863
FXUS63 KIND 291408
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
908 AM EST Sat Nov 29 2025

.KEY MESSAGES...

- Winter Storm Warning/Advisory for much of central Indiana

- Snow amounts of 4-7 inches in the Warning area, 1-4 in the Advisory

- Additional snow chances Monday night into early Tuesday, especially
  for south/southeast counties

- Wind chills at night...into the teens through Monday night...and
  then possibly single digits Tuesday night through Thursday night

&&

.MESOSCALE UPDATE...
Issued at 908 AM EST Sat Nov 29 2025

Dynamical mesoscale environment unfolding across central Indiana
this morning and over the next 90 minutes we will continue to see
even more impressive atmospheric elements present themselves.
Currently the WSR-88D shows a large footprint of reflectivity
expanding northeast from Illinois, although aircraft data is still
showing a large dry layer at the surface to around 3kft agl which is
eroding the leading edge of the reflectivity as it approaches the
Indy metro area. Further northwest there is an impressive band of
precipitation and with the cold air at the surface the atmosphere is
allowing full dendrites to reach the surface and rates are hovering
around .5 inches per hour to near 1 inch. The bigger driver will be
the strength of the warm air advection that is already pushing into
Southwest Illinois and progged to reach Indiana by early afternoon.

As the atmosphere steadily saturates, this will cool temperatures
down while dew points rise from the moisture surge. Some hi-res
guidance continues to indicate a robust mid-lvl fgen band advancing
northeast into west central Indiana, which will help to decrease the
condensation pressure deficit that we presently still have. This
will allow a burst of snowfall, potentially some moderate snow at
the start, with large efficient dendrites quickly falling to the
surface. Visibilities will additionally drop rapidly to around a
half mile or at times lower than this.

We will do another mesoscale forecast discussion around 11 am est.

&&

.SHORT TERM (Today and tonight)...
Issued at 300 AM EST Sat Nov 29 2025

A winter storm will bring first snow, then a mix of rain and snow to
central Indiana through tonight. Snow will impact travel, especially
across the northern forecast area, with the northwestern area seeing
the worst impacts. No changes have been made to headlines with this
update. Snowfall amounts have been lowered some in the south and
tweaked elsewhere.

Isentropic lift will arrive by the start of the Today period, but it
will have to overcome an initially very dry lower atmosphere. By
noon, much of the northern three quarters of the area will have seen
snow, so will have likely or higher PoPs there this morning. Lift
will be weaker across the southeastern quarter, so will keep PoPs
lower there.

This initial lift will move north this afternoon, with roughly the
southern half seeing a relative lull during the early to mid
afternoon hours. Forecast soundings show drier air returning to the
southern half of the area during this time. Will lower PoPs there,
but keep high PoPs north where forcing will continue. In the far
south, temperatures may be able to warm enough that some rain might
mix with any snow that falls during this time.

Later this afternoon into the early evening, another surge of lift
will move into the entire area, ahead of the approaching frontal
system and an increasing 850mb jet. An upper jet moving in will
provide additional forcing. Will have high PoPs return to all areas.
The precipitation will eliminate the drier low levels in the
southern forecast area and allow temperatures to briefly cool again
there. Mainly snow will be expected with this initial cooldown.

Warm advection ahead of the surface cold front will allow warmer air
to move north and change precipitation to a rain/snow mix or just
plain rain later during the evening into the early overnight. Colder
and drier air will rush in during the remainder of the overnight,
cooling things back down but also lowering precipitation chances.

The northern forecast area will see the longest period of mainly
snow and will also see the longest period of forcing. Thus feel that
the warning still looks good there. Delaware County looks to be even
closer to the edge of conditions warranting a warning, but with
uncertainty left it in the warning.

The I-70 corridor remains the area of most uncertainty and biggest
bust potential. If drier air lingers there longer and/or warmer air
gets to this area faster, amounts will be lower than expected. Even
if this doesn`t happen, there will likely be a tight gradient across
counties in this area. For example, Marion County may see 4-5 inches
in the far northwest but only around 2 inches southeast.

Across the south, amounts may be lower due to the drier air
lingering this afternoon and warmer temperatures.

Winds will increase as the low pressure system to the northwest
deepens, with gusts near 35 mph tonight.

Given that this is an early season event and a busy travel period,
will leave the Warning and Advisory alone, even though some areas of
these may not reach criteria. In addition, as temperatures fall back
to below freezing tonight into Sunday, what has melted will
refreeze, especially on untreated surfaces.

&&

.LONG TERM (Sunday through Friday)...
Issued at 324 AM EST Sat Nov 29 2025

Unseasonable to anomalous cold to continue into first week of
December...along with occasional chances of accumulating snow.
492 dm H500 Polar low displaced to Hudson Bay will lead quasi-split
synoptic pattern over North America mid-latitudes...by directing
steady flow of polar to arctic surface high pressure down Plains and
across Midwest through the long term.  Opportunities for primarily
snow precipitation-type will range from lingering flurries/-SHSN on
Sunday...another, quick-hitting, weather system Monday night into
early Tuesday...and low certainty for possible light overrunning at
the end of the period.

The short term`s storm system will depart southeastern Michigan for
southeastern Canada Sunday...while the elongated tail of its
supporting short wave slides over the northern Midwest.  Subtle
surface reflection of this trough may be able to utilize dry
adiabatic lapse rates below 925 mb to shake out a few snow showers
and several flurries, especially from Lafayette to Rushville and
points north/east, although little to no additional accumulation is
expected.

Greater attention is now turning to increasing potential for light
to moderate snowfall surrounding the Monday night timeframe...when a
mid-level short wave embedded in the wintry flow quickly lifts from
the Ozarks to Lake Erie...while interacting with a surface weakness
expected to track across Kentucky.  Resultant snow is expected
Monday night, with an overnight burst most likely for far southern
and southeastern counties where moderate snowfall is possible by
early Tuesday.  Subfreezing readings will promote slick surfaces
where untreated.  Lower confidence for late week precipitation
chances where another overrunning type set-up could bring light snow
or mixed precip into the CWA, although this may be difficult to
realize as strong high pressure aligned just to our north may now
allow more than clouds and virga.

Afternoon highs will most often be around 30F...while overnight
minimums as high as the 15-25F range, also include 2-3 frigid nights
through the mid- and perhaps late week where lows of 3-13F will be
common amid the thicker snow pack north of the I-70 corridor.
Wind chills will struggle to exceed 25 degrees and will consistently
drop into the teens to single digits at night.  The colder mid- to
late week could easily support wind chills below zero Wednesday
night and Thursday night for the region`s northern half.  Time
should be limited outdoors, especially at night and when winds are
elevated... utilizing multiple layers of clothing.  The highest
December daily record low temperature at Indianapolis is on 12/5
(8*F, 1886)...the current forecast low that morning is 10F.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 604 AM EST Sat Nov 29 2025

Impacts:

- Deteriorating conditions through the day in snow
- Visibility will go IFR first into the afternoon followed by
  ceilings late afternoon into the evening
- Worst prolonged conditions will be at KLAF. Best overall
  conditions at KBMG.
- Winds veering through the day with gustiness increasing

Discussion:

Snow will have to moisten the lower atmosphere this morning, then
visibility will drop first. Ceilings will eventually follow. Lower
than IFR conditions will occur in heavier snow, with KLAF having the
highest odds for these.

Rain will mix with the snow late today into this evening from south
to north. After a cold front moves through overnight, precipitation
will diminish with conditions improving to MVFR.

Winds will veer throughout the day then become westerly overnight.
Gusts will increase this afternoon with gusts near 30kt possible
overnight.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 10 AM EST Sunday for INZ021-028>031-
035>041-043>047.

Winter Weather Advisory until 10 AM EST Sunday for INZ042-048-
049-051>057-060>065-067.

&&

$$

MESOSCALE...Beach
SHORT TERM...50
LONG TERM...AGM
AVIATION...50