303
FXUS63 KIND 180055
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
855 PM EDT Thu Jul 17 2025

.KEY MESSAGES...

- Daily storm chances continue through at least early next week with
  cooler temperatures through Friday.

- Strong to severe storms Saturday with the potential for flooding,
  especially into the morning hours on Sunday.

- Likely hazardous heat conditions towards next Tuesday and beyond
  with heat indices in the 100s.

&&

.MESOSCALE UPDATE...
Issued at 854 PM EDT Thu Jul 17 2025

As of 845PM, not much has changed with thoughts on the ongoing
heavy rain with the main area of concern near Ellettsville which
has seen 90 minutes of heavy rain with much of Monroe county
seeing at least occasional heavy rain. There has been some
additional development to the south where heavier rain fell
earlier, but that is moving fast enough to limit impacts.

The outflow boundary is generally stalling along much of the broken
line which is limiting the northern progression, but also bringing
additional areas into potential concern for flooding as storms stop
moving.


Previous discussion below:

As of shortly after 7PM, coverage of rain continues to slowly
increase but the stronger convection has begun to decrease with
latest lightning rates trending slowly downward with the loss of
daytime heating. There is a slow northerly moving outflow boundary
that continues to initiate additional convection with a broken area
of storms stretching from south of Terre Haute to south of
Shelbyville. These storms are slowly propagating northward but there
are isolated areas where storms are remaining more rooted in place
which is causing pockets of flooding.

Flooding was worst earlier towards Daviess county with additional
heavy rain north of Vernon and in the Farmersburg area. Will be
watching the Bloomington area as they have seen heavy rain with 1/4
mile visibility for the last 10 minutes and with the very urban
nature of the town, flooding danger is greater.

The 12Z NAM has handled the ongoing convection better than most
models for the second day in a row, so will be leaning the forecast
in that direction through at least the early overnight with the
expectation that this convection will continue to slowly move
northward but should only reach around the I-70 corridor before the
loss of daytime heating helps to weaken the outflow and cut-off
additional propagation.

&&

.SHORT TERM (This evening through Friday)...
Issued at 254 PM EDT Thu Jul 17 2025

Rest of Today and Tonight.

As of early this afternoon, shower coverage is minimal with a few
residual showers across the far south eastern counties. A diffuse
frontal boundary is currently across far southern Indiana which will
be the focus point for additional thunderstorm development into the
afternoon and evening hours. This will likely keep the
shower/thunderstorm potential to a minimum through around 00Z. There
remains a lot of uncertainty as to how conditions will evolve going
into the afternoon hours with significant model swings between the
hourly HRRR runs as it struggles to initiate and maintain convection
in a hot and humid airmass with only marginal forcing. Based on the
current location of the front the better chance for heavier rain
looks to be more across far southeastern Indiana so have elected
against a Flood Watch for our southeastern counties, but will
continue to monitor radar trends into the evening for any potential
need for Advisory/Warning products.

A lack of shear should prevent any significant organization with
these storms with the most likely outcome being scattered showers
with a few storms developing over the next few hours and continuing
into the late evening hours. Storm motion should be fast enough to
limit the flooding threat, but many locations in southern Indiana
have seen at least one round of heavy rain in the last week which
will create areas that are more susceptible to brief flooding. Some
models try and keep convection going into the later overnight hours
but without a more robust LLJ, a lack of moisture flux should limit
the coverage. There will be a potential for patchy fog across
southern Indiana towards daybreak tomorrow, especially in areas that
see rain tonight but with expected widespread cloud cover, dense fog
looks unlikely at this time.

Friday.

The front should be along the Ohio River by Friday which will limit
the rain potential for much of central Indiana, but expect to see at
least partly cloudy skies through much of the morning hours with
residual saturation in the low levels. These clouds will begin to
clear later into the afternoon, but that should limit the higher end
temperatures with highs closer to the mid 80s.

&&

.LONG TERM (Friday night through Thursday)...
Issued at 254 PM EDT Thu Jul 17 2025

Friday Night through Monday...

Typical, hot, humid weather with daily chances for convective
showers and thunderstorms are expected to persist through the
weekend.

The upper pattern through the weekend appears to remain mainly zonal
across Indiana and the Great Lakes, with several embedded short
waves within the flow expected to pass on Saturday and again on
Sunday. The lower levels will continue to be dominated by strong
high pressure southeast of Central Indiana, which continued provide
a flow of warm and moist air into Central Indiana. Forecast
soundings continue to suggest plenty of diurnal CAPE available on
both Saturday and Sunday with values in excess of 2500 J/KG with
steep lapse rates favorable for convection. Thus with plenty
moisture available, favorable forcing passing aloft along with
diurnal heating will continue to result daily chances for showers
and thunderstorms. PWATS will continue to be very high through the
weekend, over 2 inches. Should the same location be stuck with
multiple rounds of heavy rain, flooding may be threat.

Temperatures and dewpoints through the weekend will remain quite
high. Dew points are expected to linger around 70 with daily highs
in the upper 80s to around 90.

Monday through Thursday...

The upper pattern is expected to begin to change on Monday, going
from a zonal flow to a more of a ridging pattern aloft with strong
high pressure aloft settling over the Ohio and mid-Mississippi River
valleys. The ridge and high pressure aloft will help to steer any
forcing dynamics well north of Central Indiana, toward Ontario.
However, a very hot and humid air mass will remain in place through
the middle of next week. The high aloft will provide subsidence
through midweek, helping to trap moisture within the lower levels.
Dew point temperatures are expected to reach the upper 70s to around
80 by mid week, resulting in some of the most humid weather Central
Indiana typically sees during the course of the year. With daily
high temperatures in the low to mid 90s, heat index values are
expected reach the mid 100s, resulting some of the hottest
temperatures of the summer.

Forecast soundings during this stretch show ample CAPE available
each afternoon through midweek. Thus with the very moist air mass in
place, daily afternoon showers and thunderstorms cannot be ruled
out. We will continue to include low chances for daily showers and
storms with during each afternoon and evening.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 652 PM EDT Thu Jul 17 2025

Impacts:

- Convection at BMG and HUF through at least 04Z, lower threat at
  IND through 06Z
- MVFR cigs 08Z to 14Z

Discussion:

Shower coverage will continue to increase through 01Z with a gradual
northward progression of ongoing thunderstorms. Greatest impacts
will be at BMG with brief LIFR to IFR vsbys and MVFR cigs. Vsbys
will be closer to IFR and HUF and IND. Additional convection may
continue through the night but coverage will be minimal and doesn`t
warrant a mention in the TAF at this time. Cigs will drop into MVFR
to potentially IFR late tonight into tomorrow morning. Winds will be
generally northwesterly at 4-8kts but will be variable, especially
during periods of convection.


&&

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

$$

MESOSCALE...White
SHORT TERM...White
LONG TERM...Puma
AVIATION...White