IND issues Area Forecast Discussion (AFD) at Sep 23, 9:47 AM EDT081
FXUS63 KIND 231347
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
947 AM EDT Wed Sep 23 2026
.KEY MESSAGES...
- Cooler weather will continue through the week, with afternoon
temperatures staying below seasonal averages
- Drizzle and light rain showers through tonight.
- Persistent mostly cloudy skies will begin to break towards Friday
&&
.FORECAST UPDATE...
Issued at 946 AM EDT Wed Sep 23 2026
The forecast remains in good shape with only minor adjustments
needed. Low stratus and patchy drizzle is still ongoing this morning
as a mid-upper level low remains overhead. Drizzle is expected to
mostly taper off by the afternoon once ceilings improve slightly
thanks to marginal diurnal heating. Mostly quiet weather conditions
are then expected, but marginal forcing and lingering low-level
moisture may promote isolated showers this afternoon into the
evening. Extensive cloud cover will keep temperatures below normal
today. Look for highs to remain in the 60s.
&&
.DISCUSSION (Today through Tuesday)...
Issued at 309 AM EDT Wed Sep 23 2026
Strong surface high pressure remains in place over southeastern
Canada. East-northeasterly flow and moisture advection continues
from the Mid-Atlantic states westward towards Indiana. Widespread
stratus has been in place since yesterday.
Aloft, an upper-level low is advancing into Indiana from the west.
This feature has allowed the surface wind field to gain cyclonic
curvature. Combined with steepening lapse rates aloft, this has lead
to broad lift within the stratus deck. Drizzle has developed across
most of the region as of 3am this morning.
Today and Tonight
Drizzle should continue into the morning hours, before diurnal
mixing causes it to diminish somewhat. Light rain showers may become
the more dominant precipitation mechanism. As such, slight to chance
PoPs will be carried today. Precipitation chances increase this
evening into tonight as the upper low settles in. Drizzle may once
again become more prominent during the overnight hours.
Ceilings will be low today, with cloud bases only 500 to 1000 feet
above ground level. Diurnal mixing may allow this to rise to between
1500 to 2500 feet. Overcast skies are expected through tonight.
These clouds should keep temperatures suppressed as we've seen in
previous days. We will go below guidance with highs only climbing
into the low to mid 60s. Lows however will be on the warmer side of
guidance, due to the insulating effect of the low clouds.
Thursday
Things begin to change on Thursday as the upper-level low continues
southeastward. After it departs, surface high pressure to our north
once again becomes the dominant feature. Broad subsidence and low-
level dry air advection will help dissipate the stratus. This may
take most of the day, unfortunately, so we are still expecting
mostly cloud skies.
Temperatures a bit warmer than Wednesday are likely, given breaks in
the clouds and less rain/drizzle. Highs in the 60s are still the
most probable outcome. As for lows, a more dramatic difference is in
store for Thursday night. With clearing skies, light winds,
efficient radiational cooling is anticipated. This should help
temperatures drop to the coolest values we've seen since spring.
Lows in the 40s to low 50s are likely across most of the region by
Friday morning. Patchy fog may be possible as well.
Friday Through Tuesday.
Increasing subsidence aloft along with weak upper level flow will
keep cloud cover at bay Friday into the weekend bringing
temperatures closer to normal for this time of the year. Dry air
advection continues, with min RH values dropping below 40 percent
across south central Indiana which combined with the drier
conditions of late, may need to be monitored for a low-end fire
danger. Near calm winds will help to limit that threat.
Looking further into early next week, temperatures in the lower 80s
look to return as the surface flow gradually gains a more southerly
component along with gradually increasing rain chances towards late
Tuesday ahead of the next system.
&&
.AVIATION (12Z TAF Issuance)...
Issued at 625 AM EDT Wed Sep 23 2026
Impacts:
- MVFR/IFR ceilings through the forecast period.
- Patchy drizzle this morning, light rain showers and drizzle into
Wednesday night.
Discussion:
Strong surface high pressure remains in place over southeastern
Canada, providing northeasterly winds between 5-10kt across
central Indiana. Moisture advection from the east has allowed
extensive cloud cover to develop and persist since Tuesday.
An upper-level low is arriving from the west and this has allowed
the surface wind field to gain cyclonic curvature. The primary
effect this will have is to cause the stratus layer to thicken and
for patchy drizzle to develop. We have already seen drizzle over
most of the region since midnight. Patchy drizzle should continue
into the morning hours Wednesday. Ceiling and visibility
reductions into IFR territory are likely this morning, especially
from IND to BMG.
Drizzle diminishes later this morning as diurnal mixing intensifies.
However, this may allow for light rain showers to develop during the
afternoon. Showers and renewed drizzle then continue into tonight,
potentially through 12z Thursday. IFR conditions once again
possible overnight.
Winds remain out of the northeast through the TAF period around
10kt, decreasing a bit after 00z.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Melo
AVIATION...Eckhoff
DISCUSSION...White/Eckhoff
Source:
IND issues Area Forecast Discussion (AFD) at Sep 23, 9:47 AM EDT---------------
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