812
FXUS63 KIND 311721
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
121 PM EDT Sun Aug 31 2025

.KEY MESSAGES...

- Dry and quiet weather for the remainder of the holiday weekend

- Below average temperatures to continue for much of the upcoming
  week

- Next chance for rain arrives Tuesday and continues into early Thursday
  followed by another round of cooler/drier air late week

&&

.FORECAST UPDATE...
Issued at 933 AM EDT Sun Aug 31 2025

No changes necessary to the going forecast this morning.

Crystal clear skies have greeted most of central Indiana on this
cool final morning of climatological summer. Low level thicknesses
suggest highs will climb into the mid 70s to around 80 across the
area under this ample sunshine today, which is very near persistence
and the going forecast.
50-925 mb
&&

.SHORT TERM (Today and tonight)...
Issued at 244 AM EDT Sun Aug 31 2025

Surface analysis early this morning continues to show strong high
pressure in place across the Great Lakes. This system was dominating
Central Indiana/s Weather, resulting mostly clear skies with light
and dry easterly winds. Aloft, water vapor showed sharp ridging in
place over the Northern Plains and Central Canada, while a trough of
low pressure was found over eastern Canada and New England. This was
resulting in a dry, northerly flow aloft with subsidence. Dew points
across the area were in the upper 40s and lower 50s.

Today and Tonight...

Our weather will continue to be controlled by the strong upper
ridging to the north that will slowly sag southeast. Meanwhile the
previously mentioned upper trough is suggested to broad and become a
weak cut-off low over the middle Atlantic states. This will keep
Indiana in a favorable location for subsidence aloft today and
tonight. In response to this change in the upper levels, the surface
high over the Great Lakes is expected to expand and become more
elongated. This will continue to keep an dry, cool and continental
easterly surface flow across Central Indiana today and tonight.

Forecast soundings again show a dry column through the period with
unreachable convective temperatures. Thus Mostly Sunny skies with
only a few passing CI or high CU will be expected along with mostly
clear skies tonight. Again highs will reach the middle to upper 70s
with lows in the upper 40s and lower 50s.

&&

.LONG TERM (Monday through Saturday)...
Issued at 244 AM EDT Sun Aug 31 2025

Upper-level analysis shows large-scale troughing over the Midwest
and northeastern US. Ensemble guidance is in good agreement showing
this pattern holding steady through the forecast period. As such,
below-average temperatures are expected to continue through the
majority of the coming week.

The overall pattern looks dry, for the most part, as northerly
surface flow keeps deep moisture displaced to our south.
Additionally, atmospheric disturbances embedded within the jet
stream are being shunted south around the base of the trough. A lack
of moisture and a lack of forcing gives little reason to expect rain
any time soon.

The next decent chance of rain looks to be in the Tuesday/Wednesday
timeframe. Guidance is showing low pressure strengthening and
occluding to our north, with a cold front passing through the area
as well. Some surface moisture could creep north in response to the
deepening system. Rainfall amounts are uncertain, and will depend on
the position and strength of the system along with how quickly the
cold front passes through. As of right now, generally light amounts
are shown by most deterministic guidance.

Regardless of rainfall, an unseasonably cool air mass looks to drop
southward behind the front. ECMWF/GFS deterministic guidance shows
850mb temps between 3-6 degrees C, which could allow for low
temperatures potentially into the upper 30s assuming ideal
radiational cooling (clear skies and light winds). Blended guidance
has low to mid 40s, which seems reasonable for now given the
uncertainty in strength/position/timing of the occluding low. The
blend, however, shows highs in the mid to upper 60s Thursday and
Friday. This may be a bit pessimistic, since the sun angle is still
quite high and we have recently been running warmer than guidance
under optimal boundary layer mixing conditions.

Trends within guidance have been minimal, but a trend towards a
slower more occluded low has occurred within GEFS ensemble guidance.
Meanwhile, the ECMWF has shifted a bit further north. Overall, these
trends have been minor so far and does not represent a significant
change from previous forecasts.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 120 PM EDT Sun Aug 31 2025

Impacts:

- VFR conditions through the forecast period

Discussion:

Quiet for the terminals through the period. There will be an
increase in high clouds from the west over the next 12 hrs ahead of
broadly divergent area at 300mb over the mid MS/MO valleys. E-NE
winds will occasionally gust to near 12 kts this afternoon at KLAF
and KIND thanks to a deep mixed boundary layer and winds from 10-15
kts in the 2-5 kft layer. However, the only substantial impact for
these conditions will be some low level turbulence.

Winds will decrease and back 10-20 degrees in the evening owing to
diurnal tendencies. Overnight, ceilings will increase to scattered
in the north with a broken deck of cirrus expected later in the
night at KBMG and KHUF. By tomorrow morning the upper level
divergence fields tend to weaken and the cirrus deck is expected to
gradually diminish from the NW, while E-NE surface winds will
increase by late morning.

&&

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

$$

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