387
FXUS63 KIND 161859
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
259 PM EDT Thu Oct 16 2025

.KEY MESSAGES...

- Dry weather through Friday

- Active weather with rain and thunderstorms expected late Saturday
  into Sunday along with occasional wind gusts of 30-40 mph.

- Turning cooler following frontal passage Sunday and Monday with
  additional rain chances Monday night into Tuesday.

&&

.SHORT TERM (This evening through Friday)...
Issued at 259 PM EDT Thu Oct 16 2025

One more night and day of fairly benign weather will occur across
central Indiana through Friday, as the region remains in close
proximity to an upper level ridge axis that will move out of the MS
valley and into the Ohio Valley during the period. Despite
relatively tranquil weather, increasing high cloud cover will occur
late tonight into tomorrow associated with a shortwave trough /with
origins in the tropics/ moving out of the southern plains tonight
into central Indiana by tomorrow afternoon.

At the surface, high pressure centered over the eastern Great Lakes
will move east into the eastern seaboard. Meanwhile several areas of
low pressure will deepen along a cold front over the central and
northern plains. As a result, the surface pressure gradient will
increase from the southern plains into the Great Lakes region. For
central Indiana this means S-SE winds will increase and average from
10-15 mph with some gusts to 20 mph during the afternoon, stronger
than we`ve recently seen. Despite warm advection associated with the
approaching longwave trough/cold front, the increase in cloud cover
should keep high temperatures roughly the same Friday as was the
case Thursday /low-mid 70s/.

&&

.LONG TERM (Friday night through Thursday)...
Issued at 259 PM EDT Thu Oct 16 2025

Our primary forecast challenge in the long range is towards the
early portion of the period as a significant trough looks to take
shape over the Midwest. Currently, the synoptic situation over North
America can be described as ridging over the Plains with troughing
on both the west and east coasts. The west coast trough has lead to
lee cyclogenesis across NE Colorado and the resulting low is moving
northeastward. Guidance takes this low well north of us into Canada
with a cold front trailing southward through the central US.

Friday Night into Saturday

By Friday night, the aforementioned cold front will be slowly sliding
southward into the Great Lakes with warm air advection increasing
ahead of it. That will help keep temperatures well above average as
we head into the weekend. Despite increasing clouds, guidance shows
temperatures climbing into the 80s on Saturday with some locations
potentially in the mid to upper 80s across our far south. Unlike
recent warmth, surface winds should be a bit more gusty this time
around. Guidance depicts a rather tight MSLP gradient leading to
southerly winds gusting to 30mph at times.

As moisture streams northward during the day Saturday, the cold
front will be approaching Indiana. Aloft, a piece of the western
trough is also likely to be approaching from the southwest with an
even more potent trough diving southeastward out of the northern
Plains. These two troughs begin to phase over Indiana, leading to
cyclogenesis just to our north or northeast. Some questions remain
as to how efficient the phasing process is or if it even happens at
all. Additionally, timing on each of the features mentioned above is
still in question. As such, forecast uncertainty remains and further
changes are likely as guidance comes into better agreement.

Regardless, most scenarios lead to enough forcing for showers and
thunderstorms on Saturday. Though exact timing and coverage cannot
be pinned down just yet, a few details can be discerned. With deep
troughing along with a potent low-level jet, there should be enough
wind shear aloft to organize developing convection. Most guidance
shows shear vectors roughly parallel to the cold front which would
favor a linear convective mode. As such, straight line winds would
be the primary convective hazard. Discrete convection is possible
further southwest due to a more intense LLJ and a more westerly
shear vector at the base of the trough. Therefore, uncertainty with
trough position, phasing, and timing could impact convective mode
and hazards...so stay tuned for updates.

Sunday Onward

Showers should continue into Sunday as the upper-level trough swings
through, likely ending by sunset. Much cooler temperatures then
follow with readings returning to normal (mid 60s / mid 40s). Wrap-
around winds may be quite gusty as the departing low continues to
intensify. Blended guidance shows gusts in the 30-40mph range. This
of course also depends on how the upper-trough evolves.

Ensemble guidance shows an active jet pattern taking hold with
another trough arriving Monday into Tuesday. Another round of
showers and storms is possible along with a reinforcing shot of cold
air. Ensembles diverge a bit thereafter but retain large-scale
troughing through the remainder of the period.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1258 PM EDT Thu Oct 16 2025

Impacts: None - VFR thru period

Discussion:

Pesky low cloud deck with ceilings between 040-050 at western TAF
sites is expected to continue to gradually erode from the
northeast through 21z owing to drier air advection originating
from surface high pressure centered over Lake Huron. A few mid
clouds centered over northern Illinois will move over the upper
level ridge axis centered over the MS valley and may produce
scattered coverage of clouds for northern TAF sites overnight. A
greater chance of broken to possibly overcast cloud cover will
come late tonight through tomorrow as an area of cirrus develops
north-northeast from TX into the region as the upper ridge axis
pushes east.

Surface winds will remain generally light easterly /6-8 kts/ through
the late afternoon, before diminishing to under 5 kts by late
evening. As the area of surface high pressure gradually shifts se
away from the Great Lakes and low pressure deepens over the
northern plains, surface winds will become SE and increase to as
high as 10-12 kts by tomorrow afternoon owing to the presence of a
well mixed boundary layer and increasing surface pressure gradient.


&&

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

$$

SHORT TERM...Crosbie
LONG TERM...Eckhoff
AVIATION...Crosbie