grids as this depicts the 
scenario well. Also...soundings show that with warm moist air from 
the southeast infiltrating over the area the air mass will remain fairly 
unstable...with minimal-moderate cape/MUCAPE values. Therefore 
mention of isolated thunders was kept. Lows tonight middle-upper 40s 
north to near 50 S. 


Short term... 
focus then turns to Thursday where all models seem to be good agreement 
on the overall pattern. Another secondary...much stronger/compact 
upper low gets ejected from the SW US on Wednesday where it is prognosticated to 
shift newrd and eventually to a position across the Central Plains 
on Thursday. This feature will bring a better shot of precipitation to the 
region. Again...current forecast appears to be in good shape...left 
90% probability of precipitation with chance for thunder in grids. Debated on whether to 
elevate thunder to likely...as Storm Prediction Center has placed the forecast area in 
a general risk...but have some doubts at this point as how much the 
atmosphere will destabilize this far north. For now think chance 
thunderstorms fits the profile. In any case...showers could 
produce periods of heavy rain...especially with any thunder...as 
precipitable waters  are running close to an inch. So widespread quantitative precipitation forecast amounts of 
0.5-1" look pretty reasonable. Thinking that precipitation should be 
somewhat steady enough through Thursday/Friday night that flooding should not 
be as much of an issue...though will certainly need to keep an eye 
on this system and update forecast if trends change. 


For Friday...it appears the area could get dry slotted once again 
before additional precipitation get wrapped back up into our area with the 
aide of a southern stream system for the weekend. For now trended 
probability of precipitation back to chance from likely on Friday. 


Extended... 
upper low hangs around the Ohio Valley at least through 
the weekend so have continued with rain chances/mostly cloudy skies 
and cooler than average highs during that time. By Monday this could 
be improving and went with that scenario although ensemble 
disagreement is pretty high by that point. 


&& 


$$ 


Ind watches/warnings/advisories...none. 


&& 


$$ 


Public...kwiatkowski/sflechtner 
aviation...nield