049
FXUS63 KIND 022008
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
308 PM EST Tue Dec 2 2025

.KEY MESSAGES...

- Areas of freezing fog tonight, potentially dense in spots.

- Light snow Wednesday night, minor accumulations possible before
  Thursday morning commute

- Wind chills just near or just below zero will be across northern
  areas early Thursday and again Thursday night/early Friday.

- Accumulating snow is possible Sunday and again next Tuesday.

&&

.SHORT TERM (This evening through Wednesday)...
Issued at 308 PM EST Tue Dec 2 2025

Winter arrived with full force for the first week of December
with widespread snow and very cold temperatures! While additional
winter weather remains in the forecast through the week, the main
focus for the short term period will be the chance for freezing fog
and low clouds tonight into tomorrow morning.

Satellite and observations show cloudy and cold conditions over the
Ohio Valley and Great Lakes as high pressure this afternoon. Latest
soundings from around the region show a classic arctic airmass set
up with moisture and clouds stuck within the boundary layer under
quasi inversion/isothermal layer from 600-900mb. The area of high
pressure slides eastward overnight increasing subsidence over the
state and sharpening the low level inversion...further keeping low
clouds in place. Winds become southerly overnight across Indiana
with weak warm air advection over the fresh snowpack potentially
resulting in freezing fog for portions of the area. Most hi-res
guidance depicts fog quickly this evening and continuing through the
overnight.

Confidence is only moderate in the exact locations fog may develop
tonight as there will be a mix of low stratus and fog throughout the
state. Confidence is high that the evening continues with widespread
stratus, holding steady through the night for the northern 2/3 of
the state. As winds become southerly tonight, fog should begin to
develop within the Wabash River Valley and low lying areas first.
Thinking there will be more fog across South Central Indiana later
tonight as some guidance shows breaks in the stratus there by
sunrise. Fog may be dense at times and with temperatures below
freezing, would not be surprised if a light glazing of ice develops
on surface in areas where fog sticks around through the night.

Conditions improve during the day on Wednesday as southerly winds
and low level mixing work to clear out the fog and lift the stratus
deck. An incoming system from the northwest however keeps mid to
high level clouds over Central and North Central Indiana through the
day tomorrow, while better clearing takes place further south. Areas
getting sunshine likely rise above freezing into the upper 30s,
while cloudier locations across the north remain in the low to mid
30s. The LLJ strengthens overhead tomorrow and despite lower mixing
heights, afternoon wind gusts to 20 mph are still possible.

&&

.LONG TERM (Wednesday night through Tuesday)...
Issued at 308 PM EST Tue Dec 2 2025

A shortwave trough over northern Saskatchewan/Manitoba will move SE
into the Great Lakes over the next 24 hrs. A strong cold front /of
arctic origins/ and 1035 mb surface high pressure in the wake of the
front will move SE from the northern plains into the region
Wednesday night into Thursday. Forecast soundings indicate 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 so have
bumped up pops in the northeast part of the forecast area to around
50 percent. Accums generally less than an inch are expected
in this portion of the forecast area with only trace to 0.5 inch
amounts further south.

Snowfall will come to end by 12Z Thursday as the arctic 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 by 12Z. This will lead to wind chills as
low as -5 by 12Z Thursday in NW Zones to 5 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 the southern stream shortwave moving out of the
southern plains into the MS Valley. 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 5-10
in the Indy Metro between 06-12Z Friday. In addition to the low
temperatures and wind chills, soundings indicate patchy freezing
fog is possible late Thursday night/early Friday.

Forecast confidence on precipitation chances and timing diminish 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 out of western Canada into the Central CONUS/Great Lakes
between this weekend into early next week. Medium range guidance is
in remarkably good agreement with one particular shortwave
supporting another snow event on Sunday/Sunday night. Recent NBM
trends of higher pops from 25-35 percent area wide seems reasonable
for this event. Yet another shortwave is expected to traverse the
region at the end of the forecast period with guidance showing lower
end pops for Tuesday. Needless to say with the longwave pattern
favoring continued NW flow and reinforcing shots of arctic air, and
a healthy snowpack below normal temps will continue through the
extended.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1246 PM EST Tue Dec 2 2025

Impacts:

- Slow improvement to MVFR this afternoon, then deteriorating cigs
and vis overnight

- Advection fog likely tonight with IFR or worse visibilities
  possible

Discussion:

Satellite imagery shows low stratus hanging tight across Indiana
with only a slow improvement to low MVFR cigs through the rest of
the afternoon. Westerly winds at or below 10 kts this afternoon
becoming southerly overnight at or below 6 kts. Warmer air over the
new snowpack should result in lowering stratus overnight to IFR
levels in addition to advection fog. Confidence is lower on where
fog will be the worst; however thinking KLAF, KHUF, and KBMG have
the best chance at seeing brief periods of LIFR cigs and vis from
fog within the 03-12z timeframe.

Southerly winds should help mix out the lower stratus and fog late
tomorrow morning, so have conditions beginning to improve from 14-
16z to at least MVFR levels. Cigs may even improve to VFR by
tomorrow afternoon ahead of the next frontal system approaching.


&&

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

$$

SHORT TERM...CM
LONG TERM...Crosbie
AVIATION...CM