IND issues Area Forecast Discussion (AFD) at Sep 6, 9:39 PM EDT472
FXUS63 KIND 070139
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
939 PM EDT Sat Sep 6 2025
.KEY MESSAGES...
- Dry and cooler through early in the upcoming week including nights
with lows in the 40s
- Warming trend back to the 80s as the upcoming week progresses
- No chance for rain across central Indiana through next weekend
&&
.FORECAST UPDATE...
Issued at 939 PM EDT Sat Sep 6 2025
Winds have diminished quickly this evening, and much of the area had
mostly clear skies. With a dry airmass in place, temperatures have
fallen quite quickly this evening. Many areas were near the 5th
percentile of blended guidance.
Satellite shows patchy stratocumulus remaining across portions of
the area, with more upstream. These will pass through at times
overnight, making skies briefly partly cloudy. Adjusted sky cover as
needed to reflect this.
Changed hourly temperature forecasts to match the quick cooldown,
and tweaked low temperatures down some in favored cold spots. Will
continue to monitor to see if numbers need further adjustment.
&&
.SHORT TERM (This Evening through Sunday)...
Issued at 149 PM EDT Sat Sep 6 2025
Comfortably cool afternoon in progress across central Indiana.
Breezy westerly winds combined with scattered cu and temperatures at
17Z ranging from the mid 60s to lower 70s.
Cool but quiet weather is the story through the weekend as much of
the eastern half of the country will be under the influence of a
deep upper level low near James Bay. The trough associated with the
low will amplify into Sunday with unseasonably cool mid level
heights across the Ohio Valley.
Diurnal cu has formed across much of the northern 2/3 of the
forecast area early this afternoon. Expect subtle expansion over the
next few hours before diminishing quickly near sunset as heating is
lost. The breezy conditions will continue as well through late day
with peak gusts periodically around 20mph. Skies will clear for
tonight with light westerly flow as the surface high settles across
the region. Deeper subsidence will advect into the region from the
northwest on Sunday which will limit cu development well below
levels this afternoon. Still though...model sounding analysis does
lend support for at least a few flattened cu to develop underneath a
strong mid level inversion. Winds will veer to northwest on the
front flank of the surface high poised to center across the region
Sunday night.
Temps...tonight will be the first of several nights with ideal
radiational cooling conditions. Lows should fall into the 40s across
the forecast area with a potential for temps as low as near 40 in
some of our typical cool spots across the northern half of the
forecast area. Lows level thermals support highs Sunday similar to
this afternoon...ranging from the upper 60s to lower 70s.
&&
.LONG TERM (Sunday Night through Saturday)...
Issued at 149 PM EDT Sat Sep 6 2025
A deep upper level trough centered near James Bay will maintain the
early taste of Fall through Monday with unseasonably cool air and
the coolest mornings for central Indiana since May. The trough will
move away to the east being replaced by more zonal flow aloft by as
the week progresses...transitioning further to upper ridging by late
next week with growing confidence in a return to summer like weather
for the middle of the month.
High pressure at the surface and the presence of the upper trough to
the northeast will keep the much cooler Canadian airmass aloft
overhead with well below normal heights and temperature anomalies to
start Sunday night with subtle improvement beginning Monday. Despite
sunny skies highs will remain in the upper 60s across the north to
low to mid 70s further south on Monday...a solid 10 degrees below
normal for early September. Strong radiational cooling and a cool
airmass aloft will support low to mid 40s for Monday morning. The
coolest locations will be across the Wabash River Valley and in
North Central Indiana where a few of our normal cool spots may slip
as low as the upper 30s.
The overall pattern begins to shift as the upcoming week
progresses...leading to a gradual warming trend back to the 80s but
with dry weather persisting. The aforementioned upper trough will
finally pull away from the region during the first half of the week
with the surface high moving off to the east as well. The
combination of return flow on the backside of the departing high
pressure in tandem with a steady recovery in mid level heights
support the onset of the warming trend that will bring daytime highs
back into the 80s by late week. Dry conditions will produce large
diurnal ranges as temperatures quickly fall after sunset...possibly
as great as 35 degrees by the end of the forecast period.
Forecast confidence lowers by late week as longer range guidance and
ensembles struggle to resolve fully how the pattern evolves. For now
higher confidence exists in a warm and dry forecast continuing into
next weekend and quite possibly well into the following week with
daytime highs consistently in the mid and upper 80s.
&&
.AVIATION (00Z TAF Issuance)...
Issued at 649 PM EDT Sat Sep 6 2025
Impacts:
- None expected
Discussion:
Winds will continue to diminish this evening. Winds will pick back
up Sunday with northwest winds around 10kt or less expected then.
Dry air should keep fog at bay overnight.
Guidance is hinting that patches of stratocumulus will continue
through the night, but these will be VFR. A few VFR cumulus will pop
up again on Sunday.
&&
.FIRE WEATHER...
Issued at 149 PM EDT Sat Sep 6 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. 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
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...50
SHORT TERM...Ryan
LONG TERM...Ryan
AVIATION...50
FIRE WEATHER...Ryan/CM
Source:
IND issues Area Forecast Discussion (AFD) at Sep 6, 9:39 PM EDT---------------
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