425
FXUS63 KIND 061040
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
640 AM EDT Sat Sep 6 2025

.KEY MESSAGES...

- Isolated very light showers along and south of I-70 through
sunrise

- Dry and cooler through early next week with multiple nights with
  lows in the 40s

- Warming trend back to the 80s by later next week

- Beyond early Saturday, no chance for rain across central Indiana
  through the end of next week

&&

.SHORT TERM (Today and tonight)...
Issued at 243 AM EDT Sat Sep 6 2025

.Today and Sunday..

Another beautiful weekend is in the forecast for all of Central
Indiana as high pressure moves in overhead keeping conditions sunny
and dry. The only focus for the short term is the slight chance for
a light shower early this morning before skies clear out by the
afternoon. Current satellite imagery shows widespread mid and high
level clouds streaming in from the southwest, ahead of an
approaching trough axis. The main surface front and associated
convection are well to the southeast with surface high pressure
advecting in much drier and cooler air in the lower levels. A weak
wave riding along the front will provide enough lift to spark off
isolated showers, mainly along and south of I-70 through about
sunrise. Latest ACARs soundings show enough mid level saturation to
support a few showers aloft, but with a 3km dry layer near the
surface it will be hard to get more than a trace of rainfall to
reach the ground. Keeping 20-30 PoPs south of I-70 through 11z, but
do not expect any of these showers to put a dent in the developing
drought across the state.

Surface high pressure becomes the dominant weather influence over
Central Indiana through the next 7-10 days, keeping conditions very
dry locally. As the upper trough pushes east and surface high
pressure builds in, much drier air will filter in at all levels
working to clear clouds out from west to east during the mid morning
hours. Despite ample sunshine for the rest of the weekend, troughing
overhead will keep a relatively colder and drier Canadian airmass in
place. Well below normal surface and 850mb temperature anomalies for
this time of year only support highs in the upper 60s to low 70s
while optimal conditions for radiational cooling at night will
result in large diurnal temperature ranges and cold overnight lows
in the low to mid 40s Saturday night and Sunday night. Lows Sunday
night may approach record territory in the Wabash River Valley and
portions of North Central Indiana.

.Fire Weather...

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 toward the NBM10th percentile to account for
such dry conditions and afternoon mixing bringing down even drier
air to the surface. Wind gusts to 20-25 mph this afternoon and
evening with low RH values will lead to an elevated fire risk. While
afternoon winds will be weaker on Sunday, min RH values may still
reach critical fire weather thresholds.

&&

.LONG TERM (Sunday through Friday)...
Issued at 300 AM EDT Sat Sep 6 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 slow pattern change through
the week results in a slow warming trend back to the 80s, which may
persist into next weekend.

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. 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.

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 warm and dry forecast continuing
into next weekend into the following week with daytime highs
consistently in the mid and upper 80s. Would not be surprised to see
another 90 degree day for Central Indiana if this dry pattern
continues into the following week. WPC has the Ohio Valley
highlighted in a slight risk for extreme heat for this time of year
from September 13th-16th. 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 (12Z TAF Issuance)...
Issued at 640 AM EDT Sat Sep 6 2025

Impacts:

- Wind gusts of 15-20kt this afternoon

Discussion:

VFR conditions are expected through the period. Satellite imagery
shows mid and high level clouds streaming in overhead ahead of an
approaching upper trough. The back edge of the clouds is already
nudging into NW Indiana early this morning and will quickly move
southeast through the state over the next several hours.

Otherwise, expect a quick clearing trend late morning, with mainly
clear skies for the rest of the day outside of any afternoon
cumulus. Expect a typical diurnal curve for wind speeds, with light
WNW winds this morning increasing to 10-15 kts and gusts to 20 kts
in the 15z-23z timeframe. Winds become light or calm again overnight
tonight as high pressure builds in overhead. Very low threat for fog
tonight in the Wabash River Valley, but confidence is too low to put
this in the TAF.

&&

.Fire Weather...

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 toward the NBM10th percentile to account for
such dry conditions and afternoon mixing bringing down even drier
air to the surface. Wind gusts to 20-25 mph this afternoon and
evening with low RH values will lead to an elevated fire risk. While
afternoon winds will be weaker on Sunday, min RH values may still
reach critical fire weather thresholds.

&&

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

$$

SHORT TERM...CM
LONG TERM...CM
AVIATION...CM