205
FXUS63 KIND 031855
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
255 PM EDT Thu Apr 3 2025

.KEY MESSAGES...

- Flood Watch through Sunday morning with rounds of moderate to
  heavy rain and total rainfall potentially as high as 6 to 8 inches

- Some strong to severe storms possible again later Friday into
  Friday night

- Widespread, significant river flooding expected late week into
  next week

.SHORT TERM (This Evening through Friday)...
Issued at 255 PM EDT Thu Apr 3 2025

Yesterday`s cold front is now south of Indiana, stretching roughly
from northeast Texas through Arkansas and Tennessee, and then
northeast into Kentucky. With our location north of the front, we`ve
experienced cooler and quieter weather. That will change as a mid-
level wave rides northeast along the boundary overnight.

Rain is beginning to enter Indiana as of 18z. Higher-resolution
guidance shows showers expanding in coverage through the overnight.
For the most part, rain will be light to moderate and stratiform in
nature. This is because large-scale forcing from the mid-level wave
along with isentropic upglide are our primary sources of lift.
However, some elevated buoyancy may creep northward through the
night allowing for some embedded convection.

Higher-resolution guidance is beginning to catch onto the idea of a
training band of elevated storms, leading to a band of heavier
rainfall totals. As of right now, the greatest likelihood of this
would be from Indianapolis southward to the Ohio River. Guidance
varies on amounts but 1 to 2 inches is entirely possible where this
band sets up.

FLASH FLOOD POTENTIAL

Flash flooding potential seems low overnight, mainly due to the
limited coverage of deep convection. However, as mentioned above, if
a band of embedded convection develops and persists over an
area...it wouldn`t take much to lead to localized flash flooding.
Mesoscale and radar trends will need to be monitored closely
overnight.

See the Long Range Discussion below for flood potential Friday night
onward.

&&

.LONG TERM (Friday Night through Thursday)...
Issued at 255 PM EDT Thu Apr 3 2025

...MULTIPLE ROUNDS OF HEAVY RAIN THROUGH SUNDAY MORNING...
...SIGNIFICANT FLOODING POSSIBLE...

High confidence concerns for significant flooding across the Ohio
Valley as additional rounds of moderate to heavy rainfall will
impact the region Friday night through early Sunday.  A highly
amplified and blocky upper level pattern across the country anchored
by a deep trough over the Intermountain West and a strong ridge off
the southeast US coast will place the Ohio Valley within deep
southwest flow that will maintain a rich fetch of moisture from both
the equatorial Pacific and the Gulf. Additionally the sharp
baroclinic zone that will align north of the stagnant frontal
boundary across the region will further promote strong lift and
convergence with a strong upper jet supporting divergence aloft. As
has been mentioned...this setup is historically supportive of a
prolonged risk for heavy rainfall and flooding for the Ohio Valley
and central Indiana.

Friday Night through Sunday

Rainfall coverage will expand back north across the forecast area
late afternoon Friday as the front moves into central Indiana as
surface waves ride along the boundary. Precip efficiency levels will
be excellent as deep convergence up through 700mb aligns with the
axis of highest precip water values above the climatological max and
near 300% of normal for early April. This continues to favor another
round of widespread heavy rainfall over the entire forecast area
from late day Friday through Saturday morning. Additional rainfall
amounts of 1 to 3 inches look likely which will only exacerbate
ongoing flooding.

Rainfall coverage and rates may diminish briefly again Saturday
morning before the arrival of a stronger surface wave into the
region by late Saturday triggers the final wave of rainfall into the
Ohio Valley for Saturday afternoon and night with the frontal
boundary shifting back to the southeast of the region as the night
progresses. Despite slightly lower PWAT values...low level profiles
remain ideal for heavy...efficient rainfall to impact the forecast
area for several hours before transitioning to lighter and more
scattered rain late Saturday night as the trailing upper level
trough moves in from the west. Flooding concerns will be maximized
through early Sunday.

Temperatures may struggle to climb out of the 40s on Sunday with a
stiff northerly wind and periodic light showers and maybe a
few snowflakes making for a miserable end to the weekend.

An additional 3 to 5 inches of rain are likely across the forecast
area from late Friday through Sunday with highest amounts south.
This would be in addition to the 1 to 3 inches that fell Wednesday
night and the rain expected later today and tonight. These rainfall
amounts will produce significant flooding...especially along
rivers...creeks and streams and within poor drainage areas. High
confidence exists that the heavy rainfall anticipated through Sunday
could be one of the highest impact flooding events for central
Indiana over the last 15 years. A reminder that the Flood Watch
continues through 12Z Sunday.

Monday through Wednesday

After the wet and mild regime...a deep upper level trough will
overspread the eastern half of the country next week with high
confidence in cooler than normal conditions developing. Highs
through the first half of next week will only range from the mid 40s
to mid 50s with those temperatures subtly modifying later next
week. There is also likely to be multiple nights with subfreezing
lows with potential for frost. There will be a few opportunities
for mainly light precipitation as well as multiple weak waves
aloft swing through the region. Cannot rule out a few snowflakes
mixing in with rain at times.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 141 PM EDT Thu Apr 3 2025

Impacts:

- Wind gusts near 20kt at times today

- Rain returns later this afternoon with some MVFR conditions
  possible this evening

- A second round of rain arrives Friday afternoon and evening

Discussion:

Light rain is beginning to move into central Indiana and should
reach all terminals by 00z. Rain continues on and off through the
night with perhaps a few lightning strikes. Rain is expected to
decrease in coverage after sunrise Friday. There may be a couple
hour break during the afternoon hours before more rain showers
arrive near the end of the TAF period.

Winds are out of the west right now, but should gradually become
northerly tonight and then northeasterly by morning. Finally, winds
become easterly Friday afternoon and evening. A few gusts up to 20kt
possible through this evening but otherwise no significant gusting
is expected.

Ceilings gradually lower with time as the rain moves in. MVFR
conditions are likely overnight tonight and then again Friday
evening with the second round of showers.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Sunday morning for INZ021-028>031-035>049-
051>057-060>065-067>072.

&&

$$

SHORT TERM...Eckhoff
LONG TERM...Ryan
AVIATION...Eckhoff