720
FXUS63 KIND 201046
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
646 AM EDT Mon May 20 2024

.KEY MESSAGES...

- Some showers and thunderstorms possible in the northwest and north
  late today into tonight.

- An isolated strong to marginally severe storm cannot be ruled out
  northwest late today into this evening.

- Unseasonably warm through Tuesday...highs in the mid to upper 80s,
with overnight lows as high as 70F Tuesday night

- 1-2 rounds of strong/severe t-storms possible Tuesday night
through Wednesday evening...especially north/west of Indianapolis

&&

.SHORT TERM (Today and tonight)...
Issued at 303 AM EDT Mon May 20 2024

Early this morning, an upper level ridge remained across central
Indiana. An old surface boundary was near the far northern forecast
area, but all convection that had been associated with it had ended.
Convection was ongoing across Iowa and Missouri associated with an
upper wave.

The aforementioned convection should move northeast in the upper
flow overnight and into the daylight morning hours today. Central
Indiana will see some high clouds from these through the first half
of the day today.

Later today, another upper wave will move toward the area and then
weaken as it moves in tonight. This, plus perhaps the tail of
another upper wave that will move farther northwest of the area will
bring some forcing. Instability will be present thanks to
temperatures in the mid and upper 80s with dewpoints in the 60s.

Thus, will add some low PoPs to the northwest and far northern
forecast area very late today (21Z or so) into tonight. Best shear
and forcing will remain northwest of the area, but there is enough
instability for some gusty winds and hail, especially in the far
northwest.

Farther southeast in central Indiana, some CAMs do bring in storms
tonight with the southern upper wave. However, instability will be
on the wane, and forcing will be diminishing as the wave weakens.
Will keep the remainder of the area dry for now but will have to
watch trends in the wave`s behavior during the day today.

The clouds today will not be enough to significantly limit heating,
so highs again will be in the upper 80s to perhaps 90 in a few
areas. With no change in airmass, lows tonight will remain in the
60s.

&&

.LONG TERM (Tuesday through Sunday)...
Issued at 303 AM EDT Mon May 20 2024

Tuesday through Wednesday...

Unseasonable warmth approaching record highs for late May will be on
display for a third and final day Tuesday as central Indiana
continues to catch the western side of an amplified upper ridge
extending from South Texas to Maine.  Meanwhile the next weather
system will be deepening over the Plains, with surface low pressure
advancing from Kansas to the Twin Cities while dropping to 990 mb...
and perhaps a stray light shower along a weak warm-frontal type
boundary during the day Tuesday.  Larger focus will be subsequent
risk of convection going into Tuesday night where showers/t-storms
are expected to enter at least western/northern counties...and
possibly continue into the Indy Metro later at night.  This threat
is conditional, with greater chances north/west and overall later at
night.  Appears damaging winds and large hail would be greatest
threats, with coverage most likely around the Upper Wabash Valley.

Wednesday should see the slow west-to-east passage of the system`s
cold front while the deep surface low departs across Ontario.
Despite several convective ingredients, including 2000-2500 J/kg of
CAPE and adequate lapse rates...latest guidance is showing less
confidence in forcing aloft/lift as well as variable levels of
vertical wind shear across the CWA.  Certainly afternoon to evening
storms are on the table, likely in a linear orientation ahead of and
then with the arriving front...although coverage of strong/severe
cells could be limited by less lift.  Convection may linger into
overnight hours across eastern/southern zones with a slower frontal
passage perhaps per lack of flow aloft.  Mid-week temperatures will
exhibit a downward trend from near-record warmth...with highs
trending from upper to low 80s...and morning lows decreasing from
around 70F to near 60F.

Thursday through Sunday,,,

Despite the cold front having passed the region...the corresponding
frontal zone lingering just to our south, and the poor attempt of
weak surface high pressure to advance any closer than the Great
Lakes...at least slightly above normal temperatures will continue
through the late week.  Stronger short wave troughs will continue to
be focused across southern Canada and the northwestern CONUS,
leaving more of a quasi-disturbed zonal pattern of small, embedded
vort maxs flowing from the central Plains through the Midwest.

Brief precipitable water minimums should occur around Thursday night
before moderate humidity returns to central Indiana.  Occasional,
diurnally-enhanced, isolated/scattered showers can be expected,
especially with the small wave expected to lift to the Ohio Valley
around Friday...and then towards latter portions of the weekend when
the next cold front arriving from the northwest promotes organized
showers and at least isolated thunder.  Temperatures should display
a fairly slow/steady moderation with early-summer like readings
increasing from the mid-upper 70s to low-mid 80s.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 645 AM EDT Mon May 20 2024

Impacts:

- MVFR fog may linger very early at KLAF
- Gusts of 15 to 20kt possible this afternoon

Discussion:

Some fog may linger at KLAF into the first hour of the TAF period.
Otherwise VFR conditions are expected.

Some cumulus will pop up this afternoon, and there will be passing
mid and high clouds. Isolated convection will be possible 22Z-06Z or
so at KLAF, but odds are too low to include.

&&

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

$$

SHORT TERM...50
LONG TERM...AGM
AVIATION...50