726
FXUS63 KIND 281033
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
533 AM EST Sun Dec 28 2025

.KEY MESSAGES...

- Near record highs today

- Narrow convective line with the potential for brief wind gusts in
  excess of 50mph and perhaps a tornado will move across central
  Indiana early this evening

- Peak wind gusts at 45 to 50mph across the northern half of central
  Indiana at times tonight and Monday

- Rapidly falling temperatures into the teens and 20s tonight and
  Monday with wind chill values near zero at times

- Much colder weather through the upcoming week with chances for
  light snow Wednesday night

&&

.SHORT TERM (Today and Tonight)...
Issued at 320 AM EST Sun Dec 28 2025

Areas of drizzle have increased across the northern half of central
Indiana early this morning with showers moving into the northern
Wabash Valley as a warm front was draped across the region. 07Z
temperatures varied widely due to the position of the warm
front...ranging from the upper 40s over north central Indiana to the
mid 60s over the lower Wabash Valley.

The meteorological pieces are starting to fall into place early this
morning as low pressure currently over the central Plains undergoes
intense cyclogenesis over the Great Lakes tonight as it is
influenced by a strengthening upper level low diving out of the
Canadian prairies. This will result in an eventful next 24 to 36
hours across the Ohio Valley that will frankly have a little bit of
everything. Near record warmth initially today will be followed by
the risk for a narrow convective line with locally damaging winds
this evening as a powerful cold front sweeps across the forecast
area...followed by an abrupt end to the recent warmth as
temperatures tumble rapidly tonight and winter settles back in for
the region to cap 2025. And if this all was not enough...maybe the
most impactful feature from this storm system will be the onset of
strong gradient winds highlighted by gusts peaking at 50mph at times
tonight into Monday. A lot to unpack below.

Through Late Afternoon

As mentioned above...the warm front currently sits NW-SE from just
north of KHUF to near KBMG and Seymour. The boundary will lift north
through the morning in response to the surface low tracking through
the Missouri Valley and into western Illinois by early afternoon.
Drizzle and showers continue to develop and expand east north of the
warm front and this will continue through daybreak with a specific
focus across far northern portions of the forecast area as an area
of stronger 850mb flow tracks through the lower Great Lakes. Model
soundings show the development of subtle elevated instability across
northern Illinois and Indiana by 12Z and through mid morning with
the potential for a few rumbles of thunder across far northern
counties.

Dry conditions are expected across the southern half of the forecast
area by daybreak and this will expand north to encompass the rest of
the area by midday as the warm front lifts into lower Michigan by
early afternoon. Low level moisture will remain trapped beneath the
inversion that has lingered to some degree across the area since
Wednesday night resulting in a cloudy day. Despite the clouds...
increasing southwest winds will raise afternoon temperatures to near
record levels in the mid and upper 60s with the potential for a few
spots to rise just above 70 in far southern counties. The record
high for Indy of 65 from 1984 is in danger of being broken. Those
southwest winds will become gusty as a 50-55kt low level jet arrives
for the afternoon.

This Evening and Tonight

Stronger convection is expected to develop in the vicinity of the
surface low and attendant cold front by mid to late afternoon as a
narrow axis of deeper moisture and weak but sufficient SBCAPEs
around 500j/kg sets up from near KSTL into north central Illinois.
This will overlay a broad area of strong BL shear values that would
support the development of a thin convective line with pockets of
damaging winds as it rapidly moves east towards the Indiana border
by early evening. Hodographs to our west by late day do support
supercell development with some directional shear present and would
at least suggest a non-zero tornado threat. However...drier air
aloft with an inversion near 700mb in addition to the lack of
surface heating will be limiting factors for a more substantial
tornado risk immediately to our west. Instability levels will drop
off further east into the forecast area this evening with weak lapse
rates with the threat for organized severe weather becoming
increasingly conditional as the line progresses eastward.

Ultimately...the setup most favors a narrow convective line/QLCS
that will develop to our west then press rapidly across the forecast
area in the 2230Z to 02Z timeframe. The line may not even have much
if any lightning but it will have the potential for brief and
localized damaging wind gusts as the primary threat with the strong
LLJ winds being pulled to the surface. This sort of a setup does
present a risk for rotators along any kinks in the line that develop
but winds will become increasingly parallel to the mean flow and
subsequently reduce any directional shear component as the line
pushes east across the forecast area. The tornado risk locally is
conditional and based on above thoughts...the greatest threat for a
tornado will reside over the northern Wabash Valley where the
available instability and directional shear will best align.

Intense cold advection will commence immediately with the frontal
passage which will enable strong gradient winds gusting potentially
up to 50 or 55mph at times through the evening. Have introduced a
Wind Advisory for the northern 2/3 of central Indiana beginning at
23Z tonight and continuing into Monday as a result. Gusts will drop
back slightly overnight but remain near advisory level all night.
A dry slot advecting into the Ohio Valley behind the front will
pinch off available moisture rather quickly with increasing
confidence in little to no snow before precipitation ends
overnight.

Besides the winds...the other significant impact in the postfrontal
environment will be the rapid drop in temperatures from the low and
mid 60s ahead of the boundary to temperatures nearly 40 degrees
colder within a 6 to 8 hour period which does presents a risk for a
flash freeze. While the strong postfrontal winds will help evaporate
surface moisture...any residual standing water on untreated surfaces
such as bridges and overpasses will likely freeze rapidly before it
can dry along with areas where water had ponded earlier in the
night. By daybreak Monday...most areas will see temps from the mid
teens into the lower 20s with wind chills near if not just below
zero.

Monday

The surface low will lift into Ontario and western Quebec Monday but
a trailing surface trough will pivot across the lower Great Lakes
and into the northern half of the state into the afternoon. Despite
limited moisture...lapse rates will steepen as the cold advection
regime continues and will likely lead to scattered flurries and a
few snow showers across the northeast half of the forecast area.
Progressively drier air advecting in from the west by late day will
bring an end to flurries and increasing sunshine from the west as
lingering moisture departs off to the east.

The gradient winds and cold temps will remain the primary impacts on
Monday with gusts across the northern half of the forecast area
peaking at 45 to 50kts into the afternoon before gradually
decreasing as the pressure gradient relaxes. Highs will only reach
the mid and upper 20s with wind chills no higher than 10 to 15
degrees in the afternoon.

&&

.LONG TERM (Monday through Saturday)...
Issued at 320 AM EST Sun Dec 28 2025

A much colder weather, more seasonable winter pattern sets up for
next week across the Great Lakes and Ohio Valley. A few weak clipper
systems bring light snow chances midweek, but overall no major
weather systems of concern in the long term other than minor systems
passing through.

Over the next week, the Eastern CONUS will feel the effects of a
negative NAO as blocking increases over Canada and the North
Atlantic. As a result, deep troughing remains in place over Southern
Canada with a strong northwest flow pattern setting up from
northwestern Canada down into the Ohio Valley. The upper jet remains
strong through the period in response to a sharp low level thermal
gradient across the CONUS, with Indiana entrenched within the colder
arctic airmass at the surface. The main focus in the long term will
be on a few weak clippers traversing southeast within the upper flow
into the Great Lakes. Uncertainty increases by next weekend and into
the following week as long range guidance/ensembles hint at a more
progressive and relatively milder pattern setting up with more
influence from the southern branch of the upper jet.

Mid Next Week...

The first in a series of clipper systems drops southeast into the
upper Great Lakes on Tuesday. The jet streak and associated surface
reflection track closer to the Canadian border, keeping the best
forcing for ascent and any precipitation north of Central Indiana.
The main impacts from this system will be a surface wind shift to
the west-southwest and a brief temperature moderation as weak warm
air advection modifies the arctic airmass in place. West-southwest
winds Tuesday work to slowly erode the cold air at the surface;
however temperatures may still struggle to get out of the upper 20s
much of the day. A non-diurnal temperature curve is expected Tuesday
evening as elevated winds and continued weak WAA keep temperatures
steady in the upper 20s to low 30s through the night. A brief period
of above freezing temperatures is expected on Wednesday before
Canadian high pressure moving in from the northwest works to pull
the arctic airmass back south into Indiana.

The next wave within the upper jet dives southeast out of Canada
into the Ohio Valley Wednesday night into Thursday morning. This is
the one to watch for the possibility for light snowfall across
Central Indiana. While this clipper looks fairly weak with little to
no surface reflection and only a weak mid level perturbation, there
may be enough lift under the exit region of the jet to squeeze out
light snow showers locally. Confidence is low in finer details of
this clipper as it is several days away and details may change
between now and then. But the overall pattern setting up supports
below freezing temperatures and the chance for light snow showers
Wednesday night into Thursday. Keeping PoPs at or below 40 percent
00z-12z Thursday for now to keep snow shower wording in the
forecast.

.Next Weekend...

Going into the weekend, high pressure extending from NW Canada into
the Ohio Valley slowly shifts eastward; however low level
temperatures will be slow to respond as the colder, dense airmass at
the surface slowly retreats. Longer range guidance and ensembles
hint at a system developing in the Plains then moving across the
Southern CONUS this weekend. Coming out of a blocking northwest flow
pattern, it is expected that guidance will not handle this
transition well, so low confidence remains in the forecast for next
weekend. Keeping the forecast on the drier side with temperatures
moderating back above freezing for the weekend. Introducing low
PoPs, under 20 perfect for the weekend to account for the potential
for a system over the Southern US possibly bringing moisture far
enough north for precipitation locally. Will update the long term
accordingly as confidence increases in the overall pattern evolution
as the colder northwesterly flow pattern finally breaks.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 533 AM EST Sun Dec 28 2025

Impacts:

- Low stratus primarily at MVFR levels through late day
- Scattered showers at KLAF this morning
- A narrow axis of heavier rain and thunder with wind gusts
  near 40kts expected early this evening with the cold front
- Southwest winds gusts peaking at 25-30kts this afternoon, veering
  to westerly tonight and increasing to 40kts

Discussion:

Low stratus continued across the region early this morning as a warm
front lifts north through the area. Winds north of the front are SE
but will veer to southerly once the front lifts north over the next
few hours.

As the front shifts north of the terminals later this morning...
southwest winds will become gusty with ceilings remaining
predominantly at MVFR levels. Scattered showers remain possible at
KLAF through mid morning...otherwise expect mainly dry conditions
through late day. A powerful cold front will arrive early this
evening with a narrow convective line impacting the terminals
between 23Z and 01Z. Along the line...visibilities will drop to a
mile with the potential for winds to gust up to 40kts if not a bit
higher. Rain will quickly shift east with the cold front this
evening as winds veer to westerly with frequent gusts at 30-40kts
continuing through daybreak Monday.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 6 PM this evening to 5 PM EST Monday for
INZ021-028>031-035>049-051>057.

&&

$$

SHORT TERM...Ryan
LONG TERM...CM
AVIATION...Ryan