567
FXUS63 KIND 101739
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1239 PM EST Wed Dec 10 2025

.KEY MESSAGES...

- Rain moves through this morning; additions rain showers
  transitioning to a rain/snow mix is expected the afternoon

- Wind gusts of 30 to 40 mph throughout the dayinto

- Accumulating snow likely Thursday night into Friday

- Arctic outbreak expected this weekend with low temperatures near
  or below zero...and potentially dangerous sub-zero wind chills

&&

.FORECAST UPDATE...
Issued at 1003 AM EST Wed Dec 10 2025

The forecast is on track so far for today as wet, windy, and cooler
conditions overspread the state. Satellite and radar imagery show
the bulk of this morning`s rain pushing off to the south and east
with leftover showers moving in from the west. Observations indicate
winds have already shifted to the west behind the cold front with
gusts approaching 40-45 mph at times. The main focus for today will
be continued windy conditions, falling temperatures this afternoon,
and the transition to a period of drizzle and snow showers.

Steepening low  level lapse rates as cold air advection moves in
aloft support continued stronger wind gusts of 40-45 mph mixing down
to the surface through the next several hours. The LLJ is expected
to weaken some this afternoon, so expect a slow diminishing trend
for wind gusts from 40-45 mph this morning to 25-35 mph by this
evening.

In addition to strong winds, cold air advection should keep
temperatures near steady this morning in the upper 30s to near 40
before falling to near freezing later this afternoon and evening.
Expect scattered to numerous rain showers this afternoon within the
cyclonic flow pattern around an area of low pressure to the north.
Thermal profiles on local soundings and CAMs indicate snow may mix
in at times later this afternoon before dryer air pushes in tonight
shutting off most of the precipitation. Best chance for a full
transition to snow showers and lingering flurries will be in
northeastern portions of the state, as additional moisture off Lake
Michigan may saturate the lower levels and DGZ enough to support
snow shower activity. Little to no accumulations expected, but a
dusting is not out of the question north and east of the Indy metro
area tonight. Overall expect a blustering, wet, and cool day across
Central Indiana.

&&

.SHORT TERM (Today through Friday)...
Issued at 250 AM EST Wed Dec 10 2025

Today through Thursday afternoon:

Central Indiana will now face a succession of Alberta Clipper lows
over the coming days, the first of which reached the Great Lakes
region last night, and the last of which will move through on
Saturday. Todays low, will be strong, but will pass well to the
north, keeping temperatures well above freezing (currently 42 in
Indianapolis), minimizing overall impacts to central Indiana.
Numerous showers are expected to pass through most of central
Indiana throughout the morning hours ahead of a strong cold front.
Total rain amounts for central Indiana are likely to be less than a
quarter inch. Despite less overall impacts, the strength of this
system will still have some, mostly due to strong winds. A robust
jet streak will not be far off the surface around 50-60kt, but an
inversion will keep the worst of the winds away from the ground;
still gusts in the 30 to 40 mph range are possible throughout the
morning. As the inversion breaks some late this morning into the
early afternoon, a few gusts may exceed 40, but the jet streak
should be east of central Indiana by the time greatest mixing occurs.

The bulk of the lift will be east of the area by 15Z today, but
there still will be some modest vorticity advection within the
parent trough, along with modest lapse rates that likely will lead
to scattered showers at times late this morning through the
afternoon. This second round of precipitation will be undercut by
some strong CAA during the afternoon hours, of which will likely
lead to some mix of rain and snow at times. This should not
accumulate to much of anything, but a quick light coating of slush
within strongest showers is possible. Winds will continue to be
gusty with the tight pressure gradient and cold advection promoting
mixing down of stronger winds aloft. Wind gusts around 40 mph are
likely, especially north.

The strong push of CAA along with lingering stratus in the broader
cyclonic flow will likely lead to scattered flurries this evening
through early portions of tomorrow. These flurries likely will not
cause any impact. That said, further NE, enhanced low level moisture
downstream of Lake Michigan could allow for a few stronger snow
showers to develop within this same synoptic setup. These snow
showers still likely wont cause much impact but a dusting of snow is
possible tonight into tomorrow in the Muncie, Winchester region.

Thursday evening through Friday morning:

As stated, central Indiana will remain in the path of strong upper
level NW flow, and an efficient set up for quickly developing lows
out of the Canadian Rockies. The second of these systems is expected
to pass through late Thursday through Friday morning. The previous
system brought through strong CAA, of which will sink the baroclinic
zone southward placing central Indiana in a goldilocks zone for both
cyclogenesis and temperatures cold enough for snowfall. This second
low will be weaker than Wednesday`s system, but will likely still
have just as much forcing as it pushes across a strong baroclinic
zone.

These clipper systems along strong temperature gradients typically
produce narrow corridors of moderate QPF, and this one is expected
to be no different. The emphasis is on narrow, as this will lead to
a wide range of QPF outcomes in certain locations, with still almost
48 hours until snowfall onset. This means take each forecast with
some potential of error, as the greatest axis of snowfall could move
25-50 miles depending on where the baroclinic zone is placed
following the cold push after today`s system. Currently, this axis
is most likely to be along the I-74 corridor.

Model soundings showcase a deep isothermal layer as the low arrives
between -6C and -10C. This isn`t the most ideal temperature for
efficient dendrite growth, and therefor SLRs are currently expected
to be somewhere between 10-14:1 across central Indiana. This in
combination with 0.2-0.3 inches of QPF puts the highest likelihood
of snowfall to be between 2 and 4 inches. Slightly higher amounts
are possible where the strongest frontogenetical forcing occurs as
this forcing will likely be slightly further aloft and within more
ideal DGZ temperatures.

Forecast timing has a bit more confidence, as the margin of error is
larger and ensembles have a tighter spread. Currently snow is
expected to reach the Indiana border between 4-7PM on Thursday and
continue through 10AM on Friday morning.

&&

.LONG TERM (Thursday through Tuesday)...
Issued at 250 AM EST Wed Dec 10 2025

Cold pattern to trend from unseasonable to anomalous this weekend,
before moderation expected by end of the period...with additional
light snowfall possible.  H500 cut-off short wave to plunge slightly
within polar flow this weekend...from south-central Canada, across
northern and eastern Great Lakes.  Paving a path for associated
elongated arctic surface high pressure to build/track from North
American Plains during the early weekend...to the Great Lakes/
Midwest by Sunday night.

Vort max speeding around the bottom of the upper cut-off Saturday,
from Quad Cities area into Ohio, will induce another clipper-type
system. Additional light accumulating snowfall is likely for most of
the region within perhaps a 15-hour period around the Saturday to
Saturday evening timeframe.  Bursts of moderate to perhaps briefly
heavy snow are possible, especially north of I-70 which will be
closer to supporting forcing.

Arctic ridge to quickly build into central Indiana on the hind legs
of Saturday`s disturbance, with what should be clearing skies
Saturday night promoting readings near/below zero.  Very cold
conditions...possibly approaching Indianapolis` record low of
negative 4 degrees Sunday morning...should last into Monday morning,
with highs Sunday held below 15F across most zones...and consecutive
early mornings below zero for most locations north of I-70.

Wind chill values to fall to around zero for many spots Friday
night, yet only rebound Saturday to 5-15 degrees for most locations.
Advisory criteria wind chills are currently forecast for both
Saturday night and Sunday night across portions of the region...with
wind chills during the day Sunday likely held below zero for some
northern counties.

Early workweek to feature noticeable moderation back to more
reasonably cold levels...with Monday`s max/min readings hopefully
both noticeably higher than Sunday`s marks.  Low confidence in
potential for freezing drizzle/rain given weak overrunning set-up
with surface readings most likely in the 20s.  Long term to end with
temperatures possibly climbing above freezing.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1239 PM EST Wed Dec 10 2025

Impacts:

- Gusty winds 25 to 35kt through this evening

- MVFR ceilings with intermittent IFR within SHRASN.

- MVFR cigs persist into tomorrow

 Discussion:

Gusty winds from 25-35 kts persist across Central Indiana this
afternoon and are expected to continue into this evening. Gusts
gradually diminish after sunset through 06z, remaining elevated
through the night at 6-11 kts from 280-320 deg.

Satellite and radar imagery shows scattered rain and snow showers
pushing in from the north and west, with the most widespread
activity expected near KLAF where cigs and vis may briefly drop down
to IFR levels at times over the next several hours. P-type should
change from mainly rain at 18z to a rain/snow mix to all snow
through this evening from NW to SE. Even outside of any showers,
expect MVFR conditions at all sites through the overnight hours.
Shower activity diminishes after sunset with only scattered drizzle
and flurries overnight.

Cigs may briefly lift to VFR levels during the day tomorrow before
the next round of precipitation arrives tomorrow evening, with IFR
or worse cigs and vis due to widespread snow.

&&

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

$$

UPDATE...CM
SHORT TERM...Updike
LONG TERM...AGM
AVIATION...CM