964
FXUS63 KIND 170202
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1002 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.

&&

.FORECAST UPDATE...
Issued at 1001 PM EDT Tue Jul 16 2024

A few changes were made to the forecast regarding patchy fog
potential and precipitation chances. Current radar imagery shows
quiet weather conditions across all of central Indiana as the
atmosphere remains somewhat convectively overturned. Latest ACARS
soundings show gradual moistening has occurred in the last few
hours ahead of an approaching upper trough. Subtle moisture
advection combined with modest forcing may be enough to support
isolated showers or storms through the night. However, CAMs have
continued to trend down in convective coverage thus confidence in
precipitation has lessened. POPs were decreased through daybreak
for this reason.

Current satellite imagery shows some breaks in the clouds across the
region. This combined with light winds and damp grounds is expected
to promote patchy fog development late tonight. Any fog that
develops should quickly mix out by mid-morning Wednesday. Look for
overnight temperatures to settle into the upper 60s and low 70s.

&&

.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 (00Z TAF Issuance)...
Issued at 747 PM EDT Tue Jul 16 2024

Impacts:

- Chance for showers or a few storms overnight

- Chance for MVFR visibilities from fog late tonight into early
  Wednesday morning

Discussion:

An upper wave will pass across Indiana late tonight into Wednesday
morning, with the best forcing found across southern Indiana. There
is a chance for showers and a few storms overnight, but confidence
in coverage is too low thus VCSH was mentioned at all TAF sites
late tonight. VCTS was taken out of the TAFs as model trends
continue to signal that most convection will remain south of the
area.

Some patchy fog will develop late tonight with a chance for MVFR
visibilities at a few sites. This should mix out by mid-morning
Wednesday. High pressure and VFR conditions will return on Wednesday
morning as high pressure begins to build across the region.


&&

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

$$

UPDATE...Melo
SHORT TERM...BRB
LONG TERM...Eckhoff
AVIATION...Melo