Area forecast discussion 
National Weather Service Indianapolis in 
1232 am EDT Thursday Aug 28 2014 


Update... 
aviation section has been updated below. 


&& 


Synopsis... 
issued at 227 PM EDT Wednesday Aug 27 2014 


A one day respite from heat and humidity Thursday as a slightly 
cooler and less humid high pressure system moves across the Great 
Lakes and pushes the surface front to the Ohio Valley. A trough 
moving northeast out The Rockies will lift the surface boundary 
back to the Great Lakes by Friday to return the heat and humidity 
for the weekend. Another trough should reduce the heat and 
humidity again but not until after the Labor Day weekend. 


The one day heat respite should also remain rain free but the 
return of the front...heat and humidity Friday also renews the 
daily threat for storms. The main thrust of The Rockies trough 
will arrive Saturday and bring the highest threat for 
storms...before the next trough and highest threat arrives by next 
Tuesday. 


&& 


Near term /tonight/... 
issued at 637 PM EDT Wednesday Aug 27 2014 


Have updated to confine slight chance probability of precipitation and isolated thunder 
wording to south of Interstate 70 in accordance with latest radar 
trends and satellite presentation. Little to no cumulus with any 
sort of vertical extent in the city and northward...thus do not 
expect storms here as heating is waning. 


Any isolated storms will likely die off by 10 PM if not 
earlier...and will continue with a dry forecast for the remainder 
of the night beyond then. Previous discussion follows. 


Issued at 227 PM EDT Wednesday Aug 27 2014 


Forecast problem is whether storms will occur and what part of 
central Indiana if any. 


Cumulus field over indy and to the north has little vertical 
development...much more like that seen in a Post-frontal 
setting...compared to the sharp edged and tall cumulus towers of 
recent days that produced rain and storms. Lone cell down near 
Louisville firing out of cloud bases near 3500 feet compared to 
nearby ragged bases around 2000 feet. Lone cell near Quincy and 
lone shower west of Terre Haute are moving east-southeast bound along the 
convective cloud boundary and instability gradient. All said... 
will keep an early evening rain/storm threat which will fall along 
and south of i70 and this boundary will settle south and dissipate 
a little after sunset. 


Dewpoints still riding high in the 70s but middle and lower 60 
dewpoints not far to the north and will filter in overnight. 
Expect min temperatures near the current forecast of lower 60s north to 
near 70 in the far south as it takes a while for air to dry out 
without significant wind. 


&& 


Short term /Thursday through Saturday/... 
issued at 227 PM EDT Wednesday Aug 27 2014 


Forecast issue is return of precipitation timing. Models are 
starting to come into better agreement on this and have used a 
blend. 


Have dropped rain chances in many areas Thursday as high pressure 
moving across Great Lakes takes control. A fair amount of middle 
cloud debris spilling over upper ridge Thursday from system 
lifting into the upper Midwest will mean periodic sunshine. That 
combined with lower dewpoints and lower starting temperatures 
Thursday will mean most locations will have a noticeable change 
to the airmass...not substantial but noticeable. Far southwest 
counties closest to the returning surface front may have a slight 
threat for a shower Thursday afternoon but lift and moisture is 
somewhat limited relative to recent days. 


Stronger warm advection and further northeast lift of the surface 
front Friday will mean a return to higher temperatures and dewpoints back 
towards 70 resulting in better chances for storms. This storm 
threat increases even more Saturday as The Rockies short wave 
trough of today crosses the Great Lakes. 


As for temperatures...both mins and maximums will do a slow rebound 
after Thursday and return to lows not far from 70 by Friday and 
highs back near 90. Should Saturday be a relatively cloudy and 
stormy day...that may keep highs back in the upper 80s. 


&& 


Long term /Saturday night through next Wednesday/... 
issued at 200 PM EDT Wednesday Aug 27 2014 


Ensembles indicate an unsettled weather pattern will continue as one 
trough moves across the region early in the period...only to be 
followed by another...possibly deeper trough Monday of next week. 
This will allow for daily chances for precipitation as upper 
disturbances rippling through the flow interact with a frontal 
system. Will continue to carry probability of precipitation throughout the extended. 
Allblend initialization appears to handle this pattern well. 


&& 


Aviation /discussion for the 280600z taf issuance/... 
issued at 1232 am EDT Thursday Aug 28 2014 


VFR through the period...with the possible exception of khuf and 
kbmg where MVFR fog is possible there late tonight and early 
Thursday. 


A weak frontal boundary will remain near stationary across the lower 
Ohio and middle Mississippi Valley through Thursday night and then move 
northeast Friday. Drier air will spread into at least kind and klaf 
tafs which should limit any threat of MVFR fog there. Dewpoints 
will be a little higher at khuf and kbmg which may allow a period of 
MVFR fog there. 


On Thursday...expect scattered cumulus with scattered to broken middle 
clouds as showers and thunderstorms increase to our west. An 
isolated cumulonimbus may spread into west and southwest sections later 
Thursday or Thursday evening...but chances are low and will not 
mention at this time. 


Winds will be northeast up to 5 knots overnight and become east on 
Thursday. 


&& 


Ind watches/warnings/advisories...none. 


&& 


$$ 


Synopsis...tucek 
near term...tucek/nield 
short term...tucek 
long term....smf 
aviation...jh 


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