230
FXUS63 KIND 181036
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
636 AM EDT Thu Sep 18 2025

.KEY MESSAGES...

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

- Heat, low afternoon RH values through Friday may elevate fire
  weather concerns, but light winds should limit overall concerns

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

&&

.SHORT TERM (Today and tonight)...
Issued at 252 AM EDT Thu Sep 18 2025

Stagnant dry and unseasonably warm/hot pattern to continue into the
late week as the slowly-weakening subtropical upper ridge hangs
tight over Indiana.  Broad trough over the northern Plains will
begin to spin into the Upper Mississippi Valley...slowly sliding the
ridge`s axis across Indiana through the short term.  This should
feature the epitome of clear skies and calm/very light winds...
promoting both patchy fog towards dawn this morning and high
temperatures this afternoon 1-2 degrees higher than Wednesday.

Readings into the upper 80s (northeast) and low 90s (southwest) will
again couple with lighter winds to promote higher ozone levels...so
the Air Quality Alert has been extended through midnight tonight for
the same zones - which exclude west central and northwest counties.
The other potential hazard, albeit marginal, is an elevated fire
weather risk.  Continued drier conditions has primed fuels...yet
afternoon minimum relative humidity values only falling to around 30
percent, along with very light winds should mitigate this threat.

Subtle moderation trend will be displayed again tonight, with most
locations falling to minimums about 2-3 degrees higher than at the
start of the short term. Expect lows mainly around 60F...with lows
60s northeast of Indianapolis, low 60s inside I-465, and south/west
of Bloomington. Maximum relative humidity values generally below 90
percent should mitigate organized fog, yet patchy pre-dawn
visibility reductions are again possible.

&&

.LONG TERM (Friday through Wednesday)...
Issued at 248 AM EDT Thu Sep 18 2025

The recent blocking pattern aloft will gradually begin to break down
this weekend in response to an approaching upper trough from the
northwest. Temperatures will remain very warm into the weekend with
isolated to scattered convection largely holding off until Sunday.
The upper trough will slowly settle across the region early next
week followed by a slow moving cutoff upper level low that has
suddenly shifted the forecast to a more unsettled regime that may
end up lasting for a large portion of next week. It does appear
there is a growing threat for much needed rainfall that will focus
especially during the first half of the week.

Model guidance continues to trend slower in breaking down the omega
block aloft with the likelihood of little no threat for any rain
through early Sunday other than isolated showers in the Wabash
Valley. Moisture return remains the underlying problem for greater
rainfall coverage through the second half of the weekend aided by a
strong surface ridge to our east and abnormally dry antecedent
conditions over the Ohio Valley. Highs will again be around 90 on
Friday with mid and upper 80s common for the weekend.

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 (12Z TAF Issuance)...
Issued at 635 AM EDT Thu Sep 18 2025

Impacts:

- MVFR/Brief IFR visibility possible in fog at KLAF/KBMG through 13Z
  this morning

Discussion:

Mainly VFR conditions will continue into Friday morning over central
Indiana terminals.  Brief pre-dawn MVFR/IFR is possible again at
KHUF/KLAF/KBMG through 13Z this morning.

Quasi-stationary upper ridge will continue to drift east over the
region today...continuing generally SKC through 16Z. Mainly
afternoon cumulus should have less coverage than recent days,
followed by some passing cirrus tonight.

Calm or very light/variable winds to prevail this morning...before
winds sustained at 3-5KT this afternoon, most likely veer through
southwesterly directions at KIND.

&&

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

$$

SHORT TERM...AGM
LONG TERM...Ryan
AVIATION...AGM