Area Forecast Discussion
Issued by NWS Northern Indiana

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637
FXUS63 KIWX 201930
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
330 PM EDT WED JUL 20 2016

.SYNOPSIS...
Issued at 330 PM EDT Wed Jul 20 2016

Mainly dry conditions will persist into Thursday morning before a
warm front brings low chances for showers and storms into the
forecast Thursday afternoon and evening across northern Indiana
and southern Michigan. Lows tonight will range between the mid 60s
and low 70s...with highs on Thursday into the upper 80s and low
90s. Afternoon heat indices will likely near 100 degrees. Hot and
humid conditions will continue Friday into the weekend with lows
in the 70s and highs in the upper 80s to mid 90s. Heat indices
each afternoon may exceed 100 degrees. There is also a chance for
thunderstorms through the period, best chances Friday morning and
again Sunday into Sunday Night.

&&

.SHORT TERM...(This Evening through Friday)
Issued at 330 PM EDT Wed Jul 20 2016

Heat/Humidity builds and low shower/storm chances Thursday-Friday...

Very humid/hot airmass over the Central US under expansive upper
ridge will continue to slowly fold east into the local area tonight
into Thursday with afternoon heat indices Thursday anticipated to
approach 100F into our IN/sw MI zones. Associated Instability
gradient/weak warm front has been fairly active across the
Mid/Upper MS Valleys the last couple of days and will need to be
monitored as it mixes into our IN/MI counties overnight into
Thursday. However, expect bulk of convection tonight to re-focus
more into the western/northern Great Lakes on nose of moisture
channel/LLJ. This activity will then need to be watched into
Thursday afternoon as boundary layer destabilizes and a
outflow/leftover boundary tries to spark sct convection into our
IN/MI counties. Probabilities of seeing any
redevelopment/convection this far south remains very low however
given northward bypass of any flow/forcing and capping concerns as
upper ridge becomes better established locally.

A low amplitude/convectively aided shortwave is then expected to
propagate ese through the Northern/Central Great Lakes later
Thursday Night into Friday briefly breaking down ridge. This
feature will bring slightly better chances for showers/storms
during this time as associated convective complex could hold
together south into a very moist environment early Friday morning
(best chances north)...with iso-sct redevelopment possible along
composite outflow Friday afternoon amid extreme instability (best
chances across ne IN/nw OH in the afternoon). If any storms can
develop they would pose an isolated wind/heavy rain threat at best
given lacking deep layer shear/flow. Otherwise, dangerous
heat/humidity the larger story on Friday with dewpoints expected
to be in the 70s and sfc ambient temps into the low-mid 90s by
afternoon. How warm we get/how extreme heat indices area will be
dependent on cloud debris which remains a bit uncertain at this
fcst range.

&&

.LONG TERM...(Friday Night through Wednesday)
Issued at 330 PM EDT Wed Jul 20 2016

Hot/humid weekend...then cooler/less humid/dry into early next
week...

Heights rebound with deeper moisture/weakening frontal boundary
likely stalling over or just south of the area Friday Night through
early Sunday will continue to support humid conditions and low
chances for showers/storms. The next low amplitude shortwave to
crest/flatten Central US upper ridge will drag a frontal system and
renewed theta-e surge through around Sunday/Sunday Night. This looks
to be the best opportunity for rain/storms (best chances in the
afternoon/evening) given weak height falls and better flow. Much
drier/less humid air then spills in for the first half of next week
post-frontal.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 136 PM EDT Wed Jul 20 2016

Convection to the west of Indiana this aftn will likely provide
some high overhead cloud deck to KSBN with some diurnal cu for
both sites. SSW winds of 7 to 10 kts will subside this evening to
around 3 kts. An isolated tstm is possible this aftn, but opted
to not mention in fcst.

&&

.IWX Watches/Warnings/Advisories...
IN...Heat Advisory from 2 PM Thursday to 8 PM EDT Friday for INZ006-
     007-009.

     Heat Advisory from 2 PM EDT /1 PM CDT/ Thursday to 8 PM EDT /7
     PM CDT/ Saturday for INZ003>005-008-012>018-020-022>027-
     032>034.

MI...Heat Advisory from 2 PM Thursday to 8 PM EDT Friday for
     MIZ077>081.

OH...Heat Advisory from 2 PM Thursday to 8 PM EDT Friday for OHZ001-
     002-004-015.

LM...NONE.
&&

$$

SYNOPSIS...Steinwedel
SHORT TERM...Steinwedel
LONG TERM...Steinwedel
AVIATION...Frazier


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