IND issues Area Forecast Discussion (AFD) at Jul 19, 3:00 PM EDT211
FXUS63 KIND 191900
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
300 PM EDT Sat Jul 19 2025
.KEY MESSAGES...
- Strong to severe storms possible this afternoon and early evening,
with damaging winds the primary threat. Heavy rain and flash
flooding will also be threats, which will persist through the
weekend into early next week.
- Hot and very humid next Wednesday-Friday, yielding widespread and
potentially dangerous maximum heat indices in the 100s.
&&
.SHORT TERM (This evening through Sunday)...
Issued at 259 PM EDT Sat Jul 19 2025
THIS AFTERNOON
Radar trends have shown multiple storm clusters developing over
Illinois and portions of southern Indiana. These clusters are
generally non-severe, but have posed a flooding threat especially on
their flanks due to training / back-building. Flooding or even flash
flooding remains the primary hazard for the remainder of today.
ACARS soundings out of IND show a saturated column with weak to
modest lapse rates. The CAPE profile is tall and skinny, with values
around 1000-1500 J/Kg. Additionally, the sounding also indicates a
deep warm cloud layer of about 12,000 feet. As such, convection this
afternoon will likely be very efficient at producing high rainfall
rates. Rates between 1-2 inches per hour should be common in
convective cores, with perhaps rates to 3 inches per hour possible.
We have already seen flooding across portions of Knox County with up
to 3 inches occurring over a relatively short period of time. These
storms have since drifted south of our CWA. Upstream activity may
evolve in a similar manner...basically, storms develop and form a
cold pool which allows additional activity to propagate slowly
upstream (south or southwest). Corfidi upshear vectors are therefore
quite slow...around 12kt.
Flash flooding / flooding will be possible where storm motions are
slow and favor back-building or training.
Severe weather remains possible, but is becoming less of a concern
based on latest trends. The primary hazard today will be sporadic
marginally severe wind gusts. Such gusts are most likely where
bowing segments / localized surges occur.
Temperatures have likely reached expected highs for the day. As
rainfall moves across Indiana surface temps should begin to drop.
TONIGHT
Shower and thunderstorms could persist into the night as a residual
boundary left behind by today's activity moves northward. Some CAMs
are picking up on this but there remains little consensus, which is
to be expected given the dependence on prior convection. CAMs can
struggle depicting mesoscale features such as cold pools, and as
mentioned above can struggle when multiple rounds of convection are
possible...since each round depends a bit on the previous round.
Given weak synoptic forcing, these dependencies are high and CAMs
will likely continue to struggle. So take various CAM runs with a
grain of salt.
SUNDAY
A very similar situation as described during the tonight period.
Rounds of storms are possible along a NW-SE oriented boundary with
weak overall synoptic forcing. As such timing and location of storms
is uncertain. Heavy rainfall and flooding, along with a low chance
of a strong wind gust, remain the primary convective hazards.
Expect high temperatures to be lower near and just north of the
boundary due to clouds/showers.
&&
.LONG TERM (Sunday night through Saturday)...
Issued at 259 PM EDT Sat Jul 19 2025
The forecast philosophy from the previous discussion remains, and
no major changes were needed to the long term period with the
latest suite of guidance. The previous discussion will be
retained.
------------Previous Long Range Discussion--------------
Widespread hot and humid conditions expected to return for the
latter half of the long term, with potential dangerously high heat
indices. But first, more reasonable warm (yet humid) days to be the
rule late this weekend through Tuesday.
Sunday through Tuesday...
Canadian high pressure gradually tracking from the northern Great
Lakes to the Northeast will serve to keep the upper subtropical
ridge suppressed to the Heartland and points south. Corresponding
cool front along the southern edge of this northern surface ridge
will push south through the region Sunday, with the frontal zone
likely eventually pushing well south of the CWA...yet with the
center of the high passing well to our north, expect limited
reduction in surface dewpoints through Tuesday. Light east/
southeasterly breezes to be the rule through Monday and Tuesday as
the high passes to our north/northeast.
Scattered to perhaps numerous showers and t-storms will linger over
portions of the region amid the slowly passing frontal zone Sunday
into Monday. With potential for stronger storms amid this north-
south instability gradient...although so far low confidence in
heavier rainfall amounts for any particular location. Considerable
cloudiness with modest CAA will promote resultant mainly low to mid-
80s for highs Monday. Most pleasant conditions likely around the
Monday night to early Tuesday timeframe when passing northern high
should build furthest south/west into the region.
Wednesday through Friday...
Surface ridge to rearrange and amplify along eastern seaboard,
encouraging a prolonged light to moderate southwesterly flow into
Indiana...which will serve to build the upper subtropical ridge
northward into the Midwest. Widespread mid to possibly upper-70s
dewpoints will be the lead actor...coupled with afternoon highs
around the low 90s...to potentially produce daily maximum heat index
values around 100-110 degrees. This would be the highest heat
indices so far this year, and would warrant Heat product headlines.
Cannot rule out widely scattered, diurnally-driven convection,
especially toward the end of the long term...when the next, albeit
likely weak, northern stream wave will attempt to drag modest
forcing into the Midwest.
&&
.AVIATION (18Z TAF Issuance)...
Issued at 121 PM EDT Sat Jul 19 2025
Impacts:
- Mainly VFR, but periods of MVFR will be possible this afternoon
with SHRA/TSRA this afternoon and with BR overnight.
- Showers and storms expected 18Z-22Z across the TAF sites.
Discussion:
Decaying MCS over IL will be pushing across the TAF sites this
afternoon, early in the TAF period. Cloud cover through the morning
hours has limited heating somewhat along with instability. HRRR
suggests the continued progression of the showers with a continued
weakening trend. Thus have trended to a 2-3 hour window of
prevailing rain showers and vcts for the few residual rumbles of
thunder that will be possible.
CAM's have been haphazard in handling convection greater than 12
hours out. Although the HRRR suggests some lingering convection
tonight, there is low confidence for this given the afternoon rain
will limit heating and instability. Thus have left out precip mention
for now. However recent rain and a lingering boundary along with
light winds is still a good recipe for overnight diurnal fog.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Eckhoff
LONG TERM...AGM/Eckhoff
AVIATION...Puma
Source:
IND issues Area Forecast Discussion (AFD) at Jul 19, 3:00 PM EDT---------------
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