Indiana’s Weather For Today

Brighter and colder today, as strong high pressure enters the weather chat from the Plains.

Clouds return late tonight and tomorrow.

Technical discussion via NWS Indianapolis:

All eyes are on a system expected to arrive on Wednesday. Guidance
has largely come into consensus on its evolution and timing, though
some differences remain (primarily in the mesoscale). Thermal
profiles suggest that both rain and snow are possible for portions
of central Indiana. Minor accumulations are also possible…which
will be discussed below along with associated impacts.

As of 06z Tuesday, satellite imagery shows a large plume of moisture
advancing inland over the California coast. This feature should
progress eastward, ejecting into the Plains late tonight into
Wednesday. A broad baroclinic zone will simultaneously reside over
the Midwest, emplaced by yesterday`s cold front. The approaching
system should act upon this baroclinic zone leading to an east-west
oriented area of frontogenesis. Guidance shows precipitation
breaking out in response to the frontogenetical forcing. However, a
very dry lower atmosphere may prevent much of this initial precip
from reaching the ground. It may take several hours before the lower
column saturates enough for precip to begin at the surface. Wet bulb
temperatures may be right around freezing, where precip begins as
rain before transitioning to snow due to evaporational cooling. Best
chances for snow Wednesday afternoon are north of I-70, as
temperature profiles are warmer with southward extent. Regardless,
not much precipitation may end up reaching the ground south of I-70,
at least initially, as the best frontogenesis may be in the northern
half of our CWA. Heavier rates may be an important factor for
overcoming the dry lower atmosphere for much of the day.

Further west, lee cyclogenesis ahead of the parent vort max should
be ongoing during the day Wednesday. The shortwave and resulting
surface cyclone, though weak, should progress eastward passing south
of Indiana through Kentucky. Precipitation expands in coverage as
the low approaches Wednesday evening. In locations that escaped the
initial round of precipitation, that changes around and after
sunset. Thermal profiles south of I-70 still look quite marginal, at
best, and rain is the preferred precip type here. Snow may briefly
mix in before the system exits Thursday morning. Across the northern
portions of our CWA, precipitation may switch over to snow and
remain snow for the duration of the event. Even here, thermal
profiles are marginal…with most guidance showing surface temps a
degree or two above freezing. Fresh cold air will not be ingested
into this system, so snow will depend on diabatic processes along
with evaporational cooling. Accumulations and impacts may be rate-
driven, especially where one or more mesoscale bands set up (03Z RAP
shows such a scenario). Areas that find themselves under a mesoscale
band may “over-perform” compared to surrounding locations by a
couple of inches. On average, however, amounts will be light
due to the marginal temperatures (lower
snow-liquid ratios and some melting) and limited duration of
precipitation. Accumulations should primarily occur on elevated and
grassy surfaces.

Strong cold air advection ensues once the system departs on
Thursday. Temperatures fall into the 20s Thursday night and may
struggle to reach freezing again Friday afternoon. Cold
northwesterly flow is expected to persist through the weekend. Multi-
model ensemble guidance retains a strong signal for continued east
coast troughing. Therefore, well-below average temperatures are
likely through the first week of December. Such patterns are
typically dry, though a few periodic light precipitation events may
occur.

INDY SEVEN DAY FORECAST
Today: Mostly to partly sunny. High 44.

Tonight: Partly to mostly cloudy. Low 33.

Wednesday: Cloudy, with afternoon showers. High 44.

Wednesday Night: Scattered showers, mixing with and changing to snow. Snow accumulation of an inch or less. Low 32.

Thanksgiving Day: Mostly cloudy morning. Partly sunny afternoon, with a few sprinkles or flurries possible. High 41.

Thursday Night: Partly to mostly cloudy. Flurries possible. Low 23.

Friday: Partly sunny and much colder. High 29.

Friday Night: Mostly clear. Low 16.

Saturday: Partly to mostly cloudy. Flurries possible. High 30.

Saturday Night: Partly cloudy. Low 15.

Sunday: Mostly sunny. High 26.

Sunday Night: Mostly clear. Low 16.

Monday: Mostly sunny. High 29.

NWS CHARTS FOR TODAY/TONIGHT