315 
FXUS63 KIND 271130
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
730 AM EDT Sat Sep 27 2025

.KEY MESSAGES...

- Patchy fog tonight across central Indiana

- Dry and unseasonably warm through Monday, highs in the 80s

- Slight downward trend in temperatures Tuesday-Thursday to only 
  slightly above normal...while continued dry under ample sun

&&

.SHORT TERM (Today and tonight)...
Issued at 300 AM EDT Sat Sep 27 2025

Weak upper level troughing will make way to weak upper level riding 
in response to height rises in front of a cut-off low over the four 
corners region. Surface impacts to this low amplitude upper level 
shift will be minimal, with slight decreases in dew points and 
therefor larger diurnal swings each day. The main forecast problem 
during the short term will be the potential development of patchy 
fog. Broad subsidence maintained clear skies, with surface 
temperatures quickly falling towards saturation. Luckily tonight, 
dew point depressions are even greater, decreasing the coverage of 
any fog development this morning.  That said, given calm winds low 
lying valleys or waterways are likely to fog up with visibilities 
between 1-5SM between 9 and 12Z.

Temperatures will be slightly warmer today with central Indiana 
under greater subsidence and therefore more efficient near surface 
warming processes. Given 850mb temperatures around 15C and an 
afternoon near dry adiabatic PBL; surface temperatures are likely to 
push into the low 80s with a few areas reaching 84 to 85F. 

Conditions for fog should become less favorable Saturday night as 
additional ground moisture evaporates throughout the day. Still, 
moisture is abundant enough for now that some instances of dense fog 
cannot be ruled out. The best chance of fog is in areas that saw the 
most rainfall, in agricultural/rural areas, and along river valleys.

&&

.LONG TERM (Sunday through Friday)...
Issued at 308 AM EDT Sat Sep 27 2025

Broad-headed upper subtropical ridge extending from the northern 
High Plains to southeastern Ontario on Sunday...will morph into a 
quasi cut-off of dry and unseasonably high heights over the Great 
Lakes and Midwest into the midweek...courtesy of a rather broad, yet 
overall weak/disorganized upper trough retrograding over the 
southeastern CONUS into the Ohio Valley.  A potential tropical 
storm/hurricane approaching the Carolina coast into the Midweek may 
track into the southeastern trough, and potentially bring showers 
into Kentucky.  Higher confidence surrounds the strengthening 
northern jet riding zonal above the upper ridge...which should shift 
a strong autumnal surface ridge from central Canada at least 
partially into the Midwest...if not entirely so by the late week as 
latest guidance is suggesting.

This will translate to a often mostly clear long term, with probably 
SCT high cloud around Tuesday-Wednesday off of the tropical 
circulation.  The alignment of the upper ridge will promote 
northeasterly flow, although the lack of surface gradient early in 
the period will struggle to produce 10 mph flow.  The increasingly 
active pattern between the approaching trop and plunging Canadian 
high will promote gusts around 10-15 mph during midweek afternoons.
Unseasonable warmth will be the rule under the upper ridge through 
the early week.  Sunday's normal high in Indianapolis is 74F, with a 
record of 91F...the current forecast max is 86F.

The midweek gusts flowing out of the staunch Canadian surface ridge 
centered over Hudson Bay...will facilitate a subtle but steady drop 
in readings.  This should translate to afternoon maximums steadily 
decreasing from mid/upper 80s on Monday to around mid/upper 70s by 
Thursday.  While overnight minimums will likely display a drop from 
above normal upper 50s to more seasonable readings across the 
Wednesday timeframe.

Have kept all long term periods rain-free across the IND CWA, 
although some guidance members continue to bring at least isolated 
showers through the Ohio Valley to our far southern zones within the 
late Tuesday to Wednesday night timeframe.  While stray showers are 
possible within this window near US-50...it would take a lobing vort 
to be swung by the weakening tropical circulation over South 
Carolina, as far west as the Middle Mississippi Valley to have 
associated moisture make it through very dry lower levels. 
Confidence so far here is low, yet will be reassessed with future 
updates.

While fire weather conditions are unlikely, especially following 
moderate to heavy rainfall earlier this week...daily minimum 
relative humidity values will drop to near 30 percent amid the 
unseasonable warmth Sunday-Monday, and again Thursday-
Friday...albeit never with higher gusts.  The normal max/min at 
Indianapolis during the long term falls from 74/52...to 71/50.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 730 AM EDT Sat Sep 27 2025

Impacts:

- Brief IFR/MVFR possible in fog through 13Z at KHUF/KLAF

Discussion:

Brief MVFR/IFR conditions in fog is possible at KHUF/KLAF through 
13Z, although any reduced visibility will most likely be brief or 
intermittent.

VFR conditions will otherwise continue to prevail over central 
Indiana terminals into Sunday morning...as an upper ridge builds 
over weak surface high pressure stretched across the Midwest. 
Continued very light winds will often be variable during 
morning/overnight hours, with generally westerly headings this 
afternoon at KIND/KLAF. Expect areas of FEW to perhaps SCT afternoon 
cumulus today.

&&

.IND WATCHES/WARNINGS/ADVISORIES...None.
&&

$$

SHORT TERM...Updike
LONG TERM...AGM
AVIATION...AGM