IND issues Area Forecast Discussion (AFD) at Sep 23, 7:49 PM EDT108
FXUS63 KIND 232349
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
749 PM EDT Tue Sep 23 2025
.KEY MESSAGES...
- Dense fog this morning
- Milder with daily chances for showers and a few thunderstorms
through Thursday
- Dry yet warm Friday into next week
&&
.SHORT TERM (This evening through Wednesday)...
Issued at 259 PM EDT Tue Sep 23 2025
Satellite shows gradual clearing across most of the region.
Temperatures have rebounded quickly, with most showing mid to upper
70s as of 2pm. A few thunderstorms are forming just northwest of
Lafayette, which are moving east southeast. We've bumped up PoPs a
bit across our northwest to account for this. Current RAP soundings
show modest instability with weak lapse rates. However, a long
straight hodograph with about 25kt of shear is also shown. This may
allow for some organization and a small hail threat this afternoon.
Tonight
Satellite shows a vort max and associated storm complex across
Missouri, which is heading eastward. How this system evolves will
have implications for how much rain we get and where it falls. Three
scenarios exist, each discussed below:
Scenario 1: The system wraps up and intensifies, bringing a large
swath of heavy rain and thunderstorms to central Indiana. This
scenario is shown by the ECMWF and NAM, and depends on a more
compact and consolidated vort max as well as some convective
augmentation. Should this scenario occur, a more concentrated area
of rainfall is likely...with embedded convection. Amounts could
range from 1-3 inches or locally higher. This is the least likely
scenario.
Scenario 2: The system remains weak and disorganized. This scenario
is shown by the GEM and GFS. In this scenario, the vort max remains
disjointed with the bulk of the energy sliding to our south. Only
the southern half of our CWA sees rainfall with only light amounts.
Scenario 3: Something in between. The third possibility is a little
of both, with modest low sliding east over our CWA. Showers and
thunderstorms are likely, with locally heavy amounts, but rainfall
is more spotty in nature. The RAP is the solution most similar to
this scenario. This is the most likely scenario.
Regardless, it is important to note the wide range of solutions and
model disagreement for a system that is less than 24 hours out.
Thankfully, we have recent observations to compare to since the
system is beginning to take shape as of this writing. Surface
observations and recent radar trends point us towards scenario 3. As
such, we have likely to categorical PoPs across our CWA with the
highest rainfall totals in our southern half. Trends will need to be
monitored overnight as the system evolves...in case these need to be
adjusted upward or downward.
Wednesday
Rain should linger into Wednesday before gradually tapering off
during the afternoon. Lingering cloud cover should keep temperatures
down compared to today, with highs in the low to mid 70s. The chance
of scattered showers and thunderstorms remains during the afternoon,
especially if the system is weaker and takes longer to depart.
&&
.LONG TERM (Wednesday night through Tuesday)...
Issued at 259 PM EDT Tue Sep 23 2025
Wednesday Night and Thursday...
Rain is expected to be continuing on Wednesday Night before tapering
off on Thursday. The models suggest the deep upper low over MI and
IN, along with an associated trough axis, stretching southwest to
MO, passing across Indiana overnight, providing forcing. A
favorable set-up remains in place within the lower levels as an
associated surface low will be pushing across Indiana with cyclonic
flow in place. Forecast soundings show ample moisture available
amid these dynamics. Thus chances for rain will be high. Given the
clouds and rain expected, will trend lows toward the lower 60s.
The upper low and associated trough axis is suggested to have exited
northeast of Central Indiana by Thursday morning. Furthermore, the
associated cold front should have exited Indiana, allowing a cooler
less humid flow to arrive on northerly winds. A few lingering
showers could remain within the waning cyclonic lower level flow in
the morning, however the bigger picture here is the arrival of
subsidence in the wake of the trough axis and stronger surface
ridging building across Indiana through the course of the day from
the upper midwest. Thus the trend here will be to include small
chances for some light rain in the morning, followed by the arrival
of dry weather in the afternoon.
Friday through Tuesday...
Strong ridging aloft along with subsidence is expected to remain
across Indiana Friday through Sunday. This strong ridge is expected
to produce a broad area of high pressure, stretching from the Great
Lakes to the Central Plains this weekend. This will result in cool
and dry northeasterly surface flow across Indiana. Forecast
soundings appear on board for dry weather with a dry column with
subsidence suggested. Plentiful sunshine should allow for more above
normal temperatures this weekend.
As we approach Monday and Tuesday, some uncertainty remains as some
models have trended drier compared to previous runs as the upper
level low expected to develop over the southeastern states has
trended to remain south of Indiana at that time. Another possibility
shows a more retrograde and NW progression that could result in
shower development in southern central Indiana. Confidence at this
time is low overall. Furthermore, either way, Indiana will remain on
the north side of this system with cool and dry northeast lower
level flow in place. For now, we wont steer far from the NBM
solution which will likely be drier.
&&
.AVIATION (00Z TAF Issuance)...
Issued at 748 PM EDT Tue Sep 23 2025
Impacts:
- Showers and Thunderstorm chances increase overnight
- Cigs and vis lowering to MVFR levels overnight, possibly IFR near
daybreak
Discussion:
Main focus for the TAF period will be the incoming complex of
showers and thunderstorms through the rest of the evening and
overnight hours. Satellite and radar imagery show this complex right
along the IL/IN border and pushing northeastward as of 2330z.
Conditions should deteriorate to MVFR levels soon at KLAF and KHUF,
then at KBMG and KIND in the 02-04z timeframe. Best threat for
lightning at all sites will be before 06z, before instability wanes.
Expect showers to persist through the rest of the night with cigs
and vis possibly dropping to IFR levels 06z-14z.
Short term guidance is in agreement that showers will become more
scattered in nature by mid morning as the main wave pushes off to
the east. Lower confidence exists in how quickly cigs will lift on
the backside of the passing low pressure system. This could be a
situation where MVFR or worse cigs persist through the rest of the
day Wednesday with scattered showers.
Light southerly winds under 6 kts persist at all TAF sites through
late evening before becoming northeasterly during the overnight
hours. Expect winds to remain out of the northeast through the day
on Wednesday at or below 10 kts. Erratic wind speeds and wind
directions are possible within thunderstorm activity before 06z with
gusts up to 20-30 kts possible.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Eckhoff
LONG TERM...Puma
AVIATION...CM
Source:
IND issues Area Forecast Discussion (AFD) at Sep 23, 7:49 PM EDT---------------
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