207
FXUS63 KIND 161109
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
709 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

&&

.FORECAST UPDATE...
Issued at 659 AM EDT Tue Jul 16 2024

Quick update to extremize precipitation probabilities based on
observations. Trailing stratiform from remnant MCS is bringing
widespread rain this morning to the southern half of Indiana,
roughly. Pressure augmentations via meso high are enhancing
southerly winds as well.

The upshear growth and heaviest amounts have been in Illinois this
morning, and this will be where the greatest flood/flash flood
threat will be through the morning.

MCS is expected to have considerable impact on the environment via
overturning and remnant midlevel clouds that will impact this
afternoon`s forecast. Will sent another update covering this later
this morning.

&&

.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 (12Z TAF Issuance)...
Issued at 709 AM EDT Tue Jul 16 2024

Impacts:

- MVFR ceilings possible at KLAF at times through 16Z

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

Discussion:

Mainly VFR conditions expected for the TAF period, with a
conditional threat of MVFR/IFR in potential bands of SHRA later
today and this evening, although confidence too low to include in
any TAF at this time. TSHRA are also possible at times but
confidence also too low to note in any TAF.

Winds today will gust to 19-21KT through midday as a cold front
slowly approaches from the north...with winds veering while
diminishing later today.

&&

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

Flood Watch through late tonight for INZ060>065-067>072.

&&

$$

UPDATE...BRB
SHORT TERM...AGM
LONG TERM...MK
AVIATION...AGM