738
FXUS63 KIND 160655
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
255 AM 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

&&

.SHORT TERM (Today and tonight)...
Issued at 254 AM EDT Tue Jul 16 2024

One final day in the very humid and at least marginally hot
subtropical air mass will promote continued rain and storm chances
ahead of and following a long-needed midday cold frontal passage.
Following several rounds of isolated to scattered severe weather
through the early week...one final opportunity for organized
strong/severe storms early today will accompany a cluster of storms
approaching the region from central Illinois as of 230A this
morning.  A more marginal threat of stronger storms embedded within
increasing rain chances through PM hours is expected...courtesy
adequate instability with mediocre lapse rates, and weak vertical
wind shear through at least most of the day.

The greater hazard will be flood potential amid increasing precip
water and convergence ahead of the approaching boundary...with pwat
values boosted above 2.00 inches during midday hours for all but far
northern counties, and perhaps even briefly 2.50 inches over
southwestern zones which would be more an a 1.00 inch anomaly. What
should be a west-east band of best convergence is expected to align
with mid-70s dewpoints by midday before trending southward through
the region into the evening.  Resultant precipitation through
Tuesday night should reach 1.00 to 2.00 inches in areas, with the
potential for localized maxima of 2.00 to 4.00 inches under the most
impressive bands of training rain.  Therefore have continued two-
tier Flood Watch for all of CWA`s 39 counties...through 200PM
near/north of I-70 corridor...and through 200AM Tuesday night for
the region`s two southern tiers of counties.

A secondary concern through the short term will be one final day of
marginal heat ahead of the approaching front...lead by mid-70s
dewpoints that, when coupled with low 90s in the afternoon across
southern zones...will promote a few hours of heat indices at or just
above 100F.  This concern is somewhat conditional with generally BKN
mid-level decks expected to prevail over southern counties, which
may hold readings under 90F, and therefore heat indices under
100F...so have held off from issuing another SPS for this sub-
Advisory threat.

Turning to Tuesday night, north of I-70 and the continuing heavy
rain/flooding potential rain chances should slowly decrease as
slightly cooler ad drier air begins to enter the region.  Fog
formation will certainly be a threat over any areas where heavier
rain falls, although low certainty so far on location and timing
of any reduced visibility. Temperatures will have one final
near/above normal day Tuesday with mid to upper 80s the general
rule, and perhaps low 90s across the southern tier...with lows in
the upper 60s to around 70F then expected Tuesday night. More
noticeable drop in humidity and readings will occur early in the
long term following the frontal zone`s passage.

&&

.LONG TERM (Wednesday through Monday)...
Issued at 254 AM EDT Tue Jul 16 2024

Big changes are in store for the long term as surface high pressure
moves in, in the wake of a cold front. This will bring in a much
drier and not as hot airmass starting Thursday. Wednesday is more up
in the air as a cold front is expected to be over south central
Indiana, perhaps even south of the CWA by 12z. That said, the dry
air will take awhile to move in and with a sharp upper trough over
the western Great Lakes and upper Midwest and lingering strong
instability, will keep thunderstorm chances going with 40-60% PoPs
over our far southern tier tapering off to 20% PoPs over our far
northern tier, further away from the front.

Thursday looks to be the most pleasant day a dry column per
soundings supporting near full sunshine. Meanwhile,  low level
thermals support well below normal temperatures with highs only in
the 70s and combined with dew points in the 50s, it will be a
welcomed respite from the heat and humidity. As the airmass
gradually modifies with high pressure overhead, temperatures will
creep back up to near normal late in the weekend or early next week.
The next chance of convection looks like it will hold off until next
week as the high moves off to the east allowing for a gradually
return of southerly flow to potentially interact with an upstream
broad trough.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 133 AM EDT Tue Jul 16 2024

Impacts:

- One or two rounds of strong/severe TSHRA crossing region through
at least 12Z from NW to SE...MVFR or worse possible within TSHRA

- MVFR ceilings possible Tuesday morning, but low confidence

- Southwesterly winds gusting to around 20KT midday Tuesday...before
veering to westerly while decreasing by 22Z

Discussion:

Thunderstorm complex currently crossing central Indiana will
continue to advance southeastward while weakening into pre-dawn
hours.  A second TSHRA complex will track from central Illinois into
the region during pre-dawn hours...possibly impacting KHUF/KBMG
through 14Z.

Less confidence in convective potential Tuesday ahead of a slowly
approaching cold front, with threat of TSHRA greatest along/south of
I-70.  Higher confidence in -SHRA/TSHRA late Tuesday and Tuesday
night amid frontal passage with low-VFR/MVFR possible at KIND after
06Z.

Gusts to 40KT will be possible under stronger cells through 14Z at
KIND/KHUF/KBMG.  Outside of storms/outflow, generally SW winds will
be sustained under 15KT through dawn...with gusts up to 20KT after
15Z Tuesday after of a slight wind shift to westerly Thursday
afternoon with the cold fropa.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 2 PM EDT this afternoon for INZ021-028>031-
035>049-051>057.

Flood Watch from 8 AM EDT this morning through late tonight for
INZ060>065-067>072.

&&

$$

SHORT TERM...AGM
LONG TERM...MK
AVIATION...AGM