136
FXUS63 KIND 020628
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
228 AM EDT Tue Jul 2 2024

.KEY MESSAGES...

- Warmer today
- Thunderstorm chances Wednesday through Friday
- A few severe storms with damaging wind possible Wednesday
- Cooler and drier this coming weekend

&&

.SHORT TERM (Today and tonight)...
Issued at 228 AM EDT Tue Jul 2 2024

We will be on the windward side of prograding and gradually
dampening mid-upper ridge today. This is often the warm side as
lower tropospheric warm plume advects in from the southwest. There
is some spread in model guidance for temperatures this afternoon
which appears to be related to mixing characteristics and
interaction of the surface-based mixed layer with the warm plume
aloft. A non-GFS blend weighted toward ECMWF and MOS camps are
warmer and seem more realistic in this environment. This will place
the entire area in the mid to upper 80s.

It also appears the warm plume will be quite dry, and capable of dew
points on the lower end of the model spectrum. This is a typical
bias in these situations of shallow moisture return and mixing into
a pronounced warm/dry layer. Although fuels are green and
insufficient wind thresholds indicate fire spread isn`t a concern,
we did make this adjustment to more accurately convey afternoon
humidity within our standard fire weather products.

Lower tropospheric moisture advection will increase considerably
tonight as lower latitude reservoir of moisture reaches Indiana
coincident with subsiding mixing. Within a fairly stout warm
advection regime, blended model guidance shouldn`t need much
adjustment. The only potential caveat would be a slightly steeper
drop immediately after peak mixing as a dry environment has stronger
radiative cooling. But, this would level off quickly as low-level
warm/moist advection regime strengthens overnight.

Modeled IVT shows richer moisture through a deep layer relegated to a
fairly narrow warm conveyer belt near and ahead of the cold front.
It appears most mid-upper cloudiness will hold northwest of our area
until tonight, and frontal convective band may approach in the pre-
dawn hours. Substantial weakening and remnant light precipitation
with extensive midlevel clouds is the most likely outcome for
central Indiana very late Tuesday night.

&&

.LONG TERM (Wednesday through Monday)...
Issued at 228 AM EDT Tue Jul 2 2024

On Wednesday, the trough/ridge pattern should support a slow-moving
weakly baroclinic cold front positioned over central Indiana.
Anomalous rich moisture through a deep layer coupled with surface
heating should result in moderate instability. Westerly wind aloft
is modest but should result in 20-30-knots supporting organized
multicell clusters. This is a good setup for sporadic wind damage
potential with the most intense convective cells. The limiting
factors for a more organized and/or greater magnitude severe episode
will be (1) absence of dry midlevel layer somewhat limiting intense
cold pool formation, and (2) marginal deep layer shear.
Nevertheless, one or more bowing segments with swaths of wind damage
could still form. The threat appears greatest across roughly the
southern half of Indiana given modeled frontal timing relative to
diurnal destabilization.

There is some uncertainty on Thursday (July 4th) with regards to
convective coverage and timing. There has been a subtle trend toward
weaker low-latitude mean ridging (to our south) and a more amplified
upstream trough (to our northwest). Thus, midlevel heights are lower
across Indiana compared to previous model cycles. The diminishing
warm conveyor belt and deep subtropical moisture plume will probably
be to our south, and our air mass may be overturned from the
previous day`s convection. It appears that replenishment of moisture
and noteworthy destabilization may not occur until later in the day
when modest low level jet expands across Indiana. This would
potentially result in some warm advection-driven convection later in
the evening and overnight. Also, there is some signal for an
upstream synoptically-driven convective complex. Mid-upper flow is
quite weak to sustain this into Indiana late Thursday night or early
Friday, however. Rather, there may be a tendency for this to upshear
propagate into the mid-Mississippi Valley. Later in the day on
Friday, timing of frontal forcing with diurnal destabilization may
result in the best convective coverage south and east of our area.

The post-frontal air mass next weekend should be cooler and less
humid, albeit not as pleasant as this last cool/dry air mass that`s
currently departing. Modest moistening and destabilization early
next week preceding the next shortwave trough will result in
increased rain chances. Timing and intensity remain uncertain given
increasing ensemble spread by this time.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 1250 AM EDT Tue Jul 2 2024

Impacts:

-None

Discussion:

VFR conditions will prevail. Moisture stream and deep cloudiness
preceding the next system should hold west of us through the TAF
period. Some shift in MSLP pattern will result in winds veering
slightly during the early morning. As mixing commences a shift from
easterly or east-southeasterly to more southeasterly can be
expected.


&&

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

$$

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