000
FXUS63 KIND 180542
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
142 AM EDT Thu Apr 18 2024

.KEY MESSAGES...

- Severe storms and locally heavy rain are possible late Thursday
  into Thursday night
- Colder but dry for the weekend, chance for frost Saturday and
  Sunday night

&&

.FORECAST UPDATE...
Issued at 858 PM EDT Wed Apr 17 2024

Satellite loop and obs were indicating most of central Indiana has
scattered out or is clear with the exception of the area from Howard
county southeast to Randolph county, where the southern edge of a 5K
foot cu was rotating through around the negatively tilted Great
Lakes upper wave. This wave will continue to lift northeast tonight
and result in mostly clear to clear skies over central Indiana.

Temperatures were dropping behind the cold front but will
drop even quicker into the 50s and 40s overnight as the surface
pressure gradient relaxes and sunset puts an end to mixing setting
the stage for a temperature inversion and good radiational cooling
potential. Any gusts should be over with in the next hour or two.

&&

.SHORT TERM (This evening through Thursday)...
Issued at 255 PM EDT Wed Apr 17 2024

Cold front is moving through the forecast area as of 18Z with
convection confined to far northeast portions of central Indiana.
Storms have managed to approach severe levels but the more intense
activity so far this afternoon has been further to the northeast
across northeast Indiana and west central Ohio. Mid afternoon temps
ranged from the upper 60s over the northern Wabash Valley to near 80
over far southern portions of central Indiana with occasional wind
gusts peaking over 40mph.

After the front traversing the region shifts east in the next hour
or two...expect a brief lull in the active weather pattern that will
last through late afternoon before focus shifts to a quick moving
low and associated cold front poised to bring convection and perhaps
another threat for severe weather back to parts of the forecast area
by Thursday evening.

Storms will be out of the northeast forecast area by 1930Z or
shortly after...leaving us with a warm and windy rest of the
afternoon and early evening. Clouds will linger across northern
counties for the next few areas but clearing is quickly expanding
into the lower Wabash Valley and they will expand east into the
early evening...with skies becoming mostly clear elsewhere as weak
surface ridging builds in. Winds will remain gusty through around
sunset as model soundings show a well mixed boundary layer with
steep lapse rates that will continue to be efficient in pulling
stronger winds to the surface. SPS for the gusty winds handles this
well with no adjustments needed. As the ridge arrives during the
evening...expect winds to drop back substantially to 10kts or less
for the overnight.

The high pressure will hold serve well into Thursday with a warm
W/SW flow and mainly clear skies through midday. Focus though will
turn towards a developing surface wave over the High Plains late
today that will eject east overnight and Thursday...moving into the
mid Mississippi Valley by late day. Impacts locally will be minimal
until early evening with expectations of robust convective
development to our west likely evolving into a squall line with a
damaging wind and large hail risk approaching the Wabash Valley by 22-
23Z Thursday. More on this will be discussed in the Long Term
section below as storms and locally heavy rainfall persist into
Thursday night. Prior to the arrival of convection late day...expect
winds to increase yet again during the afternoon along with a slow
but steady increase in mid and high clouds.

Temps...slightly cooler evening tonight as much of the forecast area
will drop back into the upper 40s and lower 50s. With the increasing
likelihood of abundant sunshine well into the afternoon for Thursday
and a quick shot of warm advection ahead of the surface wave should
aid in boosting highs into the upper 70s and lower 80s across the
southern half of the forecast area.

&&

.LONG TERM (Thursday night through Wednesday)...
Issued at 255 PM EDT Wed Apr 17 2024

Thursday evening/Thursday night...

A surface low moving through early in the period is expected to
bring widespread precipitation to the area with the potential for
severe storms. Thunderstorms will likely develop along the
associated cold front earlier in the day across MO/IL before growing
upscale into a MCS. Moderate destabilization combined with modest
deep-layer shear over central IN supports the potential for severe
weather. The primary convective hazards are damaging wind gusts and
large hail, but isolated tornadoes and heavy rainfall are also
possible. Look for the cold front to move through later in the night
allowing for cooler/drier air to filter into the area.

Friday through Monday...

Quiet weather conditions are expected for several days as surface
high pressure remains dominant over the region. Aloft, guidance
shows a few weak upper level disturbances traversing the region may
help to keep some clouds around at times over the weekend. A LLJ
associated with the disturbance moving through Saturday will
likely help promote breezy conditions. Expect temperatures to
trend cooler heading into the weekend due to cold air advection.
Lows dropping into the 30s both Saturday/Sunday night combined
with relatively light winds could support the potential for
frost. There is higher confidence in frost Sunday night into
Monday morning at this time since guidance shows mostly clear
skies and lighter winds. Slightly higher winds Saturday night and
the potential for more cloud cover leads to more uncertainty.
Highs are generally going to range from the mid 50s to low 60s
over the weekend before warming up early next week.

Monday night through Tuesday...

Rain chances return late Monday night into Tuesday as a low pressure
system moves across the Great Lakes Region. Blended guidance wants
to bring in POPs early Monday night. but it appears there will
still be dry air in place. POPs were adjusted slightly for this
reason. Return flow ahead of the approaching system should allow for
temperatures to continue moderating.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 142 AM EDT Thu Apr 18 2024

Impacts:

- Thunderstorms and MVFR and briefly worse flying conditions after
  23z Thursday.

- Gusty northwesterly winds near end of TAF period.

Discussion:

Northwesterly winds around 5-8kt are expected to gradually become
light and variable by morning. Winds gradually gain a southeasterly
component during the late morning and afternoon hours ahead of an
approaching cold front.

High-level clouds should increase through the day as the front
approaches. By about 00z, showers and thunderstorms will begin
working their way in from the west. Expect MVFR conditions for a few
hours as these storms pass through, with perhaps briefly worse
conditions in the heavier storms.

The front should be through near the end of the TAF period, and
winds will become northwesterly and gusty with gusts up to 25kt
possible.

&&

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

&&

$$

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