Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 241736

Area Forecast Discussion
National Weather Service Northern Indiana
136 PM EDT WED AUG 24 2016

Issued at 357 AM EDT Wed Aug 24 2016

Shower and thunderstorm chances will increase through Thursday
ahead of a slow moving cold front. Locally heavy rain will once
again be a concern. Highs will be in the upper 70s to middle 80s
with lows around 70.


.SHORT TERM...(Today through Thursday)
Issued at 357 AM EDT Wed Aug 24 2016

Challenging forecast with respect to shower/storm chances across the
region until cold front and upper level features depart Thursday

Convection has been ongoing to some extent well back to the west
from southern Minnesota into northern Missouri. 2 areas of storms
have now merged (one moved SE out of SW Iowa, the other was in NW
Missouri). HRRR/ESRL HRRR/RAP have all handled this activity fairly
well as track it east over the next several hours. Prior to its
arrival...nose of increasing theta e air resided over central
Illinois with 30 to 40 kt low level jet just to the west. The same
models all suggest widely scattered shower (storm?) activity to
develop in the 8 to 10z window over SW areas and then move east
through 12z. Originally dismissed as noise...but recent radar echos
from Lk Michigan to Indy give some credence to having something
mentioned. Have retained a pre-1st period mention in the zones for
slgt chc to chc pops for now to handle this part. Timing of earlier
mentioned convection would be after 14z with a weakening trend
expected as low level jet temporarily weakens. Have went chc pops
into late morning to handle the upstream convection.
Departing/weakening convection could hamper any substantial heating
which would limit development until approach of the next wave late
this afternoon into evening.

Will hold onto likely pops this evening as low level jet ramps up
again and help get storms going. PWATs will increase to 2 inches or
greater making localized flooding an issue. Some of the same Hi-Res
models used for today shows coverage may not be as widespread as
previously thought and possibly confined more NW.

Finally...cold front will approach the region with at least
scattered showers and storms. Impacts from overnight convection and
subsequent heating will all be key factors in additional rain
chances. Went high chance pops for now with potential to need to
increase. Severe threat for today and tomorrow on the lower end but
still something to watch.


.LONG TERM...(Thursday Night through Tuesday)
Issued at 357 AM EDT Wed Aug 24 2016

Main shortwave energy will move well NE of the area with dry
conditions returning to the area for a few days before the next wave
ejects from the western states towards Sunday. Forecast will
continue riddled with slight chc to chance pops through the
remainder of the period as timing and impacts of several weak waves
move through the area on the periphery of upper level ridging over
the SE states. Entire upper air pattern remains somewhat suspect
into next week as impacts from a tropical system are unknown for the
area at this time.


.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 135 PM EDT Wed Aug 24 2016

Shortwave currently moving across the area and supporting some
decaying showers and storms along leading theta-e ridge. Increased
low level moisture supporting some low MVFR ceilings along and
immediately behind line of showers with some brief IFR not out of
the question at KSBN. Weak instability is keeping thunder very
isolated so far but a secondary area of convection is forming
across northern Illinois and could bring a few SCT storms to the
terminals this afternoon. Confidence in thunder is not high so
kept just VCTS for now. Timing also a bit uncertain, though best
chances should be during late afternoon and early evening. Expect
low clouds to scatter late this evening but another round of MVFR
possible toward daybreak, especially at KSBN.


.IWX Watches/Warnings/Advisories...


LONG TERM...Fisher

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