381
FXUS63 KIND 132340
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
640 PM EST Mon Jan 13 2025

.KEY MESSAGES...

- Quick moving cold front/upper wave may produce light snow around a
  half inch or so Tuesday with isolated amounts near 1 inch.

- Temperatures below zero with slightly cooler wind chill values
  Tuesday night into Wednesday morning

- Warm up to end the work week, with rain likely Friday night.
  Uncertainty remains high on the potential for a rain/snow mix

&&

.SHORT TERM (This evening through Tuesday)...
Issued at 219 PM EST Mon Jan 13 2025

Rest of This Afternoon...

Quiet but cold weather will continue this afternoon. The lower
atmosphere remains quite dry, with dewpoints running well below much
of guidance. This dry air has helped prevent the clouds that
guidance had suggested from forming. Will thus go more optimistic
with sky cover. Temperatures will remain cold.

Tonight...

Clouds will increase tonight ahead of an approaching clipper system.
Temperatures will fall quickly this evening when cloud cover should
be lowest, but radiational cooling will be tempered some by winds
remaining up. Nevertheless, cold temperatures will rule tonight with
lows in the single digits above zero common. Wind chills will likely
get below zero at times overnight.

Tuesday...

The clipper system will move through mainly during the morning
hours. Large scale forcing looks decent with the system, but overall
moisture is relatively limited. However, there is good forcing and
moisture within the dendritic growth zone, so it should be more
efficient in producing snow with what moisture is available.

The DESI viewer shows that ensembles are in decent agreement that
some snow will fall across at least part of the forecast area.

Will raise guidance PoPs and keep likely PoPs across much of the
northern forecast area, with chance PoPs elsewhere. PoPs will peak
during the morning (or perhaps early afternoon east) when forcing is
best.

Given snow ratios around 20 to 1, some areas could see near an inch.

Temperatures will only reach the upper teens to lower 20s most areas
(perhaps middle 20s far south). Readings may fall some in the
afternoon behind the cold front.

&&

.LONG TERM (Tuesday night through Monday)...
Issued at 219 PM EST Mon Jan 13 2025

Throughout the long-term, the Ohio Valley will continue its
placement within meridional upper level flow, with the long wave
pattern consisting of a ridge over the West Coast and troughing over
New England. The end result will be large temperature swings and
multiple chances for precipitation over the next several days.

Initially, central Indiana will be much colder than normal as high
pressure ushers in beneath strong CAA following Tuesdays clipper
passage. The combination of clearing skies, and an additional thin
layer of snow will likely push much of central Indiana below zero on
Wednesday morning. Luckily, winds should remain fairly light,
allowing for minimal differences in wind chill temperatures.

This high pressure will remain through Thursday, with continuous dry
conditions over a 48 hour period Wednesday through Thursday night.
The bulk of the 850mb cold air axis will shift eastward with time,
allowing for a warming trend beginning on Thursday once winds shift
toward southerly; expect highs in the 30s.

Friday will be the warmest day of the week as strong low level WAA
pushes into the Ohio Valley. Light precipitation within modest
moisture advection during the day on Friday is possible, but a
majority of the QPF is expected Friday night as isentropic lift
increases ahead of a developing short wave. With temperatures
remaining well above freezing Friday evening and night, all
precipitation should fall initially as rain. However, with the
shortwave becoming positively tilted, greater 850-700mb cold air on
the back side of the surface low may allow for a brief transition of
a mix of rain/snow as the wave departs on Saturday.

Much colder air is expected behind this shortwave with ensemble
guidance indicating multiple standard deviations from climatological
normals attached with the emergence of arctic air early next week.
This looks to be delayed until a clipper passage Sunday into Monday,
but guidance is still varied on strength and timing of the clipper
system. Ensemble members are also varied on where the axis of cold
air will be positioned early next week. This looks to be the coldest
air of the seasonal thus far, but in order to get near record
temperatures (negative teens), a snow pack will be needed from
Sunday`s clipper, and the axis will have to shift east of the
current ensemble mean.

Looking at the extended, the colder then normal conditions look to
continue through most of next week towards the end of January.
However, a greater troughing influence in the Eastern Pacific is
expected in weeks 2-3, of which could allow for some moderation as
we enter February.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 640 PM EST Mon Jan 13 2025

Impacts:

- MVFR ceilings return Tuesday morning along with some snow. Brief
  IFR conditions possible in heavier snow.

- Winds with gusts up to 25kt on Tuesday. Southwesterly to start
  shifting to northwesterly in the afternoon.

Discussion:

VFR conditions expected through most of tonight. Clouds increasing
around 10z, with snow likely by 15z. Best chance of snow is from LAF
to IND, with lesser chances from HUF to BMG. In addition to MVFR
ceilings, snow may briefly become heavy enough to bring IFR
visibilities at times. Snow should begin exiting the area by 19z.
VFR conditions return around 00z.

Winds should remain under 10kt tonight from a generally west-
southwesterly direction, increasing during the day Tuesday as the
system responsible for the snow moves through. Speeds may top out
around 15kt with gusts as high as 25kt. Once the system passes, a
shift to northwesterly is anticipated. Speeds decrease by 00z to
under 10kt.

&&

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

&&

$$

SHORT TERM...50
LONG TERM...Updike
AVIATION...Eckhoff