010
FXUS63 KIND 140113
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
913 PM EDT Wed Aug 13 2025

.KEY MESSAGES...

- Isolated showers and thunderstorms this afternoon.

- Slightly cooler and drier air today through Thursday night.

- Hot and humid Friday through early next week. Heat index values
  near or exceed 100 at times likely Saturday through Monday.

- Greater threat for thunderstorms to develop early next week ahead
  of a cold front with cooler and drier air expected by mid week.

&&

.FORECAST UPDATE...
Issued at 908 PM EDT Wed Aug 13 2025

Surface analysis late this evening shows strong high pressure in
place over Ontario, sagging southward into Illinois and Indiana. The
remains a diffuse, poorly defined cold front were found near the
Ohio River. Radar is becoming quieter as the very isolated storms
south of Indianapolis diminish as the heating of the day is lost.
GOES16 shows mostly clear skies across the forecast area, except for
a few diminishing CU across the southeastern third of the state.

Overnight, clear skies are expected to remain in place as our
weather will be controlled by the surface high to the north with
light NW winds. Forecast soundings show a dry column and subsidence
will remain in play. Models suggest dewpoint depressions overnight
will once again fall to 1-3F. Thus some patchy fog overnight cannot
be ruled out as lows should be mainly in the mid to upper 60s.

&&

.SHORT TERM (This evening through Thursday)...
Issued at 327 PM EDT Wed Aug 13 2025

Morning stratus has been slow to diminish and persists in a small
area north of Muncie and near Bloomington. Though slow, the process
has been steady and much of the previous stratus field has now
evolved into a scattered cumulus field. As more sunshine filters
through boundary layer instability has increased. This is also noted
by the appearance of the cumulus as they grow taller. ACARS
soundings out of IND show a weak capping inversion becoming less and
less defined. In fact, it may not even be there anymore as a few
showers are beginning to show up on radar east of Indianapolis.

Continued near-surface destabilization is likely this afternoon as a
weak cold front drifts southward through central Indiana. This front
may act as a focal point for convection, but the wind shift is so
weak that it may not matter all that much. Showers and thunderstorms
may develop randomly through the afternoon with a greater likelihood
along and ahead of the boundary. ACARS soundings show weak and
relatively uniform flow below 500mb, with increasing winds above
that. A distinct layer of dry air is also noted above 500mb, which
may lower the equilibrium level enough that parcels do not encounter
the stronger winds before leveling off. Still, a few updrafts may
gain enough height to tap these stronger winds and produce a long
anvil pointing northeastward. This may allow for greater storm top
venting but overall will have little effect as lapse rates are weak.
Nevertheless, some of the strongest cells may cause brief sub-severe
wind gusts.

Shower and storm activity should rapidly diminish after sunset as
instability is lost and the front pushes southward. Guidance shows
drier air filtering in from the north in the post-front environment
with dew points dropping into the low 60s. An isolated shower along
the front may still be possible overnight, but this seems like a low-
probability scenario as of right now. Patchy fog may once again
develop tonight times as skies clear, but will be limited compared
to this morning. Best chance of fog is across our south where the
front will be slower to pass through.

Thursday looks to be quite similar to today despite the frontal
passage. Temperatures should climb into the mid to upper 80s like
today but with lower dew points. The front may stall over our
southern counties or just south of our CWA border, which may allow
for very isolated showers and thunderstorms.

&&

.LONG TERM (Thursday night through Wednesday)...
Issued at 327 PM EDT Wed Aug 13 2025

The forecast turns to hotter to start the extended going into the
weekend. There is a subtle signal on many of the deterministic as
well as ensemble models for some isolated convection on Friday
afternoon associated with a weak shortwave /presently over the
northern corn belt/ which crosses the forecast area. However,
upstream soundings indicate a substantial capping inversion already
exists over the MS and MO valleys and thus any threat for precip
should remain negligible in line with the NBM pops under 10 percent.

As a deepening upper trough moves into the west coast, a strong
upper ridge centered over the four corners will shift east into the
plains Friday and into the MS valley by Saturday. By 12z Sunday the
ridge center is forecast to be just west of Central Indiana, with
500mb heights around 595dm, about as high as we`ve seen this summer.
This suggests that ridge rider pattern aforementioned yesterday will
likely initially be shunted further north as indicated by the 13/12Z
Euro model. However, for sake of consistency have opted to keep in
low pops in the far northern portion of the forecast area Sunday
afternoon. Confidence is increasing however that high temperatures
will be in the lower 90s Saturday and into the 93-97F range by
Sunday. With surface dewpoints ranging from 70-75F, expectation is
for a round of heat indices near to above 100F and very close to
advisory criteria by Sunday.

After Sunday the pattern becomes gradually more unsettled as the
upper ridge slowly breaks down thanks to approaching shortwaves from
the northern plains and to a greater extent the deepening longwave
trough over eastern Canada. There a slightly greater chance for a
ridge rider convective event in the northern parts of the forecast
area on Monday afternoon in line with much of the model guidance
which indicates a slight southward displacement of the ridge center.
Hot temperatures in the 90-95F range along with the possibility of
heat advisory criteria is expected to continue Monday despite some
increase in high cloud cover. More uncertainty exists with the hot
temperatures continuing into Tuesday based on any lingering
influences of convective outflow/clouds debris from Monday. However,
another day of temperatures into the lower 90s is very possible area
wide.

A fairly strong cold front should enter the forecast area sometime
late Tuesday/early Wednesday with a much greater threat for
widespread precip expected. Subtle influences from the eventual
track of Hurricane Erin could enhance of diminish the threat for
heavy precip with this system by helping slow down or accelerate the
associated cold front. In the wake of the front cooler and drier air
will build southward into Central Indiana by late Wednesday as a
1025mb high builds over the Great Lakes region.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 608 PM EDT Wed Aug 13 2025

Impacts:

- Mainly VFR this TAF period.
- MVFR Fog possible overnight at LAF/HUF/BMG.

Discussion:

Diurnal convection across Central Indiana will quickly end this
evening as heating wanes and the lingering cold front across
southern Indiana drifts slowly further south. HRRR agrees, showing
these isolated showers and storms dissipating.

Overnight, light winds and small dew point depressions will lead to
fog development, mainly at the more rural TAF sites. There has been
little overall change in the air mass, and given the fog this
morning, some fog overnight seems reasonable.

On Thursday, subsidence aloft along with surface high pressure
moving through Ontario and controlling Indiana/s weather will lead
to VFR conditions with NE winds and a few diurnal afternoon VFR CU.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...Puma
SHORT TERM...Eckhoff
LONG TERM...Crosbie
AVIATION...Puma