517
FXUS63 KIND 140144
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
944 PM EDT Fri Jun 13 2025

.KEY MESSAGES...

- Numerous showers and thunderstorms through much of weekend

- Heavy downpours and localized flooding will be the primary threat
  through Saturday evening

- Daily risk for showers and isolated thunderstorms through next
  week, with a chance of severe next Wed-Thurs

- Warm and muggy conditions are expected through the upcoming week
  with some relief by the end of next week behind a cold front.

&&

.FORECAST UPDATE...
Issued at 943 PM EDT Fri Jun 13 2025

With instability waning, rainshowers have generally now been
confined to along the boundary over northern central Indiana, and
near the low pressure center to the west. With that said, dew points
still remain in the upper 60s, allowing for some weak instability
and isolated convective showers to remain in between.

As the night progresses, continued moisture convergence along the
boundary to the north will likely continue periodic showers over
over the Lafayette to Kokomo to Muncie region. Coverage will likely
increase throughout the night south of the boundary as the low nears
as well.


Grid updates are out.

&&

.SHORT TERM (This evening through Saturday)...
Issued at 256 PM EDT Fri Jun 13 2025

Rest of Today and Tonight.

The pattern will remain messy through the short term period with a
weak trough aloft and surface low currently situated over Missouri.
A LLJ to the east of the low continues to advect moisture into the
Ohio Valley with scattered showers ongoing across much of the area.

Models are struggling on how to manage convective initiation into
the evening with the NAM developing a dry slow with limited coverage
into the evening while the HRRR has more widespread convection.
Trended the forecast more towards the HRRR with good synoptic
agreement in isentropic lift after 21Z with saturation through much
of the column. QPF will be highly variable based on the storms
motion, but generally expectations are most locations should see
around a half inch. Coverage on the higher end amounts may not be
quite as high as the HRRR suggests, but with PMM showing of
widespread 1-1.25 inches there is good agreement that at least
some locations may see these higher end amounts. Highest chances
towards the Indy metro region look to be later in the evening with
a good chance for a lull through 8PM.

The severe potential will be low with the poor lapse rates with the
column nearly moist adiabatic, but can`t rule out an isolated
damaging wind gust. Model parameter space shows some shear in the
low levels which could allow for brief weak rotating updrafts, but
without more widespread clearing instability will struggle to rise
high enough for more organized convection.
Flooding remains the main concern through today, but with fairly dry
conditions the last few days, the flash flood guidance has risen to
around 2-3 inches for most locations which will limit the threat
until the weekend when additional rain chances arrive.

Widespread cloud cover will persist through the night with some non-
dense fog possible late tonight into tomorrow with some light
sprinkles/mist as the cloud deck drops to around 700ft. Heavier rain
will stick around the northern counties as the aforementioned
surface low gradually pushes into the area.

Saturday.

By Saturday morning the low will stall over southern Illinois as it
begins to occlude with the LLJ gradually weakening. This will limit
the steering flow aloft and slow shower/storm motion. Broad
isentropic ascent aloft will allow for a return to scattered
showers and isolated thunderstorms but with the slower motion, the
flooding threat will increase especially after much of the area will
see periods of moderate to heavy rain today. QPF will be even more
spotty tomorrow with some areas seeing little to no rain and
isolated areas seeing upwards of 1-2 inches.

With the low nearby and very weak flow aloft, there is a heightened
risk for cold air funnels tomorrow. Lapse rates will be nearly moist
adiabatic with very low LCLs which combined with the weak near
surface convergence near the front will create nearly ideal
conditions. With numerous outdoor activities tomorrow, will be
issuing an SPS to highlight the threat for cold air funnels and will
reevaluate the threat tonight when confidence on the axis of highest
potential increases.

&&

.LONG TERM (Saturday night through Friday)...
Issued at 256 PM EDT Fri Jun 13 2025

The large scale upper level pattern affecting North America through
the extended will continue to be dominated by a neutral to weakly
negative NAO with negative PNA teleconnections. As a result this
pattern will be dominated by occasional weaknesses in the height
fields over the North Atlantic reflected into eastern North America
with an active/retracted Pacific jetstream over the North Pacific,
resulting in downstream fairly strong upper low/troughing over the
eastern Gulf of Alaska south into/near western North America. A pair
of fairly weak upper level highs will exist near 30N latitude. One
high being the typical "Bermuda High" with the other remaining
generally over the Desert SW.

A shortwave weakness between the pair of upper level highs/ridges
will be located over the MS valley at the start of the period and
will very slowly shift eastward, thanks to little to no jetstream
support through most of the period. Although periods of dry are
likely in the 2-7 day period, there will be less of them that the
wet periods, thanks to additional shortwave trough /convectively
reinforced/ energy moving SE out of the central and northern plains
and reinforcing the MS Valley shortwave height weakness.

Low temperatures through the period will generally remain above
normal, thanks in part to the tropical nature of the airmass /PWATs
near 120% normal/ with lows 65-70F. High temperatures will not be
overly hot /less than 25 percent chance of exceeding 90 F in the
next 7 days/, but the high moisture content and near to slightly
above normal temperatures in the 80s will provide for humid
conditions and apparent temperatures at times between 90-95F,
especially early-mid next week.

The threat for severe thunderstorms is low through the first half of
period with an isolated damaging wind gust not out of the question.
The severe thunderstorm threat increases later in the period when a
stronger shortwave trough moving SE out of the northern plains
guided by a stronger jetstream moves into the western Great
Lakes/Ohio Valley region. SPC has areas to the W-NW of Indiana in
the Day 6 severe thunderstorm outlook with the potential for that
severe outlook/threat to expand into Indiana or continue into Day 7
(next Thursday) depending on timing/convective evolution.

Heavy rainfall will continue to be the primary hazard.
Aforementioned high PWATs /1.6 to 1.9 inches/ will continue through
the period. This combined with generally slow storm motions will
lead to localized flooding tomorrow into tomorrow night and again
most likely Tuesday-Wednesday.

A cold front associated with the stronger shortwave is currently
progged to move through Central Indiana sometime late Thursday. The
quietest day of the period looks to be Friday behind that front
with conditions slightly cooler with lower humidity and no chance of
precipitation.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 735 PM EDT Fri Jun 13 2025

Impacts:

-Cigs generally MVFR to IFR after 20Z
-MVFR vsbys due to rain through much of TAF period
-Brief TSRA possible, but unlikely

Discussion:

Rain coverage has increased this afternoon with peak coverage
expected during the evening. Cigs are currently VFR but will drop
to MVFR this evening before becoming IFR for much of the night
with lowered vsbys even outside of showers. Rain coverage will
decrease during the overnight before increasing again by mid-
morning tomorrow. Thunder coverage will be minimal outside of a
period during the evening today and afternoon tomorrow, but still
too low for even a PROB30 mention for any sites outside of IND.

Winds will generally remain light out of the southeast through the
TAF period with brief convectively induced winds possible.


&&

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

$$

UPDATE...Updike
SHORT TERM...White
LONG TERM...Crosbie
AVIATION...Updike