715
FXUS63 KIND 161859
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
259 PM EDT Tue Jul 16 2024

.KEY MESSAGES...

- Thunderstorms with strong winds possible early today, mainly
southwest of Indianapolis

- Flash flooding possible across portions of the area today
and tonight, especially along and south of Interstate 70

- Dry weather along with a break from the heat and humidity Thursday
through this weekend

- A return to warm and humid weather with thunderstorm chances next
week.

&&

.SHORT TERM (This evening through Wednesday)...
Issued at 259 PM EDT Tue Jul 16 2024

Significant convective overturning occurred across central Indiana
with the morning MCS. The classic "onion" sounding in a convectively-
processed environment is present with vertical redistribution of low
level moisture. The near-surface layer is moist still with mid 60 to
low 70 degree dew points, and this is modifying gradually through a
deeper layer. However, the upstream environment has continued to be
convectively active on the western flank of the cold pool, so
moisture will not be as rich as originally thought. Nevertheless,
surface heating should eventually be sufficient for isolated to
scattered convection, with no preference initiation area apparent
yet. Along the synoptic front as it drives southeastward tonight,
additional convection will be possible, but should be limited in
coverage and intensity. CAPE/shear parameter space indicates severe
storms are unlikely. Opportunity for flash flooding is limited now
to where heavier cells occur over moist/near-saturated ground.

Convection will be possible in modestly unstable environment ahead
of the front Wednesday, across roughly the southern half of the
area. Convective hazards should be limited to localized flooding and
lightning, with probability for severe being quite low given
expected parameter space. Any chance of more intense convection and
strong wind gusts would occur during the afternoon as surface
destabilization occurs, and probably in the far south or just south
of our area, along the front. Meanwhile, the post-frontal air mass
will be drier and cooler, and this will be a noticeable change by
late in the day tomorrow.

&&

.LONG TERM (Wednesday night through Tuesday)...
Issued at 259 PM EDT Tue Jul 16 2024

An upper-level trough and cold front are currently approaching
Indiana form the north. These features will bring about a pattern
change where cooler and drier air take hold through the coming
weekend.

Ensemble guidance is in fairly good agreement regarding the timing
and magnitude of the trough. Temperatures at 850mb dip as low as 10-
14 degrees C, which corresponds to highs in the upper 70s / low 80s
assuming full mixing. Overnight lows may dip into the upper 50s in
rural locations, low 60s elsewhere, with good radiational cooling
potential. Dew points drop as well, and the remainder of the week
and this weekend should be rather pleasant for mid July.

Ensembles show a strong blocking pattern taking shape over CONUS.
The aforementioned trough is modeled to just sit over the midwest.
The cool/dry continental air mass will have to moderate in place,
rather than quickly exiting eastward. Deterministic guidance shows a
slow but steady increase in moisture around the back end of a
surface high pressure over the southeast states. The air mass
overhead gradually becomes warmer and more moist by Monday or
Tuesday. With no synoptic systems impacting the region due to the
blocked flow, precipitation chances should arise from diurnal
convection typical of hot humid air masses.

By the middle to end of next week, signals within guidance show a
strong ridge over the western states breaking down. In turn, the
warm air mass to our west begins to advect eastward. This should,
combined with the weak moist southerly flow, should lead to a
gradual warming trend next week.

FORECAST CONFIDENCE

Confidence in the temperature forecast is good. There is strong
model consensus on troughing through this weekend leading to near-
normal to cooler-than-normal temperatures along with dry conditions.
Confidence in a return to warmer and more humid conditions next week
is also good.

Confidence in precipitation chances next week is average. A trend
towards warmer and more buoyant air is likely, but the
shower/thunderstorm potential will largely depend on diurnal
instability and mesoscale features that are not yet resolvable at
this time.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 108 PM EDT Tue Jul 16 2024

Impacts:

- VFR Conditions this afternoon.

- Afternoon TSRA possible at HUF and BMG.

- Overall TSRA possible at all Taf Sites, best chances south.

- Any TSRA will result in brief MVFR to IFR conditions.

Discussion:

Convective complex over southern IL is expected to remain southwest
of the TAF sites this afternoon. Forecast soundings show convective
temperatures may be reached this afternoon, resulting some diurnal
CU. HRRR suggests by late afternoon isolated convection may be
possible over HUF and BMG. Thus a VCTS window was used at that time
given the warm and humid air mass.

Overnight, another upper wave is suggested to pass across Indiana,
with the best forcing found across southern Indiana. Forecast
soundings at most spots trend toward saturation overnight, while the
HRRR suggests convection pushing across BMG IND and HUF overnight.
Best confidence for this is at BMG which is closest to the lingering
boundary that remains from earlier convection. Thus have used a
tempo group for BMG while other locations only get a VCTS wind for
lower confidence at this time. Any TSRA that strikes a TAf site may
result in MVFR/IFR conditions.

High pressure and VFR will return on Wednesday morning as high
pressure begins to build across the region.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 2 AM EDT Wednesday for INZ060>065-067>072.

&&

$$

SHORT TERM...BRB
LONG TERM...Eckhoff
AVIATION...Puma