744
FXUS63 KIND 110211
AFDIND

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

.KEY MESSAGES...

- Accumulating snow likely Thursday night into Friday where a narrow
swath of 3-5+ inches of snow may fall before the Friday morning
commute

- Arctic outbreak expected this weekend with low temperatures near
or below zero...and potentially dangerous sub-zero wind chills down
to -20F.

- Another round of snow expected Saturday with additional
accumulations possible across Central Indiana

&&

.FORECAST UPDATE...
Issued at 910 PM EST Wed Dec 10 2025

Lake induced snow showers remain the primary impact this evening...
focused mainly to the northeast of the Indy metro. Isolated snow
showers and scattered flurries continued over the remainder of the
area with exception of the lower Wabash valley. Temperatures have
fallen below freezing over most of the region as of 02Z.

The ongoing snow showers coming off Lake Michigan will continue for
the next few hours before the deeper moisture plume shifts east and
low level flow begins to back. The primary area impacted so far this
evening has been from northern Madison southeast across Delaware and
into northeast Henry County with light accums. Since 01Z though...a
new narrow snow band has developed from Hamilton County southeast
towards Rushville. This band will likely impact the northeast Indy
metro through about 03-0330Z and will cause minor accums up to a
half inch or so in spots.

Most of the heavier snow showers will move out of the area by 06Z
but with upper level energy continuing to drift across the
region...flurries are likely to linger through daybreak across the
northeast half of the forecast area. Wind gusts will continue to
relax over the next few hours as the surface pressure gradient
weakens.

Temps...lows will fall into the mid and upper 20s across the region.


UPDATE on Thursday Night Snow...

We have introduced a Winter Weather Advisory for all but the lower
Wabash Valley and the far northeast portions of central Indiana.
With recent model trends bringing the onset of snowfall in a bit
faster late Thursday, the Advisory will go into effect at 22Z
Thursday and run through 15Z Friday. We are highly confident in 2 to
as much as 5 inches within the advisory area with a narrow band of
locally higher amounts. That band at this point appears likely to
align in the vicinity of the I-74 corridor but there could still be
additional adjustments to the axis of higher amounts over the next
12 to 18 hours. Regardless...this will be an impactful snowfall for
the region with travel becoming difficult Thursday evening and
continuing through the morning rush Friday. Stay tuned.

&&

.SHORT TERM (This evening through Friday)...
Issued at 312 PM EST Wed Dec 10 2025

A very active weather pattern is ongoing across Indiana this week
with multiple chances for snowfall and much colder temperatures on
the way.

Through Thursday afternoon...

Latest satellite and radar imagery show Indiana within a cyclonic
flow pattern of an area of low pressure over Southern Ontario. A
strong low level jet aloft in addition to steepening low level lapse
rates due to CAA has resulted in wind gusts of 35-45 mph throughout
the afternoon. Wind gusts persist into the evening hours, slowing
diminishing below 30 mph tonight as the LLJ wanes.

Temperatures are following a non-diurnal curve today, falling slowly
toward freezing by this evening as northwesterly winds advect a much
colder airmass into the state. Observations and forecast soundings
show an environment conducive for rain transitioning to snow showers
as deep enough cold air interests with deep enough low level
moisture. Surface temperatures are still above freezing this
afternoon with even warmer ground temperatures, so not expecting
accumulating snow within these snow showers. Deeper moisture pushes
off to the east with the main low during the overnight hours;
however lingering moisture and any moisture advection off of Lake
Michigan may keep the chance for isolated snow showers and flurries
around, mainly north of the I-74 corridor.

Thursday evening through Friday morning...

CONFIDENCE INCREASING IN ACCUMULATING SNOW ACROSS CENTRAL INDIANA

The main forecast concern over the next several days will be the
threat for accumulating snow across Central Indiana as a clipper
system dives southeast into the midwest, tracking right over the
state. Central Indiana remains in the path of strong upper level NW
flow, and an efficient set up for quickly developing lows out of the
Canadian Rockies. The system from today brought strong CAA, of which
will sink the baroclinic zone southward, placing central Indiana in
an ideal location under the jet streak aloft for both enhanced lift
and cyclogenesis within a cold airmass supportive of snow.

These clipper systems, which track 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 36 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. Latest guidance and thinking places the location of highest
QPF and snowfall potential between the I-70 and I-74 corridors.

Latest forecast soundings today continue to indicate 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 0.2-0.4 inches of
QPF puts the highest likelihood of snowfall to be between 3 and 5
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. Best
forcing for ascent under the entrance region of the jet streak aloft
looks to be in the 02-08z timeframe. Will monitor closely where
banding sets up as this will indicate where higher snow amounts will
set up.

There looks to be a sharper cut off on snow amounts on the south
side of the system within South Central and SW Indiana, where there
may be a tight temperature gradient. It is possible that surface
temperatures rise at or above freezing Thursday night in the SW
portion of the area as the low pressure system tracks across the
state, significantly limiting snowfall amounts further south and
possibly leading to a mix of rain at times. The current snowfall
forecast may not show a sharp enough cut off on the south side of
the system and will be fine tuned with the next few forecast
updates.

If trends continue, winter weather headlines may be needed for the
accumulating snow threat Thursday night into Friday. Expect major
travel impacts Friday morning as the bulk of the snow is expected to
fall before and close to the morning rush hour.

&&

.LONG TERM (Friday night through Wednesday)...
Issued at 312 PM EST Wed Dec 10 2025

Another round of snow is likely on Saturday. An upper level trough,
surging Arctic air, weak low pressure, and an upper level jet will
all combine to provide forcing across central Indiana on Saturday.
Moisture will have not been cleared out from the previous system,
so this forcing will have moisture to work with.

The result will be snow spreading across the area from west to east
Saturday, ending later in the day (potentially into the evening).
Some differences remain in guidance on the amounts and location of
the higher amounts.

At the moment, another 1 to 3 inches of snow look to be a good bet
for a large portion of the area.  Higher amounts are possible,
especially with some frontogenetical forcing in the area potentially
leading to banding. (Blended guidance`s 24 hour snowfall 25th
percentile is around 1 inch with 75th percentile 4-5 inches in
locations with the highest totals).

Arctic high pressure will build in for Sunday and Monday, providing
bitterly cold conditions. Air temperatures will likely be below zero
across portions of the area early Sunday and early Monday. Before
the center of the high moves nearby, winds will make it feel even
colder Saturday night into Sunday morning. There is the potential
for wind chills from -10 to -20, which would require headlines. Will
continue to monitor closely as the location of the deepest snow
cover will have an impact on temperatures.

The high will provide dry weather through Tuesday. As the area gets
on the western side of the high, warm advection will return
temperatures into the 30s for Tuesday and potentially even the 40s
on Wednesday. A system could bring some precipitation by Wednesday,
but it looks to be just rain if temperatures warm as expected.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 614 PM EST Wed Dec 10 2025

Impacts:

- Gusty winds ending this evening
- MVFR ceilings with flurries/light snow showers tonight
- MVFR conditions continue through midday Thursday
- Snow arrives with rapidly deteriorating conditions early Thursday
evening

Discussion:

Scattered light snow showers and flurries continue this evening
under a predominantly MVFR ceiling. There have been a few breaks in
the lower stratus at KLAF but anticipate that will fill back in over
the next few hours. Scattered light snow showers and flurries will
linger for much of the night then diminish Thursday morning as weak
surface ridging builds in. Northwest winds continue to gust near
25kts currently but should drop off by late evening as the pressure
gradient relaxes.

MVFR stratus will hold Thursday morning but should see ceilings rise
up to low VFR levels for most of the afternoon as the surface ridge
axis passes through the Ohio Valley. Westerly winds will back to
southwest by late day at less than 10kts.

Widespread snow will expand into central Indiana from the northwest
by early Thursday evening with conditions rapidly deteriorating
through the evening as snow rates increase.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 5 PM Thursday to 10 AM EST Friday
for INZ028>030-035>037-039-043>048-051>057-060>065-070>072.

&&

$$

UPDATE...Ryan
SHORT TERM...CM
LONG TERM...50
AVIATION...Ryan