130
FXUS63 KIND 220818
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
318 AM EST Mon Dec 22 2025

.KEY MESSAGES...

- Light rain and drizzle expected tonight into Tuesday, patchy fog
  possible as well.

- Moderating pattern into the middle of the week with unseasonably
  mild conditions expected Wednesday-Friday

- Breezy conditions develop Monday with winds gusts to 25 mph

- Near record high temperatures in the 60s possible on Christmas Day

&&

.SHORT TERM (Today and tonight)...
Issued at 318 AM EST Mon Dec 22 2025

Synoptic analysis reveals broad ridging extending across most of the
CONUS, with troughing over the far PacNW and NE. The primary ridge
axis is across the central Plains. A progressive jet remains well to
our north, roughly along the US Canada border. A weak shortwave is
riding this flow and will help initiate surface cyclogenesis this
morning over the northern Plains. The resulting surface low, while
weak, will then track northeastward over the Great Lakes.

The approaching system should generate a modest low-level jet (30-
40kt at 925mb) later this morning, which will promote moisture
advection northward. By this afternoon (21z-00z), a thick shield of
low-level stratus is expected to arrive. Despite moisture advection,
it is not deep and there is limited forcing aloft. Our primary
source of forcing is isentropic ascent associated with the modest
LLJ. Precipitation is therefore limited to light rain/sprinkles or
drizzle. Dreary conditions should persist tonight into Tuesday
before the LLJ drifts eastward with the departing system.

Patchy fog is possible tonight into Tuesday as well, given the high
level of boundary layer saturation expected. However, brisk
southerly winds and the depth of the stratus layer should promote
drizzle rather than fog. However, some patchy fog cannot be ruled
out.

In terms of temperatures, we`ll see our coldest readings this
morning before mid/high cloud cover rolls in. Warm air advection
today should lead to highs near 50. Clouds, wind, and continued warm
air advection will keep temps mild overnight with lows in the 40s.

&&

.LONG TERM (Tuesday through Sunday)...
Issued at 318 AM EST Mon Dec 22 2025

Tuesday through Christmas Day...

Broad subtropical upper ridge to build north over much of CONUS,
with axis positioned along the Plains, maintaining 576 1000-500 mb
layer thickness over central Indiana into the day Thursday.
Corresponding surface pattern to feature weak high pressure over
Deep South and into the Gulf...and often-weak frontal boundary,
quietly crossing region Tuesday...before meandering from Tennessee
Valley early Wednesday, to probably back north of the CWA by late
Christmas Day.

Main forecast concerns through the mid-week will focus around the
combination of moisture advection under a generally impressive
inversion below 850mb...which will support widespread low stratus,
and potential fog.  Visibility reductions may be greatest Tuesday
night when diminishing breezes and several hours of mostly clear
skies are expected.

Temperatures trends and spatial distribution of anomalous to near-
record readings have lowest confidence on Christmas Day given model
divergence on northward warm front progress.  Certainty is lowest
for central/northern zones, yet still a good chance that low 60s
make it to most of the region.

Otherwise the Wednesday to early Christmas Day timeframe will bring
at least low chances for rain showers around more organized rain
coverage possible around the Wednesday night period when a small
disturbance embedded in the upper ridge passes over the region,
although low certainty on rainfall amounts for any particular
location.

Friday through Sunday...

Return to a more zonal upper pattern will oversee steady decrease in
temperatures back to near normal levels by the end of the long term.
Potentially another very mild day Friday if boundary/any passing
open wave surface low pressure continues to our north.  Stronger
transition expected by the end of the weekend as strengthening cold
frontal zone crosses the Midwest in conjunction with southern
portion of amplified polar high pressure expected to cross the
southern Plains.  The normal max/min for Indianapolis for the long
term is 38/24.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 1245 AM EST Mon Dec 22 2025

Impacts:

- Light southerly winds increasing tomorrow afternoon with gusts to
  20 kts

- MVFR stratus arriving from the south late Monday afternoon and
  evening

- Drizzle and potential IFR condition possible Monday night

Discussion:

Light and variable winds persist for a few more hours before winds
become southeasterly before sunrise. By this afternoon a 25-35 kt
southwesterly low level jet moves overhead. Gusts up to 20 kts are
possible into the evening hours as stronger gusts mix down to the
surface. Winds should gradually become more southerly with time.

Mid/high-level cloud cover should gradually increase ahead of an
approaching system over the Plains. Strong moisture advection
associated with this system will bring MVFR stratus northward near
between 20z-00z, but confidence is low in how quickly cigs may drop
before 00z tomorrow evening.

After 00z, guidance shows stratus rapidly fill in allowing all
terminals to become MVFR or lower. There is a good signal for
drizzle at times Monday night into Tuesday, so we will introduce it
into the TAFs along with minor reductions in visibility. Some
guidance depicts further reductions, potentially into IFR
territory...but model agreement is not as high regarding this. We`ll
include a SCT006 group for now to show this potential.

&&

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

$$

SHORT TERM...Eckhoff
LONG TERM...AGM
AVIATION...Eckhoff