651
FXUS63 KIND 070638
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
238 AM EDT Sun Sep 7 2025

.KEY MESSAGES...

- Dry and cooler through early this week including nights with
  lows in the 40s

- Warming trend back to the 80s as the week progresses

- No chance for rain across central Indiana through next weekend

&&

.SHORT TERM (Today and tonight)...
Issued at 237 AM EDT Sun Sep 7 2025

Today.

Another much cooler than normal day is expected for today as surface
and upper level northwesterly flow continues across central Indiana
with a broad trough across the Great Lakes region. As of early this
morning, winds have been near calm with mostly clear skies outside
of a stratocu deck at around 7500ft. Temperatures have already
fallen into the mid 40s to low 50s with another few degree drop
towards daybreak expected. With the stronger northwesterly flow
today, afternoon highs will end up on the cooler end with many areas
ending up only reaching the upper 60s to low 70s.

The boundary layer will deepen to around 5000ft this afternoon with
near saturation near the top which will allow for at least diurnal
cu but not quite as widespread as yesterday due to the drier surface
air. Winds at the top of the boundary layer will be in the 10-15 mph
range, so wouldn`t be shocked to see a few wind gusts up to 15 mph
reach the surface but generally expect winds to remain in the 8-12
mph range. Surface dew points will mix down during the day with
afternoon min RH values likely near 30 percent which combined with
the recent dryness to create some slightly elevated fire weather
concerns. Additional details on that will be in the fire weather
section below.

Tonight.

Any diurnal cu will dissipate by sunset with mostly clear skies
along with near calm winds expected again for tonight. Ideal
radiational cooling conditions will allow for the coldest night of
the recent stretch of weather with many locations dropping into the
low 40s with isolated upper 30s likely. There may also be some frost
formation in the most ideal locations such as ditches but any
coverage should be extremely limited.

&&

.LONG TERM (Monday through Saturday)...
Issued at 237 AM EDT Sun Sep 7 2025

A deep upper level trough centered near James Bay will bring an
early taste of Fall to the region on Monday with unseasonably cool
air and the coolest morning for central Indiana since May. Surface
high pressure will be the dominant weather influence locally next
week keeping abnormally dry conditions in place with little to no
chance for rain in the next 7-10 days. A synoptic pattern change
through the week results in a slow warming trend back to the 80s,
which may persist into next weekend and the following week.

The period begins with a deep upper trough over the NE CONUS and
surface high pressure directly overhead. Monday will be the coolest
day in the extended range, starting off on a very cold note for this
time of year. High pressure centered overhead provides optimal
conditions for radiational cooling. With such dry conditions and a
cold Canadian airmass overhead, expect temperatures to plummet into
the low 40s by Monday morning. Would not be surprised to see a few
upper 30s in rural, low lying areas across North Central Indiana.
Temperatures rebound into the low to mid 70s by Monday afternoon as
winds become southerly and high pressure slides off to the northeast.

The overall pattern begins to shift going into mid next week,
leading to a warming trend back to the 80s... but still without any
rain chances locally. Upper troughing pulls off to the northeast
with increasing heights toward seasonal norms by Tuesday. Surface
high pressure briefly moves overhead Monday then moves off to the
northeast, switching low level flow around to the south and
advecting warmer air northward. Upper level height increases and
slowly warming 850mb temps indicate a pattern favorable for a
warming trend through the week with highs reaching the upper 70s to
mid 80s Tuesday through Friday. Dry conditions will still lead to
larger diurnal ranges as temperatures quickly fall after sunset,
with lows in the upper 40s to low 50s Tuesday then increasing to the
mid to upper 50s by late in the week. It is worth mentioning that
diurnal ranges may be larger than what mid to long range guidance
suggests due to such dry conditions. Therefore, adjusting highs for
the long term toward the NBM75th-90th percentile.

Forecast confidence somewhat decreases toward the end of the period
as longer range guidance and ensembles struggle to resolve how this
pattern evolves as weak storm systems approach from the west. For
now higher confidence exists in a hot and dry forecast continuing
into next weekend and the following week with daytime highs
consistently in the mid and upper 80s. Would not be surprised to see
additional 90 degree days for Central Indiana if this dry pattern
continues into the following week. CPC has the Ohio Valley
highlighted in a slight risk for extreme heat for this time of year
from September 14th-18th. This may come to fruition if conditions
remain dry and waves riding over the ridge and associated convection
remain north of the region. Will be watching this timeframe closely
and updating the forecast accordingly.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 1242 AM EDT Sun Sep 7 2025

Impacts:

- None.

Discussion:

VFR conditions expected through the TAF period with passing stratocu
through the remainder of the overnight and few to sct cu returning
this afternoon. Can`t rule out an isolated wind gust to around 18kts
this afternoon, but generally expect northwesterly winds of 8-12kts
through the day before dropping to near calm during the overnight.


&&

.FIRE WEATHER...
Issued at 237 AM EDT Sun Sep 7 2025

The lack of significant rainfall over the last several weeks has
resulted in abnormally dry and minor drought conditions to develop
across Indiana. With little to no rain in the forecast for the next
7-10 days, there may be an elevated fire weather threat each
afternoon as daily min RH values fall into the 20% range. Lowered
afternoon dew points each day toward the NBM10th percentile to
account for such dry conditions and afternoon mixing bringing down
even drier air to the surface. The one factor keeping the fire
weather threat lower is the lack of wind. Despite deep mixing, very
weak low level flow should keep winds under 10 kts through the
period. Will continue to monitor the extended forecast for
increasing fire weather concerns.

&&

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

$$

SHORT TERM...White
LONG TERM...CM
AVIATION...White
FIRE WEATHER...CM