Area forecast discussion 
National Weather Service Indianapolis in 
636 am EDT Thursday may 23 2013 


Update... 
the aviation section has been updated below. 


&& 


Synopsis... 
issued at 420 am EDT Thursday may 23 2013 


A large upper level trough will swing through the area today 
accompanied by a secondary cold front. This will bring showers 
today and significantly cooler temperatures into the weekend 
across central Indiana as a large area of surface high pressure 
settles across the region. This will also provide a break from the 
recent unsettled weather. 


&& 


Near term /today/... 
issued at 420 am EDT Thursday may 23 2013 


Fairly straightforward forecast today. Upper trough will finally 
swing through the area along with a reinforcing cold front which 
will bring the significant cool down to the area. Temperatures 
will likely not rise much in the northwestern forecast area today 
as the front will begin to push into the area this morning. Some 
opportunity for warming will exist across the southern forecast 
area this morning before the front and associated thick low level 
cloud cover sweep into the area. 


The upper trough should spark some scattered showers...especially 
late this morning into middle afternoon...as low level moisture 
remains...and some very weak instability may be present ahead of 
the front. However...most unstable cape values hardly even 
Register in the 100-250 j/kg range...and even this mainly across 
the southeastern third of the area. While an isolated rumble of 
thunder would not be completely shocking...especially if some 
mixing occurs and creates some breaks in the cloud cover...this 
seems unlikely and low probability enough to carry only showers 
and no thunder mention. 


A MOS consensus bumped up slightly and with a tightened gradient 
appears best on maximum temperatures today...and agrees well with upstream 
maxes. Temperatures are likely to be falling across much of the 
area this afternoon in the wake of the front. 


&& 


Short term /tonight through Saturday night/... 
issued at 420 am EDT Thursday may 23 2013 


Beyond a very slight chance of a lingering shower in the far 
eastern forecast area just past 00z...sensible weather in the 
short term will be none as high pressure drops into the region. 
Skies should clear quickly across the area tonight and this along 
with ongoing cold advection should allow temperatures to bottom out in 
the low to middle 40s. Clear skies will continue at least into Friday 
and Friday night. Ample sunshine should allow maximum temperatures during the 
day to exceed guidance by a degree or two. Min temperatures should warm 
gradually but not quite as fast as guidance depicts with only some 
limited middle and high cloud cover to inhibit overnight cooling 
likely late in the period. 


Models do want to produce some light quantitative precipitation forecast Saturday and Saturday 
night along a weak baroclinic zone lifting into the area. 
However...forecast soundings depict very dry low levels...and 
appreciable moisture return will be a struggle with midlevel 
ridging across the Gulf Coast states. May very well see some 
thunderstorm development over the top of the upper ridge in the 
central/northern plains late in the short term...but with the 
aforementioned dry air and essentially none instability...this 
activity would be unlikely to persist this far east. 


&& 


Long term /Sunday through Wednesday night/... 
issued at 152 am EDT Thursday may 23 2013 


Temperatures will gradually warm through early next week. Models continue to 
depict a weak upper level disturbance making its way into central 
Indiana from the northwest Sunday into Monday...which could possibly bring 
showers and isolated thunderstorms to the area. Seeing as we will 
still have a surface high over the area confidence is still as to 
whether this will pan out. Left probability of precipitation at slight to low chance 
(20-30%). Dry again Monday night through Tuesday and then another system 
approaches the area by middle week next week. High temperatures warm into the 
low 80s by Wednesday. 


&& 


Aviation /discussion for 231200z taf issuance/... 


Issued at 625 am EDT Thursday may 23 2013 


Tafs becoming mostly MVFR ceilings this morning and then VFR by 
late this evening. 


Low pressure will track east across the Great Lakes and a trough 
of low pressure will rotate across central Indiana. Lower ceilings 
will spread southeast across central Indiana late this morning. 
Light scattered showers will also occur. As the trough of low 
pressure rotates on to the southeast. Much drier air will spread 
in from the northwest by this evening and rapid clearing possible 
towards end of the forecast period in some areas. 


Winds will become northwest around 15 knots by midday. Winds will 
diminish this evening as low pressure trough moves on to the 
southeast. 


&& 


Ind watches/warnings/advisories... 
none. 
&& 


$$ 


Synopsis...nield 
near term...nield 
short term...nield 
long term....smf 
aviation...smf 


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