IND issues Area Forecast Discussion (AFD) at Aug 15, 1:40 PM EDT
275
FXUS63 KIND 151740
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
140 PM EDT Fri Aug 15 2025
.KEY MESSAGES...
- Hot and humid through early next week. Heat index values near or
exceeding 100 at times likely Saturday through Tuesday.
- Greater threat for thunderstorms to develop Tuesday and Wednesday
ahead of a cold front with cooler and drier air expected by mid week.
&&
.FORECAST UPDATE...
Issued at 959 AM EDT Fri Aug 15 2025
Another hot summer day expected across Central Indiana with highs
reaching or exceeding the 90 degree mark. Satellite imagery shows
mainly sunny skies this morning, but expect a few afternoon cumulus
to develop once low level mixing kicks in. Kept today's highs in
line with short term guidance, in the lower 90s; however afternoon
heat indices may exceed 100 along and south of the I-74 corridor as
humidity levels increase further south. Low level flow is very weak,
so not expecting winds to increase substantially despite deeper
mixing later today. Winds should largely remain under 4-8 mph.
Watching for the possibility of weakening storm complexes to push
towards Central Indiana from the Northwest tomorrow and Sunday.
Uncertainty remains in the longevity and southward progression of
these potential MCSs; however forecast updates will likely be needed
later today to account for increasing storm chances along and north
of I-70 the next few days.
&&
.SHORT TERM (Today and tonight)...
Issued at 301 AM EDT Fri Aug 15 2025
Early This Morning...
Some weak lift ahead of an approaching upper trough was generating
some patchy clouds around 6000FT. Otherwise, skies were clear and
winds light. These conditions have allowed some patchy ground fog to
form in some favored areas.
Expect the above conditions to persist through the early morning
hours with nothing coming along to change things.
Today...
Any patchy fog will mix out very early in the period. The weak upper
trough will move through during mainly the first half of the day,
continuing to produce some patchy clouds with it.
As the upper trough exits, an upper high will nudge its way into the
area. At the surface, high pressure to the east of the local area
will allow a southerly component to the wind. These will bring
higher dewpoints back into the area.
Scattered cumulus will pop up during the day, but warming mid-level
temperatures should prevent these from growing into showers and
storms. However, cannot absolutely rule out a stray shower. Odds for
these will be less than 15 percent, so will not mention.
Highs will be around 90 today, but it will feel more like the lower
and middle 90s thanks to the higher dewpoints.
Tonight...
Cumulus will dissipate this evening, but some high clouds from
convection well to the northwest may move into the area during the
night. With the higher dewpoints and light winds expected, patchy
ground fog will develop in favored areas.
A few CAMs are showing convection riding around the upper high into
the area late tonight. However, these develop storms farther south
than would be expected given location of forcing. Will side with the
majority of CAMs and keep the area dry.
Lows will be in the upper 60s and lower 70s.
&&
.LONG TERM (Saturday through Thursday)...
Issued at 301 AM EDT Fri Aug 15 2025
Saturday through Monday...
The main focus early in the extended will be unseasonably hot and
humid conditions. Aloft, ridging remains near the region keeping an
anomalously hot airmass in place. Highs in the low-mid 90s combined
with high humidity will lead to peak heat indices reaching near 100-
105 degrees each afternoon. Increasing low-level moisture may be
enough to promote a few diurnal showers Saturday given strong
daytime heating, but potential appears too low to add any rain
chances at this time.
Guidance suggest there is another slightly higher chance for
precipitation Sunday or Monday when upstream storm complexes riding
along the ridge propagate towards the area. These storms should
weaken as they move into a less favorable environment over Indiana
with weaker forcing and deep-layer shear. However, cannot rule out
convection persisting into portions of central Indiana. Will keep
low POPs primarily over northern counties on Sunday to account for
the low potential. POPs were not added for Monday due to diverging
model solutions limiting forecast confidence.
It is typical for models to struggle with these subtle impulses
riding along the northern periphery of ridges. Rain chances will
likely need to be refined once guidance becomes better aligned. Any
convection or convective cloud debris could limit peak heat indices.
Tuesday onward...
Upper troughing setting up over the region Tuesday and Wednesday
along with a cold front moving through will support better chances
for precipitation. Uncertainty in exact details remains due to
diverging model solutions though. Expect greater coverage of showers
or thunderstorms with the threat for localized heavy rain and gusty
winds. Peak heat indices around 100-105 are still possible Tuesday
ahead of the cold front before cooler air filters in mid-late week.
Highs should generally fall into the 80s again towards late next
week with lower humidity. Rain chances will also diminish as a drier
airmass moves in.
&&
.AVIATION (18Z TAF Issuance)...
Issued at 139 PM EDT Fri Aug 15 2025
Impacts:
- Patchy fog possible again at KBMG late tonight
- Isolated storms possible after 12z tomorrow for KLAF, later in the
day for KIND
Discussion:
Mainly VFR conditions expected for the rest of today across Central
Indiana. Satellite imagery shows afternoon cumulus beginning to
develop with bases around 4500ft agl...these clouds will follow a
typical diurnal trend and diminish around sunset.
Similar set up expected tonight with light to calm winds and clear
skies, leading to good conditions for patchy fog formation in
valleys. Added fog to only KBMG...confidence is not high enough for
fog at KLAF and KHUF to include it in the TAF.
Main focus for tomorrow will be the threat for weakening showers and
storms pushing in from the northwest beginning around 12z. Guidance
over the past 24-36 hours has been consistent in showing weakening
showers and storms making it over the ridge and into Central
Indiana. This type of pattern does support an isolated to scattered
storm threat, so have introduced this in the KLAF and KIND TAFs.
Will updated the TAFs accordingly for timing later this evening and
tonight as confidence grows on the finer details of storm evolution
tomorrow. Brief periods of MVFR or worse conditions possible under
any storm.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...CM
SHORT TERM...50
LONG TERM...Melo
AVIATION...CM
Source: IND issues Area Forecast Discussion (AFD) at Aug 15, 1:40 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202508151740-KIND-FXUS63-AFDIND)
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