364
FXUS63 KIND 180658
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
258 AM EDT Mon May 18 2026

.KEY MESSAGES...

- Severe storms possible this afternoon and again Tuesday
  afternoon and evening with damaging winds, large hail and
  localized flooding

- Highs in the 80s today and Tuesday

- Storms will end Wednesday as the front shifts south, but unsettled
  weather likely returns late this week into the holiday weekend

&&

.DISCUSSION (Today through Sunday)...
Issued at 258 AM EDT Mon May 18 2026

An amplified upper level pattern for early this week anchored by a
deep trough over the northern Rockies and strong ridging over the
eastern part of the country. The ridge will gradually flatten as the
trough shifts east enabling a strong cold front to track into the
region by late Tuesday. With a warm and unstable airmass ahead of
the front...multiple opportunities for thunderstorms will exist
through Tuesday night with severe weather possible this afternoon
and potentially again Tuesday afternoon and evening as the cold
front moves through. High pressure will bring a briefly drier period
midweek before unsettled conditions return late week in response to
the front lifting back north into the region.

Today through Tuesday Night

Quiet early morning across central Indiana with clear skies. 06Z
temperatures remained warm in the upper 60s and lower 70s in many
locations.

An active 48 hours is anticipated through Tuesday night with
multiple opportunities for rain and thunderstorms and the potential
for severe weather in advance of a cold front currently over the
Plains and poised to move across the area by Tuesday evening.

An ongoing area of convection continues early this morning from the
upper Midwest southwest into central Kansas. Much of the line has
weakened from Sunday evening with the exception of the southern part
of the line over the Missouri Valley where instability and BL shear
remain more than sufficient to maintain convective intensity. This
portion of the line is likely to remain strong for the remainder of
the night with an in creasing flood risk as it sags into south
central Missouri and becomes increasingly parallel to the mean flow.
The weaker portion of the line over Iowa is of greater interest to
the forecast area as its remnants will enable the old outflow
boundary to drift into central Illinois by mid to late morning with
convection becoming reinvigorated as the outflow interacts with a
rapidly destabilizing airmass over the region.

Convection will continue to grow upscale as it tracks into the
Wabash Valley early this afternoon then presses southeast across the
forecast area. Model soundings show steepening mid level lapse rates
with SBCAPEs 2000-2500 j/kg and sufficient shear that would support
damaging winds...especially if the cold pool can mature.
Furthermore...DCAPE values approach 1000 j/kg immediately ahead of
the convective line which also lends credence to the damaging wind
risk. Abundant CAPE is present within the hail growth zone as well
and stronger cells will carry a large hail threat as well. Timing of
the greatest risk for severe weather will be between 17Z and 22Z.

Storms will weaken as they track towards the Indiana-Ohio border by
early evening as it moves away from the deeper instability and
stronger low level winds. An axis of PWATs between 1.75 and 2 inches
will support torrential rainfall and flooding. The greatest concern
will be across the southwest half of the forecast area as training
cells become a factor with the line curving back to the west along
the instability axis. Showers and embedded storms will continue into
the evening but with the airmass worked over from the afternoon
convection...the general trend will be towards rain diminishing as
weak ridging aloft reestablishes for the overnight.

Tuesday has become a bit more uncertain with respect to convective
evolution and the potential for another round of severe weather as
the model suite has sped up the arrival of the front into the
forecast area in the afternoon. More impactful though will be the
possibility of convective cloud debris by Tuesday morning from an
MCS over the Missouri Valley Monday night. That will stunt diurnal
heating and available instability and the earlier arrival of the
front during the afternoon presents the possibility that the greater
risk for more robust convection will focus across the southeast half
of the forecast area and points east late afternoon into the
evening. That being said...model soundings do continue to highlight
mid level lapse rates up to 7.5C/km with a deep layer of dry
adiabatic flow across the region combined with sufficient levels of
BL shear to support scattered stronger convection at a minimum with
the available instability. Damaging winds will again be the primary
risk from these storms with large hail serving as a secondary
threat.

The cold front will become more parallel to the flow aloft on
Tuesday night which will keep showers and thunderstorms across much
of the forecast area into Tuesday night...gradually ending from the
north overnight as drier air advects into the region.

Highs will be tricky both today and Tuesday...dependent on
convective timing this afternoon and cloud debris Tuesday. Nudged
highs both days down from the model blend with low to mid 80s for
much of the forecast area.

Wednesday through Sunday

Convection may still be ongoing across the southeast half of the
forecast area Wednesday morning but will gradually end through the
morning as the front shifts south of the region and high pressure
builds into the Great Lakes. Confidence continues to grow on the
boundary becomes quasi stationary across the Tennessee Valley into
Thursday before lifting back north into the Ohio Valley Friday as
the high passing to the north moves east into New England. The
ensemble guidance has gotten more aggressive in this solution with
scattered to numerous showers and storms Friday and Friday night as
the front lifts north through the forecast area.

Lower confidence remains for the weekend as the return of a warmer
and more unstable airmass south of the front will support at least a
daily threat for scattered convection but the lack of much agreement
in the model ensemble makes employing detail in the timing and
coverage of rainfall difficult through much of the holiday weekend.
After temperatures mainly in the upper 60s and low 70s Wednesday and
Thursday...highs will climb back into the upper 70s and lower 80s
Saturday and Sunday.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 1252 AM EDT Mon May 18 2026

Impacts:

- LLWS lasting through daybreak at KHUF and KLAF

- Peak wind gusts at 25 to 30kts today

- A line of severe thunderstorms expected during the afternoon with
  showers continuing into the evening

Discussion:

Subsidence over the region early this morning leading to mainly
clear skies. Surface winds had diminished to 10kts or less courtesy
of the nocturnal inversion but strong winds above the inversion
within the boundary layer will maintain marginal LLWS focused
primarily at KHUF and KLAF through daybreak.

A large area of convection extending from the upper Mississippi
Valley southwest into the central Plains will track east through the
morning likely weakening before restrengthening this afternoon as it
interacts with a warm and humid airmass over central Indiana. Expect
an intense line of storms likely carrying a threat for damaging
winds to move across the terminals during the 17 to 21Z timeframe.
Restrictions to IFR and lower will accompany the line. Scattered
convection should linger into the evening before gradually
diminishing in coverage.

Windy conditions will develop quickly after daybreak with peak gusts
at 25 to 30kts prior to storms arriving in the afternoon.

&&

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

&&

$$

AVIATION...Ryan
DISCUSSION...Ryan