285
FXUS63 KIND 040541
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1241 AM EST Thu Dec 4 2025

.KEY MESSAGES...

- Patchy fog possible early tonight

- Light snow likely tonight, minor accumulations possible before
  Thursday morning commute

- Wind chills of few degrees either side of zero will be across
  northern areas early Thursday and again Thursday night/early
  Friday.

- Snow is possible Sunday and again next Tuesday.

&&

.FORECAST UPDATE...
Issued at 941 PM EST Wed Dec 3 2025

Overall the forecast largely remains on track, but have made some
adjustments to the hourly POPs to focus more on the I-70 corridor
and points to the south for the better chances of snow.
Reflectivities towards Lafayette remain very low with no reports of
snow ahead of the front which currently remains near Chicago through
eastern Illinois. This increases confidence in any snow remaining
more like flurries or at least very isolated as the front arrives
after midnight. To the south, there have been a few snow reports in
a localized vort max south of I-70, but no impacts or accumulations
have been noted so far. Conditions will become more favorable for
snow later tonight in this area, but continue to expect amounts to
remain less than a half inch with very little moisture and only
meager forcing.

Patchy fog remains possible over the next few hours with most sites
in the 6-8 mile range. Winds of 5-10 mph will limit coverage to more
favored fog formation zones and as the front passes the increase in
winds should bring an end to any ongoing fog.

Main focus for tonight continues to be the very cold wind chills
post-front with sub-zero wind chills remaining likely for much of
the northwestern portions of the forecast area with morning lows in
the low teens to perhaps single digits with wind gusts to 25 mph.

&&

.SHORT TERM (This evening through Thursday)...
Issued at 303 PM EST Wed Dec 3 2025

Surface analysis shows a cold front approaching Indiana from the
northwest, extending from northern Missouri to just north of Chicago
as of 2pm. Southerly flow ahead of the front has increased to
between 10-15kt. ACARS soundings out of IND show substantial warm
air advection occurring aloft, just a couple hundred feet off the
ground. However, a strong inversion has allowed widespread stratus
to persist through the afternoon. Temperatures at the surface have
been lower than guidance so far today. Some breaks are beginning to
be noted, however, and a late-day rebound may occur for some spots.

Guidance shows winds diminishing this evening due to the MSLP
gradient weakening as the front approaches. Should clearing continue
into the early evening hours, some patchy fog is possible given a
very moist boundary layer currently in place. Dew point depressions
are only about 5 degrees as of this writing. Fog potential will be
mitigated by thick mid-level cloud cover above the stratus.
Therefore we`ve capped fog at patchy in the forecast. Fog will be
confined to the pre-frontal environment, so we`ve also removed
mention of fog beyond 06z.

Light precipitation has developed along the front over northern
Illinois and into northern Indiana. This activity has been fighting
some mid-level dry air, which shows up on the IND ACARS soundings as
well between 900-700mb. Our primary forecast challenge tonight is
whether precipitation will be able to overcome the dry air as it
heads south. Guidance hints at a few poorly-organized vorticity
filaments riding along the front, which may produce some modest
large-scale lift at times. Jet dynamics are a bit mixed, with
Indiana sitting below a jet entrance region but also an area of
upper-level confluence. Warm air advection / isentropic lift also
diminishes with time as southerly flow ahead of the front weakens.
Putting all this together, we`ll have enough forcing for at best
light precipitation. The precip should be able to overcome the dry
air as no new dry air is being advected northward (limited moisture
advection as well), so it would just be a matter of time.

In terms of amounts, a dusting to a half of an inch seems
reasonable. An isolated amount up to an inch would be the reasonable
worst case scenario.

The front itself passes through central Indiana between 02z-06z,
with a brief period of gusty NNW winds and strong cold air
advection. Temperatures rapidly dropping into the teens and single
digits is likely, with wind chills by sunrise Thursday near or a bit
below zero. High temps on Thursday will be limited by ongoing cold
air advection and residual low stratus, which could once again
linger more than guidance suggests. Expect highs in the upper teens
(north) to mid 20s (south). Very cold low temperatures in the teens
and single digits are expected again Thursday night.

&&

.LONG TERM (Thursday night through Wednesday)...
Issued at 303 PM EST Wed Dec 3 2025

Ensemble guidance shows broad troughing over the Midwest and
northeastern US. This pattern generally favors cooler-than-average
weather over Indiana, which has been the case for the past week or
so.

Some differences are noted within the large-scale pattern,
however. Namely, the lack of troughing over the southwestern US.
This troughing has been the source of recent snowfall as systems
eject from the southern Rockies and track east/northeastward. Our
primary source of synoptic activity will switch to the Pacific
Northwest, with systems coming ashore over Washington before diving
southeastward. These systems (clippers) are typically weak with
limited moisture.

Guidance shows a few of these system approach throughout the week,
passing quietly to our north. The next one of any potential
consequence may be this weekend. Almost all guidance has trended
downward in terms of impacts, however. We`ll retain low PoPs for
Sunday. A second system may approach early next week, but guidance
diverges rapidly at this point so forecast confidence is low.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 1241 AM EST Thu Dec 4 2025

Impacts:

- IFR cigs expected with potential for brief LIFR ceilings through
  08-10Z

- Brief MVFR to IFR vsbys possible due to snow/patchy fog through 10Z

- Veering winds through the period

Discussion:

IFR cigs are expected with the potential for brief LIFR ceilings
through 08-10Z. Improving conditions are then expected behind a
departing cold front which should help clear out clouds later in the
morning. VFR conditions are expected for the remainder of the period
once clouds clear out of the area.

Light snow or flurries is still possible, especially at HUF and BMG,
through 09Z with vsbys generally MVFR but briefly IFR at times. Snow
should end towards 09Z with the potential for some lingering MVFR
vsbys due to patchy fog. Winds will remain mostly in the 05-10kt
range through this morning and gradually diminish later today into
this evening. Expect veering winds through the period.

&&

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

$$

UPDATE...White
SHORT TERM...Eckhoff
LONG TERM...Eckhoff
AVIATION...Melo