476
FXUS63 KIND 012020
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
320 PM EST Mon Dec 1 2025

.KEY MESSAGES...

- A Winter Weather Advisory is in effect this evening and overnight.
Totals ranging from 1 to 5 inches across central Indiana.

- Light snow is possible late Wednesday into Wednesday night.

- Wind chills early Thursday and again late Thursday night into
early Friday will be between -5 and 5 F north of I-70.

- Light snow is again possible Sunday.

- Below normal temperatures will continue into early next week.

&&

.SHORT TERM (This evening through Tuesday)...
Issued at 319 PM EST Mon Dec 1 2025

A strong, positively tilted shortwave with the polar jet will push
eastward today, arriving this evening. Concurrently, a subtle wave
in the subtropical jet will lift northward tonight. These two
systems begin to interact late this evening through tonight,
producing widespread snow across the area. Thermal profiles are
plenty cold enough for all snow, outside of a low chance for
freezing drizzle where a mid level dry layer may limit ice crystal
growth initially.  show a cold enough air mass for all snow, at
least in our CWA. Snow totals will be tricky with this system due to
a multitude of mesoscale bands and high differences in QPF and SLRs
between them.

The initial round of snow is attached to strong 700mb frontogenesis
attached with a mid level jet streak. As this band passed through
St. Louis, it produced 1-1.5 in/hr rates and is quickly moving
eastward through central IL. The main mitigating factor will be a
substantial dry layer beneath this forcing of which will likely
delay onset of heavy snow a little this afternoon. That said, the
magnitude of forcing should still eventually overcome the dry layer,
with accumulating snow fall reaching the border as early as 4PM and
the metro by 5PM. Luckily, this 700mb forcing should be short lived
as it pushes out ahead of the height falls. Currently expectation is
for this to produce a quick 0.5-1" along and north of the I-70
corridor this evening. Due to the dry air, southern portions of the
area are unlikely to see any snow with this initial push.

The next round of snow is expected to arrive between 9PM-11PM and
continue through 4AM tonight along a corridor of strong 800-900mb
FGEN. This will likely produce another widespread 1-2" across most
of the area, but as this FGEN impinges on a strengthening baroclinic
zone, narrow heavy snow bands are likely to develop. This is where
the potential for higher end amounts of up to an additional 3-4
inches will be possible providing a high end storm total of 4-5
inches in some areas along and north of I-70.

The final round of snow will be associated with the wave attached to
the subtropical wave between 2AM and 7AM late tonight into tomorrow
morning. This wave is attached to a much strong surge of moisture,
of which could contribute to additional heavy snow bands as some weak
CSI develops on the northern edge of the wave. This will likely
produce another general 1-2 inches over southern IN with isolated
higher amounts within the aforementioned banding.


********************************************************************
Summary:

In total, all of central Indiana is expected to see snow this
evening through tonight. The far NW portions of central Indiana are
currently expected to see between 2-4" with snow ending by 3AM. The
norther I-70 corridor is expected to see the most snow with totals
ranging from 2-5", and could see very heavy rates at times
overnight. SE central Indiana including Rushville and Greensburg
could also see brief heavy snow bands at times late tonight with
totals randing from 1-4". Lowest amounts are expected to be over SW
central Indiana with totals between 1-3".

*********************************************************************

&&

.LONG TERM (Tuesday night through Monday)...
Issued at 319 PM EST Mon Dec 1 2025

The extended period starts with dry weather Tuesday night as a
surface high pressure ridge moves across the region. On the backside
of this high pressure, sw surface winds will increase ahead of
another stronger cold front/shortwave trough moving southeast
through the upper midwest/northern plains. Forecast soundings
indicate a similar profile to todays snow event with a large area of
dry air between 850-700 mb saturating fairly quickly as mid level
FGEN moves ahead of the surface front. Snow probs still seem to be a
little low in the NBM given the degree of forcing but for now have
left in 30-40 pops. Accums generally less than an inch are expected
in northern parts of the forecast area, however slightly higher
amounts are possible if quicker saturation can occur in the
aforementioned dry layer.

Snowfall should come to end by 12Z Thursday as the surface cold
front sweeps SE across Central Indiana. Wind gusts from 15-20 mph
are expected in the wake of the front and with temps falling to the
single digits in NW zones this will lead to wind chills as low as -5
by 12Z Thursday in NW Zones to 0 to 10 in the Indy Metro. Moderately
strong CAA below 850mb will lead to temps hovering in the 15-25F
range through the day Thursday. As a 1035 mb surface high pressure
builds south and east of the forecast area Thursday night this will
support generally light winds. Skies will initially be clear
Thursday evening, but high clouds are expected to increase
overnight ahead of another shortwave moving out of the southern
plains. At this time, radiational cooling is expected to be
sufficiently strong for lows to reach near or just below zero in NW
portions of central Indiana and 5-10 in the Indy Metro area and 10-
15 in south of I-70. Although winds will be light, wind chills again
around -5 are expected in NW zones and 0-10 in the Indy Metro
between 06-12Z Friday.

Forecast confidence on precipitation chances and timing wane as
we go further into the extended. Fairly strong jetstream will
remain across the Pac NW/Rockies, thanks to strong temp gradient
between the offshore CA upper ridge and the arctic air over the
northern plains/Canada. Several shortwaves are expected to move SE
in this jet pattern into the Central CONUS/Great Lakes between
Friday and Monday. Medium range guidance does seem to be in fairly
good agreement with one particular shortwave supporting another
light snow event on Sunday. Have opted to push the pops to 15-20
percent area wide Sunday instead of the hit and miss NBM guidance.
Needless to say with the longwave pattern favoring continued NW
flow and reinforcing shots of arctic air, below normal temps will
continue into next week.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 319 PM EST Mon Dec 1 2025

Impacts:

- IFR and worse return after 22Z Today in snow. LIFR at times
overnight

Discussion:

Biggest factor will be the impending snow system arriving over the
next few hours at KHUF, KIND and KLAF. Period of IFR and even LIFR
are possible for a few hours, before a delay is likely until arter
02Z tonight with additional IFR to LIFR condtions through 07Z.
Ceilings should improve tomorrow morning but are likely to remain in
MVFR until at least the afternoon.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 7 AM EST Tuesday for INZ021-
028>031-035>049-051-052.

Winter Weather Advisory from 7 PM this evening to 7 AM EST
Tuesday for INZ053>057-060>065-067>072.

&&

$$

SHORT TERM...Updike
LONG TERM...Crosbie
AVIATION...Updike