080
FXUS63 KIND 290527
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
127 AM EDT Wed May 29 2024

.KEY MESSAGES...

- Scattered showers and at least a few storms are possible late in
  the day and early tonight. Strong wind gusts are the primary
  hazard.

- Dry and Seasonable Wednesday through Friday, Rain chances Saturday
  into Sunday

&&

.FORECAST UPDATE...
Issued at 1012 PM EDT Tue May 28 2024

Convection continues to shift east in tandem with the upper wave
passing through the region. At 02Z...storms were now across far
eastern counties and slowly weakening. Temperatures late this
evening ranged from the upper 50s to near 70.

Storms so far this evening have produced pea hail and gusty winds. A
cell merger over eastern Marion County led to a brief intensification
of the storms and penny to quarter hail in a few spots between
Cumberland and New Pal. As mentioned above...convection is weakening
but still occasionally producing gusts to near 40 mph and pea size
hail. Convection should be out of the forecast area by midnight but
a few showers may pivot back down across far northeast sections of
the forecast area late tonight as the upper wave shifts east into
Ohio.

The remainder of the night will be quiet and cool...with a steady
increase in lower stratus from the northeast during the predawn
hours. Expect these clouds to be over much of the northern half of
the forecast area by 12Z Wednesday morning. Lows will fall into the
lower and mid 50s by daybreak.

Zone and grid updates out.

&&

.SHORT TERM (This evening through Wednesday)...
Issued at 252 PM EDT Tue May 28 2024

Generally northwesterly flow exists through the depth of the
atmosphere today as a trough axis resides to our east. A short wave
embedded within the broader flow is currently diving to the
southeast out of central Canada. This feature should pass just to
our north this evening and overnight. Given the cooler air aloft,
associated with the trough, lapse rates are fairly steep today. RAP
soundings show 7-8 C/Km with super adiabatic values (up near 10C/km)
very near the ground. ACARS soundings out of IND do not show this
super-adiabatic near-surface lapse rates, however. Despite the steep
lapse rates, instability is modest with values generally between 500-
1000 J/Kg. This is in part due to a lack of moisture within the
boundary layer.

Enough lift is present within and ahead of the vort max that showers
and thundershowers are shown by most guidance. Observations tend to
agree with this, as weak radar echoes are beginning to develop in
northern Illinois and even into northern Indiana. Continued growth
is expected through the afternoon with greater concentration nearer
to the vort max. Given the steep lapse rates and relatively dry
column, strong downbursts/wind gusts are the primary hazard with any
shower or storm. Activity should diminish after 00z as diurnal
heating wanes and the boundary layer stabilizes.

Overnight, expect quiet weather with diminishing winds. Low-clouds
cover may develop towards morning from the north as the vort max
swings by. Wouldn`t rule out a few light rain showers within the
area of low clouds either. These low clouds may persist into the
morning hours but should dissipate as daytime mixing resumes and the
vort max pulls away. Surface winds should pick up again as well once
the boundary layer begins to mix. Gusts upwards of 20kt are possible
at times tomorrow afternoon. Temperatures look to be a bit below the
climatological average for this time of year due to the broad
troughing aloft. Typical values at IND are 77/57.

&&

.LONG TERM (Wednesday night through Tuesday)...
Issued at 252 PM EDT Tue May 28 2024

The long term will begin with our first consistent reprieve from wet
conditions as high pressure moves in from the north.

Troughing over the Mid-Atlantic region has brought a succession of
waves through the region, but as of Wednesday, confluence in the
upper jet stream and broad AVA will aid in raising heights through
the mid to upper atmosphere. Eventually, the amplifying ridge axis
will lead to surface high pressure over the Ohio Valley. Initially,
some semblance  of surface moisture will stick around on Wednesday
(DP in the low 50s). However, by Thursday, adiabatically warmed
subsidence should drop surface dew points in the mid to low 40s.

The combination of subsidence, and drying air will lead to quiet
conditions Wednesday night through Friday. Highs will begin to
slightly increase on Thursday and Friday (Mid to upper 70s) within
well mixed PBLs. Even with deep PBLs, the lack of a LLJ should keep
winds rather calm; expect winds to top out around 10-12kts Thursday
and Friday afternoons.

The next wave of moisture/lift looks to arrive late Friday through
Saturday. Although the upper wave may arrive Friday night, the dry
low to mid levels from prior day subsidence should keep any
precipitation from reaching the ground until sometime on Saturday.
Overall this system looks to be mostly showery due to poor mid level
lapse rates, but its still too far out to have high confidence in
the details. The forecast beyond Saturday becomes much more murky
due to the relatively elevated surface moisture and remnant
boundaries and weak surface level waves in the remnants of the
Saturday upper level system.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 126 AM EDT Wed May 29 2024

Impacts:

- MVFR ceilings expected to develop around 09-13Z and persist
  through midday.

- Low chance for showers near IND around 14-17Z

Discussion:

MVFR ceilings are expected to develop around 09-13z due to a mid-
level disturbance moving across the area. MVFR ceilings should
persist through about midday before clouds lift and clear out in the
afternoon. HUF/BMG may only see a few brief hours of MVFR
conditions. There is a low chance IND/LAF could see brief IFR
ceilings. In addition, isolated showers are possible near IND around
14-17z as the disturbance moves through.

N/NW winds generally around 10 kts or less are expected through this
evening. VFR conditions return this afternoon and winds will become
very light tonight around 5 kts or less.

&&

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

$$

UPDATE...Ryan
SHORT TERM...Eckhoff
LONG TERM...Updike
AVIATION...Melo