IND issues Area Forecast Discussion (AFD) at Jul 20, 1:59 AM EDT751
FXUS63 KIND 200559
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
159 AM EDT Mon Jul 20 2026
.KEY MESSAGES...
- Dry through Monday but upper level smoke will be over the area
- Growing concern for numerous strong to severe thunderstorms with
heavy rainfall late Monday night into Tuesday
- Noticeably cooler and less humid for the second half of the week
&&
.FORECAST UPDATE...
Issued at 1007 PM EDT Sun Jul 19 2026
No major changes necessary for this evening's forecast.
We appear to be on track temperature wise, with lows likely to drop
into the 60s across the area tonight - low 60s NE to upper 60s SW.
Light winds and mostly clear skies from a cloud cover standpoint,
along with lingering near surface haze, may help reduce visibilities
late as patchy fog develops in the outlying areas. Did add a patchy
fog mention to the grids.
Otherwise, any fog will mix out in typical diurnal fashion after
daybreak, with lingering smoke likely continuing to produce hazy
skies on Monday.
&&
.DISCUSSION (This Evening through Sunday)...
Issued at 146 PM EDT Sun Jul 19 2026
Hazy conditions with a milky sky this afternoon as the elevated
smoke layer from the Canadian wildfires has settled south across
central Indiana. Temperatures at 1730Z were mainly in the upper 70s
and lower 80s with lower humidity levels as well.
A drier and slightly cooler airmass will remain across the region
through Monday as high pressure passes through the Great Lakes.
Return flow will pull moisture back north into the Ohio Valley
Monday night ahead of a cold front with increasing signals for a
convective cluster producing heavy rainfall and possibly severe
weather to move across the area late Monday night into Tuesday. In
the wake of this feature...noticeably cooler and less humid air will
advect into the region for the middle and latter part of the week.
Rest of This Afternoon through Monday
Air Quality Alerts remain in effect for all but far southern
portions of central Indiana through Monday to account for the
ongoing smoke impacts. A continued N/NE flow into this evening will
become light and variable maintaining the smoke layer over the
region but as return flow develops on the back side of the high
pressure Monday...improvements are expected in visibility and
conditions from the southwest as the bulk of the smoke shifts back
to the north into the Great Lakes.
Monday Night and Tuesday
With the upper ridge focused back west across the Rockies and
central Plains...northwest flow aloft will develop into Monday as
the Ohio Valley and Great Lakes reside on the periphery of the ridge
and in an increasingly susceptible location for convective impacts
by Monday night. The presence of the high in the area through late
day Monday will maintain dry conditions but focus will shift to a
strong upper wave riding over the top of the ridge across southern
Canada. This feature will dive southeast across the Great Lakes
Monday night in tandem with a surface low over James Bay and an
associated cold front extending back into the upper Midwest.
Confidence continues to increase in an MCS developing to our
northwest and diving towards the region Monday night.
While there remain differences with respect to the actual evolution
and track of a convective cluster...the presence of a surface wave
along the boundary will promote an enhancement of speed and
directional shear in addition to higher SRH values across the lower
Great Lakes. Timing will be a factor in whether severe convection
will make it into the forecast area and if so how far...but the
greatest risk from an MCS moving into the region will be damaging
winds especially if a mature cold pool develops. The increase in
shear and SRH however would put all severe risks in play with a
primary focus over northern parts of the forecast area. The
orientation and strength of the low level jet in tandem with a rapid
influx of deep moisture and PWATS near 2 inches supports heavy
rainfall and flooding concerns as well and this may end up becoming
the main impact with the potential of a late night/predawn timing
early Tuesday. Rainfall rates will be efficient with the freezing
level near 15kft. Still details to be worked out but potential for
impactful convection late Monday night and early Tuesday continues
to grow.
The timing and extent of the overnight/early morning convection will
have a direct impact on what takes place during the day Tuesday with
the cold front across the area. In the wake of the convective
cluster...significant uncertainty exists regarding the degree of
destabilization as there is potential for an extended period with
leftover cloud debris limiting heating. Considering the kinematic
environment...any redeveloping convection along the front would
carry an inherent severe risk. The most likely scenario however is
that the greatest potential for severe weather will be to the
southeast of the forecast area Tuesday afternoon and evening. Any
convection will depart central Indiana Tuesday evening as high
pressure takes over with a cooler and drier airmass.
Wednesday through Sunday
A broad upper level trough will settle across the eastern pat of the
country for the second half of this week as the core of the heat
ridge remains centered over the High Plains. With a large area of
high pressure dropping out of the Canadian prairies behind the
Tuesday cold front...noticeably drier and cooler air will expand
across the region and provide a break from the humidity and storms
of late. Highs will remain in the mid and upper 70s over much of the
forecast area Wednesday and Thursday with comfortable overnight lows
into the 50s.
Return flow will develop as the high shifts east by Friday with some
potential for convection to track through the Ohio Valley in tandem
with an upper level wave. High pressure will reestablish in its wake
with dry and seasonable weather next weekend as highs return to the
mid and upper 80s by Sunday.
&&
.AVIATION (06Z TAF Issuance)...
Issued at 159 AM EDT Mon Jul 20 2026
Impacts:
- MVFR visibilities much of the night due to wildfire smoke/haze
and/or patchy fog; periods IFR possible near daybreak, primarily
at LAF
- Haze persists into Monday, primarily low end VFR conditions
Discussion:
Widespread haze is expected to continue through much of the period
due to wildfire smoke from the upper Midwest and Canadian fires.
Visibilities have been fluctuating between MVFR and low end VFR at
times, and expect that to continue through the night. Additionally,
some fog formation is likely at the outlying sites. This should
remain MVFR but periods of IFR are possible late tonight to near
daybreak, particularly at LAF. Will carry a TEMPO group for IFR
there and take all sites down to 3SM prevailing with a BCFG mention.
Visibilities should improve to low end VFR by morning, with haze
continuing. Some improvement in that regard appears likely late in
the day as winds shift to the southwest, though will carry 6SM/HZ
through the remainder of the period.
Winds will generally shift from northeasterly to southwesterly
during the period, remaining below 10KT. Some variability is likely,
particularly tonight, and periods of calm winds are possible.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Nield
AVIATION...KF
DISCUSSION...Ryan
Source:
IND issues Area Forecast Discussion (AFD) at Jul 20, 1:59 AM EDT---------------
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