838
FXUS63 KIND 030156
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
956 PM EDT Tue Jul 2 2024

.KEY MESSAGES...

- Fair conditions continue tonight as humidity increases
- Marginally hot and humid Wednesday
- Rain and thunderstorm chances Wednesday through Friday, A few
strong to severe storms are possible on Wednesday and Thursday.

&&

.FORECAST UPDATE...

Main focus for the evening update has been tracking a broken line of
convection and impacts to central Indiana towards daybreak tomorrow.
As this line moves further into Illinois it continues to weaken as
was previously expected. Expectations going forward is that without
a stronger cold pool, this system will continue to weaken as it
exits the better dynamic profile of the Mississippi Valley combined
with the poor diurnal timing.

Do think that at a minimum there should be fairly robust high level
clouds across far western Indiana towards 7AM with the potential for
some very light rain, but otherwise no precipitation is expected.
The increasing clouds combined with increasing southerly flow will
allow for dewpoints to continue to rise through the night and mild
lows in the low to mid 70s.

&&

.SHORT TERM (This evening through Wednesday)...
Issued at 305 PM EDT Tue Jul 2 2024

Tonight...

Mainly quiet weather to continue tonight as the western portions of
a stacked ridge continues to drift east across central Indiana.
Southerly flow sustained up to 10 mph will veer slightly as the
surface ridge continues to depart across the eastern CONUS.  These
modest winds will steadily increase dewpoints into the 60s...while
southwesterly flow aloft advects precipitable water values to 1.70-
2.10 inches by dawn.  Can not rule out isolated showers or a stray
rumble of thunder late tonight across the region`s northwestern
zones, yet expect to impacts.  Low 70s will be the rule tonight,
with higher dewpoints likely arriving a tad too late to promote any
organized fog for southern counties.

Wednesday and Wednesday night...

Marginally hot and humid mid-summer conditions will be on full
display Wednesday ahead of an approaching cool frontal
boundary...with the potential for afternoon/evening convection
including t-storms with strong to severe straight line winds.  South-
southwesterly winds will veer to southwest during morning hours
while increasing slightly to 10-15 mph...with at times gusts to 20-
25 mph through the afternoon hours. This flow will boost dewpoints
from the upper 60s in the morning to low 70s throughout the
afternoon/evening, while promoting maximum temps in the upper 80s to
low 90s.  Decided to go with an SPS for heat indices near to just
over 100 degrees across the far southern tier of counties where
dewpoints will likely be in the mid-70s during peak heating.

PM-hours convection will likely only include a damaging straight-
line wind severe threat, although small hail could possibly reach
the ground from highest cells.  Recent trends are for less intense
storms north of I-70, yet 1500-2000 J/kg of CAPE and 20-30 kts of
wind shear should help maintain storms in a west to east motion.
Confidence greatest later in the day and for counties farther south
as indicated by some inconsistencies in latest CAM output.  A
limiting factor could be generally mediocre mid level lapse rates,
especially if early morning showers are more impressive than
expected which would also delay/limit surface-based instability.
Nonetheless expect at least scattered showers/storms over the
region`s southern third through late day and early evening
hours...with embedded damaging winds possible courtesy in part from
adequate downward CAPE.  Hopefully storm motion will be slow enough
to bring at least 0.25-0.50 inches to much of our southern zones.
Strongest storms could lead to localized flooding with shear vector
allowing for training storms, although suspect flooding threat
greater towards Ohio Valley.

Unlikely that the boundary`s southeastward progression will be great
enough to bring a noticeable drop in dewpoints Wednesday night,
especially over southern counties where 70F+ values should remain.
Areas of fog amid lighter winds will be a concern following any moderate
to heavy rainfall. Expect lows again the low 70s, with perhaps
readings able to drop below 70 in far northern areas.

&&

.LONG TERM (Wednesday night through Tuesday)...
Issued at 300 PM EDT Tue Jul 2 2024

The 4th of July forecast remains complicated with some uncertainty
regarding coverage or timing of thunderstorms. A frontal boundary
should be settled near southern portions of the area Thursday
morning. Meanwhile aloft, a low amplitude shortwave is expected to
move through providing additional forcing for storms. Showers and
thunderstorms are likely during the day given favorable forcing and
instability, but when or how widespread the convection will be is
the question. The best chance for precipitation looks to be through
the early afternoon hours before the upper wave departs.

Additional storms are still possible later in the day as the
aforementioned front continues to lift north. Weaker upper level
forcing should help to limit coverage. Marginal deep-layer shear
combined with moderate instability could support a few strong
storms. However, confidence is low in the overall threat as previous
day convection may augment the thermodynamic environment or where
the front sets up. Severe weather appears unlikely, but there is a
non-zero threat for an isolated damaging wind gusts and locally
heavy rainfall.

Model guidance continues to signal at the development of a storm
complex ahead of an approaching cold front over MO Thursday night.
These storms are expected to propagate eastward towards central IN
by daybreak Friday and gradually weaken as the complex outpaces the
more favorable deep-layer shear. There is a low chance for damaging
wind gusts, but confidence remains limited since convection on
Thursday could impact how this forecast scenario plays out.
Localized flooding will continue to be a threat, especially if
storms train over the same area. The cold front is expected to move
through late Friday with the potential for more showers and storms.

Mostly dry conditions are expected over the weekend once the front
finally moves out allowing for weak surface high pressure to settle
in. Rain chances then return late Sunday into next week with another
upper trough approaching. Temperatures look to be slightly below
normal through Saturday before returning to seasonal for the latter
half of the extended.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 709 PM EDT Tue Jul 2 2024

Impacts:

-Low potential for MVFR vsbys  due to rain at LAF or HUF towards
daybreak.
-Higher potential for MVFR to IFR vsbys/cigs due to thunderstorms at
IND and BMG mid to late afternoon.
-Southwesterly wind gusts to 22kts 15Z to 01Z.

Discussion:

VFR conditions expected through much of the TAF period outside of a
low potential for MVFR vsbys at LAF and HUF towards daybreak and a
period mid to late afternoon as thunderstorms initiate.  Confidence
is higher in the second round of convection with IND and BMG likely
to see MVFR to briefly IFR vsbys during convection. Winds will
gradually become more southwesterly towards the morning hours with
gusts to 22kts from 15Z to 01Z before becoming near calm during the
overnight.


&&

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

$$

UPDATE...White
SHORT TERM...AGM
LONG TERM...Melo
AVIATION...White