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FXUS63 KIND 231648
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1248 PM EDT Mon Sep 23 2024

.KEY MESSAGES...

- Widespread showers and a few thunderstorms through Tuesday

- Seasonable temperatures for much of the week with highs in the 70s
  and lower 80s and lows in the 50s and 60s

- Rain chances return late week into the weekend.

&&

.SHORT TERM (Today and tonight)...
Issued at 300 AM EDT Mon Sep 23 2024

Radar loop is showing only a couple of stray showers over Randolph
and Henry counties early this overnight. Surface analysis was
showing the cold front has moved to near the Ohio River, and GOES-16
RGB nighttime channel and surface obs were indicating a stratus deck
was expanding southeast to near the I-70 corridor. This area of
clouds will be expanding southeast across the rest of central
Indiana overnight. Hi-Res soundings are indicating a very moist
column with an inversion that should hold most if not all of today.
Only some drying in the near surface was noted in the soundings,
suggesting the clouds will hang around all with only some lifting of
the ceilings. This will keep temperatures way down. As such,
afternoon temperatures will only reach slightly below normal
readings in the lower to middle 70s. DESI grand ensemble 25th
percentile 2m temperatures even suggest the upper Wabash Valley may
not see 70 degrees.

GOES-16 H20 vapor imagery was showing a positively tilted trough
from Nebraska to southeastern Colorado and northern New Mexico. This
trough will move east into the Missouri Valley by 12z Tuesday. This
trough will help spin up surface waves along the Ohio Valley front.
This will result in showers returning northeastward across central
Indiana this morning into tonight with the best chances (80%) during
the overnight. Only weak instability over southwestern parts suggest
any thunder will mostly be embedded and south of I-74. PWATs to
around 1.75 inches which is above the 75th percentile for this area
along with synoptic lift suggest around a half inch of rain looks
good tonight for most areas. Again, best chances will be overnight,
when a modest 30 knot low level jet points in from the southwest.

The thick clouds and moist boundary layer will mean overnight
temperatures should remain mild in the 60s.

&&

.LONG TERM (Tuesday through Sunday)...
Issued at 300 AM EDT Mon Sep 23 2024

Guidance continues to consistently show another slug of rainfall
with a weak low pressure system continuing beyond the short term
into Tuesday, before exiting the area Tuesday night.

Beyond then, forecast confidence is modest at best, with
deterministic models in some cases quite different than even 24
hours ago, but appearing to converge around a solution that shows a
large cutoff low off to our southwest mid to late week as a
potential tropical cyclone is drawn northward into the Gulf and
gradually absorbed into the cutoff low after undergoing a Fujiwara
effect type interaction early in the weekend.

This will necessitate low to middling chances for showers Thursday
onward, though this is likely a bit overdone with some dry periods
likely in that time frame. That said, potential will exist late week
into early next for a solid soaking rainfall of perhaps a welcome 1
to 2 inches, which would be another contributor toward halting
further deterioration of the hydrologic situation, though perhaps
only producing minor improvement.

Temperatures throughout the long term will remain near to a bit
below normal given the presence of the upper low and eventually
tropical remnants, though extent in time and space of cloud cover
and precipitation as the long term wears on will have a major impact
on diurnal range.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1248 PM EDT Mon Sep 23 2024

Impacts:

- Periodic MVFR ceilings through the afternoon then returning to
IFR conditions late tonight into Tuesday morning

- Rain showers at times through the forecast period with scattered
thunderstorms also possible this evening into the overnight

Discussion:

Showers will overspread central Indiana from the southwest through
the afternoon. Likely to see ceilings linger at MVFR in some
locations with occasional rises up to low VFR as well into the
evening. Winds will be light and variable for the most part into
this evening.

The frontal boundary stalled near the Ohio River will begin its trek
back north this evening into the overnight as a surface wave tracks
along it through the Ozarks. A subtle increase in instability across
the region will bring embedded convection with showers tonight.
Ceilings will fall back to IFR levels by the predawn hours with the
potential for brief lower restrictions within any heavier rainfall
or storms. The low will then lift up into the area Tuesday as winds
swing back around to southerly. Expect additional convection to
impact the terminals on Tuesday with ceilings likely to linger at
MVFR levels due to the deep moisture present through the boundary
layer.

&&

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

&&

$$

SHORT TERM...MK
LONG TERM...Nield
AVIATION...Ryan