961
FXUS63 KIND 190116
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
916 PM EDT Thu Sep 18 2025

.KEY MESSAGES...

- Dry and very warm conditions will persist for the rest of the
  work week

- Heat and low RH values each afternoon through Friday may lead to a
  marginally elevated fire threat, but light winds should limit
  overall concerns

- Slightly cooler and more unsettled pattern developing by early
  next week with the potential for much needed rainfall

&&

.FORECAST UPDATE...
Issued at 913 PM EDT Thu Sep 18 2025

Surface analysis this evening shows broad high pressure in place
across the region, stretching from northern Ontario, south across
the Great Lakes to Indiana and then to the deep south. GOES16 shows
clear skies across Indiana, as subsidence remained in play due to
ridging aloft. Dew points remained in the middle 50s to near 60.
Water vapor imagery shows ridging aloft with subsidence in place
over Indiana and windward side lift and moisture over the
Mississippi Valley.

Little overall change is expected overnight and a persistence type
forecast will be used. The ridging and surface high are expected to
remain in place and skies will be clear. Forecast soundings are on
board with this, showing a dry column through the night. Given the
little change in overall air mass persistence type lows will be used.

Some patchy fog will be possible late overnight in more rural areas
due to light winds, clear skies and low dew point depressions.

&&

.SHORT TERM (This evening through Friday)...
Issued at 208 PM EDT Thu Sep 18 2025

Central Indiana remain is a dry and unseasonably warm/hot pattern
today, and should generally stay this way into the weekend. The
synoptic pattern currently showcases amplified troughing and
ridging, but with an organized deep low to the west, the overall
pattern will remain rather stagnant for the next few days. This
allows for strong subsidence over the region and building low level
high pressure.

The result is continued upper 80s to low 90s across central Indiana
with very light winds and deep PBLs. These conditions also support
elevated ozone levels and thus an Air Quality Alert remains in
affect through midnight tonight along with additional air quality
issues tomorrow across SE Indiana. These dry conditions along with
very dry fuel moisture will also lead to elevated wildfire concerns.

Light winds and clear skies once again tonight should lead to
idealized diurnal curves with temperatures dropping to near 60F
overnight. Maximum relative humidity values generally below 90
percent should mitigate organized fog, yet patchy pre-dawn
visibility reductions are again possible.

&&

.LONG TERM (Friday night through Thursday)...
Issued at 208 PM EDT Thu Sep 18 2025

Despite the disorganization of the upper low, intermittent CVA
alignment will still slowly push the broad area of lower pressure
eastward, of which should reach the Ohio Valley late Saturday into
Sunday. Prior to its arrival, there will be some moderate
moisture advection, but low level high pressure along with
antecedent very dry conditions should hold off any precipitation
until Sunday. SW flow should keep temperatures above normal this
weekend, although more moderated due to less low level mixing.

Moisture advection increases noticeably within the boundary layer by
late Sunday and Monday as southerly flow develops ahead of the
approaching upper level wave and the surface ridge moves further
away to the east. Precip water values rise to around 1.5 inches for
the first half of next week and with modest forcing aloft now
present as first the upper trough then the cutoff low impact the
region. There is likely to be a non-uniform response to rainfall
totals due to the scattered nature of the convection through much of
the period but any rainfall would be welcomed at this point with how
dry it has been of late. Have nudged temperatures down for Monday
through Wednesday in anticipation of more cloud coverage and
convection over the Ohio Valley as highs should be held down in to
the upper 70s and lower 80s.

High uncertainty remains for late next week into next weekend
largely due to the length of time the cutoff low lingers over the
Ohio Valley. That being said, broad upper level ridging is likely
to return to the region for the last few days of the month into
early October with a resumption of warm and dry conditions.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 627 PM EDT Thu Sep 18 2025

Impacts:

- MVFR/Brief IFR visibility possible in fog at KLAF/KBMG...otherwise
VFR.

Discussion:

Mainly VFR conditions will continue into Friday over central Indiana
terminals.  Brief pre-dawn MVFR/IFR is possible again at
KHUF/KLAF/KBMG.

Little overall change in the ongoing forecast. Forecast soundings
and time heights reveal a dry column through the period. Diurnal
cooling and small dew point depressions suggest patchy MVFR fog will
once again be possible as we have seen the past few nights.

Forecast soundings on Friday suggest attainable convective
temperatures leading to CU development. However only SCT CU is
expected with continued VFR conditions.


&&

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

$$

UPDATE...Puma
SHORT TERM...Updike
LONG TERM...Ryan/Updike
AVIATION...Puma