190
FXUS63 KIND 170531
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
131 AM EDT Tue Jun 17 2025

.KEY MESSAGES...

- Scattered light rain with a minimal threat for thunder through
  tonight across southern Indiana

- Potential severe weather late Wednesday/Wednesday night

- Much warmer this weekend with near Heat Advisory conditions by
  Sunday

&&

.FORECAST UPDATE...
Issued at 1053 PM EDT Mon Jun 16 2025

Just a few minor changes made to the near term forecast with this
evening`s update.

Satellite and radar imagery shows broken clouds over much of Central
Indiana with drier air to the north and another wave pushing in from
the south. Kept Likely PoPs for the southern and eastern third of
the state for the overnight hours as that next wave of rain moves
northward. Not very concerned with the thunderstorm threat
overnight; however a lightning strike or two isn`t out of the
question. The low level jet increases to around 15 kts and ACARs
soundings indicates enough instability to support an isolated
thunderstorm. But for the most part, mainly showers along and south
of the I-70 corridor overnight, with the greatest coverage further
south.

Another potential threat tonight is fog. A very moist airmass
remains in place with dew point depressions in the 0-3 degree range
already. The pressure gradient is weak which will allow winds to go
calm for most areas overnight. While confidence is low in exactly
where fog may develop, added patchy fog to the usual foggy spots
around the Wabash River Valley. Will have to watch how widespread
fog may develop overnight as wording may need to be enhanced to
areas of widespread if enough breaks in the clouds form to allow
better radiative cooling. Fog should quickly dissapate after sunrise.

&&

.SHORT TERM (This evening through Tuesday)...
Issued at 126 PM EDT Mon Jun 16 2025

Rest of Today and Tonight.

As of early this afternoon the coverage of light showers/sprinkles
has been gradually expanding across southern Indiana with much of
this precipitation falling from an elevated cloud deck at around
10kft. QPE has been less than a tenth of an inch so far with most
sites seeing rainfall rates of around 0.01 inches per hour. With the
abundant cloud cover and temperatures warming slower than forecast,
the instability remains near zero with a skinny CAPE profile with
near moist adiabatic lapse rates. Thus expect near zero coverage of
lightning through the remainder of the afternoon. Moving into the
evening and early overnight the LLJ will begin to ramp up on the
eastside of the near surface low pressure with good moisture flux.

Any storms that form should remain limited to the far southern and
southeastern counties with the most likely outcome being any
stronger convection remains south of the forecast area closer to the
Ohio River. Some low level clouds will begin to develop late into
the overnight with the potential for a return in pockets of non-
dense fog as the near surface saturates. Overnight lows will be mild
again tonight with most sites only dropping into the upper 60s.

Tuesday.

Some broad isentropic lift will bring isolated to scattered showers
to the southeastern portions of the forecast area through the
afternoon. Highest coverage and better chances for thunder will
remain south and east of the forecast area based on the track of the
surface low as it weakens. Drier air will be moving in aloft which
will bring gradually clearing from the northwest to southeast through
the day. Highs will climb as high as the upper 80s across the far
western and northwestern counties where clearing will be as early as
late morning with highs closer to 80 in the southeast where mostly
cloudy skies will continue into the overnight.

&&

.LONG TERM (Tuesday night through Monday)...
Issued at 126 PM EDT Mon Jun 16 2025

Tuesday Night Through Thursday.

By Tuesday night the weak low pressure system that will be bringing
precipitation to the southern portions of the state will have exited
to the northeast with the main focus being a much more organized low
across the Central Plains. There is increasing confidence in an
organized MCS developing across Nebraska and Kansas which will push
eastwards through the night. There is general model consensus that
this complex will dissipate by Wednesday morning but a meso-low/MCV
will likely move eastwards through the morning and may be a catalyst
for thunderstorms development across the Ohio Valley Wednesday
afternoon.

That is currently a possible but not the most likely outcome as
there is uncertainty that this MCV will move through Indiana with
the more likely outcome being that central Indiana remains capped
through the afternoon and early evening hours with the main threat
being during the overnight hours as forcing along the front
overcomes the cap and brings a complex of strong to severe storms
through the state.

Both instability parameters and shear will be sufficient for severe
weather with ML CAPE in excess of 2-3k J/kg and effective bulk shear
of 30-45kts.  Current thoughts are isolated storms will initiate in
Illinois during the late afternoon and early evening hours with the
potential for discrete convection and isolated tornadoes through the
evening with a more organized complex of storms moving through
during the overnight hours with damaging winds and large hail more
likely as storms become elevated with the nocturnal inversion sets
in. Thunderstorms will move out by Thursday morning with the pattern
shift to the warmer and more humid airmass settling in by Friday.

Friday Through Monday.

A strong upper level ridge will dominate the weather pattern for
Friday into the weekend with a 595dm ridge expected to be overhead
Saturday into Sunday with weak southerly surface flow. This will
help to push temperatures into the low 90s with dew points gradually
rising into the mid 70s towards Sunday. Peak heat indices will rise
into the low 100s with the potential for pockets as high as 105.
Heat Risk maps show widespread major conditions Sunday and Monday
which makes sense with both the hot daytime conditions and mild and
muggy nights. Heat headlines will likely be needed, especially when
you factor in the relatively mild start to summer and this being the
first widespread 90s and first widespread days of dew points in the
mid 70s.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 131 AM EDT Tue Jun 17 2025

Impacts:

- MVFR to high end IFR ceilings expected to develop in the next few
  hours, persist through midday

- Patchy fog possible through daybreak

- A few showers near IND early, showers possible midday near BMG

Discussion:

With a very moist airmass in place and a stationary boundary to our
south, expect deteriorating conditions through the night, primarily
driven by ceilings, but with visibility restrictions possible as
well. Widespread MVFR is expected with pockets of IFR, particularly
where winds are lightest and in closer proximity to the boundary
(highest IFR chances at HUF/BMG).

These conditions will persist through midday to early afternoon
depending upon the site, before VFR returns by 16-19Z.

Winds will be calm to light and variable overnight, becoming
southerly or southwesterly during the day on Tuesday at 5-8KT.

Showers will be possible at times, particularly near IND early in
the period and near BMG around midday into early afternoon today.
Showers will be possible at all sites but have attempted to narrow
down the time frame as much as possible.

&&

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

$$

UPDATE...CM
SHORT TERM...White
LONG TERM...White
AVIATION...Nield