214
FXUS63 KIND 290850
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
450 AM EDT Sat Jun 29 2024

.KEY MESSAGES...

- Rain showers and isolated thunderstorms through Saturday
- Cooler Sunday and Monday, heat returns on Tuesday and Wednesday
- Rain/storm chances return Wednesday onward

&&

.SHORT TERM (Today and tonight)...
Issued at 146 AM EDT Sat Jun 29 2024

Forcing for ascent this morning is primary from warm/moist
advection preceding a low amplitude shortwave trough upstream. The
effects of the shortwave itself are otherwise minimal on our
atmosphere at this latitude. These are difficult patterns to
forecast precision with regards to timing of convection.

Current thinking is the anomalous moisture plume at both low levels
and aloft will continue supporting scattered to numerous showers,
and modest instability will support isolated thunder. A small
midlevel vorticity maxima likely augmented by ongoing convection in
Missouri may result in an uptick in convective coverage early this
morning as it moves east and interacts with deeper moisture plume.
In fact, some new convection and lightning strikes are occurring as
of this writing in west-central Illinois. This will probably expand
and reach Indiana around daybreak.

There will probably be a decrease in coverage and intensity by late
morning or midday as the core of the low level jet and moisture
plume shifts eastward. Diurnal convection may increase ahead of the
front late afternoon into the evening. CAPE/shear parameter space
may be marginally supportive of a few strong to severe wind gusts.
This should mean a relative minimum in convective coverage during
the early-mid afternoon time frame.

Temperatures should be similar to yesterday but richer influx of
moisture will result in noticeably more humid conditions. As the low-
amplitude shortwave trough passes, it will nudge a drier continental
air mass in overnight along with modest cold advection bringing
temperatures down slightly compared to previous nights.

&&

.LONG TERM (Sunday through Friday)...
Issued at 146 AM EDT Sat Jun 29 2024

Sunday and Monday...

The low amplitude meridional pattern will continue through the long
term. Initially, this will lead to cool, calm conditions with surface
high pressure and upper level troughing for Sunday and Monday, and
should allow for generally clear skies and highs around 80. Winds
will veer post frontal passage today and continue to be northerly to
northwesterly through Monday.

With mostly clear skies and dew points in the 40s, overnight lows
should be well below normal for both Sunday and Monday night.
Current forecast is for lows in the 40s each night.

Tuesday through Friday...

The next phase of the this pattern will arrive mid week, with broad
ridging developing aloft. By Tuesday, 850mb temps rise by about 5-10
degrees, which under full sun and efficient mixing corresponds to
highs in the mid to upper 80s. The primary axis of warm air will
then arrive Wednesday, with highs expected to be back into the 90s.
This upper ridge will continue to remain aloft keeping temperatures
above normal through the end of next week.

Even though upper level ridging will be in place across the Ohio
Valley, precipitation chances will still increase as a succession of
weak waves develop within broad upper level diffluence in the right
entrance region of the upper jet. This should lead to variable
thunderstorm chances Wednesday through Friday, until a frontal
boundary moves through late week, decreasing surface moisture.

Its still too early to pinpoint specifics regarding timing and
potency of thunderstorms Wednesday through Friday of next week.
Ensemble guidance is highly variable on how the low level
disturbances develop and pass through the Ohio Valley, of which will
greatly influence surface conditions over central Indiana. For now,
understand and prepare for thunderstorms to potentially interrupt
holiday plans next week, and stay alert for updates as forecast
confidence increases over the next several days.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 450 AM EDT Sat Jun 29 2024

Impacts:

- Periodic showers and isolated thunderstorms

Discussion:

Timing of showers and thunderstorms will be challenging, but appears
to maximize between 09z and 16z, with another chance of diurnal
redevelopment after 19z. Outside of thunderstorms, reasonably good
flying conditions are expected. Overcast VFR will likely prevail for
most of the TAF period with southerly winds veering slightly with
time. Forecast confidence with timing of showers and thunderstorms
in TEMPO and PROB groups is slightly below average and may require
amendments based on observational trends.

&&

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

$$

SHORT TERM...BRB
LONG TERM...Updike
AVIATION...BRB