IND issues Area Forecast Discussion (AFD) at Oct 18, 9:57 AM EDT410
FXUS63 KIND 181357
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
957 AM EDT Sat Oct 18 2025
.KEY MESSAGES...
- Showers and thunderstorms developing this afternoon then becoming
widespread this evening and tonight with locally heavy rainfall
- A few strong to severe storms possible this afternoon and tonight
with damaging winds as the primary threat
- Cooler with rain and wind gusts peaking at 35 to 40 mph Sunday
- Seasonably cool temperatures for the first half of next week
&&
.FORECAST UPDATE...
Issued at 957 AM EDT Sat Oct 18 2025
Some weak isentropic lift along with weak instability aloft has
allowed some isolated showers to develop across the northwest and
southwest portions of the area. These will continue to move east and
northeast this morning as the lift continues.
Have added slight chance PoPs in these areas this morning.
Additional scattered convection was across Illinois and was moving
northeast. Will continue to monitor this to see if it can survive
into the forecast area late this morning.
Organized stronger lift still looks to arrive late this afternoon in
the western forecast area and then spread east. Tweaked PoPs in this
time period for now and will monitor development for later changes.
Raised sky cover some this morning based on latest trends seen on
satellite. High temperatures look good for now but will also monitor
these as more cloud cover than expected could keep temperatures
lower.
&&
.SHORT TERM (Today and Tonight)...
Issued at 257 AM EDT Sat Oct 18 2025
Relatively dense cirrus shifting east across the region early this
morning as a subtle wave aloft traverses the back side of the upper
ridge. A steady S/SE wind continues at near 10mph for many locations
with temperatures ranging from the mid 50s to lower 60s at 06Z.
After a largely uneventful Fall to this point with an extended
period of warm and dry conditions...the next 24 to 48 hours will
signal the initial shift to a more unsettled and typical mid Autumn
pattern highlighted by a much more amplified flow aloft and stronger
surface lows tracking through the region every 3-5 days with greater
variability in temperatures and overall weather. A frontal boundary
will drift east into the area through the course of the day with an
increasing threat for scattered convection by this afternoon. As a
strong upper low moves across the Canadian prairies...an amplifying
trough will develop across the central Plains with phasing jet
energy initiating surface cyclogenesis along the boundary by this
evening across the Mid Mississippi Valley. The low will deepen as it
lifts across the region tonight with widespread rain...scattered
strong convection and windy conditions. The rain and wind will last
into Sunday as much cooler air arrives behind the cold frontal
passage.
The back edge of the cirrus that has been over the region since
Friday afternoon will depart to the east over the next few hours
with skies starting out mainly clear for much of the forecast area
this morning. A broken line of convection along the frontal boundary
from eastern Kansas into northwest Illinois will progress to the
northeast through daybreak. Mid level clouds associated with the
front will expand back into the northwest half of the forecast area
by late morning with an increasing potential for scattered
convection to develop along it across central and eastern Illinois
by early afternoon.
The sunshine this morning combined with broad warm advection...
increasing low level moisture and southwest winds that will become
gusty quickly will all contribute to an unstable environment with
CAPE values rising to around 1000 j/kg by around 18Z. Convection
over Illinois will lift northeast into the Wabash Valley and become
better organized as they expand across much of the northwest half of
central Indiana through late day. Potential exists for a few of
these storms to be strong to locally severe with gusty winds as the
primary threat due to a predominantly unidirectional wind profile.
Further southeast across central Indiana any convection should
largely remain isolated with the bulk of the rain holding off until
this evening. Wind gusts peaking at 25 to 30mph later today will
drop back this evening into the early overnight before increasing
substantially as the cold front passes predawn Sunday.
Showers will become widespread into the evening focused again over
the northwest half of the forecast area along the remnant boundary
as low pressure begins to organize across the mid Mississippi
Valley. May even see the area of precipitation pivot to the
northwest before expanding back east as the surface wave moves into
the region. While CAPE values will diminish through the evening...
weak instability will linger as a narrow...low topped convective
line develops ahead of the deepening low pressure and cold front and
moves across the region after midnight. The more intense portion of
the line will be south of the Ohio River and particularly from the
Tennessee Valley south where instability will be more plentiful.
That being said...plenty of BL shear will be present with a 60+kt
low level jet to support a shallow...fast moving QLCS across the
region in the 04-08Z timeframe that will have a risk to pull strong
winds briefly to the surface and carry a nonzero risk for a couple
brief spinups especially for areas near and south of I-70. Steadier
wind whipped rain will follow the line through and beyond daybreak
Sunday.
Trends continue to support widespread rainfall from 1 to 2 inches
across central Indiana through Sunday with the highest amounts
focused over the northern Wabash Valley. While localized nuisance
flooding is possible from brief periods with intense rainfall
rates...the overall dry ground conditions will mitigate any broader
flooding concerns.
Temps...nudged highs back slightly from the model blend but should
still see highs in the upper 70s and lower 80s across the forecast
area. Lows tonight will be dependent on the speed of the cold
frontal passage predawn Sunday with noticeably cooler air in its
wake. Expect temperatures falling back to the low to mid 50s from
west to east by daybreak Sunday with the potential to fall further
through Sunday morning as cold advection establishes.
&&
.LONG TERM (Sunday through Friday)...
Issued at 257 AM EDT Sat Oct 18 2025
Sunday...
Widespread precipitation will likely be ongoing at the start of the
period as a deepening low pressure system moves through with
abundant moisture still in place. This rainfall is much needed and
should help to at least slightly improve drought conditions. Expect
the low pressure system to shift east during the afternoon/evening
allowing precipitation to taper off from west to east as drier air
filters in. A tight MSLP gradient along with shallow mixing into a
strong LLJ will promote windy conditions. Wind gusts around 25-35
mph are likely with occasional gusts as high as 40 mph.
Sunday night through Monday...
Quiet weather is expected during this period with upper ridging and
surface pressure over the region. Cold air advection behind the
departing system will keep temperatures near or slightly below
normal. Look for winds to weaken Sunday night due to a relaxing
pressure gradient. Models depict the pressure gradient tightening up
again on Monday as another system quickly approaches. This will
promote breezy conditions with gusts up to 30 mph possible.
Monday night onward...
Marginal moisture return ahead of a system moving through Monday
night will limit rain chances to around 20 to 40 percent and should
keep any rainfall amounts light. An associated cold front will
provide another shot of cooler and drier air, keeping temperatures
slightly below normal. Quiet weather returns Tuesday and Wednesday
before another upper level impulse moves in late next week.
Uncertainty increases towards the end of next week as model
solutions diverge. At least subtle forcing from the upper wave and
moisture beginning to return north supports low rain chances.
&&
.AVIATION (12Z TAF Issuance)...
Issued at 617 AM EDT Sat Oct 18 2025
Impacts:
- Wind gusts up to 25kts mid morning through the afternoon
- Scattered convection developing this afternoon, more widespread
rain this evening into the overnight
- Deteriorating ceilings and visibilities by late evening
- Winds gusting up to 30kts predawn Sunday
Discussion:
Clouds have scattered somewhat early this morning although
increasing warm advection has led to ceilings developing at 6-7kft
in the Wabash Valley. Additional mid level clouds will arrive from
the west by midday ahead of an approaching frontal boundary. Winds
will become gusty rather quickly this morning...peaking around 25kts
from late morning into the afternoon.
Progressively deeper moisture will advect into the Ohio Valley
during the afternoon with scattered convection developing after 17Z
focused initially at KHUF and KLAF then later in the afternoon at
KBMG and KIND. Rain and embedded convection will become widespread
this evening as low pressure strengthens over the lower Ohio Valley.
There is potential for a brief 2-3 hour break in rain at KBMG and
KIND late this evening as the low organizes before rain expands back
east late tonight. Southerly winds will drop off this evening then
increase in the predawn hours Sunday as the cold front sweeps across
the region. Ceilings will drop to MVFR late evening into the
overnight with IFR conditions possible prior to daybreak Sunday.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...50
SHORT TERM...Ryan
LONG TERM...Melo
AVIATION...Ryan
Source:
IND issues Area Forecast Discussion (AFD) at Oct 18, 9:57 AM EDT---------------
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