FXUS63 KIND 171142

Area Forecast Discussion
National Weather Service Indianapolis IN
742 AM EDT Wed Jul 17 2019

The AVIATION Section has been updated below.


Issued at 303 AM EDT Wed Jul 17 2019

Weak area of low pressure, tropical remnants, centered over
Northwest Ohio will continue to weaken and become asborbed into a
frontal boundary that stretches west to east across Southern Lower
Michigan east through Lake Ontario. Another area of low pressure
will lift northeast into Wisconsin and pull the frontal boundary
north allowing southwest flow to build heat and humidity into the
Ohio Valley and Missouri Valley regions later this week into the
upcoming weekend.


.NEAR TERM /Wednesday through Wednesday Night/...
Issued at 303 AM EDT Wed Jul 17 2019

Early this morning scattered showers continue to rotate around the
remnants of the tropical system. Given the high PWAT values within
the atmosphere, it remains a moisture rich environment with very
efficient rainfall rates and large droplets, which is indicative
of a tropical environment. Temperatures remain very mild early
this morning with lows holding in the lower 70s and dewpoints
mirroring the temps around 70 as well. Fortunately some light
south winds is helping to keep fog development minimal, but could
see some pockets of reduced VSBYs from patchy fog prior to

Guidance has continued to back off on precip coverage today, as
the tropical remnants becomes more of an open wave and asborbed
into the approaching mid-level trough that is riding east along
the frontal boundary. Thus expect precip to come to an end across
Central Indiana by midday or early afternoon, with any precip
being scattered. Guidance has also backed off on the thick cloud
shield inhibiting the potential for very hot conditions today;
however, some erosion to the clouds is expected by later this
afternoon. This could lead to temps, under a southwest flow,
warming further into the upper 80s.


.SHORT TERM /Thursday through Friday Night/...
Issued at 303 AM EDT Wed Jul 17 2019

The main focus for the short-term will be the developing dome of
heat and humidity parked over the Ohio Valley. The longwave
pattern depicts 500hPa heights rising overhead, acting as a cap to
the atmosphere and inhibiting the potential for organized
convection. The low-level flow will turn southwesterly, as parcels
originate from the western Gulf of Mexico and Southern Plains.
Robust thermal ridge at 850hPa will advect north/northeast across
the Ohio Valley. This will all translate into a very warm/humid
setup to Central Indiana for several days beginning Thur.

Dewpoints will likely remain in the lower 70s for this stretch,
with afternoon high temps in the lower 90s. The combination will
dovetail into many locations experiencing heat index values
exceeding 105 degrees, and perhaps even warmer around 110 for the
heat island locations. Given Central Indiana will have just
experienced a few days much cooler and less humid, and this will
also be the hottest strech of days this summer, we will hoist an
excessive heat watch and could see a trend towards heat warning
both Thur/Fri. It is also the cumulative effect that is concerning
for many areas of Central Indiana.

Anti-cyclonic flow will inhibit convection for the bulk of the
medium term, shifting any convection north along the northern
periphery which is typical of these types of weather patterns.


.LONG TERM /Saturday through Tuesday Night/...

Issued at 332 AM EDT Wed Jul 17 2019

The main focus of the extended period will continue to be on the
excessive heat and humidity. A heat watch has now been issued for
Saturday and Sunday with highs progged to climb into the mid 90s.
Meanwhile, dewpoints will be in the 70s, and heat indices will
feel like 100 to 105 degrees. It won't be until early next week
when the heat breaks a little and highs drop slightly into the mid
to upper 80s.

Low chances for mainly diurnally driven convection can be expected
on Saturday. However, the shower and thunderstorm chances will
increase on Sunday as a frontal boundary stalls over central
Indiana. Additional weak forcing from a broad upper low will
provide further support for some shower and thunderstorm
development on Monday. Further out, dry conditions will prevail
Tuesday as the upper ridge becomes reestablished.


.AVIATION /Discussion for the 17/12Z TAF Issuance/...

Issued at 737 AM EDT Wed Jul 17 2019

TAF sites will range from LIFR to MVFR through mid morning then
improve to MVFR/VFR. Scattered rain showers with some isolated
embedded thunderstorms will linger into today until the remnants
of Barry exit the region. After that, VFR will become the
predominant flight category with light and variable winds.


Excessive Heat Watch from Thursday afternoon through Sunday
evening for INZ021-028>031-035>049-051>057-060>065-067>072.



Back to Main Forecast Discussion Page