266
FXUS63 KIND 020157
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
957 PM EDT Wed May 1 2024

.KEY MESSAGES...

- Multiple chances for showers and storms throughout much of the
  forecast period, with continued above normal temperatures.

- Repeated rounds of rainfall may lead to redevelopment of flooding.

&&

.FORECAST UPDATE...
Issued at 957 PM EDT Wed May 1 2024

Isolated convection had diminished across central Indiana this
evening, with a few showers south of the area. The front remains
across the southern half of the forecast area, with dewpoints in the
40s north of the front and in the 60s south of it.

The front will remain across the area tonight. An area of
thunderstorms south of St Louis at the moment is moving northeast
and looks to be associated with some upper energy moving through.
This convection should weaken as it moves into less favorable
conditions and the diurnal lessening of instability.

Models are all over the place with this convection, ranging from
high coverage of overnight to nothing. Feel that there will likely
be some isolated convection remaining by the time it moves through
given a little upper support, so expanded slight chance PoPs to much
of the area at some point overnight. PoPs can be adjusted further
once the trend in the convection becomes more clear later tonight.

Otherwise adjusted sky cover based on latest trends, and tweaked
temperatures as needed based on latest observational trends.

&&

.SHORT TERM (This evening through Thursday)...
Issued at 300 PM EDT Wed May 1 2024

Latest satellite imagery shows high clouds streaming across Indiana,
which are the result of upstream convective activity. The clouds are
thin enough for a good view of the diurnal cumulus development
currently taking place. These clouds should not be enough to prevent
highs from climbing into the low 80s for much of the area.

Going forward, a weak cold front is sliding in from the northwest.
Surface observations show this front partially through central
Indiana as of 2pm. The parent vort max is well to the north and
east, and any large-scale forcing is essentially absent.
Nevertheless, dew points are in the low 60s south of the front and
enough buoyancy may exist for some isolated showers or
thunderstorms.

Model soundings show little in the way of shear (under 30kt
effective), but relatively steep lapse rates (7.0-7.5 C/Km). Enough
DCAPE may be present for a quick downburst should any convective
core gain sufficient mass. Confidence in this occurring is very low
(less than 15 percent) but is worth mentioning.

Overnight, the front stalls across the area and begins to retreat
northward as a warm front by morning. Throughout this time, however,
the risk of an isolated shower or storm continues. Overall, the
overnight hours should feature gradually veering winds and
occasional mid to high-level cloudiness.

During the day Thursday, the now-warm front is expected to push
northward with renewed warm air advection. Temperatures at 850mb
reach between 15-20C which, combined with efficient boundary layer
mixing, could lead to surface temps well into the 80s. A few
locations may even make a push for 90 especially closer to the Ohio
River.

&&

.LONG TERM (Thursday night through Wednesday)...
Issued at 300 PM EDT Wed May 1 2024

The warm and active stretch of weather is expected to continue into
next week, as large scale pattern characterized by broad upper level
troughing over much of the country and mean subtropical ridging over
the southeastern CONUS remains in place.

While this will require PoPs throughout much if not all of the long
term period, precipitation will be primarily convective in nature,
and significantly dependent upon mesoscale influences generally
poorly resolved on such time scales. There will be ample opportunity
for precipitation, but plenty of dry periods as well - but NWP
limitations and inconsistencies preclude more detail, precision, or
confidence in the long term forecast for any one particular time
frame.

All that said, the highest chances for showers and thunderstorms
will be Friday, and then again on Monday into Tuesday, as these are
the times when a general guidance consensus exists that frontal
boundary passage and upper level support will be present to promote
more widespread precipitation.

While there is no major signal for excessive precipitation in either
ensemble situational awareness tables or experimental machine
learning, the area is already fairly wet and streamflows remain
elevated in most areas, particularly western and southwestern
Indiana, so repeated rounds of precipitation will have at least
modest potential to lead to renewed flooding concerns, and this will
require close monitoring. Hydrologic ensemble data do have signal
for this potential.

Severe storm wise, there again is little signal for significant
concerns until late in the period, when machine learning data and
CIPS analogs do show some signal toward Tuesday into Wednesday of
next week - though uncertainty is quite high given all the
aforementioned caveats.

Temperatures will remain fairly warm throughout the period, with
highs generally in the mid 70s to mid 80s and lows in the mid 50s to
mid 60s. These will obviously be highly dependent on evolution and
timing of potential convection and/or absence/presence thereof. See
little opportunity for improvement over blend approach at this time.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 643 PM EDT Wed May 1 2024

Impacts:

- Winds becoming northeast tonight then south on Thursday

- Isolated convection around into Thursday morning

Discussion:

Outside of any isolated convection, VFR conditions are expected
throughout the period.

A front will settle south of the sites tonight and then return north
through the area on Thursday. This will cause wind direction changes
through the period, finally settling on south Thursday afternoon.
With the front in the area through Thursday morning, isolated
convection is possible, but coverage/confidence are too low to
mention.


&&

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

$$

UPDATE...50
SHORT TERM...Eckhoff
LONG TERM...Nield
AVIATION...50