593
FXUS63 KIND 041856
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
256 PM EDT Tue Jun 4 2024

.KEY MESSAGES...

- Scattered thunderstorms this evening and tonight. Most storms
should remain below severe limits.

- Additional storm chances 16-22z tomorrow with the passage of the
front. A few storms may be strong.

- Below normal temperatures in the 70s late this week into the
  weekend

&&

.SHORT TERM (This evening through Wednesday)...
Issued at 255 PM EDT Tue Jun 4 2024

This evening and tonight...

Scattered showers and thunderstorms are in the forecast this evening
through tomorrow afternoon across Central Indiana. Latest satellite
imagery and surface analysis show an area of low pressure over NE
Missouri with a boundary extending SE into South Central Indiana.
With the boundary pushing through the region this evening, expect the
environment to continue to destabilize and become more supportive
of convection. ACARs soundings from IND, SDF, and STL show
sufficient moisture and surface based instability; however wind
shear is very weak resulting in a low severe weather threat. A
strong storm or two is not out of the question with strong wind gust
or hail, but most storms should remain below severe limits with
lightning and heavy rain being the main threats. Local mesoscale
features such as outflow boundaries and storm mergers may lead to
brief intensification of storms to strong to severe levels and/or
lead to repeated thunderstorm activity over an area. Greatest storm
chances and coverage this evening are along and south of the I-74
corridor closest to the boundary slowly pushing NE through the
state. Expect the most widespread convective activity through around
sunset then a slight decrease in coverage after sunset. Short-range
guidance does not handle weakly forced scattered storms well, but
confidence is moderate that periods of scattered convection will
persist into the late evening and overnight hours as the low level
jet ramps up overhead. While shear does increase some overnight, low
level instability values weaken resulting in convection likely being
elevated, keeping the severe threat low overnight.

With increased clouds and convection in the area overnight, lows
likely will not fall much below the upper 60s to low 70s tonight.

Tomorrow...

A cold front associated with the same system from Tuesday will be
approaching Central Indiana from the west tomorrow morning bringing
additional chances for storms to the region. Isolated to scattered
convection may be ongoing during the early morning hours across
Central Indiana as the region will be firmly within the warm sector
of the system in a very humid, modestly unstable, and weakly sheared
environment. Guidance does suggest a lull in convective activity
around sunrise and through the mid morning hours, however confidence
in this only moderate at best as how convection evolves further west
the night before will directly impact how everything evolves
overnight and through the morning hours. Best chance at morning
storms seems to be across Western portions of Indiana, closer to
the front and area of greater forcing.

The main front is expected to push through Central Indiana from west
to east in the 16-22z timeframe tomorrow. This round of storms has
the best chance at producing strong to severe storms; however the
risk is only marginal with the greatest threat along and east of the
I-65 corridor. Low level shear values of 15-25 kts in addition to a
modestly unstable environment ahead of a negatively tilted trough
axis to the NW may support a damaging wind and very isolated
tornado threat in the strongest storms.

Highs tomorrow will reach the mid 70s to low 80s with highs likely
occurring behind the line of storms later in the afternoon and
evening.

&&

.LONG TERM (Wednesday night through Tuesday)...
Issued at 255 PM EDT Tue Jun 4 2024

Wednesday Night Through Thursday...

By the evening hours most model guidance has the front and much of
the convection through the area and into Ohio. We could see some
lingering stratiform rain behind any storms but that should
dissipate before midnight. A secondary front arrives on Thursday
morning and could see a few very light showers/sprinkles with that.
Otherwise, expect drier and cooler conditions on Thursday with highs
in the mid to upper 70s and dewpoints falling into the 50s to upper
40s by Thursday evening.

Friday through Monday...

A ridge builds across the western US, leaving the eastern half in a
broad trough regime. A couple of weak waves move through the broad
trough but most of the forcing stays to our north over the Great
Lakes. Northwesterly flow will keep conditions seasonably cool with
highs in the low to mid 70s and lows in the low to mid 50s. Models
begin to diverge on the eventual breakdown of the trough/ridge
Sunday into early next week. The remnants of a tropical system over
the eastern Pacific gets pulled into the flow with an uptick in
PWATs over the central and southern US to end the weekend and into
early next week. This coupled with a slightly stronger wave rotation
around the backside of the eastern US trough could finally kick the
trough out. Rain chances should return Monday through Tuesday but at
this time nothing stands out for any severe risk. Ensemble guidance
is in good agreement with temps staying in the 70s through at least
Tuesday/Wednesday. Big differences begin to emerge after early next
week.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 108 PM EDT Tue Jun 4 2024

Impacts:

- Wind gusts to around 18KT out of the south, becoming westerly
tomorrow afternoon

- Scattered shower and storm after 20-23z continuing through
tomorrow afternoon.

- MVFR or worse conditions developing in showers and storms

Discussion:

Latest satellite and radar imagery shows an area of low pressure
moving NE into West Central Illinois with a boundary extending SE
into South Central Indiana. Showers and a few storms have already
been observed across far SW Indiana this afternoon. Expect
convection to increase in coverage from SW to NE through the
afternoon and evening hours. There will likely be a few rounds of
convection this evening and then again during portions of the late
evening and overnight hours. Expect cigs and vis to drop to MVFR or
worse under any convective activity this evening, then more
widespread MVFR cigs are likely to develop overnight and toward
sunrise. Potential is there for a break in convection sometime
during the morning hours Wednesday, before another line of showers
and storms develops and pushes east in the 15-20z timeframe
Wednesday. Confidence on exact timing of storms is low due to the
scattered nature of the storms and how dependent storm development
is on small mesoscale features which may not have formed yet. Higher
confidence exists in storm chances during peak heating of the day
later this evening.

Low level mixing and a tightening southerly gradient will result in
gusts of 15-20 kts this afternoon and evening. Winds will likely
remain elevated in the 8-12kt range overnight with higher gusts
under any convection.

&&

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

$$

SHORT TERM...CM
LONG TERM...Stumpf
AVIATION...CM