IND issues Area Forecast Discussion (AFD) at Sep 23, 1:39 PM EDT177
FXUS63 KIND 231739
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
139 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
&&
.FORECAST UPDATE...
Issued at 1040 AM EDT Tue Sep 23 2025
Fog is beginning to lift and improvement is noted in both surface
observations and on various INDOT traffic cameras. Our primary
forecast challenge for the near-term is the lingering stratus
leftover from the fog. Ceilings are below 1000ft for the majority of
the region. Stratus may have some staying power as only slight hints
of dissipation are noted on satellite. With stratus potentially
persisting into the afternoon hours, our temperature forecast may
need to be adjusted. We'll slow the morning temperature rise a bit
before allowing it to climb steadily during the afternoon hours. For
now we'll leave high temps alone...but should the stratus linger
longer we'll likewise have to adjust that downward.
&&
.SHORT TERM (Today and tonight)...
Issued at 329 AM EDT Tue Sep 23 2025
Early This Morning...
Fog continues to expand across central Indiana with many sites are
already near or at one quarter of a mile. This will continue through
the remainder of the predawn hours, but there may be some
variability at times. Will let the Dense Fog Advisory continue as
is.
Rain showers have been staying just south of the forecast area, so
will keep a dry forecast.
Today...
The fog will gradually mix out this morning. Current advisory is
through 9 AM, but this may have to be extended per latest hourly
guidance. Will keep a close eye and adjust if necessary.
Clouds may linger for a while as the fog mixes out, the clouds from
an approaching system will be on the increase. Thus, there may not
be a lot of sunshine today.
Thunderstorms to the northwest of the area overnight should dissipate
before reaching the area this morning. However, outflow from these
may reach portions of the northwest forecast area this afternoon.
Some weak forcing from an upper wave may interact with this to
produce some showers or storms. Will have some PoPs north to
account for this.
High temperatures will depend on how fast morning clouds break up
and how fast the arrival of clouds this afternoon occurs. Readings
could reach the lower 80s if enough sun gets through.
Tonight...
Better chances for rain arrive tonight as some stronger upper energy
moves in from the west. Moisture will be plentiful with 850mb winds
still bringing in moisture from the southwest. The forcing and
moisture should be enough to go with likely or higher PoPs most
areas overnight.
The orientation of the 850mb winds should keep the highest rainfall
amounts south of central Indiana, but far southern areas have the
potential for some locally heavy rain. HREF Probability Matched
Means show near 2 inches possible there.
Lows will be in the 60s thanks to rain and clouds.
&&
.LONG TERM (Wednesday through Monday)...
Issued at 329 AM EDT Tue Sep 23 2025
Wednesday through Thursday Night...
Broad and multi-faceted upper trough will begin its final act for
Indiana as the long term starts. This elongated, positively-tilted
and very slowly progressing wave will likely induce weak surface low
pressure near the local region Wednesday into Wednesday night.
Corresponding increasing chances and amounts of rainfall should be
focused near and south of the I-70 corridor, with the
quasi-stationary short wave...possibly allowing additional
widespread 1.00 to 1.50 inches of rain in these areas, and mainly
moderate rainfall amounts farther north/northwest. At least
isolated thunder could include a few strong storms over mainly
southern portions of Indiana, through generally late day
hours...after the surface circulation has had a chance to advect
unseasonably high dewpoints into southern counties, and better wind
shear arrives with the upper wave.
Lingering rain chances into Thursday reflect what should be drizzle
and a few lighter showers as the trough axis finally crosses the
Hoosier state. Near to slightly below normal afternoon highs in the
low to mid-70s will be the rule thanks to considerable
cloudiness...and light easterly breezes that will back to
northwesterly as the surface trough departs. At least moderate
humidity Wednesday...will begin to transition to more seasonable
levels Wednesday night amid the backed flow. Overnight lows will
consequently trend from around 60F Wednesday night to about 5
degrees lower by dawn Friday.
Friday through Monday...
Like a flipped switch...central Indiana will quietly return to what
will likely be an extended dry period starting Friday. To the south
of an increasingly active northern jet across southern Canada...will
be another subtropical upper ridge, building northward into the
Midwest for the weekend. Although, at least through the long term
period, often light northwest or northeasterly breezes will mitigate
potential heat under the 570 dm 1000-500 thickness.
Friday will be the mildest (ample-sun) day, as weak high pressure
under a zonal ridge brings mid-70s for most of the CWA. Light
westerly breezes Saturday, courtesy of a storm system crossing
southern Canada, should return highs to around 80F. Reestablishment
of surface high pressure early next week over the southern Great
Lakes should help maintain near normal overnights and more warm
afternoons around 80F amid lighter northeasterly flow under mostly
sunny skies. The normal max/min at Indianapolis through the long
term period is 74/53.
&&
.AVIATION (18Z TAF Issuance)...
Issued at 138 PM EDT Tue Sep 23 2025
Impacts:
- Showers and Thunderstorms possible at LAF this afternoon.
- Conditions deteriorate again late tonight with arrival of next
round of -SHRA/BR, possible TSRA.
- MVFR/IFR conditions tonight into Wednesday.
Discussion:
MVFR ceilings remain across portions of central Indiana but a trend
of gradual improvement has been observed. Continued improvement is
expected as we head into the evening. A brief return to VFR
conditions is likely this afternoon before the next round of rain
arrives tonight.
A thunderstorm is located about 40 miles northwest of LAF as of
17z and may drift southeastward affecting LAF between 20-23z today.
A prob30 group has been added for this afternoon for this storm.
Rain is developing over Missouri as of 17z and will continue to
spread eastward into Illinois. By about 03z, rain should begin
reaching the Illinois/Indiana border. All terminals are expected to
see rain overnight, with the heaviest from HUF to IND southward. A
few thunderstorms may occur at times as well, and a prob30 group has
been added to account for this possibility.
Otherwise, lowering ceilings and fog/mist will bring terminals back
into MVFR and possibly IFR territory overnight into Wednesday.
Improvement on Wednesday may be slow.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Eckhoff
SHORT TERM...50
LONG TERM...AGM
AVIATION...Eckhoff
Source:
IND issues Area Forecast Discussion (AFD) at Sep 23, 1:39 PM EDT---------------
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