Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 261451
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1051 AM EDT Tue Mar 26 2024

.KEY MESSAGES...

- Wind Advisory today
- Showers and few t-storms Tuesday...isolated
  severe storms possible
- Widespread frost/freeze possible Wednesday night
- Dry mid week through Friday
- Rain chances return Saturday through Monday

&&

.FORECAST UPDATE...
Issued at 1051 AM EDT Tue Mar 26 2024

Currently central Indiana sits in the warm sector as the front
itself sits over east-central Illinois. The showers along the front
are what we will be watching the rest of the day for any severe
potential. So far, there has been little in the way of even strong
storms and there has not been lightning with it thus far. Satellite
shows some spots of thinned clouds over central Indiana which
allowed warming at the surface this morning, but cloud coverage is
starting to fill back in. Satellite is also showing stable wave
clouds with the showers and behind the line.

However, there is still the potential for concerns through the day
today as warming adds some instability in an environment with strong
winds aloft and some shear at the lower levels. Lightning chances
will increase as we go into the afternoon as well as winds picking
up, both non-shower and within showers/storms, as the front moves
through. General gusts up to 40-45 mph today are forecasted with
isolated higher gusts within showers possible. Still can`t entirely
rule out a few spin ups forming later today, mainly for our NE, but
confidence remains low at this time.

&&

.SHORT TERM (Today and tonight)...
Issued at 304 AM EDT Tue Mar 26 2024

Current radar observations show steady light rain across much of the
area due to increasing low-level theta-e advection and increasing
dynamics from a deepening surface low centered over Iowa. Look for
rain to continue over the next few hour or two before rain
diminishes as a dry slot associated with the system moves in. The
dry slot is currently centered near southern IL/western KY and is
quickly progressing northeastward. Most locations will start the day
dry with only isolated light showers expected through the morning.
- Windy with rain tonight
A wind advisory is in effect through 6pm today for the potential of
wind gusts around 45-50 mph at times. WHile winds have tapered off
slightly over the past few hours, the approaching dry slot should
help to mix down stronger winds leading to more widespread gusts of
40-50 mph.

The surface low is expected to occlude across the upper midwest
later today. A cold front extending southeast from the system will
move through during the afternoon supporting the potential for
additional precipitation. Breaks in the clouds and warm air
advection should allow temperatures to warm into the 60s promoting
weak destabilization ahead of the front. Expect convective showers or
low-topped thunderstorms to develop by the early afternoon hours.
While instability will be weak (less than 500 J/KG), strong low to
mid level flow and steep low-level lapse rates could support
isolated damaging wind gusts. In addition, there is a low chance for
an isolated tornado with effective bulk shear around 30-40 kts and
low-level veering hodographs. Confidence in the tornado threat is
fairly low considering the weak instability which will tend to limit
the potential for more organized rotating updrafts. In addition,
directional shear in the lowest 0-1 km layer is modest.

Quiet conditions are expected tonight once cold air advection moves
in behind the cold front. Some patchy drizzle may develop late
tonight as increasing subsidence aloft traps low-level moisture.
Forecast soundings show a strengthening subsidence inversion above
lower tropospheric moisture supporting this. Look for winds to
quickly taper off tonight with the pressure gradient weakening.

&&

.LONG TERM (Wednesday through Monday)...
Issued at 304 AM EDT Tue Mar 26 2024

Wednesday through Friday -

Dry weather will be expected from mid week through Friday. Models
suggest a broad upper trough will be left across the Mississippi and
Ohio Valleys on Wednesday, which will push across Central Indiana on
Thursday. The best forcing with this feature will be found well to
the north of Indiana, over the Great Lakes and Ontario where the
associated upper low will be present.  Within the lower levels,  a
strong area of surface high pressure will be anchored over the
Plains on Wednesday, providing cooler NW flow to Central Indiana.

On Wednesday night, clear skies and light winds provided by this
high pressure system over Central Indiana will allow temperatures to
fall to the lower 30s, resulting in a frost or freeze.

This surface high is expected to slowly sag to the deep south by
Friday and Friday Night. This will gradually allow the lower level
flow to shift from a cool northwest flow on Wednesday to a warmer,
southwesterly flow by Friday. Forecast soundings through Friday show
a dry column, however convective temperatures appear to be reachable
on Thursday and on Friday. This will result in some diurnal flat
cumulus on Thursday and Friday.

Given the gradual warm trends as the lower level flow becomes more
southwesterly by Friday, we can expect a gradual warm on in daily
high temperatures, with highs in the low 50s on Wednesday rising to
the middle 60s by Friday.

Saturday through Monday -

Daily rain chances look to return to Central Indiana this weekend
and for the start of the next work week.  The main feature in play
during this time will be a warm front that is expected to setup
across Indiana on Saturday, and continue to linger across the state
through Monday. This feature really begins as a cusp-like area
between the previously mentioned surface high to the south and
another area of high pressure in place across Ontario and the Great
Lakes. This lower level convergence eventually evolves into a warm
frontal boundary through the weekend as surface low pressure begins
to develop in the plains states. Aloft through this time, forcing
remains minimal as weak ridging looks to be in place stretching from
the Rockies to the East Coast. A few ridge riding waves are depicted
in the flow, but at the moment they appear poorly defined and weak.
Thus confidence is low for that forcing element. Forecast soundings
on Saturday through Monday show periods of a saturation with pwats
ranging from 0.8 to over 1.2 inches through the period. This will be
indicative of passing showers that would be focused near the
expected lower level boundary. Thus for now, we will include daily
shower chances as this lower level feature remains in place.

Temperatures could be a bit tricky during this period as the warm
front is shown to meander north and south across Indiana, placing
locations in and out of the warm sector. Thus for now will stick
close to highs mainly in the upper 50s and lower 60s.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 605 AM EDT Tue Mar 26 2024

Impacts:

- SSE winds to 20+ knots and gusts to 30+ knots.

- Non-convective low level wind shear possible at times through
  mid morning

- MVFR cigs common through much of the TAF period.

- Convective showers and a few thunderstorms possible with gusts
 around 40-45 knots 16z-20z today

Discussion:

Radar shows the dry slot ahead of the approaching area of low
pressure has built across the TAF sites this morning. Mainly MVFR
and some VFR cigs will be found across the TAf sites this morning
while residing in the dry slot.

HRRR suggests shra/tsra development ahead of the cold front late
this morning, pushing across the TAF sites through early afternoon.
MVFR cigs along with gusty winds over 40 knots will be possible with
any showers and storms that pass.

As the cold front passes across the forecast area tonight, winds are
expected to subside as the pressure gradient lessens. MVFR Cigs will
still be possible overnight as cold air advection will be ongoing
and time heights continue to show saturation within the lower
levels.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 PM EDT this evening for INZ021-028>031-
035>049-051>057-060>065-067>072.

&&

$$

UPDATE...KF
SHORT TERM...Melo
LONG TERM...Puma
AVIATION...Puma


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